The effects of evaporation rate, solvent, and substrate on the surface segregation of block copolymers

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Virginia Tech


The surface chemistry of two systems of block copolymers was studied using angular dependent X-ray Photoelectron Spectroscopy poly(dimethyl (XPS). Surface concentration siloxane-b-sulfone)/polysulfone profiles of [PDMS/PSF] blends cast at several rates of solvent evaporation, and cast on several substrates were measured. Surface concentration profiles of poly(styrene-butadiene-styrene) poly(styrene-isoprene-styrene) [SIS] triblock [SBS] and copolymers cast at several rates of solvent evaporation, and cast from two different solvents were also measured. The concentration profile analyses were made using three different XPS quantification techniques. The PDMS/PSF systems were analyzed using the peak area ratio, and the SBS and SIS copolymers were analyzed using both the Cls shakeup to main ratio, and spectral measurements of the valence band. The results of this study indicate a variation in surface concentration as well as concentration gradient for different sample preparation routes. The variations can be explained by considering the rate of film formation (kinetics), polymer - solvent interactions, and polymer - substrate interactions. However, in both systems the lower surface energy copolymer block (siloxane block, or diene block) preferentially segregated to the surface for all of the sample preparation routes stUdied.