A dibromo derivative of Dewar benzene, trans-5,6-dibromobicyclo[2.2.0]hex-1-ene, was polymerized using ring-opening metathesis polymerization (ROMP). The reaction proceeded in a controlled manner as changing the initial monomer-to-catalyst ratio afforded monodispersed polymers with tunable molecular weights and growing polymer chains were extended upon subsequent exposure to additional monomer. Treatment of the halogenated polymers with an alkyllithium reagent resulted in elimination followed by isomerization to afford trans-poly(acetylene). Based on a series of mechanistic and spectroscopic studies, the transformation was proposed to proceed through a cyclobutenyl intermediate that undergoes rearrangement. The methodology was found to be versatile as triblock copolymers containing the halogenated homopolymer were prepared and converted to their poly(acetylene)-containing derivatives. The polymers were characterized using gel permeation chromatography as well as a range of spectroscopic (NMR, FT-IR, UV−vis, and Raman) and analytical techniques.

A variety of 3-substituted-4-halocyclobutenes originating from Dewar lactone (2-oxabicyclo[2.2.0]hex-5-en-3-one) were synthesized and polymerized using the Hoveyda–Grubbs 2nd generation catalyst.

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.