Phase Transition Behavior Of Hydroxypropyl Cellulose And Synthesis Of Hyaluronic Polyacrylic Acid Nanogel Using Hydroxypropyl Cellulose As Template

Natural thermal sensitive polymer hydroxypropyl cellulose(HPC)is widely used in smart materials,drug delivery and other fields because of its excellent phase transition properties.In particular,the nanogel synthesized with HPC as the template is temperature-responsive,simple,non-toxic and environmentally friendly,which is a very promising and excellent material.At present,the phase transition temperature of HPC can be reduced to varying degrees by adding small molecular salt,small molecular acid or modifying HPC.In this paper,we added hyaluronic acid,an anionic polysaccharide containing hydroxyl,carboxyl and other functional groups,to reduce the phase transition temperature of HPC through hydrogen bonding with HPC.Therefore,hyaluronic acid-polyacrylic acid(HA-PAA)nanogels can be synthesized by hydrogen bonding without saponification,avoiding the use of surfactants in reverse emulsion polymerization and emulsion precipitation polymerization.(1)Under the same pH condition,the turbidity of HA and HPC mixed solution is tested by ultraviolet spectrophotometry.Under the condition of changing the molecular weight,concentration and concentration of HA,the influence of HPC phase transition temperature is explored.The phase transition temperature of HPC decreases with the increase of HA concentration,molecular weight and HPC concentration.At different pH,the phase transition temperature of HA to HPC increases with the increase of pH,but when pH is alkaline,the phase transition temperature of HPC decreases due to the salt effect.(2)Different concentrations of acrylic acid(AA)or polyacrylic acid(PAA)were mixed with the blended solutions of HA and HPC,and turbidity test was carried out by UV-visible spectrophotometry.Because of its large molecular weight,PAA could shield more of the combination between HPC and water,so that the phase transition temperature of HPC was lower than that of the mixed solution containing AA,and when the pH of the solution was lower than p Ka3.0 of HA,1wt% PAA can reduce the phase transition temperature of HPC in the mixed solution of HA and HPC to below 10 ℃,which is a good temperature changing material for smart windows.(3)With acrylic acid as monomer,hydroxypropyl cellulose as template,N,Nmethylenebisacrylamide as crosslinking agent,ammonium persulfate as initiator and sodium metabisulfite as catalyst,HA-PAA nano hydrogels were synthesized under the condition of 20℃ water bath by non-saponification polymerization of hyaluronic acid through hydrogen bonding.The particle size and dispersion of HA-PAA nanogel were studied under different acrylic acid concentration and hyaluronic acid concentration,as well as the effects of different crosslinking agents and catalysts on the properties of the nanogel.The responsiveness of pH was also verified,which provided the necessary conditions for drug release.