writer：Jingli Yang,?ab Shuang Liu,?ab Ying Xiao,b Guorong Gao,b Yuanna Sun,b Qingzhong Guo,a Jiangyu Wu*a a
keywords：responsive, hydrogel, nanocomposite, strength, toughness
source：期刊
specific source：J Mater Chem B
Issue time：2016年
Multi-responsive hydrogels with high strength have great significance for potential applications in smart
soft devices. However, it remains a challenge to incorporate multiple responsive moieties with energy
dissipation mechanisms. Herein, multi-responsive nanocomposite hydrogels with high compressive
strength and toughness were synthesized via in situ copolymerization of N-isopropylacrylamide (NIPAM)
and acryloyloxyethyltrimethyl ammonium chloride (DAC) in an aqueous dispersion of exfoliated LAPONITEs
RDS with a minute amount of N,N0-methylenebisacrylamide (MBAA) as a crosslinker. The combined use
of clay and MBAA is demonstrated to be favorable for the high strength and toughness, and helped in
avoiding precipitation of clay nanosheets, which otherwise occurred upon addition of cationic DAC.
The effect of the NIPAM/DAC molar ratio, MBAA and clay contents on the properties of the
hydrogels has been systematically investigated. Compression tests showed a compressive strength
up to 6.2 MPa, with fracture strain higher than 90%. The presence of ionic DAC moieties in the
hydrogels rendered a very high swelling ratio up to 40 (g g1). These hydrogels were responsive to
temperature changes due to the presence of NIPAM units, with the transition temperature (Ttrans)
dependent on the molar ratio of NIPAM and DAC monomers. The internal electrostatic repulsion of
the NIPAM/DAC copolymer network changed upon exposure to solutions with different pH and/or
ion strength. Cyclic swelling–shrinking was demonstrated by shuttling the gels between pure water
and 0.1 mol L1 NaCl solution.