A Comparison of Modeling Approaches for Dispersion Homopolymerization of MMA and Styrene in Supercritical CO2

Influence of structure and solubility of chain transfer agents on the RAFT control of dispersion polymerisation in scCO2

Reversible addition-fragmentation chain transfer (RAFT) dispersion polymerisation of methyl methacrylate (MMA) is performed in supercritical carbon dioxide (scCO2) with 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) present as chain transfer agent (CTA) and surprisingly shows good control over PMMA molecular weight. Kinetic studies of the polymerisation in scCO2 also confirm these data. By contrast, only poor control of MMA polymerisation is obtained in toluene solution, as would be expected for this CTA which is better suited for acrylates. In this regard, we select a range of CTAs and use them to determine the parameters that must be considered for good control in dispersion polymerisation in scCO2. A thorough investigation of the nucleation stage during the dispersion polymerisation reveals an unexpected "in situ two-stage" mechanism that strongly determines how the CTA works. Finally, using a novel computational solvation model, we identify a correlation between polymerisation control and degree of solubility of the CTAs. All of this ultimately gives rise to a simple, elegant and counterintuitive guideline to select the best CTA for RAFT dispersion polymerisation in scCO2.

Modeling of RAFT polymerization of MMA in supercritical carbon dioxide using the PC-SAFT equation of state

The PC-SAFT equation of state was applied to the study of RAFT polymerization of methyl methacrylate in supercritical CO₂.

RAFT Copolymerization of Styrene/Divinylbenzene in Supercritical Carbon Dioxide

An experimental study on the kinetics of the reversible addition–fragmentation chain transfer (RAFT) dispersion copolymerization with crosslinking of styrene and divinylbenzene in supercritical carbon dioxide (scCO2) is presented. This is the first time that such a controlled polymer network synthesis is carried out in scCO2. S-Thiobenzoyl thioglycolic acid (TBTGA) and dibenzoyl peroxide were used as RAFT agent and initiator, respectively. The polymerizations were carried out in a high pressure cell with lateral sapphire windows at 80°C. The effect of RAFT agent concentration, including the case without RAFT controller, on polymerization rate, molecular weight development, gel fraction, swelling index, and particle morphology was analysed.