Preparation And Characteristic Of Medical Polymer Materials In Supercritical Carbon Dioxide

Supercritical carbon dioxide is nontoxic, non-polluting and non-flammable. It has a moderate critical condition (T_c=31.1℃,p_c=7.38 MPa), and it is a green solvent that can be used to replace traditional volatile organic solvents. Supercritical carbon dioxide has not only gas-like viscosity and diffusivity, but also liquid-like density and dissolving capacity, when it is used as a solvent, the solubility of a substance can be adjusted simply by changing the temperature and pressure. With the fast development of medicine and material science and the increasing demand for material preparation, that using supercritical carbon dioxide to develop green methods and cleaner production processes of preparation of medical polymer materials has important scientific significance and application value.In this paper, we use supercritical carbon dioxide as reaction medium and foaming agent to produce a number of medical polymer materials. The specific studies are as follows:1. Using 2-hydroxyethyl methacrylate as monomer and 2, 2′-azobisisobutyronitrile as initiator, that poly(2-hydroxyethyl methacrylate) was synthesized successfully in supercritical carbon dioxide by precipitation polymerization. It is possible to obtain white particles by changing the initial concentrations of monomer, initiator, reaction temperature, pressure as well as reaction time. It was found that the preparation of different molecular weight of poly(2-hydroxyethyl methacrylate) could by adjusting the reaction conditions.2. The poly(2-hydroxyethyl methacrylate) which was prepared in the first part of experiment was used as materials and with supercritical carbon dioxide as foaming agent. The form of poly(2-hydroxyethyl methacrylate) was power in the experiment. It is possible to obtain different mechanical properties and pore morphology of scaffolds by adjusting swelling time, temperature and depressurization rate.3. The chitosan porous membrane was prepared in the third part of experiment, than it was used as base material and grafting with acrylic acid in supercritical carbon dioxide. It is possible to obtain pH-responsive smart membrane with different graft yield by changing initiator concentration, monomer concentration, reaction pressure and reaction time. The membrane is considered for potential application in controlled release of drugs.