Kinetics of anhydride formation in xerogels of poly(acrylic acid).

The aim of this work was to study the cross-linkage of xerogels made of Carbopol of different molecular weight (polymers deriving from polyacrylic acid), and the influence exerted by different percentages of beta-cyclodextrin upon the cross-linkage percentage. Xerogels were obtained by high-pressure compression and cross-linking was studied by measuring the weight loss of different formulations over a temperature range of 70 to 190 degrees C. Kinetics of anhydride formation were found to follow a second-order mechanism with an activation energy of approximately 25 kcal mol-1.