Effect of hydrolysis on spatial inhomogeneity in poly (acrylamide) gels of various crosslink densities
Effect of hydrolysis on spatial inhomogeneity in poly (acrylamide) gels of various crosslink densities
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DOI：
10.1016/s0032-3861(03)00494-4
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发表时间：
2003-08-01
期刊：
影响因子：
4.6
通讯作者：
Okay, O
中科院分区：
文献类型：
--
作者：
Kizilay, MY;Okay, O
用静态光散射测量方法研究了不同交联密度的聚丙烯酰胺（PAAm）凝胶的空间不均匀性。以N，N′-亚甲基双（丙烯酰胺）（BAAm）为交联剂，在固定的初始单体浓度和不同的交联密度下制备凝胶。采用过硫酸铵-N，N，N‘，N’-四亚甲基二胺（TEMED）氧化还原引发剂体系引发聚合反应，并在老化凝胶中生成带电基团。凝胶制备后，通过弹性测试和凝胶状态下的光散射测量来表征。弹性测量表明，水凝胶制备中使用的交联剂分子中有91-94%被浪费在无效交联中。光散射数据的Debye-Bueche分析表明，凝胶样品内的冷冻浓度波动随着水凝胶交联密度的增加而不断增加。这种现象可以用多重交联反应来解释，这些交联反应导致最终水凝胶中形成高度交联的区域。随着凝胶在合成反应器中老化时间的延长，凝胶的浓度波动幅度急剧减小，说明酰胺基团水解成羧酸阴离子有利于凝胶样品的均质化。建立了一个热力学模型来解释老化凝胶中反离子的渗透压的实验结果。(C) 2003 Elsevier Ltd.版权所有。
The spatial inhomogeneity in poly(acrylamide) (PAAm) gels of various crosslink densities has been investigated with the static light scattering measurements. The gels were prepared using N,N'-methylenebis(acrylamide) (BAAm) as a crosslinker at a fixed initial monomer concentration but at various crosslink densities. Ammonium persulfate-N,N,N',N'-tetramethylethylenediamine (TEMED) redox initiator system was used to initiate the polymerization reactions as well as to create charged groups in the aged gels. The gels were characterized by elasticity tests and by light scattering measurements at a gel state just after their preparation. Elasticity measurements show that 91-94% of the crosslinker molecules used in the hydrogel preparation were wasted in ineffective crosslinks. Debye-Bueche analysis of the light scattering data indicates frozen concentration fluctuations within the gel samples, which increase continuously with increasing crosslink density of the hydrogels. This phenomenon was explained with the multiple crosslinking reactions leading to the formation of highly crosslinked regions in the final hydrogel. The extent of concentration fluctuations was found to decrease drastically with increasing time of aging of gels in the synthesis reactor, indicating that the hydrolysis of amide groups into carboxylate anions facilitates the homogenization of the gel samples. A thermodynamic model was developed to explain the experimental observations in terms of the osmotic pressure of counterions in the aged gels. (C) 2003 Elsevier Ltd. All rights reserved.