Preparation of diphenylsilylene polymers containing main-chain acetylene and (hetero)aromatic groups: χ(2) non-linear optical and other properties

Article abstract of DOI:10.1016/0022-328X(93)80382-L

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>, Cu and PPh3, the solvent being either triethylamine or triethylamine with toluene.Depending on the Z group and thesolvent 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 χ⁽²⁾ active, the value of r₃₃ being 0.8 pm V^-1 following fixed electrode poling at 17.5 V μm^-1.The polymers did not melt below the decomposition temperature, and all transitions shown in the DSC thermogram at 300 deg 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 deg C and continuing up to ca. 750 deg C.The residues was composed of α-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.