| For the traditional high international phase emulsion(HIPE)polymerization,a large number of volatile organic solvents are demanded,which can hardly be removed from the products,thus results in environmental issues.This drawback can be partially resolved by the employment of non-toxic,uninflammable and abundant carbon dioxide(CO2)instead of organic solvent,to prepare HIPE.However,the solubility of CO2 is poor.In order to obtain stable CO2-in-water(C/W)emulsions,it is imperative to synthesize high-efficient stabilizer.So far,most CO2-philic stabilizers are expensive,as well as the complex synthetic routes and difficult purification process,all of which diminish the cost-efficiency and environmental friendly of C/W emulsions.In this thesis,commercial polyvinyl alcohol(PVA)which contains polyvinyl acetate(PVAc)group was used as an effective stabilizer,and successfully prepared a series of C/W HIPE.Macroporous materials such as PVA,polyacrylamine(PAM),PVA-chitosan and PVA-alginate,were also synthesized.The main contents are listed as follows:(1)The research progress and application on CO2-philic polymers in recent years are reviewed.(2)The preparation of PVAc - PVA random copolymer and C/W emulsion.The emulsifying capacity of alcoholysis PVAc oligomer(M w≈ 3000 g/mol)and esterified commercial PVA.Meanwhile,non- modified PVA exhibits excellent emulsifying properties.C/W emulsions which stabilized by commercial PVA are stable even at high temperature(T = 80 ℃)。(3)The application of PVA hydrogels which prepared in C/W emulsion as well as PVA hydrogel scaffolds in the field of tissue engineering.Under the condition of no extra stabilizer,PVA macroporous emulsion - templated materials with interconnected pores and tunable pore size(5.52-21.07 μm)have been obtained by use of high international phase C/W emulsion-templated polymerization.This method is convenient,cost-effective,scalable and environmental friendly indeed.Furthermore,we demonstrated the use of PVA hydrogels as tissue engineering scaffolds,as human embryonic lung fibroblast cells and H9c2 cardiac muscle cells proliferated and penetrated into them(4)C/W emulsion - templated polyacrylamides macroporous materials have been synthesized and applied to tissue engineering.Using partially hydrolyzed commercial PVA as stabilizer,PAM macroporous materials with interconnected pores and tunable pore size are obtained by use of high international phase C/W emulsion template-polymerization.In addition,we also discussed the influence of the concentration of stabilizer,the molecular weight of PVA and the reaction conditions to pore structures.Macroporous materials with smaller pore size could be acquired when increased the concentration of stabilizer.It should be considered by the combination of viscosity and the interactions of PVA and CO 2 when the influence of the molecular weight of PVA to the pore structure has been discussed.Macroporous materials with smaller pore size could be acquired under relatively low temperature and pressure.H9c2 cardiac muscle cells have been cultivated successfully in PAM macroporous materials.Moreover,they can easily grow and proliferated on the surface of porous PAM scaffolds,which demonstrated good biocompatible and availability of producing artificial organs with the help of three-dimensional printing technology.(5)The preparation of PVA macroporous composites by using C/W emulsion -templated method.PVA-chitosan and PVA-alginate macroporous composites have been synthesized using this method.Although PVA - chitosan macroporous materials have low density,irregular pore sizes and easy to collapse,they are really suitable for the growth of cells.The H9c2 cardiac muscle cells shown good capacity of adhesion and proliferation.The PVA-chitosan materials exhibited prominent biodegradability.In terms of PVA-alginate composites,the pore size of PVA-alginate hydrogels could be affected by the ratio of alginate and PVA and the order of adding aqueous Ca Cl2 solution.At the same time,the addition of alginate reduced the water adsorption rate of sample,and enhanced mechanical properties of the composites. |
