Synthesis and thermal properties of poly(oligomethylene-cycloalkylene)s with regulated regio- and stereochemistry

Abstract

This article focuses on the synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes to afford polymers with 1,3-trans-cyclopentylene groups and oligomethylene spacers alternating along the polymer chain. Pd complexes with a C2 symmetric structure enable isospecific polymerization of 4-alkylcyclopentenes, and the resultant isotactic polymers show liquid-crystalline properties. Cyclopolymerization of 1,6-heptadiene by bis(imino)pyridine Fe and Co catalysts produces poly(ethylene-1,2-cyclopentylene) with cis and trans-stereochemistry, respectively. Synthesis of poly(oligomethylene-1,4-cyclohexylene)s with trans or cis structure can be achieved by Pd-catalyzed isomerization polymerization of alkenylcyclohexanes or methylenecyclohexanes. The polymers with 1,4-trans-cyclohexylene show a high melting point that depends on the length of the oligomethylene spacer in the polymer. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry. Synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry are described. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes and alkenylcyclohexanes to afford poly(oligomethylene-1,3-cyclopentylene)s with trans structure and poly(oligomethylene-1,4-cyclohexylene)s with trans or cis structure, respectively. Poly(ethylene-1,2-cyclopentylene) with cis and trans-stereochemistry can be obtained by Fe- and Co-catalyzed cyclopolymerization of 1,6-heptadiene, respectively. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry.