Ultrahigh Deformability Of Ionic Nanocomposite Hydrogels With Stimuli Response

In this thesis, stimuli-responsive nanocomposite hydrogels (NC gels) with ultrahigh tensibility were synthesized by in-situ copolymerization of functional monomers and acrylamide or N-isopropylacrylamide in the aqueous suspension of hectorite clay Laponite and Laponite was used the cross-link. The stability of the suspension containing ionic monomers was investigated in detail. On this basis, we chose suitably ionic monomers and prepared ionic NC gels with ultrahigh tensibility by in-situ copolymerization of functional monomers and acrylamide or N-isopropylacrylamide in the aqueous suspension of Laponite. The main contents and the results of the work are as follows:1. Positively chargeable nanocomposite hydrogels (NC gels) were synthesized by in situ copolymerization of acrylamide (AM) and 2-(dimethylamino) ethyl methacrylate (DMAEMA) in an aqueous suspension of hectorite clay Laponite XLS. The stability of the Laponite suspension containing DMAEMA was monitored by its transmittance, viscosity and zeta potential. The suspensions containing 6 w/v% Laponite and 20 w/v% total monomers were transparent (transmittance ~ 90 %), with a viscosity of 2.5~3.3×10-3 Pa?s depending on the DMAEMA content for 30 minutes. The absolute value of the zeta potential decreased by the addition of DMAEMA and then leveled off at about 5 mol% DMAEMA. The polymerization was initiated either by redox or UV radiation to fabricate the NC gels. Elongation at break and tensile strength decreased with increasing DMAEMA content in monomers up to 17 mol%. As expected from the protonation of DMAEMA, the NC gels containing more than 5 mol% DMAEMA showed pH-responsive swelling; the gels were swollen at pH < 4 and shrunken at pH > 4. In comparison with the redox-initiated NC gels, the UV-initiated NC gels possessed a more homogeneous structure with higher transmittance, better mechanical properties, and a larger equilibrium swelling ratio at pH < 42. Ionic strength-response nanocomposite hydrogels with ultrahigh tensibility were synthesized by in-situ copolymerization of N-isopropylacrylamide (NIPAm) and 2-Acrylamide-2-methylpropanesulfonic acid sodium (AMPSNa) in the aqueous suspension of hectorite clay Laponite XLS. The stability of the Laponite suspension containing ionic monomers and the tensile properties of the NC gels were investigated. Addition of ionic monomer AMPSNa was found to reduce the stability of the suspension. The tensile properties for these ionic NC gels were excellent and the tensile strength was larger than 130 kPa and the elongation at break was 1000 ~ 1500 %. NIPAm/AMPSNa/Laponite XLS NC gels had temperature- and ionic strength- stimulus.