Modulating Poly(oligocyclobutane) Properties Through Backbone Modifications

Abstract

Poly(1,n′-divinyl)oligocyclobutane (pDVOCB) has emerged as a class of poly(cycloolefin) that is amenable to chemical recycling and demonstrates promising thermomechanical properties. However, their high melting temperatures coupled with insolubility makes melt processing challenging due to thermo-oxidation of internal alkenes. To address these issues, we describe a series of polymers incorporating modifications to the pDVOCB backbone and analyze the effects on material stability and processability. Intentional migration of the internal 1,2-disubstituted alkenes to an exocyclic trisubstituted position yields isomerized pDVOCB (IpDVOCB) which exhibits a depression of thermal transitions by up to 50 °C. Conversely, elimination of stereoirregularity between enchained DVOCB oligomers through alkene saturation yields hydrogenated pDVOCB (HpDVOCB), resulting in elevated thermal transitions by up to 30 °C. Furthermore, these shifts are attributed to changes in crystal defect density which is strongly influenced by chain stereoregularity. Understanding these behaviors guides future polymer design and expands the control and use of this new class of recyclable poly(cycloolefin)s.