Study Of Preparations Of Porous Polymer Coating Films And Separation Membranes Via Vapor Induced Phase Separation And Their Properties

In recent years,porous polymer membrane materials have been widely applied in many fields,such as water treatment,gas separation,energy,medicine and biology.Among the many methods for preparing porous polymer membranes,vapor induced phase separation(VIPS)has been used in the preparation of porous polymer membrane materials with specific structures based on its simplicity and good controllability.In this work,using star-shaped triblock copolymer of poly(styrene-block-butadiene-block-styrene)as the raw material,we prepared superhydrophobic coating films and oil/water separation coating films by combining spraying technique and the VIPS process.Moreover,solution of polyethersulfone(PES)was exposed to water vapor atmosphere to prepare cellular-like porous membrane material by vapor induced phase separation.Meanwhile,the factors influencing membrane morphology and structure such as the composition of polymer solution,the selection of non-solvent atmosphere,vapor exposure time and so on have been studied and discussed.The applications of the prepared materials have been tested in this work.The specific researches are as follows:Preparation and characterization of superhydrophobic and breathable coating films by vapor induced phase separation and spray-coating methodIn this work,superhydrophobic and breathable coating films were prepared in one step by combining spraying technique and non-solvent vapor induced phase separation.Star-shaped triblock copolymer of poly(styrene-block-butadiene-block-styrene)was dissolved in tetrahydrofuran and then sprayed in an ethanol atmosphere.The sprayed tiny droplets of the polymer solution facilitated the solvent evaporation and the non-solvent condensation,resulting in their fast phase separation and solidification.After complete evaporation of the solvent,a porous and superhydrophobic coating film was thus obtained,with a nanometer to micrometer inter-connected nodular morphology.Water contact angle(CA)was measured with a water droplet of 5 ?L.Water contact angle.of the pure(SB)4 coating film was 152.0±1.0°,which could be defined as superhydrophobic surface.In addition,inorganic nanoparticles of SiO2 were added to the spray solution to further enhance the superhydrophobicity of the coating films,and the mechanical properties of the coating films could be improved by thermal treatment.The water-vapor permeability of the coating films was also studied.The experimental result showed that the coating had superhydrophobicity and excellent water-vapor permeability.Therefore,such coating films would have the great potential for practical applications such as preparing waterproof but breathable textile.Preparation and characterization of superhydrophobic coating films by vapor induced phase separation and spray-coating method and their application of oil/water separationStar-shaped triblock copolymer of poly(styrene-block-butadiene-block-styrene)and polydimethylsiloxane(PDMS)were dissolved in tetrahydrofuran and then sprayed onto stainless meshes in an ethanol atmosphere.After complete evaporation of the solvent,the coating films were treated at 60? in an electrical oven for 12h in order to make the PDMS in the coating films completely cross-linked.As a result,the coating film with rough surface could be obtained by non-solvent vapor induced phase separation combined with spray-coating technique.The addition of PDMS could improve the superhydrophobicity and solvent resistance of the coating film.When the(SB)4/PDMS mass ratio of up to 30:10,the surface contact angle from 151.6±0.6° up to 157±1.1°,with a further increase of PDMS content,the solvent resistance of coating films increased,the swelling rate decreased from 371%to 146%.The result of oil/water separation experiment showed that,even after 20 cycles of oil/water separation,the coating films could keep the separation efficiency more than 99%which showed a good application prospect.Preparation and characterization of Polyethersulfone porous membrane by vapor induced phase separation pretreatmentPolyethersulfone(PES)and hydrophilic additive polyvinylpyrrolidone(PVP)and poly(ethylene glycol)(PEG)were dissolved in N-methyl-2-pyrrolidone(NMP).The polymer solution was casted on a glass substrate and exposed in a water-vapor atmosphere,and then placed in precipitation bath of water.The porous membrane with cellular-like pore structure was prepared with two-step method of vapor induced phase separation pretreatment and immersion precipitation method.The SEM images of the resultant membranes exhibited that the addition of hydrophilic additives such as PVP and PEG changed the pore size of the membranes and improved the connectivity of the pores.The wettability of the membranes was measured by the contact angle instrument.It was found that the hydrophilicity of the membranes was enhanced by the addition of hydrophilic additives.Moreover,the pure water flux of the membranes increased from 2.0 L/(m2·h)to 69.3 L/(m2·h)and 50.2 L/(m2·h)by the addition of PVP and PEG.