Eleven samples of poly{n-hexyl- [(S)-3-methylpentyl]silylene} (PH3MPS) ranging 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, sedimentation 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 range of M, 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 degreesC. The viscometry has also been made on a PH3MPS sample in n-hexane and methylcyclohexane at 25 degreesC. In these solvents, the global conformation of PH3MPS is essentially the same as that in isooctane at the same temperature.