The reaction locus in supercritical carbon dioxide dispersion polymerization. The case of poly(methyl methacrylate)

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.

RAFT dispersion polymerisation of methyl methacrylate is performed in scCO₂ with 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) present as chain transfer agent (CTA) and surprisingly shows good control over PMMA molecular weight.

Two-compartment kinetic Monte Carlo modelling of electrochemically mediated ATRP

Novel eATRP mechanistic insights are formulated, considering a two-compartment kinetic Monte Carlo model with catalyst concentration gradients accounted for.

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.

Copolymerization ofD,L-lactide and glycolide in supercritical carbon dioxide with zinc octoate as catalyst

The objective of the study is the development of a new technique based on supercritical technology for the production of bioabsorbable polymeric microparticles containing pharmaceutical principles, for their use in the controlled release of medicines. For this purpose, the ring-opening copolymerization of D,L-lactide and glycolide in supercritical carbon dioxide, using zinc(II) 2-ethylhexanoate (ZnOct2) as catalyst, was studied. The polymer obtained with ZnOct2 has similar characteristics to that obtained with stannous octoate (SnOct2), the conventional catalyst used up to now for this kind of polymerization process. Experiments were performed at various reaction times, pressures, and stirring rates. The most outstanding result was found by varying the stirring rate, where particles forming agglomerates seem to be obtained at the greater agitation levels.