AN INVESTIGATION OF POLYMERIZATION VIA REDUCTIVE COUPLING OF CARBONYLS

The viability of carbonyl coupling in the presence of low-valent titanium has been investigated as a step propagation, condensation type polymerization mechanism to create polyvinylene and polypinacol polymers. Although it has been reported by Feast that 4,4'-dibenzoylbiphenyl can be polymerized to number-average degree of polymerization of 100, this study showed that, while oligomers and low molecular weight polymers can be formed, polymers with molecular weights exceeding 6000 could not be synthesized. Polymerization stiffness is a factor; solubility and mechanistic explanations for these results are presented. A threefold increase in molecular weight was observed when the more flexible polypinacol rather than the polyvinylene structures were synthesized, corroborating previous evidence regarding the influence of chain flexibility.