Experimental and theoretical investigation of optical properties of poly-(1-trimethylsilyl-1 propyne) molecules in solution

The optical anisotropy of poly-(1-trimethylsilyl-1 propyne) (PTMSP) molecules has been studied by flow birefringence. High positive birefringence was detected which is one order of magnitude higher than that of a polymer with a similar structure, poly-vinyltrimethylsilane (PVTMS). Semiempirical quantum-chemical calculation of the optical anisotropy of the polymer molecules under investigation was carried out. It was established that high optical anisotropy of molecules (with a low anisotropy of the monomer unit) indicates that these macromolecules exhibit high intramolecular orientational order. This is also confirmed by the correct choice of the ordered helical model in the quantum-chemical calculation of the optical anisotropy of PTMSP molecules. This model gave good quantitative agreement between the theoretical and experimental optical and geometric parameters of the macromolecules being investigated. (C) 1999 Elsevier Science Ltd. All rights reserved.