A high pressure photon correlation study of bulk poly(methylacrylate). Comparison with relaxation processes in poly(ethylacrylate) and related polymethacrylates

Abstract

We report results of the photon correlation polarized light scattering study on the dynamics of bulk polymethylacrylate (PMA) in the temperature range of 7–76 °C and in the pressure range 1–2100 bar. A single relaxation process with a distribution of relaxation times represents the experimental photon correlation functions. The temperature and pressure dependence of the mean relaxation time are analyzed in terms of the VFT and WLF equations. The parameters obtained are discussed in terms of the rotational isomerization model and the free volume model. The results obtained in light scattering agree well with dielectric and mechanical relaxation data. In the case of polyethylmethacrylate (PEMA) and polybutylmethacrylate (PBMA), two overlapping relaxation modes are found. The values of the activation parameters and the relaxation time at the glass transition temperature (Tg) thus obtained characterizing the dynamics of a polymer melt above Tg are compared for PMA, PEA, PEMA, and PBMA.

Effect of pressure and temperature on chromophore reorientation in a side-chain nonlinear optical polymer

“…First, the activation volume increased with decreasing temperature. The increase of ⌬V* with decreasing temperature is consistent with previous dielectric relaxation studies of poly(methyl acrylate) 27 and polypropylene oxide 28 and the photon correlation studies of poly-(methyl acrylate) 29 and poly(ethyl acrylate). This is reasonable because the density of a polymer decreases with increasing temperature.…”

Effect of temperature and volume on structural relaxation time: Interpretation in terms of decrease of configurational entropy

“…In this work, by using the values of f P ðT Þ g T ðP atmÞ found from the analysis of relaxation time data, and the thermodynamic data from the literature, we calculated the values of dT g /dP| P=atm (Eq. (6)) and we compared with the experimental ones [30][31][32]. The predicted values are in good agreement with the experimental data ( Table 2).…”

“…(4) for the calculus of configurational entropy. In the first column are reported the experimental values obtained from (a) differential thermal analysis data [30], (b) photon correlation polarized light scattering measurements [32], (c) specific volume measurements [31]. In the second column the values calculated by Eq.…”

Thermodynamic interpretation of the scaling of the dynamics of supercooled liquids

“…Specific techniques for measuring relaxation of glass-forming liquids under high pressure include neutron scattering 8,9,10,11 , light scattering 12,13,14,15,16,17,18,19 , viscosity 20,21,22,23,24,25,26,27 and dielectric relaxation 28,29 . The latter has the advantage of providing a broad frequency range (routinely ten decades and even more at ambient pressure), which is essential since relaxation times vary by many orders of magnitude in the supercooled regime.…”