Dispersion Polymerization of Methyl Methacrylate in Supercritical Carbon Dioxide:  An Investigation into Stabilizer Anchor Group

Abstract

New stabilizers for the dispersion polymerization of methyl methacrylate (MMA) in supercritical carbon dioxide (scCO2) were prepared and studied in terms of their anchor group architecture. The same perfluoropolyether (PFPE) chain was used in each case as the CO2-philic portion of the stabilizer and four different PMMA-philic headgroups were investigated as anchoring units: an alcohol, an acetate group, a methacrylate unit, and a PMMA block. When compared to the stabilizing ability of PFPE−alcohol, incorporation of an anchor group as small as an acetate group, or a reactive group such as a methacrylate unit, was found to have a dramatic effect upon the dispersion polymerization of MMA in scCO2. Their incorporation led to a significant increase in PMMA yield and molecular weight and an improvement of the morphology of the polymer product. A method for the synthesis of PFPE-b-PMMA diblock copolymers is reported via atom transfer radical polymerization (ATRP) from a PFPE−bromoester macroinitiator in a fluorinated solvent (pentafluorobutane). This method allows the controlled synthesis of PFPE-b-PMMA diblock copolymers with well-defined architecture. These copolymers were found to be effective stabilizers in scCO2, leading to excellent PMMA yield with high molecular weight and a fine morphology. The effect of PFPE and PMMA block length on the copolymer stabilizing ability was also studied to probe the influence of the stabilizer anchor-soluble balance (ASB). In addition, the phase behavior of each stabilizer in CO2 or a mixture of CO2/MMA was studied to elucidate the effect of stabilizer structure on CO2-philicity and stabilizing ability.

GMA-functionalized reactive stabilizer for polymerization of methyl methacrylate in supercritical CO2: effect of stabilizer, initiator and monomer concentrations

“…[7][8][9][10]13,16,20 The particle size of PMMA synthesized using GMA-PDMS stabilizer was similar with the size of PMMA prepared with fluoro and fluoro copolymer stabilizer, which had a range of 2-5 µm. 8,12,13,15,16 Effect of Initiator Concentration. Figure 5(A) and 5(B), prepared with the data in Table II (Run No 4, 6~8), show the effect of AIBN concentration on the yield and molecular weight of the PMMA product.…”

“…9,10 Block copolymers containing CO 2 -philic fluoro groups were also used to stabilize the dispersion polymerization of MMA. 11,12 Howdle et al used acid-terminated perfluoropolyether (Krytox 157FSL, DuPont) as a stabilizer for PMMA polymerization. 13,14 They also demonstrated PMMA polymerization using the stabilizer grafted with fluorinated groups and containing carboxylic groups.…”

Polymerization of methyl methacrylate in carbon dioxide using glycidyl methacrylate linked reactive stabilizer: Effect of pressure, reaction time, and mixing

“…One part contains CO 2 -philic fluoro or silicone repeat units in the backbone or pending structures, whereas the other part has compatible components to growing polymers. [10][11][12][13] Some researches used cosolvents with surfactants to enhance the stability of the dispersion polymerization in CO 2 . 14, 15 Using a reactive surfactant is another approach for the polymerization of vinyl monomers in supercritical CO 2 .…”

Mild synthesis of poly(HEMA)-networks as well-defined nanoparticles in supercritical carbon dioxide

“…13,16,[18][19][20][21][22][23][24][25] These polymers present unique physico-chemical properties due to their low surface energy, high thermal and chemical stability. 36,37 As well as their relatively high solubility in scCO2 these polymers have found applications in the dispersion polymerisation of many vinyl monomers such as methacrylate derivatives 13,16,[38][39][40][41][42] (MMA, HEMA, or others methacrylate esters), acrylonitrile 20,43 , N-vinylpyrrolidone 25,44 , styrene 22 resulting into well-defined spherical particles.…”