Unperturbed chain dimensions of poly(di-n-hexylsilane), poly(methyl-n-propylsilane), and poly(di-n-butylsilane)

Unperturbed chain dimensions of poly(di-n-hexylsilane) (PDHS), poly(methyl- n-propylsilane) (PMPrS), and poly(di-n-butylsilane) (PDBS) have been evalua ted by a combined use of static light scattering, size exclusion chromatogr aphy (SEC), and SEC-multiangle laser light scattering. The a solvents and c haracteristic ratios (C-infinity's) of the individual polysilanes were dete rmined as follows: PDHS, a mixed solvent of n-hexane (58.2 wt %) and 2-prop anol (41.8 wt %) at 25 degreesC and C-infinity = 42.5; PMPrS, a mixed solve nt of n-hexane (62.6 wt %) and 2-propanol (37.4 wt %) at 25 degreesC and C infinity = 19.9; PDBS, n-hexane at 19.1 degreesC and C-infinity = 42.3. The se C infinity values show that the polysilanes in the theta state are much more extended and rigid than ordinary carbon backbone polymers. On the basi s of the results, the conformational characteristics of the three polysilan es are discussed by reference to their UV spectra.