Structural characteristics of double network gels with extremely high mechanical strength
Structural characteristics of double network gels with extremely high mechanical strength
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DOI：
10.1021/ma049506i
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发表时间：
2004-07-13
期刊：
影响因子：
5.5
通讯作者：
Shibayama, M
中科院分区：
文献类型：
--
作者：
Na, YH;Kurokawa, T;Shibayama, M
用动态光散射(DLS)研究了具有极高机械强度的双网络凝胶的动态特性。由高度交联的聚(2-丙烯酰胺基-2-甲基丙磺酸)(PAMPS)作为第一网络和松散交联(或未交联)的聚丙烯酰胺(PAAM)作为第二网络形成DN凝胶。DLS结果表明，在第二网络的低交联密度下，除了凝胶模式(快模式)外，还存在慢模式的存在，从而提高了凝胶的强度。慢模式的动力学不能用第一网络中第二组分的运动来解释，但它类似于PAAM聚合物在半稀溶液中的平移运动。在与慢模式的松弛时间成反比的剪切速率下，观察到机械强度的强烈的速度依赖性。这些结果表明，可能存在第一网络的大“空洞”，存在于“空洞”中的PAAM聚合物在DN凝胶中扮演着“分子裂缝堵塞器”的角色，防止裂缝扩展到宏观水平。
The dynamic aspect of double network (DN) gels showing an extremely high mechanical strength has been investigated by dynamic light scattering (DLS) measurements. The DN gels are formed from highly cross-linked poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the first network and loosely cross-linked (or non-cross-linked) polyacrylamide (PAAm) as the second network. The results of DLS show that the presence of slow mode besides the gel mode (fast mode) enhances the strength of DN gels at the low cross-linking density of the second network. The dynamics of the slow mode cannot be explained in terms of reptational motion of the second component in the first network, but it is similar to the translational motion of PAAm polymers in a semidilute solution. A strong velocity dependence of the mechanical strength is observed at a shear rate close to the inverse of the relaxation time of the slow mode. These results suggest that large "voids" of the first network may exist, and PAAm polymers that exist in "voids" act as a "molecular crack stopper" in DN gels, keeping the crack from growing to a macroscopic level.