The Preparation And Abilities Of Chiral Hydrogels Based On Amino Acid Devirates

The hydrogels were gotten increasingly attentions due to the strong ability of adsorbing water, intelligence, biocompatibility and degradation, and thus could be used in drug delivery system, tissue engineering, water retention agent and so on. However, the low mechanical strength might limit their application at some degree. Meanwhile, the chial materials were got investigated due to the occurrence of "thalidomide incident", which was induced by misusing chial compound and leaded the deformity of newborn babies. Chiral hydrogels were prepared mainly by polymerization of helical materials and monomers contained optical activity and could be used in chiral recognition and release. This paper prepared new pH responsive chiral hydrogels and tough chiral hydrogels by free radical polymerization and free radical micellar polymerization respectively. The main works were listed as follows:First, we prepared new pH sensitive hydrogels by free radical polymerization, namely, using L(D)-NAA as monomer and the inclusion complex based on PEGDA and α-CD as comonomer, APS as initiator to intiate the system to form hydrogels. PNAA chains rendered the hydrogels with pH responsibility and optical activity, PEGDA had two functions:1. Introduce the hydrophilic a-CD on the main chain -CH2CH2O-; 2. Crosslink the L(D)-NAA to form hydrogels by the C=C double bands at the end of the PEGDA chains. We investigated the amount of a-CD on the properties of the hydrogels and found that the swelling ratio of the hydrogels was the biggest when the ratio was 1:3. Meawhile, the swelling ratio of the hydrogels was small as 2 times when in the acid environment, and the swelling ratio could be large as 40 times when in the akaine environment, which proved the pH responsibility of the hydrogels. The measurement of CD and UV-vis indicated the optical activity of the hydrogels. And the investigation of chiral recognition and chiral release on chiral materials LHP and DHP revealed that the hydrogels based on L-NAA preferentially adsorbed DHP and released LHP. So this hydrogels could be used in chiral drug release system.Secondly, we designed and prepared the new chiral hydrogels based on hydrophobic association, the hydrophobic function was used as crosslinking points to improve the mechanical strength of the hydrogels. With the emulsifion of the gelatin, the hydrophobic monomer C18 contained long alkyl group could copolymerized with hydrophilic monomer NAA, and after adding initiator APS and without any chemical crosslinker, the hydrogels could be formed. The obtained hydrogels possessed the properties, such as tensile, compression and knot without breakage, which the chemical hydrogels didn’t have. We investigated influence of the hydrophobic/hydrophilic ratio on the properties of the hydrogels and found that the increasement of the ratio leaded the increasement of the mechanical strength of the hydrogels, which was mainly due to the increase of the hydrophobic crosslinking points. And the CD and UV-vis measurements on the hydrogels after swelling in the water testified the optical activity of the hydrogels. At the same time, due to the presence of network and the long alkyl chain in the C18 chains, the permanent rod shape hydrogels could be change into temporary spiral shape, and after the high-temperature, the temporary spiral shape could recovered gradually to its original rod shape, namely, the hydrogels demonstrated intesting shape memory behavior. So the hydrogels could be investigated and used as smart materials.