This is the first report about the ring-opening polymerization of thiolactide, which is the thioester analogue of lactide. The cyclic condensation of thiolactic acid gave rac-thiolactide, which underwent the ring-opening polymerization by a combination of thiol as the initiator and DBU as the catalyst. The polymerization was in equilibrium, showing that the monomer conversions were as low as 20% in solvents. The bulk polymerization at r.t. led the monomer conversions around 50%, and the molecular weights of the polymer products increased with decreasing the amount of the thiol initiator. The MALDI-TOF mass spectra revealed that the hexane-insoluble polythiolactide (M_n = 3000–3500, PDI = 1.3–1.6, 20–30%yield) had not only the linear but also the macro cyclic structures. A much weaker base, pyridine, worked as the catalyst, showing the lower activity but leading the polymerization to a more controllable fashion. DFT calculation suggested that rac-thiolactide has the smaller ring-strain than rac-lactide, which agreed with the lower polymerizability of rac-thiolactide. Polythiolactide showed the higher degradability for alkaline hydrolysis and UV photolysis than polylactide. Copolymerization of thiolactide with thioglycolide was also studied.

这是关于丙交酯的开环聚合反应的第一篇报道，后者是丙交酯的硫酯类似物。巯基乳酸的环状缩合得到外消旋-丙交酯，其通过硫醇作为引发剂和DBU作为催化剂的组合进行开环聚合。聚合反应处于平衡状态，表明在溶剂中单体转化率低至20％。在rt的本体聚合导致单体转化率约为50％，并且聚合物产物的分子量随着硫醇引发剂的量的减少而增加。MALDI-TOF质谱显示不溶于己烷的聚硫丙交酯（M _n = 3000–3500，PDI = 1.3–1.6，20–30％的收率）不仅具有线性结构，而且具有大环结构。较弱的碱吡啶用作催化剂，显示出较低的活性，但导致聚合反应更可控。DFT计算表明，rac-硫丙交酯的环应变比rac-丙交酯小，这与rac-硫丙交酯的可聚合性较低有关。聚硫丙交酯显示出比聚丙交酯更高的碱性水解和紫外线光解降解性。还研究了巯基丙交酯与巯基乙交酯的共聚合。