Theoretical structural characterization of polydiethynylsilane — a new nonlinear optical material

Abstract Recently, a novel π-conjugated polymer, polydiethynylsilane (PDES), with excellent nonlinear optical properties has been reported. The structures of several isomeric forms for PDES have been characterized theoretically. The results show that the four-membered ring structure is the most plausible and some dialkyl, ethynylsilane groups may insert in the backbone of PDES as sequential copolymers. These results were obtained using the molecular orbital method at the ab initio level (3–21 G ∗ modified) and molecular mechanics method with potentials derived from ab initio calculations. We have also calculated the second-order polarizability.