聚甲基丙烯酸甲酯伽马弛豫的复介电常数的理论评估，量子化学和线性响应理论研究

IF 4.3 3区化学 Q2 CHEMISTRY, MULTIDISCIPLINARY

ACS Omega Pub Date : 2024-11-06 DOI:10.1021/acsomega.4c0710010.1021/acsomega.4c07100

Shin’ichiro Okude*, Junwei Shen and Shinichiro Nakamura*,

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引用次数: 0

摘要

人们普遍认为，聚甲基丙烯酸甲酯（PMMA）的γ弛豫是由连接主链的侧链围绕 C-C 键的受阻旋转运动引起的。然而，解释这一过程的物理模型一直不为人知。混合密度泛函理论计算表明，PMMA 分子内受阻旋转的活化能为 6.53 kcal/mol。该活化能导致了分子内阻碍旋转的摩擦系数。根据线性响应理论，利用计算出的活化能值评估了摩擦系数的定性值。采用洛伦兹模型，利用摩擦系数的计算值来计算 γ 松弛的复介电常数。复介电常数的计算值与实验结果相当吻合。

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Theoretical Evaluation of Complex Dielectric Constant for Gamma Relaxation of Poly(methyl methacrylate), A Study of Quantum Chemistry and Linear Response Theory

It is widely accepted that the γ relaxation of poly(methyl methacrylate) (PMMA) arises from the hindered rotational motion of the side chain around the C–C bond, which links to the main chain. However, the physical model to explain this process has been unknown. The hybrid density functional theory calculation showed that the PMMA intramolecular hindered rotation has an activation energy of 6.53 kcal/mol. This activation energy causes the friction coefficient to the intramolecule to hinder rotation. The qualitative value of the friction coefficient was evaluated on the basis of linear response theory by using the calculated value of the activation energy. The Lorentz model is adopted to calculate the complex dielectric constant of the γ relaxation using the calculated value of the friction coefficient. The calculated value of the complex dielectric constant agreed reasonably well with experimental results.

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来源期刊

ACS Omega Chemical Engineering-General Chemical Engineering

CiteScore

6.60

自引率

4.90%

发文量

3945

审稿时长

2.4 months

期刊介绍： ACS Omega is an open-access global publication for scientific articles that describe new findings in chemistry and interfacing areas of science, without any perceived evaluation of immediate impact.