The alternating copolymer of lactic acid and glycolic acid (PLGA) is a highly promising next generation biodegradable material for biomedical and pharmaceutical applications due to its uniform degradation behaviors in addition to its ability to form stereocomplexes. However, versatile synthetic methods toward the narrowly dispersed alternating PLGAs with controlled molecular weights and desired end functionalities have been largely unexplored. Herein, we report the organocatalytic regioselective ring-opening polymerization (ROP) of optically active methylglycolides (L- and D-MGs) to produce highly alternating PLGAs. The ROP of L-MG using a phosphazene base P₂-t-Bu/alcohol system in THF at −78 °C achieved the highest regioselectivity (P = 0.95) as well as a good control over the molecular weight (M_n = 6.6–15.6 g mol⁻¹), with a relatively narrow dispersity (Đ = 1.21–1.29). Furthermore, alternating PLGA diol as well as azido-, ethynyl-, and poly(ethylene glycol) monomethyl ether-end-functionalized alternating PLGAs was successfully obtained by employing the corresponding functional alcohol initiators. An enantiomeric 1 : 1 blend of PLGAs prepared from L- and D-MGs formed a stereocomplex with a crystallinity and melting point comparable to the reported data for the stereocomplex from the perfectly alternating PLGAs produced via a polycondensation approach, which implies the high degree of the alternating sequence of the obtained copolymers.

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乳酸和乙醇酸高度交替共聚物的有机催化开环聚合方法

乳酸和乙醇酸的交替共聚物（PLGA）由于其均一的降解行为以及形成立体复合物的能力，因此是用于生物医学和制药应用的极有前景的下一代可生物降解材料。然而，尚未广泛开发针对具有受控分子量和所需末端官能团的窄分散交替PLGA的通用合成方法。本文中，我们报道了光学活性甲基乙交酯（L-和D -MGs）的有机催化区域选择性开环聚合（ROP），以产生高度交替的PLGA。使用磷腈碱P ₂ - t的L -MG的ROP-Bu /醇体系在-78°C下的THF中具有最高的区域选择性（P = 0.95），并且可以很好地控制分子量（M _n = 6.6–15.6 g mol ^-1），分散度相对较窄（Đ = 1.21-1.29）。此外，通过使用相应的官能醇引发剂，成功获得了交替的PLGA二醇以及叠氮基，乙炔基和聚乙二醇单甲醚末端官能化的交替PLGA。由L-和D- MG制备的PLGA的对映异构体1：1混合物形成了立体络合物，其结晶度和熔点与报道的完全交替的PLGA立体络合物的报道数据相当通过缩聚方法，这意味着获得的共聚物的高度交替顺序。