Dialkylsilylene-spaced divinylarene copolymers having alternating donor and acceptor chromophores are designed and synthesized. The rates of photoinduced electron transfer (PET) depend on the nature of the substituent on silicon. A replacement of the methyl substituent by the bulky isopropyl group has been shown to enhance the rate of PET. The results are rationalized in terms of the Thorpe - Ingold effect, which would bring the neighboring donor and acceptor chromophores in closer proximity. The STM images of the isopropyl-substituted copolymers are more folded than those of the methyl-substituted analogues, and these results are consistent with the outcome of photophysical studies of these copolymers.