The hierarchical bulk molecular structure of poly(acrylamide) hydrogels: beyond the fishing net
The hierarchical bulk molecular structure of poly(acrylamide) hydrogels: beyond the fishing net
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DOI：
10.1039/d0sm01536a
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发表时间：
2020-11-14
期刊：
影响因子：
3.4
通讯作者：
Spencer, Nicholas D.
中科院分区：
文献类型：
--
作者：
Gombert, Yvonne;Roncoroni, Fabrice;Spencer, Nicholas D.
水凝胶的聚合物结构在文献中通常呈现为类似于渔网。然而，这种简单的视图无法完全捕捉这些材料的所有独特属性。对于自由基聚合的乙烯基水凝胶中的本体结构的详细描述至关重要的是对交联剂分布的透彻理解。本工作着重于四官能交联剂在水凝胶系统中的精确作用：丙烯酰胺-N，N '-亚甲基双（丙烯酰胺）。小于4 nm的交联剂和它们的附聚物的簇，以及具有从100 nm到μ m范围的尺寸的聚合物域，已经通过X-射线和可见光散射被识别。放置在该系统的大量文献的背景下，这些观察结果表明水凝胶网络结构内的聚合物的异质组织，并且可以通过单体和交联剂的不同聚合行为来解释。再加上基于溶胀实验和扫描电子显微镜结构观察的聚合物网络链长近似值，这些结果表明水周围口袋的聚合物网络的层次结构。
The polymeric structure of hydrogels is commonly presented in the literature as resembling a fishing net. However, this simple view cannot fully capture all the unique properties of these materials. Crucial for a detailed description of the bulk structure in free-radical polymerized vinylic hydrogels is a thorough understanding of the cross-linker distribution. This work focuses on the precise role of the tetra-functional cross-linker in the hydrogel system: acrylamide-N,N '-methylenebis(acrylamide). Clusters of crosslinker smaller than 4 nm and their agglomerates, as well as polymer domains with sizes from the 100 nm to the mu m-range, have been identified by means of both X-ray and visible-light scattering. Placed in the context of the extensive literature on this system, these observations demonstrate the heterogeneous organisation of the polymer within the hydrogel network structure, and can be accounted for by the different polymerization behavior of the monomer and crosslinker. Together with polymer-network chain-length approximations based on swelling experiments and structural observations with scanning electron microscopy, these results indicate a hierarchical structure of the polymer network surrounding pockets of water.