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

Shin'ichiro Okude; Junwei Shen; Shinichiro Nakamura

doi:10.1021/acsomega.4c07100

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

ACS Omega. 2024 Nov 6;9(46):46263-46269. doi: 10.1021/acsomega.4c07100. eCollection 2024 Nov 19.

Authors

Shin'ichiro Okude¹, Junwei Shen², Shinichiro Nakamura²

Affiliations

¹ School of Business Administration Meiji University (Dual enrollment in the faculties of School of Business Administration, School of Agriculture, and School of Science And Technology)1-1 Kanda Surugadai 1-chome, Chiyoda-ku, Tokyo 101-8301, Japan.
² Priority Organization for Innovation and Excellence, Laboratory for Data Science, Kumamoto University, Kumamoto860-8555, Japan.

Abstract

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.