Probing the Impact of Chain Architecture on Segmental Dynamics in Semi-Crystalline Poly(oligocyclobutane)

Recently, a new family of alkene-spaced semi-crystalline poly(oligocyclobutyl) (pDVOCB) polymers derived from butadiene has been synthesized. These unique polymer microstructures have demonstrated promise as chemical recyclable polymers with excellent retention of their tunable, thermomechanical properties. However, due to the high crystallinity innate to this microstructure, information regarding their segmental dynamics has been difficult to detect via traditional calorimetry as the heat capacity increment is small due to the small amorphous fraction. In this work, the molecular dynamics of a series of pDVOCB polymers are studied via experimental relaxation dynamics techniques. Leveraging the improved sensitivity of these techniques to chain relaxations, insights into the effects of varying monomer architecture, tacticity, and molecular weight are obtained. Further, secondary relaxation processes are found to occur at lower temperatures, related to the local movements of cyclobutyl units. This improved understanding of molecular motions in pDVOCB, as well as the governing factors influencing them, provides insights into structure-property relationships important for the design, processing, and applications of these chemically recyclable polyolefins.