ELECTRONIC ABSORPTION AND STRUCTURAL-PROPERTIES OF POLY(DI-NORMAL-BUTYLSILYLENE) PRECIPITATED FROM SOLUTION AT LOW-TEMPERATURE

The Si backbone in crystalline poly(di-n-butylsilylene) (PDBS) has been shown to be a 7/3 helix, which is in marked contrast to the trans chain conformation of poly(di-n-hexylsilylene) (PDHS). The electronic absorption properties of these two polymers are almost identical in solution but are entirely different in the solid state. In this work, we show that a new, long-wavelength-absorbing solid form of PDBS can be prepared by precipitating the polymer from dilute solution at low temperature. The structure of the new form is investigated using29Si NMR and X-ray diffraction. On the basis of NMR and UV absorption, we conclude that the new polymorph of PDBS is characterized by a trans conformation, although it contains substantial intra- and intermolecular crystallographic disorder, unlike PDHS. © 1990, American Chemical Society. All rights reserved.