Systematic Investigation of Silicon Substitution on Single Macromolecule Mechanics

Abstract

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.