Morphological studies of poly(olefin sulfones) by light scattering

Abstract

Poly(olefin sulfones) are readily degraded by an electron beam and thus could be used as electron beam resists. However, films greater than 3000 A thick crack during formation and especially during solvent development following exposure to an electron beam. As crystallinity accentuates cracking owing to swelling stresses at the crystalline–amorphous interface, the morphology of various poly(olefin sulfones) was studies by light scattering. Materials investigated were solvent-cast and hot-pressed films of poly(butene-1 sulfone) (PBS), poly(cyclopentene sulfone) (PCPS), poly(bicycloheptene sulfone) (PBCHS), and two terpolymers of poly(cyclopentene sulfone–co–butene-1 sulfone), in which the molar ratios of cyclopentene to butene-1 were 50/50 (TP1) and 70/30 (TP2). All hot-pressed samples showed scattering patterns characteristic of randomly oriented rod-like superstructures 8–10 μm in length. Among the solvent-cast films, however, only PBS and TP2 samples scattered light indicative of crystallinity. Scattering from these samples were analyzed in terms of “random orientation fluctuation” light scattering theory. Correlation distances of 1.7 and 1.5 μm for the PBS and TP2, respectively, were obtained. The solvent-cast crystalline films (PBS and TP2) had a tendency to crack during dissolution as did the amorphous films of PCPS and PBCHS, indicating that cracking depends on the glass temperature as well as crystallinity. Only the amorphous terpolymer TP1 did not crack, presumably owing to its relatively low glass temperature effected by the butene-1 moiety.