Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan.
Biomacromolecules. 2011 Sep 12;12(9):3299-304. doi: 10.1021/bm200775r. Epub 2011 Aug 4.
Photolysis of poly(L-lactic acid) (PLLA) has many unclear points, such as the degradation mechanism, kinetics, products, and racemization mechanism. To clarify these features of PLLA photolysis, we examined the relationship between photolysis and racemization. The hexad stereosequential analysis of photodegraded PLLA was investigated to specify the racemized positions within a chain in comparison with hydrolysis and thermal degradation. Results from (13)C NMR spectra of UV-irradiated PLLA samples indicated that the samples have racemized d-lactate units at chain ends. From the comparison of racemization behavior among photolysis, hydrolysis, and thermal degradation, it was confirmed that the preferential racemization behavior of each of these three degradation processes is characteristic and distinct, being identified as chain-end racemization, poor racemization, or internal-unit racemization, respectively. The characteristic chain-end racemization behavior of photolysis was first confirmed in this study.
聚 L-乳酸（PLLA）的光解存在许多不清楚的地方，例如降解机制、动力学、产物和外消旋化机制。为了阐明 PLLA 光解的这些特征，我们研究了光解与外消旋化之间的关系。通过对光降解 PLLA 的六元立体序列分析，与水解和热降解进行比较，确定了链内消旋化位置。UV 辐照 PLLA 样品的 (13)C NMR 谱结果表明，样品在链端具有消旋的 d-乳酸单元。通过对光解、水解和热降解中外消旋化行为的比较，可以确认这三种降解过程各自的优先外消旋化行为是特征性和独特的，分别为链端外消旋化、差外消旋化或内部单元外消旋化。本研究首次证实了光解的特征性链端外消旋化行为。
