Cationic Ring-Opening Photopolymerization of Long-Chain Epoxides in the Rotator Phase: Confirmation, Mechanism, and Combination

Rotator-phase photopolymerization has been developed in the field of free-radical addition polymerization since the photopolymerization in the rotator phase was first proposed, and other mechanisms urgently need to be extended. Herein, four long-chain glycidyl ethers were synthesized, and their polymorphic behavior was studied by differential scanning calorimetry and X-ray diffraction. Among all, the octadecyl glycidyl ether (OGE) and the hexadecyl glycidyl ether (HGE) are proven existing rotator phases. The cationic ring-opening photopolymerization of the OGE in the rotator phase was achieved, and the highest conversion reached 68.6% at 30 °C, which is even higher than that of liquid-state photopolymerization at adjacent higher temperatures (27.2% at 40 °C). The mechanism was discussed and explained with the aid of a molecular dynamic simulation. In order to further develop the cationic ring-opening photopolymerization in rotator phases at relatively low temperatures, three types of long-chain compounds were chosen to separately blend with the OGE to construct binary systems. The conversion of the OGE at 20 °C (17% in the pure OGE system) could be obviously improved in all binary systems, and the maximum conversion could reach 56%. Subsequently, the interactions of different long-chain compounds on the OGE and the effect on polymerization behavior are both discussed.