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基于改进的旋转异构态方法,推导了对称双取代基高分子链的均方回转半径和均方偶极矩公式,用于研究聚四氟乙烯(PTFE)、聚二甲基硅烷(PDMS)和聚乙烯(PE)链构象依赖的性质.计算得到长链聚四氟乙烯PTFE4(四态模型)和PDMS的构型参数值分别为0.44·mol0.5·g-0.5和0.43·mol0.5·g-0.5,PDMS链的相应温度系数值-7.32×10-3K-1,它与PTFE和PE的值(约-1.00×10-3K-1)相差较大.得到长链PTFE和PDMS的均方电偶极矩特征比结果都很小,如PDMS链的特征比为0.27,说明虽然PTFE和PDMS的侧基键C—F和Si—CH3都有强极性,但其聚合物却是非极性的电介质,具有较好的电绝缘性能,可见高分子链的构象和结构也对聚合物极性和电学性质有很大的影响.得到短链PTFE和PDMS(重复单元x<10)均方偶极矩表现出明显的端点效应,特征比随x的改变而呈现明显的波动,这与Flory等的计算结果一致.
Based on the improved method of rotational isomerization, the mean square radius of gyration and mean square dipole moment formula of symmetrical disubstituted polymer chains were deduced for the study of polytetrafluoroethylene (PTFE), polydimethylsilane (PDMS) And polyethylene (PE) chains. The calculated configuration parameters of long chain polytetrafluoroethylene PTFE4 (four-state model) and PDMS were 0.44 · mol0.5 · g-0.5 and 0.43 · mol0 .5 · g-0.5, the corresponding temperature coefficient of PDMS chain is -7.32 × 10-3K-1, which is quite different from the value of PTFE and PE (about -1.00 × 10-3K-1) The mean square dipole moment characteristic of PDMS is very small, for example, the characteristic ratio of PDMS chain is 0.27, which indicates that although both sidechain C-F and Si-CH3 of PTFE and PDMS have strong polarity, their polymers But it is a non-polar dielectric, has good electrical insulation properties, showing that the polymer chain conformation and structure also have a great influence on the polarity and electrical properties of the polymer. Short chain PTFE and PDMS (repeat unit x <10 ) The mean square dipole moment shows obvious endpoint effect, and the characteristic ratio shows obvious fluctuation with the change of x, which is consistent with the calculation result of Flory et al.