Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street, W. Hamilton, ON L8S 4M1, Canada.
Molecules. 2021 Jan 5;26(1):231. doi: 10.3390/molecules26010231.
A simple, mild and efficient method to prepare HSi- or HOSi-telechelic, high-molecular-weight polydimethylsiloxane polymers (to 41,600 g·mol) using the one-shot hydrolysis of MM is reported; titration of the water allowed for higher molecular weights (to 153,900 g·mol). The "living" character of the chain extension processes was demonstrated by adding a small portion of MM and B(CF) (BCF) to a first formed polymer, which led to a ~2-fold, second growth in molecular weight. The heterogeneous reaction reached completion in less than 30 min, much less in some cases, regardless of whether it was performed neat or 50 wt% in dry toluene; homogeneous reactions in toluene were much slower. The process does not involve traditional redistribution, as judged by the low quantities (<3%) of D produced. However, it is not possible to avoid Chojnowski metathesis from MDDM giving D, which occurs competitively with chain extension.
本文报道了一种简单、温和且高效的方法，可使用 MM 的单次水解制备 HSi-或 HOSi-封端、高分子量聚二甲基硅氧烷聚合物（高达 41600 g·mol）；通过滴定水可以得到更高的分子量（高达 153900 g·mol）。通过向第一个形成的聚合物中加入少量的 MM 和 B(CF)（BCF）来证明链延伸过程的“活性”特征，这导致分子量增加了约 2 倍。无论是否在干燥的甲苯中以纯态或 50wt%进行反应，非均相反应都能在不到 30 分钟内完成，在某些情况下甚至更短；在甲苯中的均相反应则慢得多。该过程不涉及传统的重新分配，这可以从生成的 D 的低含量（<3%）来判断。然而，无法避免 MDDM 产生 D 的 Chojnowski 复分解反应，该反应与链延伸竞争发生。
