Configurationally Constrained Crystallization of Brush Polymers with Poly(ethylene oxide) Side Chains

The influence of physical confinement on the crystallization of poly­(ethylene oxide) (PEO) has received much attention in past years. Here, rather than constraining the crystallization of the polymer by a physical or geometric boundaries, the influence of the constraints imposed by the chain architecture on the crystallization of the PEO was investigated, where the PEO chains were anchored to a poly­(norbornene) (PNB) backbone. In this brush or comb-type polymer, the crystallizable polymer PEO are side chains comprising the bristles of the brush while the PNB comprises the spine. The brush or comb-type polymers were synthesized by the ring-opening metathesis polymerization (ROMP) of a NB-modified macromonomer. Here, the crystallizable PEO is anchored to the PNB backbone, placing constraints on the PEO during crystallization and annealing. The crystalline morphologies, crystallization kinetics, melting behavior, and crystal structure of the resultant polymers were investigated by polarized optical microscopy (POM), different scanning calorimetry (DSC), and X-ray scattering. Constraining the PEO to the PNB backbone was found to significantly influence the mobility of PEO chains, the degree of crystallinity, the crystal thickness and the equilibrium melting point. Increasing the molecular weight of the PEO or annealing at higher temperature alleviates this constraint to some extent. In addition to crystallization, the influence of annealing on the morphology was also investigated.