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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Low-Frequency Vibrational Motions of Polystyrene in Carbon Tetrachloride: Comparison with Model Monomer and Dependence on Concentration and Molecular Weight
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Low-Frequency Vibrational Motions of Polystyrene in Carbon Tetrachloride: Comparison with Model Monomer and Dependence on Concentration and Molecular Weight

机译：四氯化物中聚苯乙烯的低频振动运动：与模型单体的比较和依赖性和分子量的依赖性

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In this study, the low-frequency vibrational dynamics of polystyrene (PS) in CCl4 was investigated by femtosecond Raman-induced Kerr effect spectroscopy. Ethylbenzene (EBz) was also investigated as a model monomer of the polymer to elucidate the unique dynamical features of PS in solution. The broadened low-frequency spectrum of the PS/CCl4 in the frequency region below 150 cm(-1) is significantly different from that of the EBz/CCl4. Difference spectra between the PS or EBz solutions and neat CCl4, normalized to an internal vibrational mode of CCl4, clearly show a much lower spectral intensity for the PS/CCl4 than the EBz/CCl4 in the low-frequency region below ca. 20 cm(-1). This indicates that translational motions are suppressed in the PS/CCl4 compared to the EBz/CCl4. Moreover, the high-frequency motion at ca. 70 cm(-1), mainly due to phenyl ring librations, occurs at higher frequency in PS (78 cm(-1)) than EBz (65 cm(-1)). In addition, the results of concentration-dependent experiments show that the first moment (M-1) of the low-frequency difference spectra of both PS/CCl4 and EBz/CCl4 is almost independent of the concentration. The molecular weight dependence of the low-frequency spectrum in the PS/CCl4 shows that the M-1 value of the low-frequency spectral band of PS shifts to higher frequencies when the molecular weight of PS increases up to M-w = similar to 1000, which corresponds approximately to the decamer, and then remains constant upon further increasing the molecular weight.
机译：在这项研究中，在CCl 4聚苯乙烯的低频率振动动力学（PS）通过飞秒拉曼诱导克尔效应光谱研究。乙苯（EBZ）也进行了研究作为聚合物的模型单体，以阐明在溶液中的PS的独特动力学特征。在低于150厘米（-1）的频率区域中的PS / CCl 4中的加宽的低频频谱是从该EBZ / CCl 4中的显著不同。的PS或EBZ溶液和整齐四氯化碳，标准化为CCl 4中的内部振动模式之间的差异光谱，清楚地显示在下面的约低频区域的PS /四氯化碳比EBZ /四氯化碳低得多的光谱强度20厘米（-1）。这表明，平移运动是在PS /四氯化碳抑制相比EBZ /四氯化碳。此外，在约高频运动70厘米（-1），这主要是由于苯环librations，发生在PS更高的频率（78厘米（-1））比EBZ（65厘米（-1））。此外，依赖于浓度的实验的结果表明，无论是PS /四氯化碳和EBZ / CCl 4中的低频差光谱的一阶矩（M-1）几乎不依赖于浓度的。在PS /四氯化碳示出了低频频谱的分子量依赖性的是PS移位到更高频率的低频频谱频带的M-1值时PS的分子量增加至MW =类似于1000，这大致对应于十聚体，然后保持在进一步提高分子量恒定。

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