New approach for synthesis of poly(ethylglyoxylate) using Maghnite-H + , an Algerian proton exchanged montmorillonite clay, as an eco-catalyst
Résumé
In this works, we have explored a new method for a green synthesis of poly(ethylglyoxylate) (PEtG). This method consists on using a montmorillonite clay called Maghnite-H+ as an eco-catalyst to replace triethylamine which is toxic. Cationic polymerization experiments are performed in bulk conditions at three temperatures (-40 degrees C, 25 degrees C, 80 degrees C) and in THF solutions at room temperature (25 degrees C). At 25 degrees C, an optimum ratio of 5 wt% of catalyst leads to molar masses up to 22000 g/mol in THF solutions. Polymerizations in bulk conditions lead to slightly lower masses than experiments conducted in THF solutions. However, bulk polymerization of ethyleglyoxylate remains a preferable method in order to avoid the use of a solvent and therefore to stay in the context of green chemistry. The structure of obtained polymers are characterized and confirmed by H-1 and C-13 NMR. Thermogravimetric Analysis (TGA) shows an enhanced thermal stability for end-capped PEtG compared to non-terminated PEtG. The best conversion rate (92%) is observed in bulk conditions at 25 degrees C for a reaction time of 48h. An activation energy could be calculated from bulk experiments (Ea = 6.9kJ/mol). An interesting advantage of Maghnite-H+ is an easy recoverage by a simple filtration from the polymer solution.