1996 Volume 21 Issue 3 Pages 197-204
It is well known that a segment of a multicomponent polymeric system such as copolymers selectively adsorbs and orients to the surface of the system so as to minimize interfacial free energy in response to an environmental medium. Recently, a surface molecular mobility of a multicomponent polymeric system has been investigated via dynamic contact angle (DCA) and adhesion tension (γL cosθ=γS -γSL) relaxation (ATR). These methods are useful tools to investigate these phenomena because a reorientation of surface segments directly reflect to contact angle hysteresis when a polymer is moved into a different medium. We1-6) have already reported several papers on this behavior. Here we reviewed these papers.
An interesting behavior was found for methoxypolyethyleneglycol methacrylate (MPEGMA) and methylmethacrylate (MMA) copolymers that the advancing contact angles in the second cycle of DCA were larger than that in the first cycle for these copolymers containing 30-70 wt% of MPEGMA. These behavior was explained by the molecular mobility and crystallization of PEG side chains.
For poly (vinylalkylate) s (PVAI), advancing contact angle initially increased with an increase in the side chain length and after maximum at C 10, it decreased, while receding contact angle showed a complex behavior. A large contact angle hysteresis was observed. DCA also depend on the dipping velocity. The large relaxations of adhesion tension for PVAls with side chains from C 6 to C 10 were observed. From these result, it was shown that the surface molecule of these PVAls had the large molecular mobility. Reproducibility of ATR also was observed.
DCA and ATR for methacrylate terpolymers having both hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxypolyethyleneglycol (MPEG) side chains were measured. DCA for these terpolymers showed the different composition dependency depending on the length of both side chains. Large ATR also observed.
