Polymerization of alicyclic epoxides with aluminum alkyl catalysts

Abstract

AbstractThe polymerization of alicyclic epoxides with aluminum alkyls has been investigated. In many cases, fast polymerization rates were observed at −78°C., leading to high molecular weight compounds in good yield. The infrared spectra of the polymers are consistent with the proposed polyether structure. It was found that the molecular weight of the polymers obtained in these reactions is a function of the alicyclic ring size. This was interpreted by considering the variation of molecular strain during the polymer‐forming reaction. The following order of reactivity based on estimated propagation rates has been established for the monomers: cyclohexene oxide > cyclopentene oxide > cycloheptene oxide » cyclooctene oxide. A reaction mechanism is proposed where initiation occurs through coordination of the aluminum alkyl with the epoxide, followed by successive addition of monomers to the electrophilic centers. The absence of phenyl endgroups in a relatively low molecular weight polycyclohexene oxide, prepared with Al(C6H5)3 catalyst, precludes one of the possible alternative mechanisms. The proton magnetic resonance spectra of polycyclohexene oxide, cis‐1,2‐cyclohexanediol, and trans‐1,2‐cyclohexanediol were determined in dilute chloroform solution and suggest a stereoregular poly‐trans‐ether structure for the polymers.