Temperature and Solvent Dependence of Stiffness of Poly{<i>n</i>-hexyl-[(<i>S</i>)-3-methylpentyl]silylene} in Dilute Solutions

Abstract

Eleven samples of poly{n-hexyl-[(S)-3-methylpentyl]silylene} (PH3MPS) ranging in weight-average molecular weight Mw from 3.1 × 103 to 8.7 × 105 in isooctane have been studied by light scattering at 25 °C, sedimentation equilibrium at 25 °C, and viscometry at five temperatures (−27,−15, 5, 25, and 45 °C) to determine their z-average radii of gyration 〈S2〉z, second virial coefficients, and intrinsic viscosities [η]. The 〈S2〉z and [η] data are analyzed quantitatively by the current theories on the basis of the wormlike chain with excluded volume over the entire range of Mw studied. PH3MPS is shown to be a typical semiflexible polymer with the persistence length changing from 15.4 to 5.0 nm at −27 to 45 °C. The viscometry has also been made on a PH3MPS sample in n-hexane and methylcyclohexane at 25 °C. In these solvents, the global conformation of PH3MPS is essentially the same as that in isooctane at the same temperature.