Determination of Polylactide Microstructure by Homonuclear Decoupled 1H NMR Spectroscopy,The Chemical Record

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Determination of Polylactide Microstructure by Homonuclear Decoupled 1H NMR Spectroscopy
The Chemical Record ( IF 7.0 ) Pub Date : 2021-07-29 , DOI: 10.1002/tcr.202100073
Sourav Singha Roy ₁ , Sriparna Sarkar ₁ , Debashis Chakraborty ₁

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The ring-opening polymerization (ROP) of lactide (the dilactone of lactic acid) produces poly(lactide) commonly referred to as poly(lactic acid) (PLA). The monomer lactide, has two stereogenic centers and thus, three stereoisomers are possible, namely: D-(R,R), L-(S,S) and meso-lactide. The rac-lactide is an equimolar mixture of D- and L-enantiomers. Depending upon the relative configuration of the stereogenic centers in the polymeric chain, different tacticities (isotactic, syndiotactic, heterotactic and atactic) arise in the PLA chains. The study of the tacticity of a polymer is fundamental since it plays a crucial role in determining the physical properties of the polymer. NMR spectroscopy is a powerful analytical technique for the determination of the tacticity of PLA. This article describes in details the tacticity assignment for PLA derived from ROP of rac-lactide and meso-lactide, using homonuclear proton-decoupled ¹H NMR. The detailed tetrad level assignment pertinent to the methine hydrogen signal is the key for the determination of tacticity.

中文翻译：

同核去耦 1H NMR 光谱法测定聚丙交酯微结构

丙交酯（乳酸的双内酯）的开环聚合（ROP）产生聚（丙交酯），通常称为聚（乳酸）（PLA）。单体丙交酯具有两个立体中心，因此可能存在三种立体异构体，即：D -( R,R )、L -( S,S ) 和内消旋丙交酯。外消旋丙交酯是D - 和L的等摩尔混合物- 对映异构体。根据聚合物链中立体中心的相对构型，PLA 链中出现不同的立构规整度（全同立构、间同立构、异同立构和无规立构）。聚合物立构规整度的研究是基础，因为它在决定聚合物的物理性能方面起着至关重要的作用。核磁共振波谱是测定 PLA 立构规整度的强大分析技术。本文使用同核质子解耦¹ H NMR详细描述了源自外消旋丙交酯和内消旋丙交酯的ROP 的 PLA 的立构规整分配。与次甲基氢信号相关的详细四分体水平分配是确定规整度的关键。

更新日期：2021-08-16

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