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Effects of stereo-regularity on the single-chain mechanics of polylactic acid and its implications on the physical properties of bulk materials
Nanoscale ( IF 6.7 ) Pub Date : 2017-09-08 00:00:00 , DOI: 10.1039/c7nr06483g
Bo Cheng 1, 2, 3, 4, 5 , Lu Qian 1, 2, 3, 4, 5 , Hu-jun Qian 6, 7, 8, 9, 10 , Zhong-yuan Lu 6, 7, 8, 9, 10 , Shuxun Cui 1, 2, 3, 4, 5
Affiliation  

The material properties of polylactic acid (PLA) are largely determined by its stereo-regularity (tacticity). To find out the origin at the molecular level, the single-chain mechanics of poly-L-lactic acid (PLLA) and poly-D,L-lactide (PDLLA) were comparatively investigated by single-molecule atomic force microscopy (AFM). At a low concentration, PLLA adopted a random-coil conformation in a good solvent. At a high concentration, however, the PLLA chain can be induced into a helix, which consumed additional energy during unfolding by further stretching. Due to the random arrangement of L- and D-repeating units in the PDLLA chain, PDLLA adopts a random-coil conformation at all concentrations. The difference in single-chain mechanics of PLLA and PDLLA at high concentrations may be the cause of their different macroscopic properties. This is the first report to reveal the stereo-regularity-dependent mechanics of a polymer at the single-molecule level, which may help to bridge the gap between understanding single-molecule and materials properties.

中文翻译:

立构规整度对聚乳酸单链力学的影响及其对散装材料物理性质的影响

聚乳酸(PLA)的材料特性很大程度上取决于其立构规整度(立构规整度)。为了在分子水平上找到起源,通过单分子原子力显微镜(AFM)对聚-L-乳酸(PLLA)和聚-DL-丙交酯(PDLLA)的单链机理进行了比较研究。在低浓度下,PLLA在良好溶剂中采用无规卷曲构象。但是,在高浓度下,PLLA链可被诱导成螺旋状,在展开过程中通过进一步拉伸消耗了额外的能量。由于L-D的随机排列作为PDLLA链中的重复单元,PDLLA在所有浓度下均采用随机螺旋构象。高浓度下PLLA和PDLLA的单链力学差异可能是其宏观特性不同的原因。这是第一份揭示聚合物在单分子水平上依赖立体规则性的机理的报告,这可能有助于弥合了解单分子和材料特性之间的鸿沟。
更新日期:2017-09-22
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