Thermodynamic Studies On The Preparation Of Pourous Structure By Supercritical Fluid

Recently,as the development of cell biology,molecular biology and biomaterials,tissue engineering achieve progress in study and application.The selection and preparation of ideal scaffold matearial are one important content of tissue engineering study. Supercitical fluid induced phase separation process is a new technology to preparate porous structure under the traditional phase separation process.By studying the thermodynamic in supercitical fluid induced phase separation process,we can analyse and calculate process parameters of this process and thereby optimizate the pourous preparation.Based on Flory-Huggins theory,we establish the thermodynamic model of supercritical fluid-solvent-polymer ternary systerm,and calculate the ternary phase diagram which includes binodal curve,spinodal curve and critical point using Matlab to study the phase separation behavior of supercitical fluid induced phase separation process prepararing pourous srructure.By means of analysis of ternary phase diagram,we devide the phase separation region of Supercritical fluid-solvent-polymer systerm to investigate the state of systerm in the phase separation process,and provide theoretical basis for optimization of experiment parameters and process conditions.The ternary thermodynamic calculation of ScCO2/acetone/PCL, ScCO2/dichloromethane /PLLA are gived using the thermodynamic model,and the results as following:1.The critical points results of ternary systerm showed that the critical points were near to solvent-nonsolvent axis,which indicated that the systerm were apt to polymer lean nucleation,and the ternary systerm are suitable to prepara porous structure with desirable properties.2.The thermodynamic calculation about ternary systerm of ScCO2/AC/PCL showed that as the pressure increase of temperature decreasing,the interaction parametersχ12 anχ13 decrease,namely the interaction between the nonsolvent and solvent and polymer increases. After analyzing theχ12 andχ13 effect on phase diagram,we find the effect ofχ13 on binodal curve is more significant,the average pore size of pourous structure is increase with pressure increasing underχ3 effect.3.The binodal curve of ternary systerm of ScCO2/AC/PCL are away from to polymer/solvent axis, making the one-phase region larger and the two-phase region narrower; When the systerm reached thermodynamic equilibrium,as the slope of tie lines which connect the equilibrium phase of polymer rich and polymer lean increase, the time of phase separation are shorter which makes the average pore size of porous structure decrease.4.The results of SCCO2/DCM/PLLA ternary systerm showed that the influencing trend of pressure and temperature on the nonsolvent/solvent interaction parameters and the nonsolvent/ polymer interaction parameters are similar to ScCO2/AC/PCL systerm.;The variation of the position of bimodal curve and spinodal curve and the solpe of tie lines are basically similar to ScCO2/AC/PCL systerm. As the properties of polymer are different, compared with PCL systerm, the influence of pressure and temperature to PLLA systerm is more significant.5.The analysis of the preparaed pourous structure of systerms using the results of thermodynamic calculation about ternary systerm showed that the parameters in phase diagram can explain well the effect of different parameters on the variation of pore size and morphology,and that proved that the thermodynamic calculation model of supercritical fluid-solvent-polymer ternary systerm and the calculation results are reliable.