The Preparation And Characterization Of Ion Crosslinking Hydrogels Based On Natural Polysaccharides

As a soft wet material,hydrogel has three-dimensional structure,has good deformation and can response to external stimuli.Therefor it is widely used in industry,agriculture,medical and biological fields.Natural polymer material with good biocompatibility,biodegradability and non-toxic,is good raw material to make hydrogel.In this paper we prepared three kinds of hydrogels with chitosan(CS),sodium alginate(SA)and hydroxyethyl cellulose(HEC)as raw materials.We study the mechanical properties and healing properties of the hydrogels.We prepared the water-soluble chitosan as reported but do a little modified through the modification of CS.We call the modified CS as CSGTMAC and use it with SA to prepare the physical crosslinking hydrogel.This hydrogel has self-healing performance and can response the pH and ionic stimulation and these ionic crosslinking hydrogels have good mechanical properties.Study shows that the self-healing hydrogels are not affected by shape and the time limit.The self-healing hydrogel can directly assemble by the dry powder gel through adding deionized water or they can join together by section leaching through adding a certain concentration of salt solution.In addition,the study found the degree of water swelling properties are affected by pH,in the neutral environment the degree of swelling is the lowest,but in acidic or alkaline conditions the degree of swelling will go up.This kind of ionic crosslinking hydrogels can produce continuous response in different ionic strength.This property can realize the switch of ionic strength performance.In this paper we used the infrared spectrum(FT-IR)and nuclear magnetic spectra to confirm the synthesis of CSGTMAC and characterize the mechanical property through tensile stress-strain test.In order to not introduce toxic substances,in this paper,we prepared the oxidation sodium alginate.Using amine and aldehyde produces Schiff base reaction to form chemical crosslinking.Through this way,we prepared double crosslinking hydrogel.The study found that those gels have different tensile strength due to different degree of oxidation of sodium alginate.The maximum tensile strengths are changing when CSGTMAC substitution degree is different.The higher of the substitution degree,the lower of the elongation at break.For this,we designed another double crosslinking hydrogel which has double network,using CSGTMAC/SA to form physical crosslinking network and citric acid cross-linked HEC to form chemical crosslinking network.The study found that those gels improved tensile strength of the single network CSGTMAC/SA hydrogel and rupture elongation of the double crosslinking CSGTMAC/OSA hydrogels.The strength increased about three times.