有机Lewis酸碱对催化氧硫化碳和环氧氯丙烷交替共聚

Alternating Copolymerization of Carbonyl Sulfide and Epichlorohydrin Catalyzed by Organic Lewis Pairs

氧硫化碳作为单体可与环氧化物交替共聚,是合成含硫高分子的新途径.将廉价的环氧氯丙烷与氧硫化碳共聚可以得到含硫和氯原子的高分子,本文报道了无金属催化2种单体的全交替共聚反应.采用三乙基硼和Lewis碱按2/1的摩尔比组成催化剂,可以获得全交替、高区域规整性的聚单硫代碳酸酯.研究了不同实验条件包括有机Lewis酸碱对类型、反应温度、物料配比等因素对共聚反应的影响.结果表明:无金属催化剂能获得与金属催化剂相媲美的效果,能高效催化并得到分子量低于1000 g/mol的全交替低聚物,为氧硫化碳和环氧氯丙烷的高值化利用提供了新的选项.

The alternating copolymerization of carbonyl sulfide(COS)with epoxides is an emerging approach to the synthesis of sulfur-containing polymers.Epichlorohydrin(ECH)is a low-cost,commercially available epoxide rich in chloride.The copolymerization of COS with ECH can afford a unique poly(monothiocarbonate)(PMTC)containing chloride and sulfur atoms that could be a functional material.In this work,we report for the first time the alternating copolymerization of COS and ECH using metal-free catalysts.A binary catalytic system consisting of triethyl boron(TEB)and Lewis base(e.g.PPNCl,NBu4Cl,PPh4Cl,PPh4Br,DTMeAB and DBU)afforded PMTCs with completely alternating structures(i.e.,alternating degree>99%),the head-to-tail diad content>99%.The effect of various experimental conditions including the types of organic Lewis acid-base pairs,reaction temperatures,feeding ratios on the copolyemrization were investigated through controlled experiments.The combination of TEB/PPNCl(molar ratio of 2/1)could effectively catalyze the copolymerization of COS with ECH at 0°C,with ECH conversion up to 92%,and produce the copolymer with number-average molecular weight(Mn)of 3000 g/mol that is comparable to the previous result via bifunctional metal catalyst.Although it is still a big challenge to obtain ECH/COS copolymer with high molecular weights,this work also discovers that organic Lewis pairs could efficiently achieve fully alternating oligomers with Mn less than 1000 g/mol at 30°C,providing a new option for high value-added utilization of COS and ECH.