Preparation And Performance Of Alginate Hydrogels

Alginate hydrogels have lots of unique properties,such as excellent biocompatibility,non-toxicity,biodegradability,relatively economical in use.Therefore,alginate hydrogels have been extensively researched and used in many biomedical fields.However,alginate hydrogels have the defects of poor gel controllability and low mechanical properties.Alginate hydrogels are difficult to meet the application requirements very well,which have greatly limited their extensive usages.High performance hydrogels can be prepared with synthetic polymers and alginates by interpenetrating network?IPN?.The prepared hydrogels can not only overcome the shortcomings of alginate hydrogels,but also combine the advantages of synthetic polymers and natural polymers,making it possible to prepare the hydrogels with controllable structure,good biocompatibility and excellent functional properties.The PAAm/SA semi-IPN hydrogels were prepared by free radical polymerization using acrylamide?AAm?with good biological stability as the semi-interpenetrating network component of alginate?SA?,N,N'-methylenebisacrylamide?MBA?as crosslinker,ammonium persulfate?APS?as initiator,tetramethyl-ethylenediamine?TEMED?as crosslinking accelerator.Considering the equilibrium swelling ratio and tensile properties of the hydrogels,the best preparation technology of the hydrogels were obtained.When the PAAm/SA hydrogels contained 2wt% SA and 18wt% AAm,the weights of MBA,APS and TEMED were fixed at 0.04wt%,0.6wt% and 0.8wt% that of AAm,the hydrogels had excellent swelling and mechanical properties.The PAAm/CA full-IPN hydrogels were prepared by soaking PAAm/SA semi-IPN hydrogels in the CaCl² solution containing ethanol.And the G units of SA and Ca²⁺ can form "egg box" structure.By observing the appearance and the microstructure,we can know that: the synergistic effect of ethanol and calcium chloride solution was found to reduce the swelling degree of hydrogel during ionic crosslinking process,and ethanol had no negative effect on the degree of crosslinking,resulting in close,smooth porous network structures.The improvement of the network structure of PAAm/CA hydrogels had positive effect on its mechanical properties.When the ionic cross-linking solution contained 4wt% CaCl² and 30wt% ethanol,the visual appearance and surface homogeneity were significantly improved,and the tensile strength of the hydrogel achieved to 624 k Pa from 248 k Pa.Poly?vinyl alcohol?/calcium alginate hydrogels were prepared by introducing PVA into SA,and Ca²⁺ crosslinked alginate and hydrogen bonded PVA can form PVA/CA interpenetrating network structures.The preparation method of PVA/CA hydrogels,which combined in situ Ca²⁺ releasing and freeze–thawing method,can overcome the defects of uneven cross-linking.The results showed that the hydrogels with close,regular porous network structures were obtained when the Ca²⁺ was 10 m M,the freeze–thawing times were greater than or equal to 4.The uniform three-dimensional network structure of hydrogels provided structural basis for the excellent water absorption and moisture retention,and also made the hydrogel to maintain good mechanical elasticity.