Compositional effects on mechanical properties of nanocomposite hydrogels composed of poly(N,N-dimethylacrylamide) and clay
Compositional effects on mechanical properties of nanocomposite hydrogels composed of poly(N,N-dimethylacrylamide) and clay
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DOI：
10.1021/ma034366i
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发表时间：
2003-07-29
期刊：
影响因子：
5.5
通讯作者：
Takehisa, T
中科院分区：
文献类型：
--
作者：
Haraguchi, K;Farnworth, R;Takehisa, T
在无机粘土的存在下，通过原位自由基聚合制备了由有机（聚合物）/无机（粘土）网络组成的纳米复合型水凝胶（DMAA-NC凝胶）。NC凝胶的组成可以通过改变初始反应混合物的组成来直接控制。所得的DMAA-NC凝胶大多是均匀和透明的，与它们的粘土和聚合物含量无关。通过DSC、X-射线衍射、透射电镜和拉伸力学测试，确定了其网络结构。与通过与双官能单体化学交联制备的常规化学交联水凝胶（DMAA-OR凝胶）相反，DMAA-NC凝胶表现出极好的机械性能，具有接近或大于1500%的惊人的大断裂伸长率。详细研究了DMAA-NC凝胶中粘土、聚合物和水含量等组成对凝胶拉伸力学性能的影响。随着粘土含量从C-粘土= 1增加到7（C-粘土与每单位体积水的粘土重量成比例，并且值1对应于每100 mL水0.762 g粘土），模量和极限拉伸强度几乎与粘土含量成比例地增加，但是断裂伸长率略微降低。通过改变聚合物含量超过2个数量级，观察到DMAA-NC凝胶的机械性能的性质显著改变。在较低的临界聚合物含量（C-p约为0.13）以上，断裂伸长率从接近零迅速增加到超过1000%。此后，水凝胶变成非常坚韧的NC凝胶。随着聚合物含量的进一步增加，强度和断裂伸长率在一定的聚合物含量时显示出最大值，而模量单调增加。力学性能也通过改变含水量而改变。对不同粘土含量的DMAA-NC凝胶的交联密度进行了估算。在NC凝胶网络结构模型的基础上，讨论了粘土和聚合物含量对NC凝胶力学性能的影响。
Nanocomposite type hydrogels (DMAA-NC gels) consisting of organic (polymer)/inorganic (clay) networks were prepared by in-situ free-radical polymerization of N,N-dimethylacrylamide (DMAA) in the presence of inorganic clay in aqueous solution. The composition of the NC gels could be controlled directly by altering the composition of the initial reaction mixture. The resulting DMAA-NC gels were mostly uniform and transparent, irrespective of their clay and polymer contents. From DSC, X-ray, TEM, and tensile mechanical measurements, the network structure was established. Contrary to conventional chemically cross-linked hydrogels (DMAA-OR gels) prepared by chemical cross-linking with a difunctional monomer, DMAA-NC gels exhibit superb mechanical properties with astonishingly large elongations at break, near to or greater than 1500%. The effects of the composition, such as the amounts of clay, polymer, and water content in DMAA-NC gels, on the tensile mechanical properties were investigated in detail. With increasing clay content from C-clay = 1 to 7 (C-clay is proportional to the weight of clay per unit volume of water, and a value of 1 corresponds to 0.762 g clay per 100 mL of water), the modulus and the ultimate tensile strength increased almost proportionally to the clay content, but the elongation at break decreased slightly. By altering the polymer content over 2 orders of magnitude, it was observed that the nature of the mechanical properties of DMAA-NC gels changed markedly. Above a lower critical polymer content (C-p approximate to 0.13), the elongation at break increased rapidly from near zero to more than 1000%. Thereafter, the hydrogels became very tough NC gels. With further increases in polymer content, the strength and the elongation at break showed maxima at certain polymer contents, whereas the modulus increased monotonically. The mechanical properties were also changed by altering the water content. The cross-link density was estimated for DMAA-NC gels with different clay contents. The effects of clay and polymer contents on the mechanical properties, as described above, were discussed on the basis of the network structure model for NC gel.