Rydberg and π-π* Transitions in Film Surfaces of Various Kinds of Nylons Studied by Attenuated Total Reflection-Far-Ultraviolet Spectroscopy and Quantum Chemical Calculations: Peak Shifts in the Spectra and Their Relation to Nylon Structure and Hydrogen B
Rydberg and π-π* Transitions in Film Surfaces of Various Kinds of Nylons Studied by Attenuated Total Reflection-Far-Ultraviolet Spectroscopy and Quantum Chemical Calculations: Peak Shifts in the Spectra and Their Relation to Nylon Structure and Hydrogen B
复制标题
通过衰减全反射-远紫外光谱和量子化学计算研究各种尼龙薄膜表面的里德伯和π-π*跃迁：光谱的峰移及其与尼龙结构和氢B的关系
DOI：
10.1021/jp5077005
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
Y. Ozaki
中科院分区：
文献类型：
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作者：
Y. Morisawa;M. Yasugana;H. Sato;R. Fukuda;M. Ehara;Y. Ozaki
测量了不同尼龙浇铸膜表面（厚度为50-200 nm）在145-260 nm范围内的衰减全反射远紫外（ATR-FUV）光谱，以探讨其在FUV区的电子跃迁。ATR-FUV光谱显示尼龙表面凝聚相在150和200 nm附近有两个主要吸收带。透射率（Tr）光谱也观察到特别是价激发的分析。用含时密度泛函理论（TD-DFT/CAM-B3 LYP）计算了模型体系的吸收光谱，并对几种尼龙的吸收峰进行了解析，特别是对它们的晶体取向结构和分子间氢键进行了研究.尼龙膜在150和200 nm附近的两个主要谱带分别是尼龙的σ-Rydberg 3 p和π-π* 跃迁。这些归属也与以前观察到的液体正构烷烃（n= 5-14）和液体酰胺的归属一致。Rydberg跃迁在烃链上是离域的，而π-π* 跃迁相对地局限于酰胺基团。在ATR-和Tr-FUV光谱中发现不同的尼龙的峰位置和强度的差异。α型尼龙6和尼龙6/6模型的FUV谱中π-π* 酰胺带的红移归因于晶体结构模式和分子间氢键的存在，导致π-π* 跃迁和跃迁偶极耦合的不同离域特征。
Attenuated total reflection far-ultraviolet (ATR-FUV) spectra in the 145–260 nm region were measured for surfaces (thickness 50–200 nm) of various kinds of nylons in cast films to explore their electronic transitions in the FUV region. ATR-FUV spectra show two major bands near 150 and 200 nm in the surface condensed phase of nylons. Transmittance (Tr) spectra were also observed in particular for the analysis of valence excitations. Time-dependent density functional theory (TD-DFT/CAM-B3LYP) calculations were carried out using the model systems to provide the definitive assignments of their absorption spectra and to elucidate their peak shifts in several nylons, in particular, focusing on their crystal alignment structures and intermolecular hydrogen bondings. Two major bands of nylon films near 150 and 200 nm are characterized as σ-Rydberg 3p and π–π* transitions of nylons, respectively. These assignments are also coherent with those of liquidn-alkanes (n= 5–14) and liquid amides observed previously. The Rydberg transitions are delocalized over the hydrocarbon chains, while the π–π* transitions are relatively localized at the amide group. Differences in the peak positions and intensity were found in both ATR- and Tr-FUV spectra for different nylons. A red-shift of the π–π* amide band in the FUV spectra of nylon-6 and nylon-6/6 models in α-form is attributed to the crystal structure pattern and the intermolecular hydrogen bondings, which result in the different delocalization character of the π–π* transitions and transition dipole coupling.