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yexuqing木虫之王 (文学泰斗)
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延展性极强的水凝胶 已有12人参与
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延展性极强的水凝胶添 Nature 489 (7414) 发表日期：2012年9月6日 水凝胶用在隐形眼镜中，也用作组织工程中的支架物及用在药物输送中。它们比较差的机械性能迄今限制了其应用范围，但本期Nature上报告的一种坚固且延展性好的新型材料则有可能将水凝胶带进未知领域。该新体系是一种“双网络”胶体，其中一个网络形成离子交联，另一个网络形成共价交联。这些材料的断裂能非常高：即使在含有通常会促使水凝胶中断裂形成的缺陷时，它们也能延展到超过自身长度的17倍。这些材料之所以如此结实，要归功于共价网络的断裂桥接作用以及与之相伴的、通过第二个网络中离子交联的断开所发生的能量耗散。 doi: 10.1038/nature11409 http://www.nature.com/nature/jou ... pdf/nature11409.pdf Nature | Letter Highly stretchable and tough hydrogels Jeong-Yun Sun,1, 2 Xuanhe Zhao,3 Widusha R. K. Illeperuma,1 Ovijit Chaudhuri,1 Kyu Hwan Oh,2 David J. Mooney,1, 4 Joost J. Vlassak1 & Zhigang Suo1, 5 Affiliations Contributions Corresponding author Journal name: Nature Volume: 489, Pages: 133–136 Date published: (06 September 2012) DOI: doi:10.1038/nature11409 Received 16 February 2012 Accepted 10 July 2012 Published online 05 September 2012 Hydrogels are used as scaffolds for tissue engineering1, vehicles for drug delivery2, actuators for optics and fluidics3, and model extracellular matrices for biological studies4. The scope of hydrogel applications, however, is often severely limited by their mechanical behaviour5. Most hydrogels do not exhibit high stretchability; for example, an alginate hydrogel ruptures when stretched to about 1.2 times its original length. Some synthetic elastic hydrogels6, 7 have achieved stretches in the range 10–20, but these values are markedly reduced in samples containing notches. Most hydrogels are brittle, with fracture energies of about 10 J m−2 (ref. 8), as compared with ~1,000 J m−2 for cartilage9 and ~10,000 J m−2 for natural rubbers10. Intense efforts are devoted to synthesizing hydrogels with improved mechanical properties11, 12, 13, 14, 15, 16, 17, 18; certain synthetic gels have reached fracture energies of 100–1,000 J m−2 (refs 11, 14, 17). Here we report the synthesis of hydrogels from polymers forming ionically and covalently crosslinked networks. Although such gels contain ~90% water, they can be stretched beyond 20 times their initial length, and have fracture energies of ~9,000 J m−2. Even for samples containing notches, a stretch of 17 is demonstrated. We attribute the gels’ toughness to the synergy of two mechanisms: crack bridging by the network of covalent crosslinks, and hysteresis by unzipping the network of ionic crosslinks. Furthermore, the network of covalent crosslinks preserves the memory of the initial state, so that much of the large deformation is removed on unloading. The unzipped ionic crosslinks cause internal damage, which heals by re-zipping. These gels may serve as model systems to explore mechanisms of deformation and energy dissipation, and expand the scope of hydrogel applications. |
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