Enthalpy and Dielectric Relaxation of Poly(vinyl methyl ether)
2018
Sasaki, Kaito | Takatsuka, Masanobu | Kita, Rio | Shinyashiki, Naoki | Yagihara, Shin
This study investigates the cooperative molecular dynamics of poly(vinyl methyl ether) (PVME) at temperatures above and below the glass transition temperature, Tg, using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The DSC measurements of PVME aged at temperatures below Tg 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 Tg. 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.
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