Raman spectroscopic investigation of the phase behavior and phase transitions in a poly(methyl methacrylate)‐carbon dioxide system

Abstract

Laser Raman spectroscopy, in conjunction with an optical high-pressure cell, was used to investigate the poly(methyl methacrylate)-carbon dioxide system. The Raman shifts associated with carbon dioxide molecules in the gas phase and those dissolved in the polymer were used to derive sorption kinetics of carbon dioxide and the carbon dioxide-induced phase changes in the polymer. Measurements were made in the temperature and pressure ranges in which this system is known to exhibit retrograde vitrification behavior. The Raman results on the sorption kinetics and on the onset of plasticization were in agreement with those obtained by gravimetric and calorimetric techniques, respectively. This technique provides a versatile and rapid way of characterizing polymer-gas systems and information that so far has been obtainable only through painstaking and time-consuming techniques.

Raman spectroscopic study of CO2 sorption process in poly methyl methacrylate

“…Sharp peaks appear at 1383.6 and 1279.7 cm −1 in the 30‐min spectrum, and it can be seen that the peak intensities increase with time. These peaks are assigned to CO 2 dissolved in PMMA 16. The vibrational energies of the peaks are almost constant during the CO 2 sorption.…”

“…Figure 2 shows the temporal variation of the Raman spectrum in the energy region around the CO 2 peaks at 4.5 MPa and 273 K. In the spectrum at 5 min, weak peaks are observed at 1391.6 and 1286.7 cm −1 . These peaks are assigned to CO 2 in the gas phase in contact with the PMMA sample 16. Sharp peaks appear at 1383.6 and 1279.7 cm −1 in the 30‐min spectrum, and it can be seen that the peak intensities increase with time.…”

“…Takahashi et al16 measured the Raman spectra of CO 2 dissolved in PMMA, and showed that the ratio of the peaks of the dissolved CO 2 and gaseous CO 2 can be used as a measure of the relative mass of CO 2 in PMMA. Using the same method, Yoon et al17 analyzed the diffusion process of CO 2 in a spherical PMMA sample, and showed that CO 2 diffusion in the rubbery sample is a non‐Fickian mechanism.…”

Poly <subscript L>-lactic acid (PLLA) and poly methyl methacrylate (PMMA) blends and their interaction with CO2 at sub-critical conditions

“…When the system is heated to 5°C under a constant gas pressure 3.4 MPa, a 30 rubber to glass transition occurs and therefore foams obtained will be very different in morphology. Moreover; on continued heating, a phase change from glassy to rubbery state will occurs [75].…”

“…In most polymer-gas systems the Tg-p relationship follows a linear path; 29 however, in certain polymer-gas systems with favorable interaction between molecules, a retrograde path was observed, and subsequently two transitions were detected under a constant gas pressure[49]. Diffusion coefficient of COz in PMMA at 25°C[49].The retrograde vitrification phenomenon in PMMA-CO2 was found by high pressure thermal analysis and predicted by a model that was based on lattice theory and the Gibbs-Di Marzio criterion[49,63,70,75]. Two glass transition temperatures (Tg) exist in the vicinity of the critical point of CO2 .…”