Small-Angle X-ray Scattering and Rheological Characterization of Alginate Gels. 3. Alginic Acid Gels

摘要: Alginic acid gels were studied by small-angle X-ray scattering and rheology to elucidate the influence of alginate chemical composition molecular weight on gel elasticity structure. The alginic prepared homogeneous pH reduction throughout sample. Three alginates with different sequence, two three weights each sample examined. samples fractions guluronic residues 0.39 (LoG), 0.50 (InG), 0.68 (HiG), covering range commercially available alginates, employed. excess intensity I was about 1 order magnitude larger exhibited a stronger curvature toward low q compared ionically cross-linked alginate. I(q) decomposed into components assuming that is composed aggregated multiple junctions single chains. Time-resolved experiments showed large increase in average size aggregates their fraction within first 2 h after onset gelling, which also coincides most pronounced rheological changes. At equilibrium, little or no effect observed, whereas at comparable weights, an increased increasing content recorded, probably because apparent mass domains. results suggest quasi-ordered junction zone formed initial stage, followed subsequent assembling such zones, forming domains 50 A. length being governed relative stabilizing G-blocks destabilizing alternating (MG) blocks, determines density final random aggregates. Hence, high-G give higher aggregate loosely packed shorter zones InG LoG system.