Hydrogenated Poly(Dewar benzene): A Compact Cyclic Olefin Polymer with Enhanced Thermomechanical Properties

Abstract

Dihydro Dewar benzene(bicyclo[2.2.0]hex-2-ene) was synthesized and polymerized using the Grubbs third generation catalyst. The corresponding ring-opening metathesis polymerization proceeded in a controlled manner, as determined by a linear relationship between the molecular weight of the polymer produced and the monomer-to-catalyst feed ratio as well as an ability to extend polymer chains through exposure to an additional monomer. Subsequent treatment with tosylhydrazide afforded the corresponding hydrogenated derivative. The hydrogenated polymer was found to exhibit high melting and decomposition temperatures as well as a relatively high Young’s modulus when compared to other polyolefins [e.g., hydrogenated poly(norbornene) and poly(ethylene)]. The enhanced thermal and mechanical properties were found to originate from a relatively low phase transition entropy combined with high polymer crystallinity, features that were attributed to restricted bond rotation within the repeating units of the hydrogenated polymer.