Chain scission efficiency and reactive‐ion etch resistance of alternating copolymers of styrene and olefins trisubstituted or tetrasubstituted with electron‐withdrawing groups

Abstract

Alternating copolymers of styrene (St) with electron‐deficient olefins trisubstituted or tetrasubstituted with cyano and carboalkoxy groups have been subjected to 60Co γ‐radiolysis together with a series of copolymers of methyl methacrylate (MMA) and St. The chain scission susceptibility Gs—Gx determined by membrane osmometry drastically decreases as St is incorporated in poly(methyl methacrylate) (PMMA). Whereas the alternating St‐MMA copolymer is slightly crosslinked upon irradiation, an alternating copolymer of St with diethyl 2‐cyano‐1,1‐ethylenedicarboxylate maintains a fairly high degradation sensitivity (Gs—Gx = 1.2). The reactive‐ion etch rates were determined for the series of polymers in CF4/O2 (92/8). The etch resistance is significantly increased by introduction of St units in PMMA, and the highly substituted alternating copolymer etches as slowly as the MMA(50)—St(50) copolymers. Thus the alternating copolymer of NCCH=C(CO2Et)2 with St behaves like PMMA when exposed to high‐energy radiation but is comparable to PSt in plasma environments. Copyright © 1986 John Wiley & Sons, Inc.