Real-time imaging of crystallization in polylactide enantiomeric monolayers at the air-water interface.
Real-time imaging of crystallization in polylactide enantiomeric monolayers at the air-water interface.
复制标题
空气-水界面聚丙交酯对映体单层结晶的实时成像。
DOI：
10.1021/la801747k
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Chase,DBruce
中科院分区：
文献类型：
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作者：
Kim,YoungShin;Snively,ChristopherM;Liu,Yujuan;Rabolt,JohnF;Chase,DBruce
新开发的平面阵列红外反射吸收光谱仪（PA-IRRAS）与传统方法相比具有显着优势，包括快速采集速度、出色的水蒸气补偿以及对大型红外配件（例如水槽）的出色容量。在本研究中，使用 PA-IRRAS 研究了空气-水界面处聚丙交酯对映体单层立体络合的起源。 PA-IRRAS 被用作探针来跟踪单层压缩过程中与聚合物链分子间相互作用相关的实时构象变化。研究发现，在薄膜压缩之前，当二维单层在空气-水界面上形成时，聚(d-乳酸)(PDLA)和聚(l-乳酸)(PLLA)(D/L)的混合物形成立体络合物，这表明薄膜压缩和立体络合物之间没有直接相关性。与单独 PLLA 的光谱相比，立体络合物的 PA-IRRAS 光谱在晶体敏感组分（例如 thevas(C−O−C, h) 模式）以及非晶相关组分（例如 thevs(C−O−C) 模式）中表现出明显的带移。另一方面，在压缩薄膜时获得的时间分辨 PA-IRRAS 光谱表明，单层 PLLA 和混合 PLLA/PDLA 立体复合物分别结晶成 103 螺旋和 31 螺旋，仅在晶体敏感组分中具有明显的带移。光谱的傅里叶自解卷积表明，晶体敏感成分的能带移动与聚合物链的分子间相互作用相关。
A newly developed planar array infrared reflection−absorption spectrograph (PA-IRRAS) offers significant advantages over conventional approaches including fast acquisition speed, excellent compensation for water vapor, and an excellent capacity for large infrared accessories, e.g., a water trough. In this study, the origin of stereocomplexation in a polylactide enantiomeric monolayer at the air−water interface was investigated using PA-IRRAS. PA-IRRAS was used as a probe to follow the real-time conformational changes associated with intermolecular interactions of polymer chains during the compression of the monolayers. It was found that a mixture of poly(d-lactic acid) (PDLA) and poly(l-lactic acid) (PLLA) (D/L) formed a stereocomplex when the two-dimensional monolayer developed at the air−water interface before film compression, indicating that there is no direct correlation between film compression and stereocomplexation. PA-IRRAS spectra of the stereocomplex exhibited distinct band shifts in crystalline sensitive components, e.g., thevas(C−O−C, h) mode, as well as amorphous-dependent components, e.g., thevs(C−O−C) mode, when compared with the spectra of PLLA alone. On the other hand, time-resolved PA-IRRAS spectra, which were obtained as the films were being compressed, revealed that both monolayers of PLLA and mixed PLLA/PDLA stereocomplex were crystallized into a 103-helix and a 31-helix, respectively, with a distinct band shift in crystalline sensitive components only. Fourier self-deconvolution of the spectra demonstrated that the band shift in crystalline sensitive components is correlated with the intermolecular interaction of polymer chains.