Argon sorption and partial molar volume in poly(ethyl methacrylate) above and below the glass transition temperature

Abstract

SYNOPSISSorption and dilation isotherms for argon in poly(ethy1 methacrylate) (PEMA) are reported for pressures up to 50 atm over the temperature range 5 4 5°C . At temperatures below the glass transition ( Tg = 61°C ) , sorption isotherms are well described by the dual-mode sorption model; and isotherms above Tg follow Henry's law. However, isotherms for dilation due to

Sorption of light gases in glassy poly(ethyl methacrylate)

“…The density of the obtained films corresponds to the reference value (1.12 g/cm 3 at 298 K) . The measured glass transition temperature of the films (337 ±1 K at heating/cooling rate of 1 K/min) and the coefficients of thermal expansion above and below T g [ K – and K – , respectively] are in agreement with literature data for PEMA …”

“…At a high gas concentration, the T g value can become lower than the temperature at which the polymer is saturated with gas and the glassy polymer will convert into a rubbery substance . However, the matrix of PEMA saturated with the gases used in the present work remains in the glassy state even at a dissolved gas concentration of cm – . The sorption of these gases causes only an elastic deformation of a glass structure.…”

“…33 The measured glass transition temperature of the films (337 61 K at heating/ cooling rate of 1 K/min) and the coefficients of thermal expansion above and below T g [ð5:960:1Þ310 24 K -1 and ð3:360:1Þ310 24 K -1 , respectively] are in agreement with literature data for PEMA. 15,34 In the temperature range from 160 to 330 K, the diffusion coefficients of the used gases vary by as much as four orders of magnitude (see the section "Activation energy of gas diffusion"). Therefore, at different temperatures, the films of various thicknesses (from 8 to 425 lm) were used.…”

“…When temperature is more than ∼15 °C below the glass transition temperature, the macromolecules packing of glassy polymers does not vary with temperature on the experimental time scale . The sorption of simple gases such as N 2 , Ar, O 2 , or CH 4 causes only a reversible increase in the volume of polymer glasses even at a gas concentration of 25 cm 3 (STP)/cm 3 (polymer) . This increase is due to the elastic (reversible) deformation of polymer matrix.…”

“…14 The sorption of simple gases such as N 2 , Ar, O 2 , or CH 4 causes only a reversible increase in the volume of polymer glasses even at a gas concentration of 25 cm 3 (STP)/cm 3 (polymer). [15][16][17] This increase is due to the elastic (reversible) deformation of polymer matrix. Therefore, the concentration of sorption sites does not depend on temperature and gas concentration in the polymer.…”