| Research Abstract |
A new field, which is still developing, in ring-opening polymerization has been established on the basis of a new concept that useful reactions via pi-allyl palladium intermediates create new polymerization chemistry. Cyclic monomers, which have an appropriate group to accept oxidative addition of Pd(O) at the allylic position, have been accurately designed for this new type of ring-opening polymerization with contemplation of elemental organ reations. Some of them successfully polymerized with the aid of a palladium catalyst via pi-allyl palladium complexes as the key-intermediates.
Vinyl cyclopropane derivatives having two electron-withdrawing substituents such as ester, cyano, and sulfone at alpha-position of the vinyl group polymerized to give the polymer connecting at 1.5-position. The polymerization proceeds according to a novel inter-molecular proton-transfer mechanism. Cyclic carbonate, 5,5-dimethyl-4-vinyl-1,3- dioxan-2-one, polymerized with releasing carbon dioxide in the presence of a Pd catalyst and diethylzinc/ethanol as the initiator to produce polyether. This monomer produced an alternating copolymer with cyclic acid anhydrides. Cyclic carbamate, perhydro-5,5-vinyl- 1,3-oxazin-2-one and perhydro-5-methylene-1,3-oxazin-2-one, also polymerized to give dendriform polyamine, which consisted of primary (terminals), secondary (non-branching points), and tertiary (junctions) amino moieties and incorporated the initiator, i.e., benzylamine residue as the core. The polymerization mechanism is quite interesting: the propagating end is a N-H group, which multiplies with progress of the polymerization to produce the dendriform polymers. We termed this quite new polymerization Multi-Branching Polymenzation. Additionally, these two monomers produced graft copolymers having the highly branched polyamines as the graft chains, when their polymerization was initiated with aminomethylated polystyrene.
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