Preparation And Characterization Of Novel High PH-sensitive Hydrogels

The main topic discussed in this thesis was preparation and characterization ofpH-sensitive hydrogel to resolve the problems in this kind of hydrogels' preparationand application, such as slow responsibility and fragile mechanical strength. Tosynthesis fast-acting pH-sensitive hydrogels with high mechanical property, twodifferent kinds of pH-sensitive hydrogels were prepared by way of solutionpolymerization and inverse suspension polymerization induced by free radical. On theother hand, their pH-sensitivity was discussed in a deeper degree and their appliancein drug controlled delivery system (DCDS) was also investigated preliminarily in thisthesis.Firstly, sulfadiazine monomer (SDM) prepared from sulfadiazine (SD), wascopolymerized with N-vinylpyrrolidone (NVP) by free radical induced solutionpolymerization to form pH-sensitive copolymer hydrogel P(SDM/NVP). In this thesis,a large number of different factors which influence hydrogels' pH sensitivity werediscussed such as reaction temperature, reaction time, ratio of different monomers andcrosslinked degree;and products were characterized by IR and H-NMR to affirmmonomer's special structure;also drug absorbance and delivery experiments werecarried out to investigate the feasibility of prepared hydrogels used in DCDS: drug(salicylic acid and Chloramphenical) release experiments in vitro, P(SDM/NVP)prepared in optimal conditions as drug carrier, were processed at pH 1.4 (close tostomach's pH) and pH7.4 (close to intestine's pH) respectively at 37℃ (close tohuman's body temperature). The results of the experiments above showed thatP(SDM/NVP) hydrogel prepared for 10h at 85℃ had the most desirable swellingproperties, and that hydrogels appeared more prominent pH-sensitivity withincreasing of SDM concentration from 20% to 30%, and that amount of crosslinkersshould be 1% to achieve appreciable mechanical property, and that drugs releasedmuch rapidly in pH7.4 buffered solution than in pH1.4 one.Secondly, functionalized monomer-itaconic acid (IA) was chose to copolymerizewith acrylamide (AM) by free radical induced inverse suspension polymerization toform pH-sensitive hydrogel P(IA/AM) microparticles. In this thesis, a lot of differentfactors which influence microparticles' appearance and glomeration were studied suchas modes of adding materials, types and amount of dispersants, kinds and amount ofdispersion media, concentration and ratio of monomers and amounts of crosslinkers;and factors which affect microgels' pH sensitivity were also discussed in this thesissuch as ratio of different monomers and crosslinked degree;and polymers werecharacterized by IR and SEM to affirm hygrogel's special structure and particles'appearance;also drug absorbance and delivery experiments were carried out toinvestigate the feasibility of prepared microgels used in DCDS: drug (salicylic acidand Chloramphenical) release experiments in vitro, P(IA/AM) prepared in optimalconditions as drug carrier, were processed at pH 1.4 (close to stomach's pH) andpH7.4 (close to intestine's pH) respectively at 37 ℃ (close to human's bodytemperature). The results of the experiments above showed that P(IA/AM)microparticles prepared on the condition of adding materials step by step, 2.5%span60 (/wmonomers) as dispersant, w/o (V/V)as 15:50, IA/AM (mol/mol) as 1:5.5,cyclohexane as dispersion media had the most desirable swelling properties, and thatmicrogels appeared more prominent pH-sensitivity with increasing of IAconcentration, and that amount of crosslinkers to monomers should be in a range9.4~12.5 % (w/w) to achieve excellent swelling properties and appreciableappearance, and that drugs released more in pH7.4 buffered solution than in pH1.4one.