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.

旋光相光聚合技术在自由基加成聚合领域的发展由来已久，自旋光相光聚合首次被提出以来，亟需拓展其他聚合机制。本研究中，合成了四种长链缩水甘油醚，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，十八烷基缩水甘油醚（OGE）和十六烷基缩水甘油醚（HGE）被证实存在旋光相。在旋光相中，实现了OGE的阳离子开环光聚合，最高转化率可达68.6%，在30°C时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，对该聚合机制进行了讨论和解释。为了进一步开发在相对较低温度下的旋光相阳离子开环光聚合，选择了三种长链化合物分别与OGE混合构建二元系统。在所有二元系统中，20°C下OGE的转化率（纯OGE系统中的17%）均得到了显著提高，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进行了讨论。