Theoretical simulation of the infrared signature of mechanically stressed polymer solids.
Theoretical simulation of the infrared signature of mechanically stressed polymer solids.
复制标题
机械应力聚合物固体的红外特征的理论模拟。
DOI：
10.3762/bjoc.13.165
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发表时间：
2017
影响因子：
2.7
通讯作者：
Beyer MK
中科院分区：
文献类型：
--
作者：
Sammon MS;Ončák M;Beyer MK
机械应力导致聚合物固体中链的变形，包括共价键的伸长和键角的加宽，这改变了红外光谱。在这里，固体聚合物样品暴露于机械应力的红外光谱模拟密度泛函理论计算。机械应力用明确包含外力（EFEI）方法描述。单个聚合物股线上的外部应力的不均匀分布由模拟光谱与现实力分布的卷积来解释。分别选择N-丙基丙酰胺和丙酸丙酯作为聚酰胺和聚酯的模型分子。特定力对聚合物主链的影响是涉及主链中的C-N和C-O键的振动模式的红移，而垂直于主链的自由C-O伸缩模式在很大程度上不受影响。卷积与一个现实的力分布表明，最强的红外波段上的主导作用是不是峰位置的位移，而是峰加宽和最强的带，这可能有助于在聚合物固体的机械应力的识别和量化的相对强度的特征变化。
Mechanical stress leads to deformation of strands in polymer solids, including elongation of covalent bonds and widening of bond angles, which changes the infrared spectrum. Here, the infrared spectrum of solid polymer samples exposed to mechanical stress is simulated by density functional theory calculations. Mechanical stress is described with the external force explicitly included (EFEI) method. The uneven distribution of the external stress on individual polymer strands is accounted for by a convolution of simulated spectra with a realistic force distribution. N-Propylpropanamide and propyl propanoate are chosen as model molecules for polyamide and polyester, respectively. The effect of a specific force on the polymer backbone is a redshift of vibrational modes involving the C–N and C–O bonds in the backbone, while the free C–O stretching mode perpendicular to the backbone is largely unaffected. The convolution with a realistic force distribution shows that the dominant effect on the strongest infrared bands is not a shift of the peak position, but rather peak broadening and a characteristic change in the relative intensities of the strongest bands, which may serve for the identification and quantification of mechanical stress in polymer solids.
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