Temperature and solvent dependence of stiffness of poly{n-hexyl-[(S)-3-methylpentyl]silylene} in dilute solutions

Eleven samples of poly{n-hexyl- [(S)-3-methylpentyl]silylene} (PH3MPS) rang ing in weight-average molecular weight M-w from 3.1 x 10(3) to 8.7 x 10(5) in isooctane have been studied by light scattering at 25 degreesC, sediment ation equilibrium at 25 degreesC, and viscometry at five temperatures (-27, -15, 5, 25, and 45 degreesC) to determine their z-average radii of gyration (S-2)(x), second virial coefficients, and intrinsic viscosities [eta] The (S-2)(x) and [eta] data are analyzed quantitatively by the current theories on the basis of the wormlike chain with excluded volume over the entire ra nge of M, studied. PH3MPS is shown to be a typical semiflexible polymer wit h the persistence length changing from 15.4 to 5.0 nm at -27 to 45 degreesC . The viscometry has also been made on a PH3MPS sample in n-hexane and meth ylcyclohexane at 25 degreesC. In these solvents, the global conformation of PH3MPS is essentially the same as that in isooctane at the same temperatur e.