Synthesis And Properties Of Biodegradable Polyaspartic Acid Interpenetrating Network Absorbent Resins

Polyaspartic acid absorbent resins are of a kind of biodegradable polymers with excellent water swelling properties. Because of their unique characteristics like good biocompatibility, minor toxicity and ease of synthetic, they hold great promise of many applications in environmental protection, agriculture, medicine and sanitation domains. They are also currently the hot spot of international research for absorbent resins. Unfortunately, polyaspartic acid resins preparing by chemical crosslink methods have various drawbacks such as toxic, none soluble in aqueous(e.g., intermediate product- polysuccinimide(PSI)), hard to post treatment, etc. In particular, the swelling ratio in ethanol of polyaspartic acid resins is too low to support enough drugs loading, which limits their therapy application to a great extent. Furthermore, there still exist several flaws for polyaspartic acid resin like simple structure, inferior behavior of salt tolerance, and poor thermal stability. It is generally needed to improve their comprehensive performance via chemical modification. An effective way is to utilize the interpenetrating polymer network(IPN) technology. In this research, we firstly modified PSI using 3-aminpropyltriethoxysilane( KH550) and synthesized modified polyaspartic acid(KPAsp) absorbent resin through hydrolysis cross-linking reaction in an aqueous system. Then we introduced an IPN structure into the modified system by which a functional complement and synergism were accomplished between the components. We prepared three IPN samples that are polyving akohol(PVA), carboxymethyl Cellulose(CMC), carboxymethyl chitosan(CMCTS)/KPAsp, respectively, based on their different purposes. The experimental results show all samples demonstrate excellent water swelling, salt tolerance and drug loaded characters while keeping their p H and thermal sensitivity performance. Most important of all, all samples exhibit biodegradable and biocompatible properties. The main research work and innovations of this dissertation are summarized as follows:1. Preparation for environmental friendly KPAsp absorbent resin. Modified polyaspartic acid hydrogel was synthesized by hydrolysis and crosslinking method in aqueous system using polyaspartic acid grafted 3-aminpropyltriethoxysilane(KH550) as materials. During the preparation process, the toxic product of diamine was prevented. The swelling ratio of the prepared hydrogels in distilled water, artificial blood and artificial urine was measured to be 180 g/g, 57 g/g, and 28 g/g. Meanwhile their sensitivity to salts and p H was maintained stable. The results show the prepared kasp absorbent resin could find potential applications in medical sanitation field.2. By IPN technology and using modified KPAsp and polyving akohol, we prepared KPAsp/PVA IPN hydrogel with a simple one-step method in aqueous system. It was found that, when the mass ratio of KPAsp/PVA was 1:0.5, the swelling ratio in distilled water and 0.9% Na Cl solution were 273 g/g and 89 g/g. The corresponding swelling ration in artificial blood and artificial urine was 167 g/g and70 g/g. The drug-loaded characteristics of the KPAsp/PVA IPN hydrogels were investigated by using salicylic acid as a model drug, the measured release profile was 65% in p H=9.3. We further synthesized KPAsp/CMC IPN absorbent resin via solution aggregation with two-step heating to inter crosslink the KPAsp and Carboxymethyl Cellulose(CMC). The optional synthetic condition was as follows: mass ratio for KPAsp and CMC is 1:1, temperature for second heating was 145 ℃, and the heating time was 15 min. The measured swelling ratio of KPAsp/CMC IPN resin in distilled water and 0.9% Na Cl solution were 413 g/g and 114 g/g. Similarly we studied the drug releasing behavior by using salicylic acid. the release profile reached to 76% in p H=9 environment.4. Due to the abundant-OH、-NH2、-COOH groups in carboxymethyl chitosan(CMCTS), the reaction activity and speed could be significantly improved during its complexation reaction to metallic ions. This is helpful to water treatment and recycle of precious metals. We prepared KPAsp/CMCTS IPN absorbent resin by cross linking the modified KPAsp and CMCTS tree using Glutaraldehyde as the cross-linker. When the mass ratio for KPAsp and CMCTS was 1:0.6, the swelling ratio of KPAsp/CMCTS IPN resin in distilled water and 0.9% Na Cl solution were measured to be 306 g/g and 95 g/g. Further swelling ratio in artificial blood and artificial urine was 201 g/g and 75 g/g. The drug-loaded characteristics of the hydrogels were investigated and the release profile of salicylic acid in p H=9 was 73%. Following, we investigated the p H, temperature and salt sensitivities of the IPN resin. The results show that the two resin net structure was cross linked through the introduction of IPN technology. The p H and temperature sensitivity behaviors from KPAsp are thus maintained, while the water swelling performance is improved due to the existence of CMCTS polymers.5. The kinetic analysis for drug release of the hydrogels was analyzed by Korsmeyer–Peppas theory. The results show that KPAsp hydrogel followed a Fickian diffusion controlled release mechanism, whereas for KPAsp/PVA IPN and KPAsp/CTS IPN absorbent resin the release mechanism was attributed to a non-Fickian diffusion process.