Systematic Investigation of Silicon Substitution on Single Macromolecule Mechanics

Four unsaturated poly(carbooligosilane)s (P1-P4) were prepared via acyclic diene metathesis polycondensation of new oligosilane diene monomers (1-4). These novel polymers with varying main-chain Si incorporation have high trans internal olefin stereochemistry (ca. 80%) and molecular weights (9500-21,700 g mol^-1). Postpolymerization epoxidation converted all alkene moieties to epoxides and rendered the polymers (P5-P8) more electrophilic, which allowed for single-molecule force spectroscopy studies via a modified atomic force microscope setup with a silicon tip and cantilever. The single-chain elasticity of the polycarbooligosilanes decreased with increasing numbers of Si-Si bonds, a finding reproduced by quantum chemical calculations.

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Author Stephen L Craig Chemistry