| Biopolymers are often biodegradable and nontoxic, being generated from renewablenatural sources; however, they are still in the early stages of development. They can beobtained by biological systems or chemically synthesized from biological materials. They arean alternative to petroleum-based polymers (traditional plastics). In the past decades theyhave been growing in popularity and more and more researchers are focusing on them.Sodium alginate (SA), a water-soluble polysaccharide extracted from brown seaweeds,consists of β-1,4-D-mannuronate (M) and α-1,4-L-guluronate (G) repeating units, and it is anatural copolymer with a nonregular blockwise arrangement between the G and M units. Dueto its remarkable gelation properties, biocompatibility, abundance and relatively low price,alginate has been widely used in food, fabric, and medical fields. Gelatin is a kind of peptidemixture obtained from collagen. It can be used as biomedical materials because of itsnonantigenic ability.Sodium alginate and gelatin have excellent biocompatibility and low antigenicity;however, their mechanical properties and water resistance are poor, which restrict their widerapplication as biomedical materials. It is reported that blending and cross-linking modificationcan improve the properties of polymeric materials. For protein materials, traditionalcross-linking agents (such as glutaraldehyde) have stronger cytotoxicity, which limits thewider application of gelatin as medical materials. Thus, more and more researchers areexploring the cross-linking agents that have lower cytotoxicity or no cytotoxicity.On the basis of papers research, the preparation and properties of sodium alginate/gelatin(semi) IPN films with different cross-linking agents were investigated in detail. And thecross-linking agents were included oxidized sodium alginate, genipin and glutaraldehyde.The main research results obtained are as follows:(1) Oxidized sodium alginate was prepared successfully. The effect of mol ratio ofsodium alginate and sodium periodate and reacting time on the oxidation degree of oxidizedsodium alginate were studied in detail. The results indicated that the oxidation degree ofoxidized sodium alginate increased with the increase of oxidized time. Compared with theoxidized time, the additive amount of sodium periodate was the main factor which influencesobviously the oxidation degree of oxidized sodium alginate. The oxidized sodium alginate with different oxidation degree could be obtained by controlling the additive amount ofsodium periodates.(2) Sodium alginate/gelatin (semi) IPN films were prepared, which were cross-linkedwith different cross-linking agents (glutaraldehyde, oxidized sodium alginate, genipin). Andthe preparation conditions, weight ratio for sodium alginate to gelatin, the additive amount ofa cross-linking agent, cross-linking temperature, solidified concentration and solidified time,were investigated to find out the best preparation conditions. The results showed that forsodium alginate/gelatin (semi) IPN films cross-linked with oxidized sodium alginate, the bestpreparation conditions were as follows: weight ratio for sodium alginate to gelatin was2:1,cross-linking temperature was40oC, solidified concentration was5wt%and solidified timewas30min; and for sodium alginate/gelatin (semi) IPN films cross-linked with genipin, thebest preparation conditions were as follows: weight ratio for sodium alginate to gelatin was2:1, weight ratio for gelatin to genipin was200:1, cross-linking temperature was40oC,solidified concentration was5wt%and solidified time was30min.(3) The structure, mechanical properties, water absorption, water retention, thermalstability and cross-linking degree of sodium alginate/gelatin (semi) IPN films cross-linkedwith different cross-linking agents were investigated. The FT-IR results indicated that sodiumalginate/gelatin (semi) IPNs films were prepared successfully, which were cross-linked withoxidized sodium alginate and genipin. The cross-linking mechanisms were speculatedaccording to the FTIR results. The mechanical properties results indicated that the mechanicalproperties of sodium alginate/gelatin (semi) IPNs films cross-linked with oxidized sodiumalginate and genipin were better than those of sodium alginate/gelatin blend films. Themechanical properties of (semi) IPNs films increased at first and then decreased with theincrease of gelatin content. When the weight ratio for sodium alginate to gelatin reached2:1,(semi) IPNs films owned the best tensile strength. The SEM results showed that thecompatibility of sodium alginate and gelatin was better with unobvious phase separation whenthe weight ratio for sodium alginate to gelatin reached2:1. The thermal analysis resultsindicated that thermal stabilities of sodium alginate/gelatin (semi) IPNs films cross-linkedwith oxidized sodium alginate and genipin, respectively, were similar to those of sodiumalginate/gelatin (semi) IPNs films cross-linked with glutaraldehyde. The water absorption andretaining rate of sodium alginate/gelatin (semi) IPNs films cross-linked with oxidized sodiumalginate and genipin, respectively, were good in deionized water and saline solution. |
