Carbonatation of [ethylene-glycidyl methacrylate]-based copolymers with carbon dioxide as a reagent: from batch to solvent-free reactive extrusion

The carbonatation of semi-crystalline [ethylene-glycidyl methacrylate]-based polymers (Lotader & REG; grades) was achieved using carbon dioxide as a reagent and quaternary ammonium salts as organocatalysts to transform the polymers' epoxide pendant groups into cyclic carbonate moieties. A batch reactor allowed us to assess the kinetics, dependence on a catalyst and overall potential of this carbonatation. The influence of the ammonium salt composition (anion/cation) was studied in toluene at 110 & DEG;C to circumvent the high melting temperatures of these ethylene unit-rich copolymers and obtain a homogeneous medium. The amount of catalyst, CO2 pressure and temperature were also optimized (TBAB, 5 mol% vs. epoxy content, 4.0 MPa, 110 & DEG;C) to allow for quantitative conversion of epoxides into cyclic carbonates. Subsequently, the reaction was transposed, for the 1(st) time, to reactive extrusion under CO2 using a dedicated co-rotating twin-screw extruder to allow for CO2 containment within the polymer melt. This solvent-free reactive process is perfectly adapted to semi-crystalline and/or high-T-g polymers. After optimization, a yield of up to 78% of cyclic carbonate, in addition to orthogonal epoxide, could be obtained with THAB (7.5 mol% vs. epoxy content, & SIM;30 g h(-1) of cat.) at 150 & DEG;C with an industry-compliant polymer flow rate of 2 kg h(-1). The respective reactivities of Lotader & REG; grades were compared in batch and in an extruder, unveiling this trend towards carbonatation: AX8840 < AX8700 < AX8900. Sustainability and enhanced productivity of the carbonatation methodology developed herein relies on the use of CO2 as a C1 reagent for the functionalization of epoxide-bearing polymers harnessing a continuous and clean reactive extrusion process allowing, in a single operation and a few minutes, the production of functional polymers at the kilogram scale under solvent-free conditions.

Automated summary

Using carbon dioxide as a reagent and quaternary ammonium salts as organocatalysts, the carbonatation of semi-crystalline [ethylene-glycidyl methacrylate]-based polymers was achieved. The influence of ammonium salt composition and reaction conditions on the conversion of epoxides into cyclic carbonates was studied. The reaction was also transposed to reactive extrusion under CO2, leading to high yields of cyclic carbonate.