Superabsorbent Hydrogels That Are Robust and Highly Stretchable
Superabsorbent Hydrogels That Are Robust and Highly Stretchable
复制标题
DOI：
10.1021/ma500882n
复制
发表时间：
2014-07-08
期刊：
影响因子：
5.5
通讯作者：
Raghavan, Srinivasa R.
中科院分区：
文献类型：
--
作者：
Cipriano, Bani H.;Banik, Stephen J.;Raghavan, Srinivasa R.
由丙烯酸酯或丙烯酰胺单体化学交联而成的聚合物水凝胶在水中的吸水性可达其重量的100倍以上。然而，这种凝胶通常是脆弱的，当拉伸到中等应变时(类似于50%)就会破裂。已经开发了许多策略来创建更坚韧的凝胶，包括双重联网、加入纳米颗粒作为交联剂等，但这些策略通常会延缓凝胶的吸水性。在这里，我们提出了一种新的方法，它可以产生具有优异机械性能的高吸水性水凝胶。该方法的关键是N，N-二甲基丙烯酰胺(DMAA)的自交联性。也就是说，我们进行了DMAA的自由基聚合(与离子共聚单体如丙烯酸钠一起)，但没有任何多官能团单体。由于不断增长的线性聚合物链之间的链间共价键，仍然形成水凝胶。通过这种途径形成的凝胶在未膨胀状态下可以拉伸到1350%的应变。同样的凝胶也是超级吸水性的，可以吸收高达其重量3000倍的水(据信这是一项纪录)。即使在膨胀状态下，这些凝胶在破裂前也可以拉伸到接近400%的应变，这大大超过了传统的高吸水性凝胶。基于DMAA的凝胶的优异性能归因于其网络中交联链的更均匀分布。
Polymer hydrogels synthesized by chemical cross-linking of acrylate or acrylamide monomers can absorb more than 100 times their weight in water. However, such gels are usually fragile and rupture when stretched to moderate strains (similar to 50%). Many strategies have been developed to create tougher gels, including double-networking, incorporation of nanoparticles as cross-linkers, etc., but these strategies typically retard the water absorbency of the gel. Here, we present a new approach that gives rise to superabsorbent hydrogels having superior mechanical properties. The key to our approach is the self-cross-linking ability of N,N-dimethylacrylamide (DMAA). That is, we conduct a free-radical polymerization of DMAA (along with an ionic comonomer such as sodium acrylate) but without any multifunctional monomers. A hydrogel still forms due to interchain covalent bonds between the growing linear polymer chains. Gels formed by this route can be stretched up to 1350% strain in the unswollen state. The same gels are also superabsorbent and can imbibe up to 3000 times their weight in water (which is believed to be a record). Even in the swollen state, these gels can be stretched up to strains similar to 400% before rupture, which substantially exceeds that of conventional superabsorbent gels. The superior properties of DMAA-based gels are attributed to a more uniform distribution of cross-links within their networks.