Cascade Ring Strain Release Polymerization of Cyclohexene Oxide and Derivatives Using a Mono(& mu;-Alkoxo)bis(alkylaluminum) Initiator

Cyclohexene oxide (CHO) is a usefulbuilding block forthe synthesisof novel materials and is a model substrate for polymerization catalystdevelopment. The driving force for CHO polymerization is derived fromits bicyclic structure, which combines the release of the enthalpyfrom epoxide ring-opening (ca. -15 kcal/mol) and a twist-chair-to-chairconformation shift in the cyclohexane ring (ca. -5 kcal/mol)upon enchainment. The lack of regio-defined functional handles attachedto the CHO monomer limits the ability to both pre- and post-functionalizethe resultant materials and establish structure-property relationships,which reduces the versatility of currently accessible materials. Wereport the synthesis of two series of CHO derivatives with butyl,allyl, and halogen substituents in the & alpha; and & beta; positionsrelative to the epoxide ring. Adding substituents to the CHO ringwas found to affect polymerization kinetics, with 4-substituted (& beta;)CHO being more reactive than 3-substituted (& alpha;) CHO analogs wheninitiated with a mono(& mu;-alkoxo)bis(alkylaluminum) pre-catalyst.Polymer thermal properties depended on substituent location and identity.Halogenated CHO rings were most reactive and produced the highestglass transition temperatures in the resultant polymers (up to 105 & DEG;C). Density functional theory revealed a possible mechanisticexplanation consistent with the observed differences in polymerizationrate for the 3- and 4-substituted CHOs derived from a combinationof steric and thermodynamic considerations.