Preparation And Functionalization Of A Self-driven PDA Microspheres/PVDF Hybrid Membranes Based On Membrane Micro-reactor Effect

Polyvinylidene fluoride(PVDF)membrane is one of the outstanding polymeric membrane materials and has been extensively applied in a diversity of fields such as microfiltration and ultrafiltration water treatment for industrial applications.Besides,PVDF membrane is also a promising candidate for the biomedical applications for its nontoxicity and low surface energy.However,the inherent hydrophobic nature of PVDF membrane always leads to low water permeability and gives rise to serious membrane fouling by adsorbing various contaminants during the membrane separation process.Moreover,the activation of the coagulation sequence and other complications are also prone to occur when PVDF is used as a bio-separation and blood-contacting material.Researches have shown that the hydrophilic modification of PVDF membrane is an effective method to improve the permeability,antifouling performance and biological performance.In this research,the hydrophilic modification of PVDF membrane is performed by PDA microspheres,and further functionalization of the modified membrane by AgNPs and L-cysteine.Systematic characterization and performance testing of membranes are carried out.This research is mainly composed of the following three parts:(1)PVDF/PDA hybrid membranes were prepared by in-situ generation of PDA microspheres firstly,and the research mainly explored the effect of stirring time of dopamine solution on the size and number of PDA microspheres.It was found that the experimental group of 1-day stirring of dopamine solution and 3-days stirring after adding the pristine PVDF membrane achieved the best performances.SEM observation revealed that the PDA microspheres were evenly distributed on the surface and cross-section of the membranes,and the number of PDA microspheres was much larger than that of the surface.The contact angle test results showed that the hydrophilicity of the hybrid membranes was greatly enhanced,and the best state even reach superhydrophilicity.The filtration test and static adsorption test showed that the hybrid membranes exhibited good permeability and antifouling properties.Hemolysis test and platelet adhesion test showed that the hybrid membranes had excellent hemocompatibility.(2)Then PVDF/PDA-AgNPs hybrid membranes were prepared by the direct reduction of AgNPs through the PDA microspheres to further functionalize PVDF/PDA hybrid membranes.And the research mainly explored the effect of AgNO3 solution concentration on the size and distribution of AgNPs on membranes.It was found that the AgNO3 concentration of 40 mM achieved the best performances.SEM observation revealed that a large number of AgNPs with an average particle size of 30 nm were uniformly distributed on the surface and cross-section of membranes.The contact angle test results showed that the hydrophilicity of the hybrid membranes was further improved,and the contact angle all can be reduced to 0° within I1.5 s.The filtration test and static adsorption test showed that the hybrid membranes exhibited good permeability and antifouling properties.Antibacterial performance tests all showed that the hybrid membranes had excellent antibacterial properties and antibacterial adhesion properties.And the more AgNPs immobilized on the membrane,the stronger antibacterial properties was achieved.(3)PVDF/PDA-AgNPs-Cys hybrid membranes were prepared using Michael addition reaction between-SH in L-cystcine and PDA microspheres,as well as using covalent bonding between-SH and AgNPs to form metal-thiol conjugates.And the research mainly explored the effect of cysteine solution concentration on the morphology and distribution of cysteine on membranes.It was found that when cysteine concentration reached to 3 mg/mL,more cysteine was superimposed and immobilized on the membrane in flower shapes.The contact angle test results showed that the hydrophilicity of the hybrid membranes increased with the increasing of cysteine concentration.The filtration test,static adsorption test and NOM contamination filtration test all showed that the hybrid membranes exhibited good permeability and antifouling properties.Antibacterial performance tests all showed that the hybrid membranes had excellent antibacterial properties and antibacterial adhesion properties.