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  • 151. Blute, I
    et al.
    Svensson, M
    Holmberg, K
    YKI – Ytkemiska institutet.
    Bergh, M
    Karlberg, A-T
    Solution behavior of a surfactant aldehyde – the oxidation product of an alcohol ethoxylate1999Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 150, s. 105-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has previously been shown that alcohol ethoxylates readily undergo autoxidation and that one of the major oxidation products is the surfactant aldehyde, i.e. an ethoxylate carrying a –CH2CHO group at the terminal end of the polyoxyethylene chain. In this work the cloud point, phase behavior and aggregation characteristics of the surfactant aldehyde produced by oxidation of C12H25(OCH2CH2)50H(CI2E5) are determined and compared with the values obtained with the parent surfactant. It was found that the physico-chemical behavior of the two species was very similar, which indicates that a considerable portion of the aldehyde group is in hydrated state, i.e. the surfactant aldehyde consists of a mixture of aldehyde in carbonyl form and the corresponding geminal diol. The cloud point of the surfactant aldehyde decreased rapidly with time, even when it was stored at low temperature. Also the parent surfactant and its homologue C12E6 exhibited a decrease in cloud point during storage. For instance, a 1% aqueous solution of C12E6 showed a cloud point decrease from 62 to 32°C after 4 months storage at 40°C. Such a change in solution behavior can have important practical implications.

  • 152. Blute, I
    et al.
    Svensson, M
    Holmberg, K
    YKI – Ytkemiska institutet.
    Bergh, M
    Karlberg, A-T
    Solution behaviour of a formate capped surfactant - the oxidation product of an alcohol ethoxylate.1999Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 160, s. 229-236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The solution behaviour has been investigated for an alcohol ethoxylate terminated with a formic acid ester. This compound has previously been reported to be an important degradation product in the auto-oxidation of alcohol ethoxylates. In this work we have investigated the solution behaviour of the formic acid ester surfactant C12H25(OCH2CH2)4OCHO (C12E4-OCHO). The pure formate was found to be sparsely soluble in water with no clear point at 0.1%. The critical micelle concentration was found to be 129 µM at 35°C, compared to 50 µM for the parent surfactant C12H25(OCH2CH2)5OH (C12E5). To mimic the behaviour of the oxidised surfactant, the formate was mixed in different ratios with C12E5 and the cloud point, surface tension and critical micelle concentration of these mixtures were studied. The gradual increase of formate was found to shift the cloud point and isotropic regions to lower temperatures. The cmc of the mixture was found to be lower than for the pure surfactant. The favourable interaction was analysed according to the non-ideal model by Rubingh and the interaction parameter, b, was determined to be -4, which is unusually large for a mixture of two nonionic surfactants. These results indicate that the reduction of cloud point observed during oxidation of nonionic surfactants can in part be attributed to the formation of formate esters.

  • 153. Bodin, A
    et al.
    Bäckdahl, Henrik
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Bacterial Cellulose as Biomaterial2011Inngår i: Comprehensive Biomaterials: Biologically Inspired and Biomolecular Materials, Elsevier, 2011, s. 405-410Kapittel i bok, del av antologi (Fagfellevurdert)
  • 154. Bodvik, R
    et al.
    Karlson, L
    Edwards, K
    Eriksson, J
    Thormann, E
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Aggregation of modified celluloses in aqueous solution: Transition from methylcellulose to hydroxypropylmethylcellulose solution properties induced by a low-molecular-weight oxyethylene additive2012Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 38, s. 13652-13569Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Temperature effects on the viscosity and aggregation behavior of aqueous solutions of three different cellulose ethers-methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), and ethyl(hydroxyethyl)cellulose (EHEC)-were investigated using viscosity and dynamic light scattering measurements as well as cryo-TEM. In all cases, increasing temperature reduces the solvent quality of water, which induces aggregation. It was found that the aggregation rate followed the order EHEC > HPMC > MC, suggesting that cellulose ethers containing some bulky and partially hydrophilic substituents assemble into large aggregates more readly than methylcellulose. This finding is discussed in terms of the organization of the structures formed by the different cellulose ethers. The temperature-dependent association behavior of cellulose ethers was also investigated in a novel way by adding diethyleneglycolmonobutylether (BDG) to methylcellulose aqueous solutions. When the concentration of BDG was at and above 5 wt %, methylcellulose adopted HPMC-like solution behavior. In particular, a transition temperature where the viscosity was decreasing, prior to increasing at higher temperatures, appeared, and the aggregation rate increased. This observation is rationalized by the ability of amphiphilic BDG to accumulate at nonpolar interfaces and thus also to associate with hydrophobic regions of methylcellulose. In effect, BDG is suggested to act as a physisorbed hydrophilic and bulky substituent inducing constraints on aggregation similar to those of the chemically attached hydroxypropyl groups in HPMC and oligo(ethyleneoxide) chains in EHEC.

  • 155. Bodvik, Rasmus
    et al.
    Dédinaité, Andra
    YKI – Ytkemiska institutet.
    Karlson, Leif
    Bergström, Magnus
    Bäverbäck, Petra
    Skov Pedersen, Jan
    Aggregation and network formation of aqueous methylcellulose and hydroxypropylmethylcellulose solutions2010Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 354, nr 1-3, s. 162-171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solution properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) have been investigated as a function of temperature and concentration using a broad range of experimental techniques. Novelties include the extensive comparison between MC and HPMC solutions as well as the combination of techniques, and the use of Cryo transmission electron microscopy (Cryo-TEM). The correlation between rheology and light scattering results clearly demonstrates the relation between viscosity change and aggregation. Cryo-TEM images show the network structures formed. Viscosity measurements show that for both MC and HPMC solutions sudden changes in viscosity occur as the temperature is increased. The onset temperature for these changes depends on polymer concentration and heating rate. For both MC and HPMC solutions the viscosity on cooling is very different compared to on heating, demonstrating the slow equilibration time. The viscosity changes in MC and HPMC solutions are dramatically different; for MC solutions the viscosity increases by several orders of magnitude when a critical temperature is reached, whereas forHPMCsolutions the viscosity decreases abruptly at a given temperature, followed by an increase upon further heating. Light and (SAXS) small-angle X-ray scattering shows that the increase in viscosity, for MC as well as for HPMC solutions, is due to extensive aggregation of the polymers. Light scattering also provides information on aggregation kinetics. The SAXS measurements allow us to correlate aggregation hysteresis to the viscosity hysteresis, as well as to extract some structural information. Cryo-TEM images give novel information that a fibrillar network is formed inMCsolutions, and the strong viscosity increase occurs when this network spans the whole solution volume. For HPMC solutions the behaviour is more complex. The decrease in viscosity can be related to the formation of compact objects, and the subsequent increase to formation of fibrillar structures, which are more linear and less entangled than for MC.

  • 156. Bodvik, Rasmus
    et al.
    Macakova, Lubica
    YKI – Ytkemiska institutet.
    Karlson, Leif
    Thormann, Esben
    Claesson, Per
    YKI – Ytkemiska institutet.
    Temperature-dependent competition between adsorption and aggregation of a cellulose ether-simultaneous use of optical and acoustical techniques for investigating surface properties2012Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 25, s. 9515-9525Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorption of the temperature-responsive polymer hydroxypropylmethylcellulose (HPMC) from an aqueous solution onto hydrophobized silica was followed well above the bulk instability temperature (T 2) in temperature cycle experiments. Two complementary techniques, QCM-D and ellipsometry, were utilized simultaneously to probe the same substrate immersed in polymer solution. The interfacial processes were correlated with changes in polymer aggregation and viscosity of polymer solutions, as monitored by light scattering and rheological measurements. The simultaneous use of ellipsometry and QCM-D, and the possibility to follow layer properties up to 80 °C, well above the T 2 temperature, are both novel developments. A moderate increase in adsorbed amount with temperature was found below T 2, whereas a significant increase in the adsorbed mass and changes in layer properties were observed around the T 2 temperature where the bulk viscosity increases significantly. Thus, there is a clear correlation between transition temperatures in the adsorbed layer and in bulk solution, and we discuss this in relation to a newly proposed model that considers competition between aggregation and adsorption/deposition. A much larger temperature response above the T 2 temperature was found for adsorbed layers of HPMC than for layers of methyl cellulose. Possible reasons for this are discussed.

  • 157. Bodvik, Rasmus
    et al.
    Thormann, Esben
    Karlsson, Leif
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Temperature responsive surface layers of modified celluloses2011Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, nr 10, s. 4260-4268Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The temperature-dependent properties of pre-adsorbed layers of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) were investigated on silica and hydrophobized silica surfaces. Three different techniques, quartz crystal microbalance with dissipation monitoring, ellipsometry, and atomic force microscopy imaging, were used, providing complimentary and concise information on the structure, mass and viscoelastic properties of the polymer layer. 10 Adsorption was conducted at 25 °C, followed by a rinsing step. The properties of such pre-adsorbed layers were determined as a function of temperature in the range 25 °C to 50 °C. It was found that the layers became more compact with increasing temperature and that this effect was reversible, when decreasing the temperature. The compaction was more prominent for MC, as shown in the AFM images and in the thickness data derived from the QCM analysis. This is 15 consistent with the fact that the phase transition temperature is lower, in the vicinity of 50 °C, for MC than for HPMC. The water content of the adsorbed layers was found to be high, even at the highest temperature, 50 °C, explored in this investigation.

  • 158. Bodvik, Rasmus
    et al.
    Thormann, Esben
    Karlsson, Leif
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Temperature-dependent adsorption of cellulose ethers on silica and hydrophobized silica immersed in aqueous polymer solution2011Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 1, nr 2, s. 305-314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of temperature on adsorption and the adsorbed layer properties of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) were investigated on silica and hydrophobized silica surfaces immersed in aqueous polymer solution. To achieve a concise understanding a quartz crystal microbalance with dissipation, ellipsometry, and atomic force microscopy imaging were employed. These techniques provide complimentary information on the structure, mass and viscoelastic properties of the polymer layers. Adsorption was first allowed at 25 degrees C. Next, the temperature was increased step-wise up to 50 degrees C and then decreased again. This procedure highlights the temperature dependence of the adsorbed material, as well as the hysteresis in the adsorption due to temperature cycling. A change in temperature not only affects the adsorbed amount, but also the properties of the layer as illustrated by measurements of its water content, thickness and viscoelasticity.

  • 159. Bogdanovic, G
    et al.
    Meurk, A
    Rutland, MW
    YKI – Ytkemiska institutet.
    Tip friction – torsional spring constant determination2000Inngår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 19, s. 397-405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A non-destructive technique is presented for verifying torsional spring constants used in lateral force microscopy. Various calibrations of the microscope are required and these are detailed. The technique produces reasonable values which tend to be larger than those predicted >from considerations of the cantilever dimensions. The differences are discussed in terms of length corrections and particularly the uncertainty in the thickness of the cantilevers, which has an enormous effect on the values obtained through a priori calculations. Methods for inferring the thickness are discussed. Further, artefacts in conventional force measurements related to the experiments performed here are discussed.

  • 160.
    Bogdanovic, G
    et al.
    YKI – Ytkemiska institutet.
    Sennerfors, T
    YKI – Ytkemiska institutet.
    Zhmud, B
    YKI – Ytkemiska institutet.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Formation and structure of polyelectrolyte and nanoparticle multilayers: Effect of particle size2002Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 255, s. 44-51Artikkel i tidsskrift (Fagfellevurdert)
  • 161. Bogdanovic, G
    et al.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Sliding friction between cellulose and silica surfaces2001Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, s. 5911-5916Artikkel i tidsskrift (Fagfellevurdert)
  • 162. Boschkova, K
    et al.
    Elvesjö, J
    Kronberg, B
    YKI – Ytkemiska institutet.
    Frictional properties of lyotropic liquid crystalline mesophases at surfaces2000Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 166, s. 67-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The lubricating effect of assemblies of amphiphiles at surfaces has been studied. Liquid crystalline mesophases were investigated in terms of frictional and wear properties in a pin on disc rig. It is shown that systems forming lamellar liquid crystals indeed serve as lubricating liquids, indicating that the lamellar liquid crystalline phase adsorb on the steel surface forming a lubricating tribofilm. Poor performance is obtained when the lubricating system is in a single phase, i.e. in this case a lamellar liquid crystalline region. However, good lubrication is found when the lamellar liquid crystalline phase is dispersed in the water. This is attributed to a low viscosity of the system rendering a fast relaxation of the system in order to form a new film after the disturbing action of the two sliding surfaces. The lamellar packing is altered by the addition of non-charged amphiphiles, such as short chain alcohols. Using different alcohols it was shown that aromatic short chain alcohols are detrimental to the wear. This was attributed to the Rebinder effect, i.e. a strong adsorption of the alcohol, which in turn facilitates crack formation and thus the wear. In systems with mixtures of cat- and anionic amphiphiles it was, not surprisingly found that the best lubrication is obtained with a slight excess of either surfactant.

  • 163.
    Boschkova, K
    et al.
    YKI – Ytkemiska institutet.
    Feiler, A
    Kronberg, B
    YKI – Ytkemiska institutet.
    Stålgren, JJR
    Adsorption and frictional properties of Gemini surfactants at solid surfaces2002Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, s. 7930-7935Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption and frictional properties of gemini surfactants at hydrophilic gold surfaces were measured using QCM-D (quartz crystal microbalance dissipation) and AFM. The molecular packing of a series of gemini surfactants was determined from QCM-D measurements, and the frictional behaviors of the surfactant films were characterized by employing atomic force microscopy (AFM). The results show that by changing the length of the spacer group from 3 to 12 a systematic change in the molecular packing at the surface is obtained. Furthermore, the molecular packing is seen to correlate to the frictional behavior of the surfactant film. A linear relation between the spacer group length, the adsorbed amount, and the frictional properties of the layer at the solid surface is found. This is discussed in terms of the critical packing parameter (CPP) of the surfactant, and a relation between CPP and frictional behavior is proposed. No correlation between spacer length and viscoelasticity of the adsorbed surfactant layer was detected using QCM-D. This indicates that the resolution of the dissipation factor from QCM-D measurements is not sufficient to describe the viscoelastic character of the thin surfactant film.

  • 164. Boschkova, K
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Rutland, M
    YKI – Ytkemiska institutet.
    Imae, T
    Study of thin surfactant films under shear using the tribological surface force apparatus2001Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 34, s. 815-822Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Static and dynamic behaviour of thin surfactant films in aqueous solution of hexadecyltrimethylammonium salicylate (C16TASal) were investigated using the tribological surface force apparatus. Normal force measurements show that 0.15 mM C16TASal builds up an innermost film of approximately 8¯11 Å thickness at each mica surface, indicating that the surfactant adsorbs in a flat conformation. Furthermore, the height of the force barrier at approximately 60Å is low (ca 2 mN/m) indicating that the second adsorbed layer is easily pushed out. Addition of salicylate salt to 0.15 mM C16TASal give rise to a more close packed structure, with a total thickness of 62¯65 Å, indicative of a micellar or bilayer arrangement at the surfaces. Furthermore, the frequency dependence of the shear modulus was investigated both at close separation at the innermost force barrier and at larger separations (up to 300¯400 Å). The visco-elastic measurements show that the elasticity modulus, G', dominates over the loss modulus, G'', for all studied cases, indicative of a more solid-like than liquid-like film. Finally, it is shown that shear at high contact pressures induces new aggregate structures at the surface

  • 165. Boschkova, K
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Stålgren, JJR
    Persson, K
    YKI – Ytkemiska institutet.
    Ratoi Salagean, M
    Lubrication in aqueous solutions using cationic surfactants – a study of static and dynamic forces2002Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, s. 1680-1687Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper concerns lubrication in aqueous surfactant systems where the surfactants adsorb at surfaces, in relative motion, forming either a surfactant monolayer or a multi- (liquid crystalline) layer. The surfactants were of two kinds, viz., a double chain cationic surfactant, didodecyldimethylammonium bromide, DDAB, and a single chain cationic surfactant, dodecyltrimethylammonium bromide, DTAB. Excellent film forming capability was shown for DDAB and interpreted as the result of good packing of the surfactant molecules at the surfaces, i.e., the inherent ability of the surfactant molecules to form liquid crystalline structures at the surface, resulting in good load-carrying capability. This is also reflected in the bulk properties of the surfactants, where DDAB show lamellar liquid crystalline phases at concentrations much lower than DTAB, which does not show good lubrication properties. The results are discussed in terms of film stability of a surfactant layer adsorbed at the surface, which in turn is correlated to the critical packing parameter of the surfactant, in analogy with the Kabalnov-Wennerström theory of emulsion droplet coalescence (Kabalnov, A.; Wennerström, H. Langmuir 1996, 12, 276). The systems were characterized using (i) the surface force apparatus determining the interaction forces between the adsorbed layers at the surfaces and (ii) the EHD rig (elastohydrodynamic rig) determining film formation under shear. The adsorption kinetics and composition at the surface were determined by a quartz crystal microbalance and X-ray photoelectron spectroscopy.

  • 166.
    Boschkova, K
    et al.
    YKI – Ytkemiska institutet.
    Stålgren, JJR
    Cationic and non-ionic surfactant adsorption on thiol surfaces with controlled wettability2002Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, s. 6802-6806Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have shown that thiolated surfaces work very well as model substrates in adsorption measurements using the quartz crystal microbalance-dissipation. Functionalized self-assembled monolayers were prepared from mixtures of hydrophobically, SH-C16, and hydrophilically, SH-C16OH, terminated thiols, which allowed the interfacial energy of the surfaces to be changed in a systematic way. The prepared thiol surfaces were used as substrates for adsorption of a cationic (DTAB, dodecyltrimethylammonium bromide) and a nonionic (C12EO8, octa(ethylene oxide) mono(n-dodecyl ether)) surfactant. When the fraction of methyl groups at the surfaces was increased, the adsorption for both DTAB and C12EO8 was increased. In particular, there is a transition from a micellar surfactant layer to a surfactant monolayer at 25-50% surface coverage of SH-C16 groups. In addition, the role of the counterion in the adsorbed surfactant layer for the charged surfactant is discussed in terms of contribution to the mass and viscoelastic response determined by the quartz crystal microbalance.

  • 167.
    Boutonett, Magali
    et al.
    YKI – Ytkemiska institutet.
    Kizling, Jerzy
    YKI – Ytkemiska institutet.
    Stenius, Per
    YKI – Ytkemiska institutet.
    Touroude, Raymonde
    Universite´Louis Pasteur.
    Maire, Gilbert
    Universite´Louis Pasteur.
    Monodispersed colloidal metal particles from non-aqueous solutions: Catalytic behaviour for the hydrogenation of but-1-ene of platinum particles in solution1986Inngår i: Applied Catalysis, ISSN 0166-9834, E-ISSN 1873-3867, Vol. 20, nr 1-2, s. 163-177Artikkel i tidsskrift (Fagfellevurdert)
  • 168. Boutonnet, M
    et al.
    Kizling, J
    YKI – Ytkemiska institutet.
    Stenius, P
    YKI – Ytkemiska institutet.
    The preparation of monodisperse colloidal metal particles from microemulsions1982Inngår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 5, s. 209-225Artikkel i tidsskrift (Fagfellevurdert)
  • 169.
    Boutonnet-Kizling, M
    et al.
    YKI – Ytkemiska institutet.
    Gallas, JP
    Binet, C
    Lavalley, JC
    Surface oxidation of silicon carbide: quantitative measurement and Rh effect1992Inngår i: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 30, s. 273-277Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oxidation degree of a commercial silicon carbide (SiC) powder was studied by means of Fourier transform infrared spectroscopy, using the intensity of the (SiO2) band at 450 cm-1 for measurements. Results are related to data obtained by LECO and gravimetric measurements. The influence of water in oxygen on the rate of the oxidation process was particularly examined. It was found that water alone had an oxidizing efficiency and that its mixture with oxygen increased the effect of the latter. The presence of Rh particles on SiC promoted the formation of SiO2. However, as shown by the IR study of CO adsorption, this formation embedded the metal particles. This effect can be avoided by loading Rh on a precalcined SiC sample.

  • 170.
    Brandner, Birgit D
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Hansson, Petra M
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Swerin, Agne
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Claesson, Per M
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Wåhlander, Martin
    Schoelkopf, Joachim
    Solvent segregation and capillary evaporation at a superhydrophobic surface investigated by confocal Raman microscopy and force measurements2011Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 3, s. 1045-1052Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wetting of water, a 1 : 1 water/ethanol mixture and an aqueous dodecylbenzene sulfonic acid surfactant solution on hydrophobic and superhydrophobic surfaces were studied using confocal Raman microscopy. The superhydrophobic surfaces were prepared by immersion of a glass substrate in a silica particle/fluoropolymer formulation followed by silanization. Preparation of hydrophobic surfaces was done in the same way with the exception that the silica particles were excluded from the formulation. The hydrophobic and superhydrophobic surfaces were characterized with respect to surface roughness using AFM, and by contact angle measurements using different liquids. Confocal Raman microscopy measurements in a 1 : 1 water/ethanol mixture showed an enrichment of ethanol close to the superhydrophobic surface, which could not be observed for the hydrophobic surface. Unexpectedly, the Raman spectrum of a pure water film in close proximity to the superhydrophobic surface displayed some differences compared to that of bulk water and indicated a stronger hydrogenbonding close to the superhydrophobic surface. Evidence for capillary evaporation next to the superhydrophobic surface was also found, and this results in very long-range capillary attraction between one superhydrophobic surface and a hydrophobic colloidal probe as shown by AFM colloidal probe force measurements. Addition of a surfactant or ethanol suppresses capillary evaporation.

  • 171.
    Breese, KD
    et al.
    YKI – Ytkemiska institutet.
    Lamèthe, J-F
    DeArmitt, C
    Improving synthetic hindered phenol antioxidants: Learning from vitamin E2000Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 70, s. 89-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The efficiency of various commercial hindered phenol antioxidants was studied using differential scanning calorimetry (DSC) to determine the oxidation induction time (OIT) of antioxidant solutions in squalane. It was observed that a-tocopherol has an exceptionally high antioxidant activity. In fact, after normalisation for the molecular weight and functionality of each antioxidant, a-tocopherol was twice as efficient as any of the commercial, synthetic, hindered phenols tested. Through measurements on a series of model compounds, it was possible to identify the aspects of a-tocopherol’s chemical structure that are responsible for it’s exceptional antioxidant efficiency. The results showed that the para oxygen in a-tocopherol is largely responsible for it’s exceptionally high antioxidant activity. Most commercial synthetic hindered phenolic antioxidants are based upon 2, 6-di-tert-butyl-4-methylphenol (BHT). We compared the antioxidant efficiency of BHT with that of 2, 6-di-tert-butyl-4-methoxyphenol (BHA) and found that BHA was 94% more efficient. This implies that it may be advantageous to make new commercial hindered phenolic antioxidants that are based in the more effective BHA structure instead of the conventional BHT structure used today. It is expected that addition of a para oxygen (or other electron donating groups) to the aromatic ring of existing hindered phenolic antioxidants would significantly increase their activity.

  • 172.
    Brinck, J
    et al.
    YKI – Ytkemiska institutet.
    Jönsson, A-S
    Jönsson, B
    Lindau, J
    Influence of pH on the adsorptive fouling of ultrafiltration membranes by fatty acid2000Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 164, s. 187-194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fatty acids are found in many solutions treated in ultrafiltration plants, for example, in dairy products, fermentation broth, oily waste water and bleach plant effluents from pulp mills. The influence of fatty acids on the fouling of membranes is often ignored because their concentration is rather low. However, during recent years the significant influence of fatty acids on the flux reduction of ultrafiltration membranes has attracted much attention. The pore radius of the membrane, the concentration of fatty acids and the pH of the solution all have a profound influence on the flux reduction when treating solutions containing fatty acids.In the work presented in this paper, the influence of pH on the flux reduction of an ultrafiltration membrane made of polyethersulphone was studied. It was found that there was no flux reduction under alkaline conditions, whereas the flux reduction under acidic conditions was severe. In order to elucidate the adsorption process, the adsorption of octanoic acid on a planar, hydrophobized silica surface was studied by means of in situ null ellipsometry.In the ellipsometry study a sharp increase in the amount adsorbed was observed when the concentration of undissociated acid approached the saturation concentration as the pH was decreased. This explains the observed flux reduction under acidic conditions.

  • 173.
    Brinck, J
    et al.
    YKI – Ytkemiska institutet.
    Jönsson, B
    Tiberg, F
    YKI – Ytkemiska institutet.
    Influence of long-chain alcohols on the adsorption of nonionic surfactants to silica1999Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, s. 7719-7724Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption of surfactant-alcohol mixtures at the silica-water interface was studied by means of ellipsometry. The results show that addition of even small amounts of alcohol can have large effects on the characteristics of the adsorbed layer. For example, a 20% replacement of the octa(ethylene glycol) dodecyl (C12E8) surfactants by dodecanol results in an increase in the total surface excess of 80%. The thickness of the adsorbed layer, on the other hand, is virtually unaffected by the alcohol being added. Hence, as the alcohol content increases, the adsorbed surfactant aggregates at the silica-water interface mainly grow in the surface plane. A surfactant such as C12E5, which forms relatively large surface aggregates from the start, can only solubilize a small fraction of the long-chain alcohols before the system phase separates. This fraction was found not to result in any major structural changes in the surface layer. These findings are discussed in terms of surfactant packing and in relation to observations in bulk solutions reported earlier. Our study also includes measurements of adsorption and desorption kinetics for both the surfactant and the surfactant-alcohol systems. The main finding is that the effect of alcohol is most obvious in the desorption kinetics. We conclude that the effects observed are due to differences between the surfactant and the alcohol in monomer solubility.

  • 174. Brinck, J
    et al.
    Jönsson, B
    Tiberg, F
    YKI – Ytkemiska institutet.
    Kinetics of nonionic surfactant adsorption and desorption at the silica-water interface: Binary systems1998Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, s. 5863-5876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is the second of two dealing with the adsorption and desorption kinetics of nonionic surfactants at a solid-liquid interface. The first paper described a model of the kinetics of single nonionic surfactant adsorption.1 This work is now being completed by extending the theoretical model to cover binary surfactant systems. The evolution of the total surface excess during the adsorption and desorption has been modeled and compared with experimental results obtained by in situ null ellipsometry. In this comparison, the surface behavior of the two nonionic surfactant pairs C14E6-C10E6 and C12E5-C12E8 at a planar silica-water interface was studied. These binary systems represent two different types of polydispersity: different lengths of the hydrocarbon chains and unequal numbers of ethylene oxide groups in the hydrophilic headgroups. The critical micelle concentrations (cmcs) of the surfactants in the former pair therefore differ a great deal, whereas those of the surfactants in the latter pair are similar. A comparison between experiments and simulations showed good agreement. In an attempt to further analyze the experimental results, individual amounts adsorbed and concentration profiles were calculated. The results of these simulations showed that each surfactant in a given pair has a characteristic adsorption and desorption path. According to the model, this path is determined mainly by the mutual relationship between their cmcs.

  • 175. Brinck, J
    et al.
    Jönsson, B
    Tiberg, F
    YKI – Ytkemiska institutet.
    Kinetics of nonionic surfactant adsorption and desorption at the silica-water interface: One component1998Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, s. 1058-1071Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we present a theoretical model which describes the kinetics of adsorption and desorption from a micellar solution of nonionic surfactants at a silica surface. Numerical calculations based on this model have been compared with experimental results of CnEm surfactant adsorption, obtained by ellipsometry, and show good agreement. The aim of this work was to develop a model for adsorption through a stagnant layer onto a solid, hydrophilic surface. The surface is considered to be planar and homogeneous. Outside the surface there is a micellar solution of a pure nonionic surfactant. Both monomers and micelles are considered to be able to adsorb. To facilitate the evaluation of the model, a computer program was written which solves the mathematical equations numerically. The course of adsorption and desorption of a number of short-chain CnEm surfactants has been simulated with this program. The results obtained, in terms of amounts adsorbed as a function of time, were compared with experimental data determined by time-resolved null ellipsometry. The same program was used to calculate concentration profiles outside the silica surface. Not only has this model made it possible for us to explain and better understand experimental results, but it has also allowed us to gain an understanding of how the course of adsorption and desorption is affected by parameters which are difficult to vary experimentally in a controlled way. Two examples of this, which will be discussed in this paper, are the effects of stagnant layer thickness and the relation between critical surface aggregation concentration (csac) and critical micelle concentration (cmc).

  • 176.
    Brink, C
    et al.
    Berol Nobel, Sweden.
    Österberg, E
    Berol Nobel, Sweden.
    Holmberg, K
    YKI – Ytkemiska institutet. Berol Nobel, Sweden.
    Tiberg, F
    Lund University, Sweden.
    Using poly(ethylene imine) to graft poly(ethylene glycol) or polysaccharide to polystyrene1992Inngår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 66, s. 149-156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel method of grafting poly(ethylene glycol) (PEG) or polysaccharide to polystyrene has been developed. The non-charged hydrophilic polymer is firstly grafted to poly(ethylene imine). After prior oxidation of the solid surface, the graft copolymer is subsequently adsorbed. Analysis by electron spectroscopy for chemical analysis and ellipsometry indicates a trains-and-loops arrangement of the copolymer on the surface with densely packed PEG or polysaccharide chains oriented towards the bulk water phase. Ellipsometry also shows that whereas the PEG grafting is fast, the polysaccharide grafting is more sluggish. Attachment of both graft copolymers is completely irreversible, as seen also by ellipsometry. The surfaces obtained are highly protein repellent, as shown by enzyme-linked immunosorbent assay using fibrinogen and immunoglobulin G as model proteins.

  • 177.
    Brodin, Ida
    et al.
    RISE., Innventia.
    Ernstsson, Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Gellerstedt, Göran
    RISE., Innventia.
    Sjöholm, Elisabeth
    RISE., Innventia.
    Oxidative stabilisation of kraft lignin for carbon fibre production2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, nr 2, s. 141-147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules, as well as lignin fibres originating from birch with 5 poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (Tg) was investigated. The highest yield was achieved after stabilisation at 280°C during 2h with a heating rate of 0.2°C min -1. The Tg of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.

  • 178. Bruun, H
    et al.
    Enqvist, R
    Friberg, S
    YKI – Ytkemiska institutet.
    The influence of adsorbed surface active substances on the properties of paper1975Inngår i: Svensk Papperstidning, ISSN 0283-6831, Vol. 78, s. 512-516Artikkel i tidsskrift (Fagfellevurdert)
  • 179. Bruun, H
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Studies on the interaction between tetrahydroabietic acid and ferric salt solutions1968Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 51, s. 482-488Artikkel i tidsskrift (Fagfellevurdert)
  • 180. Buchert, J
    et al.
    Carlsson, G
    YKI – Ytkemiska institutet.
    Viikari, L
    Ström, G
    Surface characterization of unbleached kraft pulps by enzymatic peeling and ESCA1996Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 50, s. 69-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Specific enzymes hydrolyzing pulp carbohydrates can be used for characterization of pulp fibres. By combining enzymatic peeling of fibre hemicelluloses with novel techniques of surface analysis, such as ESCA, new information can be obtained on the location of different components, i.e. xylan, glucomannan and lignin on the fibre surfaces. In this work unbleached kraft pulps were selectively peeled with purified Trichoderna reesi xylanase and mannanase and the structural modifications caused by the removal of the hemicelluloses were analyzed with ESCA. The removal of the accessible portion of the pine kraft xylan increased the amount of surface lignin, whereas mannan removal had no effect on the amount of lignin on the surface. In the case of birch kraft pulp the removal of accessible xylan did not enhance the amount of lignin on the surface. However, in birch kraft pulp the removal of xylan decreased the amount of extractives covering the surface.

  • 181.
    Burns, NL
    YKI – Ytkemiska institutet.
    Measurement of electro-osmosis as a method for electrokinetic surface analysis1999Inngår i: Surface Characterization Methods: Principles Techniques and Applications / [ed] Milling, AJ, Marcel Dekker, 1999, s. 113-141Kapittel i bok, del av antologi (Fagfellevurdert)
  • 182.
    Burns, NL
    YKI – Ytkemiska institutet.
    Surface characterization through measurement of electroosmosis at flat plates1996Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 183, s. 249-259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A rectangular electophoresis chamber has been constructed whereby electroosmotic fluid mobility can be determined at small non-transparent sample plates. A hydrodynamic description of fluid flow in the chamber is forwarded, and verified, for accurate determination of particle mobility and electroosmosis at sample plates. Advantages of the chamber design and technique include the ability to determine electroosmotic fluid mobility at sample plates from a single particle mobility measurement within the chamber. As demonstration of the usefulness of the technique, characterization of several polymer surfaces deposited as a thin film from a cold gas plasma was performed by determining the pH dependence of electroosmotic fluid flow. The plasma polymer surfaces include those of plasma polymerized 1,2-diaminocyclohexane, acrylic acid, and hexamethyldisiloxane. Results of the characterization include quantification of ionizable surface groups with concomitant determination of pK values of these groups. The values obtained have proven useful to explain trends in protein adsorption at these surfaces.

  • 183. Burns, NL
    et al.
    Holmberg, K
    YKI – Ytkemiska institutet.
    Surface charge characterization and protein adsorption at biomaterials surfaces1996Inngår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 100, s. 271-275Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In an effort to more fully understand the nature of protein adsorption, and the role adsorbed proteins have in mediating interfacial processes in biomaterial application, effect of surface charge is being explored. For this purpose, a novel electrokinetic technique whereby electroososmosis is measured at flat plates is being used to characterize surfaces with respect to effective surface charge and origin of charge. Protein adsorption is monitored by in situ ellipsometry or by an enzyme linked immunosorbent assay (ELISA). Correlations can then be made between the observed surface properties and biological response to the surface, including bacterial adherence and complement activation of blood proteins. Surfaces studied include a wide variety of radio frequency plasma polymers, and polysiloxane modified surfaces; all of interest as biomaterials. The plasma polymer surfaces are being used as model surfaces to study protein mediated bacterial adherence. Siloxane polymer coatings are being used to interfere with salivary pellicle and plaque formation on teeth, with different patterns in the adherence of oral bacteria observed with different polysiloxanes. In the above systems, patterns in protein adsorption related to surface charge and functionality, as well as other surface properties, can be identified. It appears that surface charge and charging properties are important factors in formation of biofilms.

  • 184. Burns, NL
    et al.
    Holmberg, K
    YKI – Ytkemiska institutet.
    Brink, C
    Influence of surface charge on protein adsorption at an amphoteric surface: effects of varying acid to base ratio1996Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 177, s. 116-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plasma polymerization of 1,2-diaminocyclohexane (DACH) results in an amino functional surface which is not stable under ambient conditions. The aging process has previously been assumed to be an oxidation initiated by residual polymer radicals. We here propose that the surface process is not an oxidation but a carboxylation. Primary amino groups react with atmospheric carbon dioxide to give carbamate groups which are stabilized by salt formation with adjacent ammonium groups. We have used a novel electrokinetic technique to measure electroosmosis and monitor the aging process. While the total number of ionizable surface groups was constant, a gradual change in the ratio of basic to acid sites at the surface was found. After 64 days the ratio of was almost 1:1. This amphoteric surface which spontaneously changed its ratio of basic to acid sites was used as substrate to investigate effect of surface charge on adsorption of two proteins, human serum albumin (HSA) and lysozyme. It was found that lysozyme adsorbs in much higher amounts than HSA irrespective of the charge at the surface. Whereas adsorption of HSA was not dependent on the change in surface charge, adsorption of lysozyme decreased with aging, i.e. as the ratio of acid to base sites at the surface approached unity. An interesting finding was that more lysozyme was adsorbed the more positively charged the surface, even at pH values where the protein carried a strong net positive charge.

  • 185. Bäverbäck, P
    et al.
    Oliveira, CLP
    Garamus, VM
    Varga, I
    Claesson, PM
    YKI – Ytkemiska institutet.
    Pedersen, JS
    Structural properties of β-dodecylmaltoside and C12E 6 mixed micelles2009Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 13, s. 7296–7303-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mixed micelles formed in aqueous solutions of nonionic surfactants n-dodecyl-hexaethylene-glycol (C12E6) and n-dodecyl-β-D-maltoside (C12G2) have been studied using small-angle neutron and X-ray scattering (SANS and SAXS) and static light scattering (SLS). Apparent micelle molar masses obtained with SLS were analyzed with a model taking into account both micelle growth and interference effects. The analysis shows that pure C12G2 forms small globular micelles whereas C12E6 and the mixtures form elongated micelles of much higher molar mass. The elongated micelles grow with increased concentration according to mean-field theory, and the masses are larger for increasing amounts of C12E6. To describe the SANS and SAXS data for C12E6 and the mixtures, it was necessary to employ a model with coexisting spherical and spherocylindrical micelles. The SANS and SAXS data were fitted simultaneously using this model with core-shell particles and molecular constraints. All mixtures, as well as pure C12E6, can be described by this model, demonstrating the coexistence of spherical and cylindrical micelles. The spherical micelles are the same size in all samples, whereas the cylindrical micelles grow in length with the fraction of C12E6 in the samples, as well as with concentration, in agreement with the SLS analysis. The mass fraction of surfactant in cylindrical aggregates also increases with the fraction of C12E6 and with overall concentration. The analysis of the SAXS and SANS data for pure C12G2 shows that the micelles are disk-shaped. The presence of elongated micelles in pure C12E6 and in the mixtures demonstrates that the behavior of the mixtures is dominated by C12E6.

  • 186. Campos, J
    et al.
    Eskilsson, K
    YKI – Ytkemiska institutet.
    Nylander, T
    Svendsen, A
    On the interaction between adsorbed layers of monoolein and the lipase action on the formed layers2002Inngår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 26, s. 172-182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We used the Surface Force Apparatus (SFA) and ellipsometry techniques to study the interaction forces and the adsorption behavior of monoolein (MO), respectively. MO was adsorbed from water to a hydrophobised mica or silica surface. In addition the effect of added lipase, Thermomyces (Humicula) lanuginosa lipase (TLL), to an adsorbed layer of MO was investigated. The force versus distance curves between two MO covered surfaces feature a strong repulsive interaction beneath 400 Å. The range of the repulsive force decreases, however, with the number of approaches. No adhesion was observed, provided that the surfaces were not taken to hydrophobic contact. The surface separation at MO¯MO contact was determined to about 55 Å. This means a layer thickness of about 27 Å, which is comparable to the thickness (25 Å) determined by ellipsometry. The repulsive force may arise from compression of a cubic phase of MO. This phase are suggested to form between the surfaces when they approach close contact due to capillary induced phase separation (CIPS) from the saturated MO solution. The repulsive force changes significantly with time after addition of TLL (concentration of about 1?10-8 M). In contrast to the force curves recorded before adding TLL, the surfaces do not seem to be completely covered with MO as we always observed an attractive force (inward jump) of similar range as was observed between pure OTE surfaces. Ellipsometry measurement of TLL action on MO covered hydrophobic surface reveals a significant and sharp decrease of the amounts adsorbed. Furthermore, the rate of decrease and reduction in adsorbed amount increased with TLL concentration.

  • 187. Carambassis, A
    et al.
    Jonker, LC
    Attard, P
    Rutland, MW
    YKI – Ytkemiska institutet.
    Forces measured between hydrophobic surfaces due to a sub-microscopic bridging bubble1998Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 80, s. 5357-5360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atomic force microscopy on hydrophobic microspheres in water reveals a strong attraction with a range of 20–200 nm, following an initial steep repulsion at long range. The data are consistent with a single ubmicroscopic bubble between the surfaces, with the attraction due to its attachment and lateral spread, and the repulsion dependent on film drainage and the electric double layer. The results provide direct experimental evidence of the existence of long-lived submicron bubbles, and of their bridging as the cause of the measured long-range attractions between macroscopic hydrophobic surfaces.

  • 188. Carambassis, A
    et al.
    Rutland, MW
    YKI – Ytkemiska institutet.
    Interactions of cellulose surfaces: Effect of electrolyte1999Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, s. 5584-5590Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The forces between spherical particles of cellulose (20-30 m) have been measured in different solutions using an atomic force microscope, with a view to understanding the interactions in a model papermaking system. At low ionic strength (0.1 mM KBr), the interaction profile is dominated by a long range double layer force and shorter ranged electrosteric force. A qualititatively similar profile is observed at high pH, but in this case both the double layer force and electrosteric force increase as a consequence of cellulose charging. Conversely, the two force contributions both decrease in the presence of calcium ions. At high ionic strength (10 mM KBr) the electrosteric force is absent and the forces appear to be due solely to double layer forces. Overall, the results show that the surface is composed of looser chains that extend out into the solution, the conformation of which is highly sensitive to the solution conditions.

  • 189. Cardenas, M
    et al.
    Elofsson, Ulla
    YKI – Ytkemiska institutet.
    Lindh, L
    Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: An in situ ellipsometry and atomic force microscopy study2007Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, nr 4, s. 1149-1156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes a combined investigation of the salivary and MUC5B films structure and topography in conditions similar to those found in the oral cavity in terms of ionic strength, pH, and protein concentration. AFM and ellipsometry were successfully used to give a detailed picture of the film structure and topography both on hydrophilic and on hydrophobic substrata. Regardless of the substrata, the salivary film can be described as having a two sublayer structure in which an inner dense layer is decorated by large aggregates. However, the shape and height of these larger aggregates largely depend on the type of substrata used. Additionally, we show that the adsorption of MUC5B is controlled by the type of substrata and the MUC5B film topography is similar to that of the larger aggregates present in the salivary films, especially on hydrophobic substrates. Therefore, we conclude that MUC5B is a major component in the salivary film when formed on hydrophobic substrates. Furthermore, we studied how resistant the salivary and MUC5B films are against elutability by buffer rinsing and addition of SDS solution. We conclude that the adsorbed proteins contain fractions with varying binding strengths to the two types of surfaces. Specifically, we have shown that the large MUC5B biomacromolecules on the hydrophobic substrates are especially resistant to both elution with buffer solution and SDS. Therefore, these large mucins can be responsible for the increased resistance of HWS films on hydrophobic substrates and can protect the intraoral surfaces against surface-active components present in oral health care products.

  • 190.
    Carlfors, J
    et al.
    YKI – Ytkemiska institutet.
    Blute, I
    YKI – Ytkemiska institutet.
    Schmidt, V
    YKI – Ytkemiska institutet.
    Lidocaine in microemulsion - A dermal delivery system1991Inngår i: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 12, s. 467-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to obtain a microemulsion that is stable at skin tempeature, the regions of existance of microemulsions of water and isoproptyl myristate were studied as a function of hydrophilelipophile balance (HLB) of nonionic surfactant mixtures. The microemulsion dissolves large amount of the local anaesthetic lidocaine. The amount of dissolved lidocaine in the microemulsion was proportional to the isopropyl myristate content and limited to its solubility in this solvent. The addition of lidocaine lowered the phase inversion temperature (PIT) of the system and increased the temperature range for microemulsion stability. The structure of the microemulsion, as investigated by proton Fourier transform pulsed-gradient spin-echo NMR spectroscopy, was found to be bicontinous. The physico-chemical properties of the microemulsion as well as the low toxicity of its components result in formulation intendend for topical administation.

  • 191.
    Carlsson, CMG
    et al.
    YKI – Ytkemiska institutet.
    Eriksson, I
    Lindström, E
    Ström, G
    YKI – Ytkemiska institutet.
    Improved wettability of chemithermomechanical pulp by oxygen plasma treatment1994Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 9, s. 72-75,83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemithermomechanical pulp has been treated by cold plasma of oxygen, nitrogen, argon or air. The wettability increases as a result of treatment by oxygen or air plasmas but decreases when argon or nitrogen plasmas are used. The initial water absorption rate can be improved by more than 100 % using an oxygen plasma. After subsequent ageing of the pulp the improvement was ca 200 %. Electron Spectroscopy for Chemical Analysis (ESCA) shows that the oxygen plasma treatment increases the oxygen content of the fibre surfaces due to oxidation and/or removal of fatty acids, resin acids, and probably also lignin. The amount of extractable material increases after the plasma treatment, probably due to oxidation and scission of the lignin and the carbohydrates. This oxidized low molecular weight material may act as a surfactant decreasing the surface tension of the absorbing liquid and thus enhance the absorption rate.

  • 192. Carlsson, CMG
    et al.
    Johansson, KS
    YKI – Ytkemiska institutet.
    Surface modification of plastics by plasma treatment and plasma polymerization and its effect on adhesion1993Inngår i: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 20, s. 441-448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adhesion between plasma-modified polyethylene (PE) and different polar polymers, as well as aluminium and steel, has been studied. The PE was modified by either oxygen plasma treatment or plasma polymerization of acrylic acid. The results show the importance of introducing polar groups on the surface of the non-polar PE in order to improve the adhesion to polar polymers as well as metals. Laminates made of plasma-modified PE and polyamide 6 (PA-6) or poly(ethylene vinyl alcohol) (EVAL-G) showed failure in PA-6 or EVAL-G when delaminated. Poly(ethylene terephthalate) (PET), which is not as polar as PA-6 or EVAL-G, showed an adhesive failure when the PE was treated with either of the plasma methods. However, when both the PET and the PE were modified, the failure occurred in the PET upon delamination. Oxygen plasma treatment of PE resulted in an increased adhesion when laminated with cellophane, with no observed material failure. The laminates composed of plasma-modified PE and aluminium or steel showed cohesive failure in the PE.

  • 193. Carlsson, CMG
    et al.
    Ström, G
    YKI – Ytkemiska institutet.
    Adhesion between plasma-treated cellulosic materials and polyethylene1991Inngår i: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 17, s. 511-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Filter paper and greaseproof paper have been exposed to hydrogen or oxygen plasma. The paper surface composition was determined by ESCA measurements. The unmodified and modified papers then were laminated with polyethylene and the adhesive strength was measured. The hydrogen plasma treatment reduces the cellulose surface and forms low molecular weight degradation products. It is shown that the reduction of the cellulose surface has no influence on the adhesion, but the degradation products strongly decrease the adhesion. Oxygen plasma treatment increases adhesion, probably by removing low-molecular-weight wood resin from the surface and by forming covalent bonds across the interface.

  • 194.
    Carlsson, CMG
    et al.
    YKI – Ytkemiska institutet.
    Ström, G
    YKI – Ytkemiska institutet.
    Reduction and oxidation of cellulose surfaces by means of cold plasma1991Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 7, s. 2492-2497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogen and oxygen plasma treatment of two cellulose materials, a filter paper of pure cellulose and a greaseproof paper with a fairly high surface content of wood resin, has been studied with ESCA as well as by contact angle or water adsorption. The hydrogen plasma treatment reduces the hydroxyl groups on the cellulose and creates low molecular weight materials. Due to the lower polarity, water adsorption is reduced. The oxygen plasma treatment of the pure cellulose both oxidizes and reduces the surface. The resin-rich paper, which has a hydrophobic nature, shows improved water wettability after both hydrogen and oxygen plasma treatments.

  • 195. Carlsson, F
    et al.
    Elofsson, U
    YKI – Ytkemiska institutet.
    Arnebrant, T
    Malmsten, M
    YKI – Ytkemiska institutet.
    Interactions between local anaesthetic agents and poly(N-isopropyl acrylamide) through phase behavior, surface tension, and adsorption measurements2001Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 233, s. 320-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    he interaction between the local anaesthetic agents prilocaine and lidocaine, on one hand, and poly(N-isopropyl acrylamide) (pNIPAM), on the other, is investigated through studies of the polymer phase behavior and through surface tension and adsorption measurements. In particular, the cloud points (CP) for pNIPAM in the presence of lidocaine and prilocaine under different conditions were compared to the effects of electrolytes and alcohols. It was found that the electrolytes affect the CP of pNIPAM in a lyotropic manner, whereas alcohols depress the CP of pNIPAM in an alkyl chain length dependent way; i.e., the longer the chain, the larger the decrease in CP. Lidocaine and prilocaine affect the CP of pNIPAM in a pH-dependent manner. Below the p Ka of lidocaine and prilocaine, these cosolutes do not substantially affect the CP in the concentration range investigated, but rather behave analogous to simpler electrolytes. Above the p Ka, on the other hand, they strongly depress the CP already at low concentrations. In parallel, at low pH, the surface tension reduction due to lidocaine or prilocaine is marginal, whereas at high pH the surface tension is reduced considerably. Thus, the poor solubility of prilocaine and lidocaine at high pH causes these to become more surface active and simultaneously interact in a more pronounced way with pNIPAM. Furthermore, it was found from ellipsometry that an adsorbed pNIPAM layer contracts when lidocaine is added, presumably due to a lidocaine-pNIPAM interaction similar to that causing pNIPAM to phase separate. Analogous to this, it was demonstrated that an adsorbed pNIPAM layer shrinks and swells reversibly when the temperature is cycled above and beneath the CP.

  • 196. Carlsson, F
    et al.
    Hyltner, E
    Arnebrant, T
    Malmsten, M
    YKI – Ytkemiska institutet.
    Linse, P
    Lysozyme adsorption to a charged surface. A Monte Carlo study2004Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, s. 9871-9881Artikkel i tidsskrift (Fagfellevurdert)
  • 197. Carlsson, F
    et al.
    Linse, P
    Malmsten, M
    YKI – Ytkemiska institutet.
    Monte Carlo simulations of polyelectrolyte-protein complexation2001Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, s. 9040-9049Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The complexation between one polyelectrolyte and one protein has been examined by employing a simple model system solved by Monte Carlo simulations. The polyelectrolyte was composed of a sequence of negatively charged hard spheres, and the protein was represented by a hard sphere with embedded pH-dependent discrete charges, the positions of which were taken from lysozyme. A short-range attractive interaction between the polyelectrolyte and the protein accounting for hydrophobic interactions completed the model. The complexation was found to depend decisively on the charge status of the protein model as well as on the presence of the short-range attractive interaction. In particular, the complexation weakens at decreasing ionic strength except for the highest positive protein net charge considered, and in the absence of the short-range attraction, a positively charged protein was required to obtain a complex. The distribution of the polyelectrolyte beads was inhomogeneous at the protein surface, and the polyelectrolyte contracted upon complexation. Finally, the protein model with discrete charges gave a stronger complex than the corresponding protein model with a homogeneous surface charge density.

  • 198. Carlsson, F
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Linse, P
    Monte Carlo simulations of lysozyme self-association in aqueous solution2001Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, s. 12189-12195Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oligomerization of lysozyme in aqueous solution was investigated by Monte Carlo simulations as a function of protein concentration, pH, and electrolyte screening. Lysozyme was modeled as a hard sphere with embedded pH-dependent discrete charges and with an attractive 1/r6-potential representing nonspecific short-range attraction. The magnitude of the 1/r6-potential was adjusted to reproduce experimental second virial coefficients. Radial distribution functions, structure factors, cluster size distributions, and orientation correlations were determined at various conditions. It was observed that increasing protein concentration, or decreasing the electrostatic repulsion between protein molecules by either reducing the protein charge or increasing the ionic strength, promoted cluster formation. Structure factors and equilibrium constants obtained were compared to those obtained experimentally and were found to capture the experimentally obtained effects of pH and ionic strength. The influence of the location of the hydrophobic site was also examined

  • 199. Carlsson, F
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Linse, P
    Protein-polyelectrolyte cluster formation and redissolution: A Monte Carlo study2003Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 125, s. 3140-3149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aqueous solutions of proteins and oppositely charged polyelectrolytes were studied at different polyelectrolyte chain length, ionic strength, and protein-protein interaction potential as a function of the polyelectrolyte concentration. One of the protein models used represented lysozyme in aqueous environment. The model systems were solved by Monte Carlo simulations, and their properties were analyzed in terms of radial distribution functions, structure factors, and cluster composition probabilities. In the system with the strongest electrostatic protein-polyelectrolyte interaction the largest clusters were formed near or at equivalent amount of net protein charge and polyelectrolyte charge, whereas in excess of polyelectrolyte a redissolution appeared. Shorter polyelectrolyte chains and increased ionic strength lead to weaker cluster formation. An inclusion of nonelectrostatic protein-protein attraction promoted the protein-polyelectrolyte cluster formation.

  • 200.
    Carlsson, G
    et al.
    YKI – Ytkemiska institutet.
    Ström, G
    YKI – Ytkemiska institutet.
    Annergren, G
    Water sorption and surface composition of untreated or oxygen plasma-treated chemical pulps1995Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 10, s. 17-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three kraft pulps and one bisulphite pulp have been studied. The surface chemical composition was determined by means of ESCA, and water sorption was studied using a dynamic contact angle tester. The surface coverage of lignin as well as dichloromethane (DCM) extractable material was found to be considerably larger than expected from bulk measurements. The results show that DCM extractable material decreases water sorption to a larger extent than lignin. Oxygen plasma-treatment improves water sorption of pulps containing large amounts of DCM extractable material and lignin due to oxidation of these compounds. Only a few seconds of exposure is needed. After ageing the improved water sorption is unchanged for kraft pulps. However, bisulphite pulp which contains larger amount of extractable material shows a decrease in rate of water sorption.

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