Effect of pH variation and crosslinker absence on the gelling mechanism of high acyl gellan: Morphological, thermal and mechanical approaches

Abstract

This article describes the preparation of superabsorbent hydrogels made of high acyl gellan without the addition of a crosslinker . Variations of the pH of the medium and different gellan solution concentrations were evaluated. The samples produced were investigated regarding their morphology by scanning electron microscopy, thermal resistance by thermogravimetry, and compressive strength by mechanical testing. Rheological tests were also performed and the swelling decree of the hydrogels was calculated. The results showed that the morphology of the samples could be modified by varying the preparation conditions, ranging from a foliaceous structure to a brittle structure, containing voids with different sizes.The hydrogels prepared with acidic pH presented less compressive strength than those prepared with basic pH. Although all the samples had swelling degree greater than 1000 %, the highest values were obtained with the samples prepared at pH 4, regardless of the concentration of the gellan solution.