title: Tough and Thermosensitive Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels with Macroscopically Oriented Liquid Crystalline Structures.
abstract: Bulk graphene oxide (GO) nanocomposite materials with macroscopically oriented GO liquid crystalline (LC) structures exhibit interesting anisotropic properties, but their facile preparations remain challenging. This work reports for the first time the facile preparation of poly(N-isopropylacrylamide) (PNIPAM)/GO nanocomposite hydrogels with macroscopically oriented LC structures with the assistance of a flow field induced by vacuum degassing and the in situ polymerization accelerated by GO. The hydrogel prepared with a GO concentration of 5.0 mg mL(-1) exhibits macroscopically aligned LC structures, which endow the gels with anisotropic optical, mechanical properties, and dimensional changes during the phase transition. The hydrogels show dramatically enhanced tensile mechanical properties and phase transition rates. The oriented LC structures are not damaged during the phase transition of the PNIPAM/GO hydrogels, and hence their LC behavior undergoes reversible change. Moreover, highly oriented LC structures can also be formed when the gels are elongated, even for the gels which do not have macroscopically oriented LC structures. Very impressively, the oriented LC structures in the hydrogels can be permanently maintained by drying the gel samples elongated to and then kept at a constant tensile strain. The thermosensitive nature of PNIPAM and the angle-dependent nature of the macroscopically aligned GO LC structures allow the practical applications of the PNIPAM/GO hydrogels as optical switches, soft sensors, and actuators and so on.
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Zhongcheng
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Peng
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Chen
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Cong
authors.initials: C
authors.lastname: Shang
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Capital Normal University , Beijing 100048, P. R. China.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Liu
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Huiliang
authors.initials: H
authors.lastname: Wang
keywords: graphene oxide; hydrogels; nanocomposite; optical switches; oriented liquid crystalline; poly(N-isopropylacrylamide); thermosensitive