Polysulfone (PSF) membranes have gained great attention in the fields of ultrafiltration,microfiltration,and thin film composite membranes for nanofiltration or reverse osmosis.For the first time,it is proposed to fabricate PSF membranes via thermally induced phase separation (TIPS) process using diphenyl sulfone (DPSO2) and polyethylene glycol (PEG) as mixed diluent.DPSO2 is chosen as a crystallizable diluent,while PEG is considered in terms of molecular weight (Mw) and dosage.We systematically investigate the interactions between PSF,DPSO2 and PEG based on the simulation calculations and solubility parameter theory.It is inferred that DPSO2 has an excellent compatibility with PSF,and the addition of PEG results in the ternary system thermodynamically less stable and then facilitates its liquid-liquid (L-L) phase separation.SEM images indicate that cellular-like pores are obvious throughout the membrane when the PEG content in the mixed diluent is 25 wt％-35 wt％.We can facilely manipulate the pore size,water flux and mechanical properties of PSF membranes with the dosage of PEG-200,the Mw of PEG or the cooling rate.The successful application of TIPS can provide a new approach for structure manipulation and performance enhancement of PSF membranes. 相似文献
Polyphenylene sulfide (PPS) microporous membranes were prepared via the thermally induced phase separation process using diluent mixtures of diphenyl ether (DPE) and diphenyl ketone (DPK). The effects of DPE ratio to DPK in the diluent mixture on the microstructure were investigated. The results showed that the pore morphology of the membranes prepared from the diluent mixture was different from those of fabricated from pure diluents. Moreover, the pore structures of the membranes were changed along with the variation of the diluent composition. 相似文献
The influence of spatial temperature gradients on the morphological development in polymer solutions undergoing thermally induced phase separation was studied using mathematical modeling and computer simulation. The one‐dimensional mathematical model describing this phenomenon incorporates the nonlinear Cahn‐Hilliard theory for spinodal decomposition (SD), the Flory‐Huggins theory for polymer solution thermodynamics, and the slow‐mode theory and Rouse law for polymer diffusion. The resulting governing equation and auxiliary conditions were solved using the Galerkin finite element method. The temporal evolution of the spatial concentration profile from the computer simulation illustrates that an anisotropic morphology (see Figure) results when a temperature gradient is maintained along the polymer solution sample. The final anisotropic morphology depends on the overall phase separation time. If phase separation is terminated at very early stages, smaller (larger) droplets are formed in the lower (higher) temperature regions due to the deep (shallow) quench effect. On the other hand, if phase separation is allowed to proceed for a long period of time, then larger droplets are formed in the low‐temperature regions, whereas smaller droplets are developed at higher temperatures. This is due to the fact that the low‐temperature regions have entered the late stage of SD, while the high temperature regions are still in the early stage of SD. The presence of a temperature gradient during thermally induced phase separation introduces spatial variations in the change of chemical potential, which is the driving force for phase separation. These numerical results provide a better understanding of the control and optimization during the fabrication of anisotropic polymeric materials using the thermally induced phase separation technique.
The Ludwig‐Soret effect was investigated in the thermally induced phase separation process via SD in polymer solutions under an externally imposed spatial linear temperature gradient using mathematical modeling and computer simulation. The mathematical model incorporated non‐linear Cahn‐Hilliard theory for SD, Flory‐Huggins theory for thermodynamics, and the Ludwig‐Soret effect for thermal diffusion. 2D simulation results revealed that the Ludwig‐Soret effect had negligible impact on the phase separation mechanism in binary polymer solutions under a non‐uniform temperature field, as reflected by the time evolution of the dimensionless structure factor and the transition time from the early to the intermediate stages of SD.
