Quantitative analysis of stereoscopic molecular orientations in thermally reactive and heterogeneous noncrystalline thin films via variable-temperature infrared pMAIRS and GI-XRD
Quantitative analysis of stereoscopic molecular orientations in thermally reactive and heterogeneous noncrystalline thin films via variable-temperature infrared pMAIRS and GI-XRD
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通过变温红外 pMAIRS 和 GI-XRD 对热反应性和异质非晶薄膜中的立体分子取向进行定量分析
DOI：
10.1038/s41428-020-00458-8
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发表时间：
2021
期刊：
影响因子：
2.8
通讯作者：
Ando Shinji
中科院分区：
文献类型：
--
作者：
Ishige Ryohei;Tanaka Kazuyuki;Ando Shinji
具有非均相结构的半晶聚合物薄膜中立体分子取向的定量估计对于开发先进的薄膜材料至关重要。掠入射x射线衍射（GI-XRD）是一种用于评价晶格取向顺序的强大技术；然而，它只提供有序区域（晶体和玻璃状液晶区域）的取向顺序。相比之下，红外（IR）p偏振多角度入射分辨率光谱（pMAIRS）可以提供薄膜中整个区域的平均取向顺序，而不考虑样品的结晶度。本文结合变温（VT） pMAIRS、静态GI-XRD和光谱椭偏仪，通过对不同正烷基链长度的线性聚（氨基-烷基酯）PAE在热固化过程中溶剂蒸发和脱水亚酰化反应生成相应的聚酰亚胺（PI）的结构演变进行精确分析，揭示了聚合物薄膜中分子取向机理。该组合方法阐明了PAE和PI薄膜具有由玻璃状液晶（有序）区和非定向非晶态区组成的非均质结构。此外，亚甲基化在非晶区比在有序（取向）区进行得更快。虽然侧链长度对PI分子取向的影响不显著，但通过比较pMAIRS和椭偏光谱，发现了PI的折射率和双折射率的异常。这些异常表明，侧链的消除反应产生了各向同性的孔洞结构，并且孔洞的体积分数随着侧链长度的增加而增加。这些结果表明，ft - pmairs和GI-XRD的结合是一种非常强大的工具，用于分析非晶（无序晶体、玻璃液晶和取向非晶）薄膜材料在其组分中进行化学反应的原位结构，并且固有地适用于各种有趣的聚合物薄膜材料。
The quantitative estimation of stereoscopic molecular orientations in semicrystalline polymer thin films with characteristic heterogeneous structures is essential for the development of advanced film materials. Grazing-incidence X-ray diffraction (GI-XRD) is a powerful technique used to evaluate the orientational order of crystalline lattices; however, it provides the orientational order of only ordered regions (crystal and glassy liquid crystal regions). In contrast, infrared (IR)p-polarized multiple-angle incidence resolution spectrometry(pMAIRS) can provide the averaged orientational order of overall regions in a film regardless of sample crystallinity. This paper combines variable-temperature (VT) pMAIRS, static GI-XRD and spectroscopic ellipsometry and reports general insight into the molecular orientation mechanism occurring in polymer films revealed through the precise analysis of the structural evolution of linear poly(amicn-alkyl ester), PAE, with different lengths ofn-alkyl chains during thermal curing, which involves solvent evaporation and dehydration imidization reactions to form the corresponding polyimide (PI). This combined method clarified that the PAE and PI thin films had a heterogeneous structure consisting of a glassy liquid-crystalline (ordered) region and a nonoriented amorphous region. Furthermore, imidization proceeded faster in the amorphous region than in the ordered (oriented) region. In addition, anomalies of refractive index and birefringence were found by comparing pMAIRS and spectroscopic ellipsometry, although the effect of the side chain length on the molecular orientation of PI was insignificant. The anomalies indicate that an isotropic void structures were generated by the elimination reaction of the side chains and that the volume fraction of voids increased with increasing side chain length. These results demonstrated that the combination of VT-pMAIRS and GI-XRD is a very powerful tool for the in situ structural analyses of noncrystalline (disordered crystal, glassy liquid crystal, and oriented amorphous) thin-film materials ongoing chemical reactions in their components and is inherently applicable to all kinds of interesting polymeric thin-film materials.
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