Molecular Dynamics and Nuclear Magnetic Resonance Studies of Supercritical CO2 Sorption in Poly(Methyl Methacrylate)

Abstract

The study of supercritical carbon dioxide sorption processes is an important and urgent task in the field of “green” chemistry and for the selection of conditions for new polymer material formation. However, at the moment, the research of these processes is very limited, and it is necessary to select the methodology for each polymer material separately. In this paper, the principal possibility to study the powder sorption processes using 13C nuclear magnetic resonance spectroscopy, relaxation-relaxation correlation spectroscopy and molecular dynamic modeling methods will be demonstrated based on the example of polymethylmethacrylate and supercritical carbon dioxide. It was found that in the first nanoseconds and seconds during the sorption process, most of the carbon dioxide, about 75%, is sorbed into polymethylmethacrylate, while on the clock scale the remaining 25% is sorbed. The methodology presented in this paper makes it possible to select optimal conditions for technological processes associated with the production of new polymer materials based on supercritical fluids.

Exploring the Conformational Equilibrium of Mefenamic Acid Released from Silica Aerogels via NMR Analysis

“…By analyzing the obtained spectral NMR data, it was possible to identify the characteristic changes in the magnitude of the chemical shift of the observed NMR signal that was used to plot the kinetic curves of the original aerogel (see Figure 4 (blue)) and the one doped with mefenamic acid (see Figure 4 (red)). The kinetic curves were approximated using a single exponential model (Equation (1)), which was previously successfully used for the study of scCO 2 sorption onto poly(methyl methacrylate) (PMMA) [ 57 ]. where δ t is the value of the chemical shift of the CO 2 signal at time t , δ 0 is the value of the chemical shift at the saturation point, k is the kinetic rate constant, and δ is the multiplier corresponding to the difference between the value of the initial value δ t = 0 (at time t = 0) and δ 0 .…”

“…These data provide reliable evidence of the influence of a mefenamic acid small amount on the sorption characteristics of the aerogel composite material, so subsequent experiments were conducted based on the relaxation characteristics by T 1 –T 2 RRCOSY of the sorption process to estimate the relative amount of mefenamic acid in the aerogel pores. This technique was previously tested on PMMA and demonstrated to be an effective method for determining the sorption characteristics of highly porous materials in a scCO 2 medium [ 57 ].…”

“…One of the populations, which appears as a non-diagonal peak, is located within the parity line T 1 = T 2 , where data representing sites of free solvent scCO 2 may be found. According to the literature, the farther the population is from the parity line, the more limited the rotational mobility of molecules is [ 57 , 60 ]. The closer the sites are to the parity line, the freer the rotational mobility.…”

Assessing the Impact and Suitability of Dense Carbon Dioxide as a Green Solvent for the Treatment of PMMA of Historical Value

“…The sorption and swelling behavior of PMMA/CO 2 systems have been widely studied, mainly via in situ experiments (i.e., while the specimens are inside the CO 2 apparatus), exploring a wide range of temperature and pressure conditions, and through different analytical methods [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ].…”

Prediction of Drug-like Compounds Solubility in Supercritical Carbon Dioxide: A Comparative Study between Classical Density Functional Theory and Machine Learning Approaches

“…Supercritical carbon dioxide (scCO 2 ) has demonstrated significant efficacy in various fields including extraction of essential oil, − seed oil, − nanoparticle formation, − impregnation, − control of polymorphic forms, − polymer synthesis, etc.…”