Synthesis And Characterization Of Hydrogel/Clay Composite Materials Cross-Linked With Chitosan

Hydrogels are the types of loosely cross-linked hydrophilic polymers that can swell, absorb and retain a large volume of water or other biological fluids. The physical properties of these polymers, often termed"smart materials", are sensitive to environmental variables such as solvent composition, temperature, or pH. Hydrogels have promising potential application in the field of drug delivery system, biomaterial culture and tissue engineering. However, the important limitation of hydrogel is its lack of biodegradability and its poor mechanical properties.The objective of this study was to develop biodegradable and well mechanical polyacrylamide(PAm) and Poly(N-isopropylacrylamide)(PNIPAAm) hydrogel with chitosan and clay Na-montmorillonite (Na-MMT). Soluble and biodegradable cross-linker N-maleyl chitosan(N-MACH) was synthesized with chitosan (CS) and maleic anhydride (MA) as materials. After the strong interaction between N-MACH and Na-MMT, with N-MACH cross-linker, a series of biodegradable composite hydrogels were synthesized by the free radical polymerization in distilled water, in which Am or NIPAAm was used as monomer. The swelling kinetics, mechanical property, and the degrading property were investigated.1. Tensile strength of N-MACH-cross-linked PAm/MMT composite hydrogel films increased significantly with increasing amount of Na-MMT up to 5 wt%(based on the monomer), followed by a decrease with further increase in Na-MMT up to 10 wt%. The mechanical property of composite hydrogel films increased significantly with added a small amount of MMT.2. The PAm and PAm/MMT composite hydrogels exhibited fast swelling kinetics. And the equilibrium swelling ratios and the swelling rate of composite hydrogels decreased with increasing MMT content.3. The N-MACH-cross-linked PAm/MMT composite hydrogel showed a significant weight loss in the SGF solution. The addition of MMT had little influence on the degradation of the PAm hydrogels.4. With added definite amount of Am, the volume phase transition temperature(VPTT) of PNIPAAm was increased from 31 oC to 37 oC ,near to the temperature of human body. The amount of the N-MACH and Na-MMT did not influence VPTT behavior of P(NIPAAm-co-Am) hydrogels evidently.5. At 25 oC, the water content of P(NIPAAm-co-Am)/MMT composite hydrogels were more than that of PNIPAAm and P(NIPAAm-co-Am) in PBS and SGF, in other words, the salt tolerance of hydrogel was increased with added MMT.6. The mechanical property of PNIPAAm hydrogels were affected by the amount of the N-MACH cross-linker and Na-MMT. And the mechanical property of composite hydrogel films increased significantly with added a small amount of MMT.7. The PNIPAAm, P(NIPAAm-co-Am) and P(NIPAAm-co-Am)/MMT composite hydrogels exhibited fast swelling kinetics in distilled water and SGF.8. Compared with hydrogels in distilled water, the PNIPAAm, P(NIPAAm-co-Am) and P(NIPAAm-co-Am)/MMT composite hydrogels exhibited faster deswelling kinetics in SGF.9. Adding MMT could improve the biodegradability of PNIPAAm and P (NIPAAm-co-Am) hydrogels.10. The thermodynamics stability was characterized by thermogravimetry. The result showed that the hydrogel had a good thermal stability. The glass temperature (Tg) of P(NIPAAm-co-Am) and P(NIPAAm-co-Am)/MMT composite hydrogels was higher than that of PNIPAAm hydrogel, and the dispersion of MMT in hydrogel exhibited well-distributed.