Wang Tao, Zheng Shudian, Sun Weixiang, Liu Xinxing, Fu Shiyu, Tong Zhen
Research Institute of Materials Science and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.
Soft Matter. 2014 May 21;10(19):3506-12. doi: 10.1039/c3sm52961d. Epub 2014 Mar 21.
In the present work, hydrophilic monomer acrylamide (AM) was copolymerized with N-isopropylacrylamide (NIPAm) in an aqueous hectorite clay suspension to prepare PNIPAm-PAM-clay nanocomposite hydrogels (NC gels). With increasing AM content, the elongation at break of the copolymerized NC gels increased but the strength as well as the hysteresis during the loading-unloading cycle decreased, showing faster relaxation due to the more hydrophilic copolymer chains with the AM segments. The elongation at break of the copolymerized NC gels was independent of the notch length and notch type, while the fracture energy was greatly increased to 3000-5000 J m(-2) from 700 J m(-2) for the pure PNIPAm NC gels. The copolymer chains resulted in this notch insensitivity by easily dispersing the stress concentration at the notch tip through disorientation of the copolymer chains and clay platelets. The copolymerized NC gels also exhibited excellent self-healing capability; the cut surfaces were connected together by simply keeping in contact for a period of time (about 4 days at 20 °C). This self-healing was accelerated by increasing the treatment temperature (about 4 h at 80 °C).
在本工作中，亲水性单体丙烯酰胺（AM）与N-异丙基丙烯酰胺（NIPAm）在锂皂石粘土水悬浮液中进行共聚，以制备聚N-异丙基丙烯酰胺-聚丙烯酰胺-粘土纳米复合水凝胶（NC凝胶）。随着AM含量的增加，共聚NC凝胶的断裂伸长率增加，但强度以及加载-卸载循环期间的滞后现象降低，这表明由于带有AM链段的亲水性共聚物链，松弛速度更快。共聚NC凝胶的断裂伸长率与切口长度和切口类型无关，而断裂能从纯聚N-异丙基丙烯酰胺NC凝胶的700 J m(-2)大幅增加到3000 - 5000 J m(-2)。共聚物链通过使共聚物链和粘土片晶取向紊乱，轻松分散切口尖端的应力集中，从而导致这种切口不敏感性。共聚NC凝胶还表现出优异的自愈能力；切割面只需简单接触一段时间（20℃下约4天）就能连接在一起。通过提高处理温度（80℃下约4小时）可加速这种自愈过程。
