Three cyclic oxoester-thioester hybrid monomers, 1 (3-methyl-1,4-oxathiane-2,5-dione), 2 (6-methyl-1,4-oxathiane-2,5-dione), and 3 (3,6-dimethyl-1,4-oxathiane-2,5-dione), were studied for anionic and cationic ring-opening polymerizations. These monomers are six-membered cyclic cross-dimers corresponding to combinations of glycolic and lactic acids with their thiol analogs. Anionic polymerizations using thiol as the initiator and 2,6-lutidine as the base catalyst were successful for the chemoselective cleavage of the thioester with the thiol propagating end. The polymerizability increased in the order of 3 < 1 < 2, which was in good agreement with the increasing ring strain order evaluated by Density Functional Theory calculations. The living character, to some extent, was suggested by the postpolymerization reactions, which involved a two-stage feed of the monomers and a thiol-ene terminal coupling reaction to form a block copolymer with PEG. Additionally, it was found that the polymerization took place in 2,6-lutidine without a thiol initiator and produced macrocyclic polymers. The cationic polymerizations took place with the aid of CF₃SO₃H and benzyl alcohol but involved side reactions with low chemoselective ring cleavage. The thioester unit caused the polymers to exhibit a lower T_g with greater thermal and photo degradability.

三种环状氧代酯-硫酯杂化单体，1（3-甲基-1,4-氧杂硫烷-2,5-二酮）、2（6-甲基-1,4-氧杂硫烷-2,5-二酮）和3（3 ,6-二甲基-1,4-氧杂噻烷-2,5-二酮），研究了阴离子和阳离子开环聚合。这些单体是六元环状交叉二聚体，对应于乙醇酸和乳酸及其硫醇类似物的组合。使用硫醇作为引发剂和2,6-二甲基吡啶作为碱催化剂的阴离子聚合成功地实现了具有硫醇增长末端的硫酯的化学选择性裂解。聚合性以3  <  1  <  2的顺序增加，这与密度泛函理论计算评估的环应变增加顺序非常一致。在某种程度上，后聚合反应表明了其活性特征，该反应涉及单体的两阶段进料和硫醇-烯末端偶联反应，以与PEG形成嵌段共聚物。此外，还发现聚合反应在没有硫醇引发剂的2,6-二甲基吡啶中发生并产生大环聚合物。阳离子聚合在CF ₃ SO ₃ H和苯甲醇的帮助下发生，但涉及低化学选择性环断裂的副反应。硫酯单元使聚合物表现出较低的T _g以及较高的热降解性和光降解性。