MOLECULAR DESIGN OF NOVEL NETWORK POLYMERS

Cationic, anionic, and radical ring-opening polymerization of spiro an d bicyclic monomers, and their application to network polymers have be en developed. Bicycle orthoesters (BOEs), spiro orthoesters (SOEs), an d spiro orthocarbonates (SOCs) were polymerized by cationic double rin g-opening. Bicyclobis(gamma-butyrolactone)s and spirobis(gamma-butyrol actone)s were copolymerized with epoxides by anionic alternating ring- opening. Polymers from SOCs bearing exomethylene groups consisted of r ing-opened and vinyl polymerized units. The degree of ring-opening of SOCs depended upon the number of rings and steric hindrance. The radic al polymerization of vinylcyclopropanone cyclic acetals depended on th e ring-size. With the monomers bearing 5- and 6-membered acetal rings, single ring-opened polymers were obtained. With the monomer bearing 7 -membered acetal ring, the polymer mainly consisted of double ring-ope ned unit. These monomers could be crosslinked by bifunctionalization. Poly(cyclic orthoester)s linked by covalent bonds with dithiols to bif unctional SOEs were crosslinked by acid catalysts, and the reversible crosslinking-depolymerization system could be controlled by temperatur e.