Effect of annealing on the surface properties of poly(n-butyl methacrylate) latex films containing poly(styrene/alpha-methylstyrene/acrylic acid)

The effect of alkali-soluble resin (ASR) postadded to emulsifier-free monod isperse poly(n-butyl methacrylate) latexes (PBMA) on the surface properties of the latex films formed was investigated using the contact angle method. The contact angles of a probe liquid (containing 50:50 wt % ethylene glyco l and water) on the film surface were determined as a function of the annea ling temperature of the film and the annealing duration. The ASR, poly(styr ene/alpha-methylstyrene/acrylic acid), was found to exude to the air/polyme r interface after annealing, as monitored using FTIR-ATR. Thus the surface properties of the films were dependent on the concentration of the ASR empl oyed, the annealing temperature, and the duration. Annealing the film at a temperature approximately equal to the T-g of ASR allows them (ASR) to unde rgo unrestricted migration to the film surface and also to expose the hydro phobic region of their chains to the surface. The more hydrophobic characte r of the film annealed at 150 degrees C with a higher contact angle as comp ared to that at 50 degrees C is a result of the change in chain conformatio n of the ASR at the surface brought about by annealing. Also, the results i llustrate that the hydrophobic-hydrophilic character of the PBMA-SAA film s urface can be changed readily by merely adjusting the annealing temperature .