PREPARATION OF DIPHENYLSILYLENE POLYMERS CONTAINING MAIN-CHAIN ACETYLENE AND (HETERO)AROMATIC GROUPS - CHI(2) NONLINEAR-OPTICAL AND OTHER PROPERTIES

Polymers having the structure [C=CSi(Ph2)C=C-Z]n (Z = 1,4-benzene, 4,4'-biphenyl, 9,10-anthracene, 2,7-fluorene, 6,6'-bipyridine, 2,5 and 2,6-pyridine, 2,5-thiophene, 2,6-p-dimethylaminonitrobenzene, 2,6-p-nitroaniline, 2,6-p-nitrophenol, 2,6-p-cyanophenol, p-tetrafluorobenzene and 2,7-fluoren-9-one) were prepared by reaction of diethynyldiphenylsilane with the appropriate (hetero)aromatic dibromide or diiodide in the presence of [(PPh3)2PdCl2], CuI and PPh3, the solvent being either triethylamine or triethylamine with toluene. Depending on the Z group and the solvent system, the weight-average molecular weight as determined by SEC ranged from 2600 for 2,6-pyridine to 34,000 for 1,4-benzene. The UV/visible spectra show absorption maxima in the region 250-400 nm. The polymer with 2,6-p-dimethylaminonitrobenzene groups was chi(2) active, the value of r33 being 0.8 pm V-1 following fixed electrode poling at 17.5 V mum-1. The polymers did not melt below the decomposition temperature, and all transitions shown in the DSC thermogram to 300-degrees-C were found to be absent on repeat scans. Thermogravimetric and thermal dynamic analysis of the polymer where Z = 1,4-benzene showed decomposition commencing at 290-degrees-C and continuing up to ca. 750-degrees-C. The residue was composed of alpha-SiC and amorphous carbon. Treatment of the same polymer with BH3/SMe2 gave rise to an insoluble polymer containing boron. The polymer where Z = 6,6'-bipyridine reacted with copper(II) trifluoromethanesulfonate to give a copper(II)-containing polymer, hydrazine reduction of which afforded the corresponding Cu(I)-containing polymer.