Synthesis Of PH-Sensitive Graft Copolymer Of Vinyl Monomers Onto Cellulose And Its Application In Drug Sustained Release

The graft copolymer of ethyl acrylate (EA) and dimethylaminoethyl methacrylate (DM) onto hydroxypropyl methylcellulose (HPMC) was synthesized in the presence of potassium persulfate (KPS) as initiator in aqueous medium. The graft copolymerization underwent four stages of kinetics including dispersion, particle-formation, growth and final stage. The influence of functional monomer DM to the decomposition behavior of initiator was evaluated. The results indicate DM and KPS can form an oxidation reduction system, consequently initiator decomposition reaction is accelerated greatly, but it still conforms to linear equation. The effects of various reaction conditions on grafting parameters were investigated in detail, such as concentration of initiator, reaction temperature, monomers amount, and monomer composition. Increasing initiator concentration and reaction temperature both benefit the graft copolymerization, but it will be instability when they were exorbitant. The true grafting yield (GT) increased and the monomer graft efficiency (GE) decrease with increasing the comonomer fraction. Increasing DM fraction embarrass the graft copolymerization, resulting in the declining GT and GE. Apropos reaction conditions and right monomer component should be considered cautiously in actual situation.Evidence of grafting was affirmed by use of FTIR. The particles with core-shell were observed through TEM. SEM and DSC thermographs imply that increasing GE can improve compatibility of HPMC with homopolymers. The tensile experiments demonstrate the graft chains reduce the intensity but enhance the flexibility of cellulose. The hydrophobic graft chains improve the moisture absorbency property. Introducing DM unit with tertiary amino groups confer a novel pH-sensitive property onto the graft copolymers and extend its application in the drug delivery system.Tablets of theophylline as the model drug were film-coated with the submicron-sized latex to study the application of the polymeric latex in drug delivery system. The effects of monomer amount and monomer composition on the drug sustained-release were evaluated respectively. Drug release is mainly controlled by diffusion and the best-fit release kinetics is achieved with first-order or Higuchi equation.Nanosized copolymer latex of HPMC-EA-DM was prepared by acidifying the submicron-sized latex particles. The dimethylamino group-containing particles ionized into quaternary ammonium and swelled with water in acidic conditions. The neutralized degree of DM unit is critical for the preparation of nanosized particles. The effects on the diameter of the latex particles of different conditions, such as concentration of DM and ratio of HCl to DM for acidification were studied respectively.