羟自由基诱导的交联和羧甲基纤维素稀水溶液中的辐射引发水凝胶形成。
Hydroxyl radical-induced crosslinking and radiation-initiated hydrogel formation in dilute aqueous solutions of carboxymethylcellulose.
机构信息
Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland; Nuclear Professional School, School of Engineering, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Ibaraki 319-1188, Japan.
Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
出版信息
Carbohydr Polym. 2014 Nov 4;112:412-5. doi: 10.1016/j.carbpol.2014.06.007. Epub 2014 Jun 11.
Ionizing radiation causes chain scission of polysaccharides in the absence of crosslinking agents. It has been demonstrated before that degradation of carboxyalkylated polysaccharides may be prevented, despite presence of strong electrostatic repulsing forces between chains, at very high polymer concentration in water (paste-like state) when physical proximity promotes recombination of radiation-generated polymer radicals. In such conditions, crosslinking dominates over chain scission and covalent, macroscopic gels can be formed. In an approach proposed in this work, neutralizing the charges on carboxymethylcellulose (CMC) by lowering the pH results in retracting the electrostatic repulsion between chain segments and thus allows for substantial reduction of polymer concentration required to achieve gelation due to domination of crosslinking reactions. Electron-beam irradiation of aqueous solutions of low pH containing 0.5-2% CMC results in hydrogel formation with 70% yield, while both concentration and dose determine their swelling properties. Time-resolved studies by laser flash photolysis clearly indicate strong pH influence on decay kinetics of CMC radicals.
电离辐射会在没有交联剂的情况下引起多糖的链式断裂。以前已经证明，尽管在水中聚合物浓度非常高（糊状物状态）时，链之间存在强烈的静电斥力，但当物理接近促进辐射产生的聚合物自由基的重组时，仍可以防止羧甲基化多糖的降解。在这种情况下，交联会超过链式断裂，形成共价的、宏观的凝胶。在这项工作中提出的一种方法是通过降低 pH 值来中和羧甲基纤维素（CMC）上的电荷，从而使链段之间的静电斥力回缩，从而可以大大减少实现凝胶化所需的聚合物浓度，因为交联反应占主导地位。电子束辐照 pH 值低的含有 0.5-2%CMC 的水溶液会导致水凝胶的形成，产率为 70%，而浓度和剂量决定了它们的溶胀性能。激光闪光光解的时间分辨研究清楚地表明，pH 值对 CMC 自由基的衰减动力学有很强的影响。
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