Enthalpy and Dielectric Relaxation of Poly(vinyl methyl ether)

• Published in: Macromolecules 2018-08, Vol.51 (15), p.5806-5811
• Main Authors: Sasaki, Kaito, Takatsuka, Masanobu, Kita, Rio, Shinyashiki, Naoki, Yagihara, Shin
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.8b00780

This study investigates the cooperative molecular dynamics of poly­(vinyl methyl ether) (PVME) at temperatures above and below the glass transition temperature, T g, using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The DSC measurements of PVME aged at temperatures below T g revealed the aging-time-dependent enthalpy relaxation. The BDS measurements revealed the structural α-relaxation process that originated from segmental chain motion at temperatures above T g. Both the enthalpy and dielectric relaxation are described via a stretched exponential function, exp­(−(t/τ)βK ), and the relaxation time, τ, and the stretching index, βK, are obtained. τ and βK of the enthalpy relaxation obtained via DSC measurements are compatible with those of the structural α-relaxation obtained via BDS measurements. This similarity indicates that the molecular origin of the enthalpy relaxation is the same as that of the dielectric α-relaxation process of the polymer, i.e., its segmental chain motion.