Research On The Separation Properties Preparation Of Poly(Arylene Ether Nitrile) Composite Membrane

Because of the inclusion of an ether bond,an aromatic ring,and a cyanogroup structure in its main chain,polyarylene ether nitriles（PEN）are a new type of high-performance polymer with good thermal stability,mechanical stability,corrosion resistance,and forming capacity.There are many potential applications in aerospace,national security,electronic communication and other specialized industries.By molecular design,specific functionalized side groups such as carboxyl and sulfonic groups are introduced in the structure to increase the surface hydrophilicity of PEN,while also providing the possibility for further functional modification,increasing its application potential in the water treatment industry.Therefore,in this thesis,functional polyarylene ether nitriles with carboxyl group in side chain was used as separation material,and functionalized modification was carried out on the basis of the structure of highly stable polyarylene ether nitriles,to explore its application potential in the field of efficient treatment of dye wastewater.Firstly,through molecular structure design,phenolphthalein was chemically reduced to phenolphthalein monomer containing carboxyl,and then with 2,6-difluorobenzonitrile,bisphenol A and other main materials,through nucleophilic substitution reaction to synthesize the side chain of different carboxyl content of polyarylene ether nitriles copolymers,and the relationship between the structure and properties of different carboxyl content of polyarylene ether nitriles was systematically studied.The best synthesis process of aryl ether nitrile with different carboxyl content,mechanical properties,molecular weight and separation of various dyes was obtained.Secondly,a polyarylene ether nitriles composite membrane was constructed based on a layer-on-layer self-assembly strategy.The carboxyl functionalized polyarylene ether nitriles（CPEN）was used as the substrate membrane,and the carboxyl group on the surface provided the reactive site for Fe³⁺or bovine serum protein（BSA）nanoparticles,and the Fe³⁺/BSA self-assembly layer was constructed.Due to the electrostatic interaction between Fe³⁺and BSA and the lack of multi-layer aggregate/particle surface connection network,the separation performance of the prepared membranes was lower than expected.The potential mechanism for the formation of the efficient multilayer structure is to construct a denser membrane structure on the surface using the polyphenol additive tannic acid（TA）during self-assembly.The multi-layer self-assembled(Fe³⁺/BSA@TA)₃membrane constructed by TA showed good separation efficiency in the low pressure vacuum filtration process,and the adsorption rates of methylene blue（MLB）and Congo red（CR）dyes were both greater than 99.8%at 0.09MPa.In addition,in the whole four cycles of filtration test,the MLB retention rate remained above 99%,indicating that(Fe³⁺/BSA@TA)₃ membrane has good stability.Finally,in order to achieve a higher utilization rate of raw materials and better dyestuff separation performance,polyarylene ether nitriles composite separation membranes were obtained by vacuum deposition method with polyarylene ether nitriles as the matrix membrane and single-layer graphene oxide（GO）as the main raw material.Nanoparticle（TA-APTES NPs）were prepared by Michael’s addition or Schiff-based reaction between TA and ampropyltriethioxy silane（APTES）.The lamellar GO membrane is functionalized to expand the layer spacing of the GO composite membrane,and its water permeability reachs 111.67 L m^-2 h^-1 bar^-1,which is about 15 times that of the original GO film.At the same time,the polyarylene ether nitriles composite separation membranes exhibit high rejection performance for a variety of dyes and salt solutions.In addition,the covalent cross-linking between TA-APTES NPs and GO films improves the long-term stability of GO composite membranes in aqueous solvents.