RADIOLYSIS OF RESIST POLYMERS .4. POLY(PARA-SUBSTITUTED-ALPHA-METHYLSTYRENE)S

In the reported experiments, the effect of parasubstituents on the radiation chemistry of poly( alpha -methylstyrene) (PMS) was compared for the fluoro (PFMS), chloro (PCMS), bromo (PBMS), isopropyl(PiPMS), and methoxy (PMeOM) derivatives. Radiolysis yields, ESR spectra, and GC-MS analysis of products were obtained. PMS and PFMS have similar low radiolysis yields, products, and product distributions. Only main-chain radicals which persist to 200 degree were observed. PCMS has increased values of G//s, G//x, and G//r. The product analysis results suggest that the presence of chlorine contributes to the primary process by dissociative electron capture and enhances the cleavage of alpha -methyl group. Irradiation of PBMS caused crosslinking and yielded few volatile products. PMeOMS and PiPMS gel readily by gamma -irradiation and may be useful as negative radiation resists.