Solubility, diffusivity, and retrograde vitrification in PMMA-CO2, and development of sub-micron cellular structures

A magnetic suspension balance was used to measure solubility of CO2 in PMMA in the temperature range 0 to 167 degreesC and at pressures to 61.2 atm. C O2 dissolves to considerable extent in PMMA, reaching a value of about 30 w t% at 0 degreesC and 34 atm. Diffusion coefficients, derived from the sorpt ion kinetics, were analyzed to extract glass transition temperature of the PMMA-CO2 system over the pressure range of 0 to about 60 atm. The results c onfirm the existence of retrograde vitrification in this system previously observed by creep compliance and high-pressure thermal analysis techniques. A fundamental understanding of the polymer-gas interactions has led to the development of novel, sub-micron cellular structures.