Graft Copolymerization, Chemical Modification And Application Properties Of Hydroxypropyl Methylcellulose

Graft copolymerization of ethyl acrylate (EA) onto water-soluble cellulose derivative-hydroxypropyl methylcellulose (HPMC) was carried out with potassium persulfate (KPS) as initiator in an aqueous medium. The process of graft copolymerization was similar to that of classical emulsion polymerization, which can be divided into three stages: nucleation, growth, and polymerization finish. The effects of monomer concentration, initiator concentration, matrix concentration, reaction temperature, and the introducing of the second functional monomers in terms of the percentage of grafting (G) and grafting efficiency (GE) were investigated. The interactions between HPMC and KPS before the graft copolymerization process in aqueous system were also investigated. The results show that the specific viscosity of HPMC solution decreases significantly with increasing the interaction time, and KPS can lead to the oxide degradation of the main chain of HPMC macromolecules. On the other hand, decomposition rate of KPS shows first-order with respect to the concentration of KPS in the presence of HPMC, which is just the same as in pure water. However, the decomposition rate constant of KPS in the presence of HPMC is 7 times higher than that of in water at 60℃. Introducing the second functional monomer, dimethylaminoethyl methacrylate (DMAEMA), into the graft copolymerization can make the graft copolymer soluble in the simulated gastric fluid. The resistance moisture absorption property increases about 5 times with the higher G value 151.89%. The potassium chloride (KCl) slow release tablet is prepared by using the graft copolymer latex as the binding agent of the tablet. When G values are 59.29%, 100.67% and the added amount is 10% or 20%, the release properties of KCl slow release tablets satisfy the requirement of China pharmacopeia. In addition, the graft copolymers obtained were characterized by FTIR, NMR, TEM, SEM, XRD, DLS and DSC techniques.Graft copolymerization of EA onto HPMC backbone was also carried out usingγ-radiation (60Co) both by the preirradiation method and by the simultaneous irradiation method in the aqueous medium. The effects of radiation environment, radiation dose, monomer concentration and reaction temperature in terms of grafting parameters were investigated systematically. With the same experimental conditions, the grafting parameters of the graft copolymer preparaed by preirradiation irradiation method are higher than those of the samples prepared by simultaneous irradiation method. With increasing the G value, the disintegration time of free film sample is prolonged.Hydroxypropyl methylcellulose phthalate (HPMCP) was preparaed by the esterification reaction of HPMC and phthalic anhydride. And then, HPMCP obtained was used as the starting material to prepare HPMCP water dispersion by the water emulsion method, during which none of the organic solvent was used. The mechanical property of HPMCP water dispersion free film can be enhanced by using HPMC as the emulsifier. HPMCP water dispersion free film has the better film forming property, and HPMCP water dispersion free films with phthalyl contents ranging from 28.17% to 33.24% are all insoluble in the simulated gastric fluid within 2 hours, which meets the challenge of China pharmacopeia. The solution rate of HPMCP water dispersion free film can be accelerated with increasing the phthalyl content or the pH values of the release medium. Increasing the thickness of the free film makes the solution rate slower.