Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers Visa övriga samt affilieringar
2017 (Engelska) Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 487, s. 88-96Artikel i tidskrift (Refereegranskat) Published
Abstract [en]
Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperatures <40 °C. A local force minimum at short separation develops at 40 °C and a strong attraction due to capillary condensation of a polymer-rich phase is observed close to the bulk phase separation temperature. The friction forces decrease in the cooling stage due to rehydration of the PIPOZ chain. A consequence of the adsorption hysteresis is that the friction forces measured at 25 °C are significantly lower after exposure to a temperature of 40 °C than prior to heating, which is due to higher polymer chain density on the surface after heating.
Ort, förlag, år, upplaga, sidor Academic Press, 2017. Vol. 487, s. 88-96
Nyckelord [en]
adsorption hysteresis, boundary lubrication, friction, PIPOZ, Poly(2-isopropyl-2-oxazoline), surface forces, thermoresponsive polymer
Nationell ämneskategori
Fysikalisk kemi Annan kemi
Identifikatorer URN: urn:nbn:se:ri:diva-26181 DOI: 10.1016/j.jcis.2016.10.021 Scopus ID: 2-s2.0-84992378692 OAI: oai:DiVA.org:ri-26181 DiVA, id: diva2:1045291
2016-11-082016-11-082019-01-04 Bibliografiskt granskad