Two double-decker silsesquioxane-based rigid-rod polymers/oligomers were synthesized using olefin self-metathesis and photolysis. In both synthetic routes, double-decker (DD) silsesquioxanes (SQs) with di- and tetra-vinyl functionalities were studied, and all products were characterized in detail by nuclear magnetic resonance (NMR), MALDI-TOF, GPC, TGA, and Fourier transform infrared (FTIR) spectroscopy. The catalytic self-metathesis of di-vinyl-functionalized DD SQs results in rigid-rod oligomers with a simple ethene bridge linking SQ cages with a decomposition temperature T_d5% of ∼530 ° C in air. Due to steric hindrance, only one ethene bridge forms between tetra-vinyl-functionalized DD SQs using either Grubb’s 1st or 2nd generation catalysts, with other vinyl groups remaining unreacted, as indicated by MALDI-TOF. As an alternative approach, photolysis of di-vinylDD SQs in the UVA and UVB regions leads to linear polymers with cyclobutane linkers between SQ cages and a T_d5% of ∼530 ° C. In both configurations, the degrees of freedom are limited solely to rotation around the single bonds joining the ethene or cyclobutane groups to the DD SQs along the chain axis, leading to rigid-rod polymers. Rigid-rod polymers remain both highly thermally stable and soluble in common solvents such as dichloromethane and tetrahydrofuran, which points to new opportunities in easily processable rigid-rod polymers. In contrast, photolysis of tetra-vinylDD SQs leads to insoluble and unmeltable products, implying a high degree of cross-linking.

中文翻译：

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以倍半硅氧烷为主链的刚性棒状聚合物的合成与表征

使用烯烃自复分解和光解合成了两种基于双层倍半硅氧烷的刚性棒聚合物/低聚物。在这两种合成路线中，研究了具有二乙烯基和四乙烯基官能团的双层 (DD) 倍半硅氧烷 (SQ)，并通过核磁共振 (NMR)、MALDI-TOF、GPC、TGA 和傅里叶变换红外 (FTIR) 光谱。二乙烯基官能化 DD SQs 的催化自复分解产生具有简单乙烯桥的刚性棒低聚物连接 SQ 笼，分解温度为T _d5%在空气中约 530°C。由于空间位阻，使用 Grubb 的第一代或第二代催化剂在四乙烯基官能化的 DD SQ 之间仅形成一个乙烯桥，而其他乙烯基保持未反应，如 MALDI-TOF 所示。作为一种替代方法，UVA 和 UVB 区域中二乙烯基 DD SQ 的光解导致线性聚合物在 SQ 笼之间具有环丁烷接头，T _d5%约530°C。在两种配置中，自由度仅限于围绕将乙烯或环丁烷基团沿链轴连接到DD SQ的单键旋转，从而形成刚性棒状聚合物。硬棒聚合物既保持高度热稳定性，又可溶于二氯甲烷和四氢呋喃等常见溶剂，这为易于加工的硬棒聚合物带来了新的机遇。相反，四乙烯基DD SQs的光解导致不溶和不可熔化的产物，这意味着高度交联。