Preparation And Application Of Porous Materials Based On Phase Behavior Of PVDF/PMMA/PLLA Blends

Polymer porous materials exhibit the advantages of both porous materials and polymers.Due to these advantages,polymer porous materials have been widely used in the fields of drug loading and catalysis et al,especially in separation technologies.Unfortunately,the "Trade-off" effect severely limits its widespread use in separation.In order to overcome this effect,on the basis of our previous works in which narrow-nanopores were fabricated according to the crystallization template,PVDF/PMMA/PLLA ternary blends have been adopted to investigate the miscibility among components and the phase behaviors in the ternary blend.After removing PMMA and PLLA by selective solvent,polymer porous materials has been prepared successfully based on the combination of phase separation and crystallization.The phase morphology of the ternary blend can be adjusted by means of composition,compatibilizer and crystallization conditions,resulting in the precise control of porous structure.Furthermore,the separation performance of the attained porous materials have been investigated.Simulation has been adopted to clarify the mechanism of enhanced separation performance.?1?Phase behavior of PVDF/PMMA/PLLA ternary blend and the preparation and application of PVDF porous microspheres: On the one hand,in ternary blends,PMMA prefers to mix with PVDF while PVDF and PLLA are immiscible,leading to the PLLA phase and PVDF/PMMA mixed phase.On the other hand,PMMA has been expelled into the "inter-lamellar" and "inter-fibrillar" regions during the crystallization of PVDF,resulting in the nano-continuous structure of PMMA.In the specimen with the composition 30/30/40,"sea-island" structures were obtained between PLLA and PVDF/PMMA.After the removal of PLLA and PMMA by selective etching,PVDF microspheres with narrow porous structure were successfully prepared and the size of the porous microspheres could be controlled by adjusting the composition and the addition of compatibilizer.Moreover,magnetic PVDF porous microspheres were successfully obtained by loading magnetic nanoparticals of Fe₃O₄.The PVDF porous microspheres exhibit good performance in oil/water separation.?2?Preparation and application of "two-channel" hierarchically porous membranes based on phase behavior of PVDF/PMMA/PLLA blend: Firstly,according to the miscibility and exclusion behavior in ternary blend,"bicontinuous" structure of PLLA and PVDF/PMMA mixed phase can be obtained by regulating the composition of the ternary blend?1/1/1?.The crystallization of PVDF results in the nano-continuous structure of PMMA.Secondly,after the removal of PLLA and PMMA by etching,"two-channel" hierarchically porous membranes has been fabricated successfully.Thirdly,the size of two channels could be controlled by means of compatibilizer and tailoring crystallization conditions.Finally,hierarchical roughness and multiple channels caused by hierarchical pores result in the better performance in emulsion?water-in-petroleum ether?separation.The hierarchical pores dependence of flux has been verified by mean of simulation.?3?Preparation and application of hierarchically porous membranes with isolatedround-pores connected by narrow-nanopores based on phase behavior of PVDF/PMMA/PLLA blend: With the help of simulation,we verified the role of isolated-round-pores in enhancing the flux of membrane.Based on the simulation results,hierarchically porous membranes with isolated-round-pores connected by narrow-nanopores were successfully obtained from PVDF/PMMA/PLLA blend with the ratio of 40/40/20.Furthermore,porous structures in two scales can be adjusted by the means of compatibilizers and crystallization conditions respectively.In separation performance,the hierarchically porous membranes exhibit twice higher flux and comparable rejection ratio of BSA comparing to the membranes only with narrownanopores.