Novel crosslinking method for preparation of acrylic thickener microgels through inverse emulsion polymerization

Novel crosslinking method was introduced for preparation of acrylic thickener microgels based on sodium acrylate and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) through inverse emulsion polymerization (IEP). Usually multifunctional vinyl crosslinkers such as methylene bisacrylamide are used in preparation of microgels through IEP. In this paper, a novel crosslinking method was introduced for microgel preparation through IEP. Diglycidyl materials were used instead of vinyl crosslinkers for microgel preparation. The effect of two diglycidyl materials such as polyethylene glycol diglycidyl ether (PEG-DGE) and ehylene glycol diglycidyl ether (EGDGE) was investigated as crosslinker in microgel synthesis. Acrylic microgels prepared through IEP can be used as a thickener for many industrial applications. The effects of parameters such as comonomer composition, drying temperature and crosslinker content on the thickening properties of microgels were investigated. According to the viscosity measurements, the microgel containing 12.5 % AMPS possessed the highest viscosity, while the lower viscosities were found to be observed for the microgels having the lower and higher percentages of AMPS. Moreover, the microgel containing AMPS showed the thickening properties over a wide range of pH and was nearly pH independent. Increasing drying temperature and amount of crosslinker led to enhance the crosslink density. The apparent viscosity was reduced and the storage modulus was increased in higher crosslink density. These microgels showed superior thickening properties in comparison to vinyl-crosslinked microgels, i.e., the thickening efficiency of PEGDGE-crosslinked microgels was significantly higher (about 500 %) than the conventional MBA-crosslinked microgels.