Synthesis Of Temperature- And PH-Sensitive Carboxymethyl Starches Hydrogels And Its Property

In this study, HylonV starch is used to prepare different sensitivities starch derivatives, for the raw material HylonV starch is nontoxic and be with good biocompatibility and biodegradability. These sensitivities starch derivatives are used to prepare temperature and pH sensitivities hydrogels. So this type of hydrogels, is researched to solve the problem that existed widely in the field of the preparation and application for temperature and pH sensitivities hydrogels. This kind of hydrogels are often biocompatibility and biodegradability.In this work,2-hydroxy-3-isopropoxypropyl starches (HIPS) with temperature sensitive, carboxymethyl starch (HCMS) with pH sensitive and 2-hydroxy-3-butylpoxypropyl carboxymethyl starches (HBPCMS) with temperature and pH sensitive are synthesized.A new kind of temperature and pH sensitive interpenetrating networks macroporous HIPS/HCMS gels were synthesized by precipitation crosslink for 4 h, using HIPS, and HCMS as raw materials, ethylene glycol diglycidyl ether (EDGE) and epichlorohydrinas (ECH) as cross-linkers respectively. Using IR to study the structure of the two hydrogel. Using SEM to study the internal morphology the two hydrogel. Using thermal gravimetric analysis to study the thermal stability of the two hydrogel. Then the swelling ratio (SR) at different temperatures and different pH conditions, the deswelling kinetics and the reswelling kinetics of the two hydrogels were studied. It indicated that the SR of the hydrogels decrease with the increasing of the temperature, and have the fastest rate of decreasing around LCST. The SR of the hydrogels increase with the increasing of the pH, and have the fastest rate of increasing in the range of 4.0-5.8. Hydrogels with higher proportion of HIPS have better temperature sensitive property. Hydrogels with higher proportion of HCMS have better pH sensitive property. The two hrdrogels show quite fast swelling and deswelling ratio. HIPS/HCMSEDGE hydrogels lose most of the water with 1 min, and need 2 min for reswelling to equilibrium state. HIPS/HCMSECH hydrogels lose most of the water with 3 min, and need 6 min for reswelling to equilibrium state. HIPS/HCMSEDGE hydrogel have good temperature reversibility, and the swelling ratio keeped almost unchanged after six heating and cooling cycles. But the pH reversibility of the HIPS/HCMSEDGE hydrogel is not very good, after eight cycles, the swelling ratio of the hydrogels droped from 59 to 48 in solution which pH is 7.3.Temperature and pH sensitive HBPCMSEDGE hydrogels were synthesized using HBPCMS as raw materials, EDGE as cross-linker. The macroporous structure has been observed by SEM under different conditions and the size of the pore becomes large with the increase of the pH. Using IR to characterize the structure of the hydrogels, and proved the existence of the carboxyl groupwere in the network. The SR of the hydrogels increases with the increasing of the pH, and have the fastest rate of increasing in the range of 3.0-5.5. Hydrogels with higher substitution degree of the carboxymethyl have faster swelling rate when the pH is 6.5. And the swelling ratio of HBPCMS-3EDGE keeped almost unchanged after swelling 2 h and HBPCMS-3EDGE need 4 h to reach swelling equilibrium. HBPCMS-3EDGE hydrogels have good temperature reversibility, and the swelling ratio keeped almost unchanged after seven heating and cooling cycles But the pH reversibility is not very good, after seven cycles, the swelling ratio of the hydrogels droped from 106 to 86 in solution which pH is 7.3, and increase from 12 to 23 in solution which pH is 3.