Efficient And Controllable Preparation Of Polymer Nanowires And Its Application In Flocculation And Nanofiltration

Polymer nanowires have many special properties due to their anisotropic morphology and structure,and are widely used in the fields of super flocculant,nanofiltration separation and lubricating oil rheological modification.Polymerinduced self-assembly(PISA)is an efficient method for preparing polymer nanomaterials.However,the experimental window for obtaining polymer nanowires is often very narrow,resulting in a very low repetition(high defective ratio)for preparing polymer nanowires,which greatly hinders the further application of polymer nanowires.In addition,the structural stability of polymer nanowire is very important to maintain the properties determined by morphology and structure.Chemical crosslinking is a common method to enhance the structural stability of polymer nanowires,which can be achieved by post-polymerization crosslinking or in situ crosslinking.Compared with post-polymerization crosslinking,in situ crosslinking is a simpler and more direct method to prepare polymer nanowires with stable structures.However,in situ crosslinking often leads to the deterioration of the activity of solvophobic chain segments,thus inhibiting the morphological transformation,and only spherical micelles with crosslinked structure can be obtained(nanomaterials with crosslinked structure and high-level morphology,such as nanowires and vesicles,cannot be obtained).Based on the above problems,in this paper,polymer nanowire with cross-linked structure was obtained RAFT reagent was prepared by RAFT polymerization.Then,using PDMAEMA as macromolecular RAFT reagent,benzyl methacrylate(BzMA)as monomer and 1,6-hexadiol dimethacrylate(HMA)as crosslinking agent,crosslinked cationic polymer nanomaterials were prepared by in situ crosslinking PISA in ethanol.The results show that the experimental window for obtaining polymer nanowires in the in situ crosslinked PISA system is significantly expanded,thus greatly improving the preparation repetition of polymer nanowires.In addition,the polymer nanowires obtained by in situ crosslinking PISA showed good structural stability and could still maintain their morphology and structure completely in a good solvent.We studied the application of polymer nanowire in flocculation and nanofiltration separation.The results show that good structural stability is very important for the application of polymer nanowire.1)Poly(2-(dimethyl amino)ethyl methacrylate)(PDMAEMA)was prepared by RAFT polymerization.Then,using PDMAEMA as macromolecular RAFT reagent,benzyl methacrylate(BzMA)as monomer and 1,6-hexadiol dimethacrylate(HMA)as crosslinking agent,crosslinked cationic polymer nanomaterials were prepared by in situ crosslinking PISA in ethanol.The study showed that the experimental window of polymer nanowires obtained by in-situ crosslinking PISA was significantly expanded,thus greatly improving the preparation repetition rate of polymer nanowires.Moreover,the polymer nanowires obtained by in-situ crosslinking PISA had good structural stability and could still maintain their morphology and structure in a good solvent.We studied the application of polymer nanowire in flocculation and nanofiltration separation.The results show that good structural stability is very important for the application of polymer nanowire.2)Aqueous PISA is environmentally friendly,solvent cost is very low,and can be used to synthesize some polymer materials with good biocompatibility,so it has attracted wide attention.RAFT polymerization is used to obtain poly(N,Ndimethylacrylamide)(PDMA)and polyacrylic acid(PAA)macromolecular reagents.Subsequently,the polymer nanomaterials were prepared by in situ crosslinking PISA with diacetone acrylamide(DAAm)and crosslinking agents N,N-methylene bis-acrylamide(BIS)in aqueous phase using a binary mixture of macro-RAFT reagents of PDMA and PAA,and the morphometric phase diagram of the polymer nanomaterials was drawn based on the results.Compared with the traditional PISA(without crosslinking agent),the experimental window for obtaining polymer nanowires in the in-situ crosslinked PISA system is significantly expanded,which improves the repetition of polymer nanowires prepared by in-situ crosslinked PISA(reduces the defective ratio).At the same time,the polymer nanowires obtained by in situ crosslinking PISA have good structural stability,and the morphology can be remained in good solvent(THF)without being destroyed.In the flocculation experiment of water dispersion with kaolin as model pollutant,the cross-linked nanowires have good flocculation effect.It is superior to uncross-linked nanowires and commercial flocculants.The nanofiltration composite membrane prepared by crosslinked nanowires can effectively remove dyes from dye wastewater(the rejection is greater than 99.5%),which indicates that the nanofiltration membrane prepared by crosslinked nanowires is expected to be used in the treatment of dye wastewater.