Preparation and Study of Glucose Sensitive Hydrogels Based on PBA Microgels
In recent years,diabetes has become a major threat to human health.Real-time detection of blood glucose concentration can reduce the complications caused by diabetes,which is beneficial to the health of patients.PBA-based hydrogels have become a research hotspot due to their strong adaptability to the environment.However,hydrogels containing PBA have long response time and low response strength to glucose at physiological pH.In this dissertation,microgels were prepared by emulsion polymerization,and composite and interpenetrating hydrogels were prepared by taking microgels as cross-linking points.The quick response of microgels was utilized to solve the problems such as long response time of hydrogels.Low response of physiological pH of hydrogels containing PBA to glucose was solved by adding aminochitosan(CS)or GO.The specific research content is as follows:(1)Poly(AAPBA-DMAA-co-AAm)microgelwaspreparedbyemulsion polymerization.The particle size of the microgel was tested and the surface of the microgel particles was smooth and the particle size was about 40nm.The thermal stability of microgels was obtained by TGA curve.The optimized experimental conditions were as follows:fixed AAPBA content,monomer ratio DMAA/AAm 6:1(mass ratio),rotational speed of 867 r/min,KPS(9 wt%),SDS(8 wt%),and MBA(1.14 wt%).The response of the microgel to glucose was investigated by weighing method.The results showed that the microgel reached the maximum swelling degree in about 10min.The equilibrium swelling was about 23.Microgels prepared with 6%AAPBA had the best response to glucose.Composite hydrogels were synthesized based on PBA microgels.The hydrogels were characterized by FTIR,TGA and SEM.The results showed that the hydrogel with 5.8%AAPBA content in the outer monomer had the best response to glucose at a pH of 8.0,and the equilibrium time was 50 min.With the increase of pH,the response strength of hydrogel increases.When pH is 8.6,the maximum swelling degree is about 7.5%.(2)Poly(AAPBA-DMAA-co-AAm)microgels were prepared by adding CS.SEM and particle size characterization showed that the particle size of the microgel was between 100 and 200 nm.The double bond content of dry microgels with different reaction time was determined by iodimetry.The response time of interpenetrating network microgels to glucose was 6 min.The hydrogels of Poly(AAPBA-DMAA-co-AAm)/CS and Poly(AAPBA-DMAA-co-AAm)CS were prepared using Poly(AAPBA-DMAA-co-AAm)microgels and Poly(AAPBA-DMAA-co-AAm)CS microgels as cross-linking points.The swelling performance of hydrogels was investigated.The hydrogels based on CS interpenetrating microgels had a faster glucose response rate,and the maximum swelling degree of physiological pH was6.2%.The hydrogel thermal stability of CS interpenetrating microgels was improved.The hydrophilicity of IPN hydrogel Poly(AAPBA-DMAA-co-AAm)/Poly(AAPBA-DMAA-co-AAm)-CS based on Poly(AAPBA-DMAA-co-AAm)microgel was enhanced,and the response to glucose under physiological pH was up to 7.5%.When the CS content was 5%,the microgel reacted for 5 h,and the addition ratio was 100%(volume fraction),the IPN hydrogel with Poly(AAPBA-DMAA-co-AAm)CS microgel as the cross-linking point had a maximum response of 23%to glucose,and the swelling time was 25 min.Compared with IPN hydrogels based on PBA copolymer microgels,the response of IPN hydrogels was increased by 2 times.(3)Poly(AAPBA-NIPAM-co-AAm)CS was prepared by emulsion polymerization based on PBA.IPN hydrogels with double sensitivity were prepared by using interpenetrating microgels as matrix.The phase transition temperature of interpenetrating microgel was between 36 to 38℃measured by absorption spectrophotometry.The phase transition temperature of IPN hydrogel was between 35to 37℃by weighing measuring swelling degree.The results show that the temperature sensitive IPN hydrogel has both environmental(temperature)and chemical(glucose)sensitivity.(4)The 10 mol%AAPBA interpenetrating hydrogel film based on CS interpenetrating microgel has strong fast optical response.The apparent diffusion coefficient(8.05×10~-88 cm~2/s)of the thin gel(0.157 mm)was lower due to the influence of glucose affinity bond kinetics or structural rearrangement.For thicker gels(0.430 mm),the diffusion coefficient was 1.1×10~-77 cm~2/s,and glucose diffusion was the speed control step.The specific reactivity of ARS fluorescent dyes in the gel and diol showed that the specific binding amount of ARS in the gel was 27μmol/mL,which was well consistent with the fixed PBA amount of 25μmol/mL in the gel.The light response of gels to glucose was reversible under physiological pH.The linear response and stability of the sensor gel make it suitable for measuring glucose or other physiological liquids in human blood.(5)Hummers method was used to prepare graphene oxide.Hydrogels containing GO were prepared by adding corresponding monomers to GO suspension obtained by ultrasonic stripping.The GO and gel were characterized by IR,XRD and TG.The thermal stability of the hydrogels added with GO was improved,and the maximum response to glucose reached 17%under physiological pH.GO-containing hydrogels were prepared based on Poly(AAPBA-DMAA-co-AAm)microgels.Due to the huge electron mobility of GO,the pKa of PBA was reduced,and the addition of GO improved the response rate of hydrogel to glucose under physiological conditions,and the equilibrium swelling time was 30 min.