Infrared spectroscopic study of CH3•••O=C interaction during poly(L-lactide)/poly(D-lactide) stereocomplex formation
Infrared spectroscopic study of CH3•••O=C interaction during poly(L-lactide)/poly(D-lactide) stereocomplex formation
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DOI：
10.1021/ma047872w
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发表时间：
2005-03-08
期刊：
影响因子：
5.5
通讯作者：
Ozaki, Y
中科院分区：
文献类型：
--
作者：
Zhang, JM;Sato, H;Ozaki, Y
利用实时红外光谱研究了聚l -丙交酯（PLLA）和聚d -丙交酯（PDLA）链在PLLA/PDLA立体配合物等温熔融结晶过程中的“特强”相互作用性质。观察到v(as)（CH3）的低频位移很小（约1 cm(-1)）， v（C=O）的低频位移较大（约5 cm(-1)）。在二维（2D）异步相关谱和二阶导数谱中，典型的蝴蝶图案表明，在v（C=0）处存在“峰移”。甲基和羰基拉伸振动模式的红移表明，PLLA/PDLA立体配合物之间的相互作用归因于(ch30)- o -…=C氢键。另一个有趣的结果是，v（C=O）波段的峰移已经发生在诱导期，这表明(ch30)-O-…=C相互作用是形成PLLA/PDLA立体配合物外消旋成核的驱动力。二维相关分析表明，在PLLA/PDLA立体配位过程中，CH3基团的结构调整发生在C-O-C主链的结构调整之前。(CH3O) - o -…=C相互作用可能是这一系列结构变化的原因。
The nature of the "peculiarly strong" interaction between the poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains was investigated by real time infrared spectroscopy during the isothermal melt crystallization process of the PLLA/PDLA stereocomplex. A very small low-frequency shift (about 1 cm(-1)) of v(as)(CH3) and a larger low-frequency shift (about 5 cm(-1)) of v(C=O) were observed. The typical butterfly pattern in the two-dimensional (2D) asynchronous correlation spectrum and the second-derivative spectra reveal that there is a "peak shift" for v(C=0). The red shifts of the stretching vibration modes of the methyl and carbonyl groups suggest that the interaction between the PLLA/PDLA stereocomplex is ascribed to (CH3O)-O-...=C hydrogen bonding. Another interesting result is that the peak shift of the v(C=O) band already occurs in the induction period, which indicates that the (CH3O)-O-...=C interaction is the driving force for forming the racemic nucleation of the PLLA/PDLA stereocomplex. Moreover, the 2D correlation analysis indicates that the structural adjustment of the CH3 group occurs prior to that of the C-O-C backbone during the stereocomplexation process of PLLA/PDLA. The (CH3O)-O-...=C interaction may be the reason for this sequence of structural changes.