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  • 1.
    Eskilsson, K
    et al.
    YKI – Ytkemiska institutet.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Equilibrium and kinetic features of triblock copolymers at hydrophobic surfaces1997In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 30, p. 6323-6332Article in journal (Refereed)
    Abstract [en]

    The adsorption of a series of (ethylene oxide-tetrahydrofuran-ethylene oxide), EOn/2THFmEOn/2, triblock copolymers has been studied at the water/hydrophobic silica interface by time-resolved ellipsometry. The copolymers form monolayers with the middle tetrahydrofuran block anchoring at the surface and the ethylene oxide groups either anchoring at the surface or protruding into the aqueous phase. The degree of anchoring of the EO chains depends critically on the surface coverage. The copolymer isotherms are generally rather well described by the conventional Langmuir expression, and the plateau surface area per polymer molecule increases linearly with the molecular weight. However, the plateau thickness exhibits a more complex behavior. At low coverages, the adsorbed layer thickness is small, and both THF and EO chains form trains at the surface. As the surface coverage increases, however, the EO chains are increasingly forced away from the surface, and the mean thickness of the adsorbed layer exhibits a relatively strong linear dependence on the surface excess. At higher coverages, closer to the adsorption plateau, a weaker dependence is observed. The thickness increase is in this latter region due to the increasing steric repulsion between protruding EO chains. Outside the adsorbed layer, we also found support for the existence of a depletion layer. We show further that there are three regimes in the kinetics of adsorption. In the first (low surface coverage), the process is diffusion controlled and the rate is proportional to the concentration difference between the bulk solution and the subsurface located just outside the adsorbed layer. In the second regime (intermediate coverages and adsorption times), the kinetics are governed by the rate of displacement of anchored EO chains by THF chains of adsorbing copolymers. In the third regime (high surface coverages), the adsorption slows down markedly due to the energy barrier caused by presence of the relatively dense brush of adsorbed EO chains. In this regime, the surface excess varies proportionally with log t, which was also observed to be the case during the desorption process.

  • 2. Eskilsson, K
    et al.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Interfacial behaviour of triblock copolymers at hydrophilic surfaces1998In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 31, p. 5075-5083Article in journal (Refereed)
    Abstract [en]

    We report on the adsorption of a series of poly(ethylene oxide)-polytetrahydrofuran-poly(ethylene oxide) copolymers, EOn/2THFmEOn/2, at hydrophilic silica surfaces and relate our findings to the corresponding behavior at hydrophobic surfaces. The adsorption of these copolymers is similar to that of poly(ethylene oxide) homopolymers at low bulk concentrations. However, the copolymer adsorption increases strongly above a certain threshold concentration. This increase, which begins more than 1 order of magnitude below the critical micellar concentration (cmc), is related to the concomitant formation of micellar-like structures at the hydrophilic surfaces. We show in this work that a commercial (ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, Pluronic F127, exhibits a similar behavior at silica. Due to surface aggregation, much thicker layers are measured on silica than at the hydrophobic surface, where the adsorption results in the formation of a monolayer structure. The adsorbed amount and layer thickness measured on bare silica tend to decrease when the bulk concentration is raised above the cmc. We infer that this is due to changes of the molecular weight distribution and relative block sizes of the copolymers in the surface aggregates, i.e., a polydispersity effect. This study also covers some aspects of the adsorption and desorption kinetics exhibited by the copolymers at silica. As is common for adsorbing polymers, the concentration dependent adsorption process is generally observed to be much faster than the desorption process. The adsorption process is in parts diffusion controlled but overall to a complex to be fully analyzed. During adsorption from solutions with bulk concentrations exceeding the cmc, a clear overshoot of the surface excess is observed after intermediate adsorption times. Again, this is interpreted as being due to polydispersity. Finally, after an initial rapid desorption regime, the surface excess exhibits a logarithmic decay with time during desorption.

  • 3.
    Hedlund, Artur
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Köhnke, Tobias
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Theliander, Hans
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF. Chalmers University of Technology, Sweden.
    Diffusion in Ionic Liquid-Cellulose Solutions during Coagulation in Water: Mass Transport and Coagulation Rate Measurements2017In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 50, no 21, p. 8707-8719Article in journal (Refereed)
    Abstract [en]

    This article describes central features of the mass transport during the coagulation in water of cellulose-1-ethyl-3-methylimidazoium acetate ([C2mim][OAc]) solutions, namely, that the diffusivities are mainly affected by the relative concentrations of water and [C2mim][OAc], that the concentration of cellulose does not affect diffusivities and coagulation rates, that the diffusivities of low-Mw compounds are similar to those in aqueous [C2mim][OAc] solutions without macromolecules, that the polymer concentration is diluted by the large influx of coagulant causing a positive net mass gain, NMG, from diffusive fluxes, and that such NMG, although observed only as a function in time, is also a function in space that has local peaks significantly higher than the mean NMG value. The conclusion from the first three findings was that the diffusion advances through a liquid phase which possesses a continuous pore network and most of the volume. The precipitated cellulose is concentrated into fibrils whose inhibitive effect on the diffusion of small molecules through the surrounding phase is marginal. This key understanding about mass transport during coagulation also simplifies numerical modeling significantly.

  • 4. Joseph, I
    et al.
    Poptoshev, E
    Vareikis, A
    Makuska, R
    van der Wal, A
    Claesson, PM
    YKI – Ytkemiska institutet.
    Adsorption of low charge density polyelectrolyte containing grafted poly(ethylene oxide) chains on silica: Effects of ionic strength and pH2005In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 38, p. 6152-6158Article in journal (Refereed)
  • 5.
    Lausmaa, Jukka
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Funktionella material (KMf).
    Spin coating and characterization of thin high-density polyethylene films2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 21, p. 7496-7503Article in journal (Other academic)
  • 6. Linse, P
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Modeling of bottle-brush polymer adsorption onto mica and silica surfaces2009In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 42, no 16, p. 6310-6318Article in journal (Refereed)
    Abstract [en]

    The adsorption of a series of charged bottle-brush polymers with side chains of constantlength on mica and silica surfaces is modeled using a lattice mean-field theory, and the predicted results are compared to corresponding experimental data. The bottle-brush polymers are modeled as being composed of two types of main-chain segments: charged segments and uncharged segments with an attached side chain. The composition variable X denotes the percentage of charged main-chain segments and ranges from X=0 (uncharged bottle-brush polymer) to X=100 (linear polyelectrolyte). The mica-like surface possesses a constant negative surface charge density and no special affinity, whereas the silica-like surface has a constant negative surface potential and a positive affinity for the side chains of the bottle-brush polymers. The model is able to reproduce a number of salient experimental features characterizing the adsorption of the bottle-brush polymers for the full range of the composition variable X on the two surfaces, and thereby quantifying the different nature of the two surfaces with respect to electrostatic properties and nonelectrostatic affinity for the polymer. In particular, the surface excess displays a maximum atX≈50 for the mica surface and at X≈10 for the silica surface. Moreover, the thickest adsorbed layer is obtained at X=10-25.

  • 7. Linse, Per
    et al.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Modeling of bottle-brush polymer adsorption onto mica and silica surfaces: Effect of side-chain length2010In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 43, no 4, p. 2076-2083Article in journal (Refereed)
    Abstract [en]

    Adsorption of a series of charged bottle-brush polymers with side chains of different length on solid surfaces is modeled using a lattice mean-field theory. The bottle-brush polymers are modeled Lis being composed of two types of main-chain segments: charged segments and uncharged segments with ill attached side chain. The composition variable X denotes the percentage of charged main-chain segments and ranges from X = 0 (uncharged bottle-brush polymer) to X = 100 (linear polyelectrolyte). Two types of surfaces are considered: mica-like and silica-like. The mica-like surface possesses a constant negative surface charge density and no nonelectrostatic affinity for either main-chain or side-chain segments, whereas the silica-like Surface has a constant negative surface potential and a positive affinity for the side chains of the bottle-brush polymers. With the mica-like Surface. ill low X the surface excess becomes smaller and at X >= 25 it becomes larger with increasing side-chain length. Hence, the value of X at which the surface excess displays a maximum increases with the side-chain length. However, with the silica-like Surface the surface excess increases with increasing side-chain length at all X < 100, and the maximum of the surface excess appears at X approximate to 10 independent of the side-chain length.

  • 8.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Structure evolution during gelation at later stages of spinodal decomposition in gelatin/maltodextrin mixtures2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 23, p. 8117-8128Article in journal (Refereed)
    Abstract [en]

    The kinetics of phase separation and gelation in kinetically trapped gelatin/maltodextrin/water gels was studied using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). The time evolution of the morphology was followed by CLSM during temperature quenches from 60°C to between 1 and 40°C. The maltodextrin concentration was varied between 2.25% and 7.5% (w/w), and the gelatin concentration was held constant at 4% (w/w). Spinodal decomposition, self-similar growth, percolation-to-cluster transition, coalescence, and diffusion of maltodextrin inclusions were observed during the progress of gelation. The start and completion of these processes, the onset of phase separation, and the relative rates of phase separation and gelation were found to determine the morphology. The characteristic wavelength showed a crossover in its growth rate power law from one-third to one in a slowly gelling, near-symmetric system. Droplet and bicontinuous morphologies were observed in off-symmetric and near-symmetric quenches, respectively. Secondary phase separation occurred at low temperatures and near-symmetric composition. Partial coalescence and contracted flocculation were observed during the progress of gelation. Stereological measurements showed that the size of maltodextrin inclusions increases and that the volume fraction decreases with increasing quench temperature. In addition, the number of the maltodextrin inclusions decreases with increasing quench temperature.

  • 9.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Williams, M.A.K.
    Lundin, Leif
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Foster, T.J.
    Hubbard, C.D.
    Phase separation induced by conformational ordering of gelatin in gelatin/maltodextrin mixtures2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 2, p. 289-297Article in journal (Refereed)
    Abstract [en]

    Mixtures of gelatin and maltodextrin in aqueous solution have been quenched to temperatures at which they are initially miscible but where gelatin ordering is initiated. In many cases phase separation was observed to occur after a significant time delay, and the dependence of these delays on quench temperature and biopolymer concentration has been studied in detail using turbidity measurements and confocal laser scanning microscopy (CLSM). Furthermore, by observing the optical rotation (OR) and turbidity of the system simultaneously, the gelatin helix content and the time delay before the onset of phase separation were monitored concurrently. The observed delay times were found to correspond to the time taken for the development of a certain degree of gelatin ordering, which drives the separation process. A further consequence of gelatin ordering is the viscosifying of the solution and, at sufficient concentrations, the formation of a gel. Therefore, rheological measurements have been used in addition to turbidity measurements and CLSM in order to monitor further the structural development of the systems. A comparison of the data obtained from these techniques shows that while the development of a certain elasticity will trap the system morphology, this elasticity is not directly related to that found at the gel point. At low maltodextrin concentrations, where phase separation was not detected by turbidity, transmission electron microscopy (TEM) has been used to examine the microstructure on a smaller length scale.

  • 10. Mellbring, O
    et al.
    Kihlman Öiseth, S
    Krozer, A
    RISE, Swedish ICT, Acreo.
    Lausmaa, J
    Hjertberg, T
    Spin Coating Characterization of Thin High-Density Polyethylene Films2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 21, p. 247-50Article in journal (Refereed)
  • 11.
    Svensson, B
    et al.
    YKI – Ytkemiska institutet.
    Olsson, U
    Thermotropic and lyotropic behavior of a PEO-PPO-PEO block copolymer2000In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 33, p. 7413-7419Article in journal (Refereed)
    Abstract [en]

    The phase behavior of the (EO)19(PO)43(EO)19/p-xylene system (where EO is ethylene oxide and PO is propylene oxide) with temperature is discussed. In this block copolymer the end blocks are crystallizable, and the middle block is noncrystallizable. Several techniques were used to delineate the phase boundaries (SAXS, WAXS, 1H NMR, 2H NMR, and DSC). An anisotropic region with a lamellar structure with semicrystalline PEO domains and amorphous PPO domains is formed at low temperatures and high copolymer concentrations. The lamellar structure has a one-dimensional swelling with increasing p-xylene concentration. The driving force for forming the anisotropic region is that the PEO crystallize at low temperatures. The amount of crystallinity in the system and the interfacial area per PEO block in the ordered region depend on the temperature and the sample composition. At high temperatures and low copolymer concentrations the system contains an isotopic solution phase

  • 12.
    Wallin, M
    et al.
    YKI – Ytkemiska institutet.
    Glover, PM
    Hellgren, A-C
    YKI – Ytkemiska institutet.
    Keddie, JL
    McDonald, PJ
    Depth profiles of polymer mobility during the film formation of a latex dispersion undergoing photoinitiated cross-linking2000In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 33, p. 8443-8452Article in journal (Refereed)
    Abstract [en]

    The first use of one-dimensional magnetic resonance imaging (MRI) to provide information on concentration and molecular mobility (as revealed by the spin-spin relaxation time, T2) as a function of depth into cross-linking latex coatings during their film formation is reported. These materials are of interest because they provide hard, chemically resistant coatings and because, being waterborne, they do not release organic solvents into the atmosphere. MRI profiles, with a pixel resolution of 9 m, are obtained at regular time intervals from a poly(vinyl acetate-co-ethylene) latex dispersion containing a difunctional cross-linker and a photoinitiator. In this complete formulation, MRI reveals that the rate of cross-linking is fastest in the middle regions of the coating. This result is explained by considering the combined effects of light scattering in the turbid latex, the inhibition of the free-radical cross-linking reaction by initial molecular oxygen, and the further ingress of oxygen from the atmosphere. A numerical model, using measured and known parameters, predicts MRI profiles that are in good qualitative agreement with those found experimentally.

  • 13. Wastlund, C.
    et al.
    Berndtsson, H.
    Maurer, F.H.J.
    Miscibility of styrene-maleic anhydride and styrene-acrylonitrile blends studied by positron annihilation lifetime spectroscopy1998In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 31, no 10, p. 3322-3327Article in journal (Refereed)
    Abstract [en]

    Blends of melt-mixed styrene - maleic anhydride and styrene - acrylonitrile copolymers were examined with respect to miscibility and free volume parameters. Differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy, and positron annihilation lifetime spectroscopy were used to judge blend miscibility. It was found that blends containing copolymers with similar amounts of styrene were miscible. Positron annihilation lifetime spectra of all blends were evaluated with the POSITRONFIT and the MELT program, where the latter can be used to obtain lifetime distributions. The mean o-Ps lifetimes (or hole sizes) of the blends were found always to be between those of the pure constituents. Pronounced negative deviations of the o-Ps intensity from weighted averages were measured in miscible blends but not in immiscible ones. Immiscible blends exhibit, on the basis of MELT evaluations, unsymmetric and broader o-Ps lifetime distributions than do miscible blends.

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