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

The effect of alkali-soluble resin (ASR) postadded to emulsifier-free monodisperse 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 glycol and water) on the film surface were determined as a function of the annealing temperature of the film and the annealing duration. The ASR, poly(styrene/alpha-methylstyrene/acrylic acid), was found to exude to the air/polymer interface after annealing, as monitored using FTIR-ATR. Thus the surface properties of the films were dependent on the concentration of the ASR employed, the annealing temperature, and the duration. Annealing the film at a temperature approximately equal to the T-g of ASR allows them (ASR) to undergo unrestricted migration to the film surface and also to expose the hydrophobic region of their chains to the surface. The more hydrophobic character of the film annealed at 150 degrees C with a higher contact angle as compared to that at 50 degrees C is a result of the change in chain conformation of the ASR at the surface brought about by annealing. Also, the results illustrate that the hydrophobic-hydrophilic character of the PBMA-SAA film surface can be changed readily by merely adjusting the annealing temperature.