氧硫化碳-环氧化物可控催化共聚及机理研究

Poly (thiocarbonate) has attractive features of polycarbonate and sulfur-containing polymer. It is potential to the application of photoconductive fiber, heavy metal scavengers and lithium ion battery materials due to its high optical and thermal properties, excellent chemical resistance, and heavy-metal recognition ability. However, to our knowledge, there is still no report on synthesizing well-defined poly (thiocarbonate)s by direct catalysis of alternating copolymerization of carbonyl sulfide (COS) and epoxides, and it is also unsuccessful to synthesize poly (dithiocarbonate)s by catalyzing alternating copolymerization of CS2 and epoxides. This is attributed to the oxygen/sulfur exchange reaction between monomers during copolymerization, which caused multiple thiocarbonate units (i.e.: -S(O)CO-, -S(O)CS-, -S(S)CO- and -S(S)CS-) in the copolymer. Aimed to solve this problem, this project will firstly focus on disclosing the mechanism of the oxygen/sulfur exchange reaction in detail. Under the guidance of the proposed mechanism, we then intend to prepare double metal cyanide complex (DMCC) catalysts with zinc-alkoxy or zinc-phenoxy groups, and use metal-nucleophilic and hydrophobic "gender" cocatalyst to suppress the oxygen- sulfur exchange reaction, to realize an easy-to-control alternating copolymerization of COS and epoxides, and afford poly(thiocarbonate)s with well-defined structure. Furthermore, the catalytic kinetics and mechanism for this copolymerization will also be explored in-depth and systematically. The results of this project will provide a new methodology to synthesize well-defined poly (thiocarbonate), and enrich the content of the polymer chemistry and C1 chemistry.

聚硫代碳酸酯兼具聚碳酸酯和含硫聚合物的优势性能，在光导纤维、重金属离子吸附剂和锂离子电池材料等方面有广泛用途。但迄今尚无催化氧硫化碳（COS）和环氧化物交替共聚合成聚硫代碳酸酯的报道，催化二硫化碳（CS2）和环氧化物共聚也只能得到含多种硫代碳酸酯链节的聚合产物，聚合可控性差，关键制约因素是催化过程中单体间的氧－硫交换反应导致聚合产物链结构复杂。针对这一问题，本项目将系统地研究氧－硫交换反应机理，以此为指导，拟制备烷氧基和酚氧基化的双金属氰化络合物（DMCC）催化剂、并通过引入亲金属性和疏水性的"两性"助催化剂等措施来抑制氧－硫交换反应，实现催化COS－环氧化物可控共聚、合成结构明确的聚硫代碳酸酯，研究催化共聚动力学和机理，在理论上将发展新的共聚机理和聚硫代碳酸酯的可控合成方法，丰富高分子合成化学和C1化学的内容，在应用上获得新的含硫高分子材料。

本项目系统深入研究了催化羰基硫与环氧化物共聚合成含硫共聚物的体系。作为环境污染物的C1单体, COS与环氧化物直接共聚是高效的固定利用方式，然而本项目之前未见成功共聚的报道；预期的产物，聚硫代碳酸酯是一类高折光指数的含硫聚合物，在光导纤维和重金属吸附材料等方面有广阔应用前景，但传统的缩聚和开环聚合等路线效率低、采用的光气和硫醇等单体剧毒；同时含硫C1单体与环氧化物的共聚，因硫和氧的差异性，有利于揭示CO2共聚的科学机制。.负责人受碳酸酐锌酶的Zn-OH键与CS2和COS反应的启发，首次开发了金属Zn和Cr络合物催化含硫C1与环氧化物的共聚体系，重要的结果如下：1）两类催化剂均能高效催化COS/环氧可控共聚，尤其Cr催化剂，其效率接近烯烃聚合催化剂；2）系统阐述了含硫C1共聚的催化剂结构效应和环氧单体的结构效应，阐明了共聚的规律；3）揭示了COS(CS2)/环氧化物共聚异于CO2/环氧化物共聚的显著特点：氧硫交换、硫阴离子诱导的高区域选择性反应和硫取代导致的共聚物结晶行为。研究结果既提供了二元不对称单体同时精确区域选择性开环加聚的新模式，也获得了一类可溶的高折光指数有机材料，发现了一条不依赖手性因素合成结晶性共聚物的新途径。