INHOMOGENEOUS POLYSACCHARIDE IONIC GELS
INHOMOGENEOUS POLYSACCHARIDE IONIC GELS
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DOI：
10.1016/0144-8617(89)90030-1
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发表时间：
1989-01-01
影响因子：
11.2
通讯作者：
SMIDSROD, O
中科院分区：
文献类型：
--
作者：
SKJAKBRAEK, G;GRASDALEN, H;SMIDSROD, O
通过钙离子扩散到海藻酸钠或果胶酸盐的溶液中形成的多糖离子型凝胶表现出不同程度的不均匀性，在这个意义上，聚合物浓度在凝胶的表面比在中心高得多。这与当κ-β时获得的均匀凝胶形成对比。角叉菜胶对钾离子进行透析，结冷胶对钾和铅离子进行透析。聚合物在海藻酸盐和果胶酸盐中的不均匀分布取决于参数，例如聚合物浓度和分子大小，以及外部储层中的凝胶诱导离子的浓度。对于藻酸盐，高比例的L-古洛糖醛酸残基略微增加了不均匀性，而非胶凝阳离子的存在强烈降低了不均匀性。提出，凝胶化是由聚合物和胶凝阳离子的相对扩散速率控制的，并且在不存在非-胶凝阳离子是不可逆的和化学计量的。一种新的简单的技术，通过扩散生成均匀的海藻酸钙凝胶也被证明。
Polysaccharide ionotropic gels formed by diffusion of calcium ions into solutions of sodium alginate or pectate exhibited various degree of inhomogeneity, in the sense that the polymer concentration was much higher at the surface than in the center of the gels. This was in contrast to the uniform gels obtained when .kappa.-carrageenan was dialyzed against potassium ions and gellan gum against potassium and lead ions. The non-uniform distribution of polymer in alginate and pectate depended on parameters such as polymer concentration and molecular size, and the concentration of the gel inducing ion in the outer reservoir. For alginate a high fraction of L-guluronate residues slightly increased the inhomogeneity, whereas the presence of non-gelling cations strongly decreased it. A theory, limited to diffusion of reactants in infinite long tubes, compared with relevant experiments, suggested that the gelation was controlled by the relative rate of diffusion of polymer and gelling cations and that the gelling in the absence of non-gelling cations was irreversible and stoichiometric. A new simple technique for generating homogeneous calcium alginate gels by diffusion was also demonstrated.