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.

自旋转相光聚合首次被提出以来，旋转相光聚合技术已在自由基加成聚合领域得到发展，而其他机制亦迫切需要得到拓展。本研究中，合成了四种长链环氧乙烷醚，并利用差示扫描量热法和X射线衍射对其多晶行为进行了研究。其中，十八烷基环氧乙烷醚（OGE）和十六烷基环氧乙烷醚（HGE）已被证实存在旋转相。在旋转相中，OGE的阳离子开环光聚合得以实现，其最高转化率在30°C时达到68.6%，甚至高于相邻较高温度下的液态光聚合转化率（40°C时的27.2%）。通过分子动力学模拟辅助，对反应机制进行了讨论和阐释。为进一步在较低温度下发展旋转相中的阳离子开环光聚合，选用了三种长链化合物分别与OGE混合构建二元体系。在所有二元体系中，20°C时OGE的转化率（在纯OGE体系中为17%）均得到显著提高，最大转化率可达56%。随后，对不同长链化合物与OGE的相互作用及其对聚合行为的影响亦进行了深入探讨。