Abstract：
Elemental sulfur, a waste product of the oil refinement process, represents a promising raw material for the synthesis of degradable polymers. We show that simple lithium alkoxides facilitate the polymerisation of elemental sulfur S8 with industrially relevant propylene oxide (PO) and CS2 (a base chemical sourced from waste S8 itself) to give poly(monothiocarbonate-alt-Sx) in which x can be controlled by the amount of supplied sulfur. The in situ generation of thiolate intermediates obtained by a rearrangement, which follows CS2 and PO incorporation, allows to combine S8 and epoxides into one polymer sequence that would otherwise not be possible. Mechanistic investigations reveal that alkyl oligosulfide intermediates from S8 ring opening and sulfur chain length equilibration represent the better nucleophiles for inserting the next PO if compared to the trithiocarbonates obtained from the competing CS2 addition, which causes the sequence selectivity. The polymers can be crosslinked in situ with multifunctional thiols to yield reprocessable and degradable networks. Our report demonstrates how mechanistic understanding allows to combine intrinsically incompatible building blocks for sulfur waste utilisation.
摘要：
元素硫,石油精炼过程中的废物，代表了用于合成可降解聚合物的有前途的原料。我们表明，简单的锂醇盐有助于元素硫S8与工业相关的环氧丙烷（PO）和CS2（源自废物S8本身的基础化学品）的聚合，从而得到聚（一硫代碳酸盐-alt-Sx），其中x可以通过所提供的硫的量来控制。原位生成通过重排获得的硫醇盐中间体，在CS2和PO合并之后，允许将S8和环氧化物组合成一个否则不可能的聚合物序列。机理研究表明，与竞争CS2添加获得的三硫代碳酸酯相比，S8开环和硫链长度平衡的烷基低硫化物中间体代表了插入下一个PO的更好的亲核试剂。这导致序列选择性。聚合物可以与多官能硫醇原位交联以产生可再加工和可降解的网络。我们的报告展示了机械理解如何允许结合本质上不兼容的构建块来利用硫废物。
