Phase Transition and Crystallization of Bio-based Comb-like Polymers Based on Renewable Castor Oil-Derived Epoxides and CO<sub>2</sub>
Jie Yang, Jincheng Dong, Yangpeng Wang, Xiao Zhang, Binyuan Liu, Haifeng Shi, Lirong He
Abstract
A series of bio-based comb-like polymers with various lengths of alkyl chains were synthesized through combining the ring-opening copolymerization of sustainable CO2 with bio-renewable castor oil-derived epoxides and the S-alkylated technique of the thiol–ene click reaction. The structure, thermal property, side-chain crystallization, and phase transition behavior of comb-like polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and wide-angle X-ray diffraction. The chain packing manner and phase transformation of side-chain crystallites for the pendent side alkyl chains on the CO2-based copolymer backbone exhibit a dependence on side-chain length, showing an increased phase-transition temperature (Tm) and phase-change enthalpy (ΔHm) from −15.0 to 70.3 °C and from 34.1 to 108.5 kJ/mol, respectively. Phase transition of the side-chain crystallites, varying from a regular trans conformation to a trans disordered conformation and then to a gauche conformation, occurs during the phase transition process. This work provides a promising strategy to achieve crystallized CO2-based copolymers and affords a facile approach to develop the structuralized polymeric materials from the molecular regulation aspect.