Systematic Investigation of Silicon Substitution on Single Macromolecule Mechanics

Four unsaturated poly(carbooligosilane)s(P1-P4) were prepared via acyclicdiene metathesis polycondensationof new oligosilane diene monomers (1-4). These novel polymers with varying main-chain Si incorporationhave high trans internal olefin stereochemistry (ca.80%) and molecular weights (9500-21,700 g mol(-1)). Postpolymerization epoxidation converted all alkene moieties toepoxides and rendered the polymers (P5-P8) more electrophilic, which allowed for single-molecule force spectroscopystudies via a modified atomic force microscope setup with a silicontip and cantilever. The single-chain elasticity of the polycarbooligosilanesdecreased with increasing numbers of Si-Si bonds, a findingreproduced by quantum chemical calculations.

Automated summary

Four unsaturated poly(carbooligosilane)s were synthesized by acyclic diene metathesis polycondensation of new oligosilane diene monomers. These polymers showed high trans internal olefin stereochemistry and molecular weights, and were further modified through postpolymerization epoxidation for single-molecule force spectroscopy studies. The single-chain elasticity of the polycarbooligosilanes decreased with increasing numbers of Si-Si bonds, as supported by quantum chemical calculations.