Acrylamide Hydrogels Preparation via Free Radical Crosslinking Copolymerization: Kinetic Study and Morphological Investigation

The simultaneous gravimetric and dilatometric techniques have been used to study the kinetics of aqueous free radical crosslinking copolymerization of acrylamide (AAm) and N,N^'-methylenebisacrylamide (MBA) at different crosslinker ratios, and reaction temperatures. In this study, the gel properties were investigated using swelling measurements and microscopic techniques. Based on the data, it was proposed that the deviation point of the results of dilatometric technique from those of the gravimetric one can be a new criterion for gel point. The monomer conversion and the equilibrium swelling ratio of the hydrogels were measured as a function of the reaction time. Experimental data showed an inverse dependence of the critical gel point on crosslinker concentration. As the MBA/AAm ratio was decreased to 0.1?wt%, the product appearance changed. In addition, the effects of temperature on the reaction rate and critical gel point were studied. At higher temperatures, the equilibrium swelling ratio reached to its minimum value earlier. Besides, the hydrogel surface became smoother.