Preparation And Characterization Of Natural Polymer Cellulose Or Sodium Alginate Based Composite Gels

Hydrogel is three-dimensional network consisting of polymer,which can absorb large amounts of water without dissolving and maintain a certain shape and strength.Due to these unique properties,hydrogels have wide applications in the fields of medical treatment,chemical industry,agriculture and so on.Natural polymers,the most abundant renew able resource on earth with biocompatibility and biodegradability,numerous new functional hydrogels materials based on natural polymers have being developed for a broad range of applications.Meanwhile,to utilize natural polymers and to develop high-valued natural polymer products are helpful to deal with the current crisis and challenges of dwindling fossil resources.In this work,several new composite hydrogels were prepared by using cellulose or sodium alginate as raw materials.The composite hydrogels were characterized by various methods,and their properties were measured.The results indicate that the composite hydrogels have improved performances such higher mechanical properties,protein retention and temperature sensitivity,meaning potential applications in the areas of biomedicine and environmental protection.Specific researches are summarized as follows:Preparation and characterization of high strength and toughness sodium alginate/poly(N,N-dimethylacrylamid)interpenetrating network hydrogelIn this part,a robust alginate/poly(N,N-dimethylacrylamide)hydrogel with a interpenetrating network(IPN)were successfully prepared.Namely,N,N-dimethylacrylamide(DMAA)and sodium alginate were firstly mixed in water,and then DMAA was initiated to polymerize to form the first network.After those,it was immersed in calcium ion solution to cross-link sodium alginate to form the second network.Finally,the composition and surface morphology of hydrogel was observed by Fourier transform infrared(FT-IR)and scanning electron microscopy(SEM),respectively.The results indicate that sodium alginate and poly(N,N-dimethylacrylamid)form a three-dimensional network gel structure with smooth pores.The effects of the amounts of components and solid content on the compressive strength and compressive recovery performance of the IPN hydrogel were investigated by means of mechanical test.The results suggest that the best mass ratio of DMAA and sodium alginate is 23.5:1.5,and the optimum solid content is 30%,and the IPN hydrogel prepared under this condition has the best compression performance.Therefore,this part of work provides a method to prepare robust hydrogel and to expand the applications of alginate.In-situ grafting polymerization of acrylamide onto regenerated cellulose composite gel and its application in membrane fieldIn this part,the cellulose was firstly dissolved by low temperature dissolution method and prepared regenerated cellulose gel.After those,it was soaked in an acrylamide aqueous solution,and then ceric ion was added to initiate the in-situ grafting polymerization of acrylamide under mild condition through heterogeneous reaction.The composition and micro structure of composite gel was studied and compared by Fourier transform infrared(FT-IR)spectroscopy,elemental analysis and scanning electron microscopy(SEM),respectively.The results indicate that the grafting rate is 64.5%,and the modified composite gel maintaining the porous structure of regenerated cellulose gel.Meanwhile,the composite gel suggest higher mechanical property and water absorption ability than pure regenerated cellulose gel,which up to 109 MPa and 347%of saturated water absorption.Moreover,the composite gel was applied to the field of membrane separation and it exhibit higher water flux(26.4 L/(m2·h·MPa)),which is more than 2 times of regenerated cellulose gel.What’s more,the bovine serum albumin rejection is also higher than that of regenerated cellulose gel.This may be due to the electrostatic repulsion between the composite gel and bovine serum albumin.Therefore,such a recyclable gel would have great potential as water absorbent,water retaining material and in membrane separation field.In-situ grafting polymerization of Poly(N-isopropyl acrylamide)onto cellulose gel and its applicationIn this work,a kind of biocompatible and temperature sensitive cellulose-based gel were successfully prepared.Firstly,cellulose was dissolved by low temperature dissolution method and prepared the regenerated cellulose gel.Then immersing it in N-isopropyl acrylamide(NIPAM)monomer solutions,and using N,N’-methylene-bis-acrylamide(MBAA)as crosslink reagent and ammonium persulfate(APS)as initiator initiated the in-situ grafting polymerization.The composition and microstructure of gel were researched by Fourier transform infrared(FT-IR)spectroscopy,elemental analysis and scanning electron microscopy(SEM),respectively.The results show that the grafting rate of poly(N-isopropyl acrylamide)is 45.7%,and the modified composite gel maintaining the porous structure.The tensile test results indicate that the maximum tensile stress and elongation at break of the modified cellulose gels increased by 1.5 times and 2 times,respectively.The temperature sensitivity of the composite gel was tested by swelling degree changing under different temperature.The results suggest that the water absorption of the composite gel is 241%at 10 ℃ and 162%at 50 ℃,which indicate significant temperature sensitivity.In addition,the adsorption properties of copper ions were also studied.The results indicate that the adsorption capacity of the composite gel is also sensitive to the temperature.Therefore,the temperature sensitive poly(N-isopropyl acrylamide)grafted cellulose composite gel is expected to be used in the field of environmental engineering.