Study On PAA And PAM Series IPN Hydrogels With High Mechanical Strength Using Two-steps Aqueous Polymerization

Macromolecule hydrogels are formed by hydrophilic or oilphilic macromolecule polymers after absorbing large amount of solvents and so swollen. Intelligent macromolecule can sense the variety of conditions and response to it. Recently, researchers are more interested in the sensitivities of the hydrogels while hold pH-sensitivity, thermo-sensitivity, ionic strength sensitivity, electronic sensitivity and ray-sensitivity etc properties.Recently, hydrogels are successfully applied in biomedicine and engineering technologies. And because the mechanical strength of the swellon hydrogels are badly, Interpenetrating network (IPN) is put forward and expanded. IPN is a new kind of functional polymer which has two different components, and each component holding its own configuration and properties. Each component in IPN hydrogels is relatively independent and can keep its own properties. So studies on synthesis and properties of IPN hydrogels mean much.This thesis brought forward a new method of making IPN hydrogels—two-steps aqueous polymerization method. The network structure and properties which were different from that obtained by copolymerization and hybrid were detailed investigated using contrast experiment. PAM/PAM IPN, PAA/Starch semi-IPN and PAM/PVA IPN hydrogels were synthesized using this simple method. The unique structures and morphologies of the IPNs were analyzed by FTIR, SEM, TGA, swelling properties and tensile strength measurements. And the results revealed that simultaneously copolymerization and blend structures existed in IPN hydrogels, and the thermostability of IPN or semi-IPN hydrogels was improved comparing with their copolymers and hybrids. Compared with conventional hydrogels, hydrogels obtained by this two-steps aqueous polymerization method have excellent mechanical strength and stable properties, and so it means much to study on this kind of hydrogels.For PAA/Starch semi-IPN hydrogel, the influences of starch content on swelling ratios and swelling rate of PAA/Starch semi-IPN hydrogels were investigated. And it revealed that the swelling of hydrogels give priority to the relaxation of molecular chains. The pH and ionic strengths sensitives were discussed. The hydrogels have typical on-off effects. The swelling behaviors of PAA/Starch semi-IPN hydrogels in salt solutions with different valencies were studied using Flory theory. The fitting curves of Flory theory to swelling ratio of hydrogels revealed that the swelling ratios in univalent solutions were coincident with the Flory theory. While for multivalent salt solutions, Flory theory could only be used as qualitative analysis. Compared with conventional hydrogels, the PAA/Starch semi-IPN hydrogels synthesized using the novel two-steps aqueous polymerization have excellent mechanical strength.For PAM/PVA IPN hydrogels, the influences of PVA and crosslinker dosages and tensile time on the mechanical strength and elongation ratio of PAM/PVA IPN hydrogels were investigated. The tensile measurements showed that with the increase of PVA and crosslinkage, the mechanical strength of the PAM/PVA IPN hydrogel increased, with a highest tensile strength and elongation of 2.4 MPa and 3000 %, respectivelyt. The toughening mechanism of separated PVA was detailed discussed. The X-ray diffraction showed that the crystal structure of PVA has changed. The macroscopical morphologies of the hydrogels made chear that rigidity of PAM/PVA IPN hydrogels increase with increasing of crosslinker and PVA .