Robust and thermo-response graphene–PNIPAm hybrid hydrogels reinforced by hectorite clay

• Published in: Carbon (New York) Vol. 62; pp. 117 - 126
• Main Authors: Zhang, Enzhong, Wang, Tao, Lian, Cuixia, Sun, Weixiang, Liu, Xinxing, Tong, Zhen
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2013; Elsevier
• Subjects: ascorbic acid; biocompatible materials; Biomedical materials; Carbon; Chemistry; clay; Clay (material); Colloidal gels. Colloidal sols; Colloidal state and disperse state; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crosslinking; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; extensibility; Fullerenes and related materials; diamonds, graphite; General and physical chemistry; Graphene; hydrocolloids; Hydrogels; Materials science; Mechanical and acoustical properties; Mechanical and acoustical properties of condensed matter; Mechanical properties; Mechanical properties of solids; Oxides; phase transition; Physical properties of thin films, nonelectronic; Physics; polymerization; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Ascorbic acid; Aqueous suspension; Gels; Mechanical strength; In situ; Conductivity; Soft matter; Polymerization; Mechanical properties; Phase transitions; Clays; Chemical reduction; Biomedical materials; Graphene; Graphene oxide; Hydrogel; Polymers
• DOI: 10.1016/j.carbon.2013.06.003
• ISSN: 0008-6223

Graphene oxide (GO) based hydrogels were proposed to be used as biomaterials and stimuli-response materials, but their poor mechanical properties restricted their applications. We enhanced GO–poly(N-isopropylacrylamide) (PNIPAm) hydrogels by hybrid with the hectorite clay through in situ polymerization for the first time. This clay was found to stabilize the GO in the aqueous suspension when a reducer was added in a redox initiating pair. These GO–clay–PNIPAm hybrid hydrogels exhibited a high mechanical strength and extensibility with the GO sheets as the cross-linker and with the hectorite clay as both the cross-linker and reinforcing agent. They were thermal-responsive with the volume phase transition at ∼34°C. Reduction of the GO with l-ascorbic acid under environmental friendly conditions resulted in a high conductivity to the graphene–clay–PNIPAm hydrogels. These graphene–clay–PNIPAm hydrogels still had desirable mechanical properties. This finding has provided an easy method to prepare strong and stimuli-response graphene–polymer hydrogels to meet the demand for the newly developed soft matter.