Preparation Of Polyacrylonitrile-based Functional Polymer Brushes By Combination Of Controlled Radical Polymerization And Click Chemistry And Its Applications

In this paper,based on the collaborative advantage of Cu?0?mediated controlled radical polymerization?Cu?0?-CRP?and click chemistry in the preparation of functional polymer brushes,the controllable polyacrylonitrile?PAN?was firstly prepared by CRP,and a series of functional polymer brushes were successfully prepared using nitrile click chemistry.Furthermore,polymer brushes comprehensive applications in self-assembly,nanofiber and Pickering emulsion were explored.The main work is as follows:?1?The functional polymer brushes of poly?acrylonitrile-g-N,N-dimethylamino ethyl methacrylate??PAN-g-PDMAEMA?has been efficiently synthesized by the combination of Cu?0?-CRP and PAN nitrile click chemistry.Firstly,the controlled molecular weights PAN and PDMAEMA were prepared by Cu?0?-CRP with ethyl bromoisobutyrate?EBiB?as initiator,tetramethylethylenediamine?TEMED?as ligand and Cu?0?as catalyst.Then,PDMAEMA-N₃ was synthesized by substitution reaction of PDMAEMA containing bromine-ended groups with sodium azide at 40 ^oC.Finally,PAN-g-PDMAEMA was prepared by the click reaction between the nitrile of PAN and PDMAEMA-N₃ under ammonium chloride?NH₄Cl?as catalyst at 120 ^oC.The polymer was further confirmed by GPC,FTIR spectrum,UV-Vis analyses,¹H NMR spectra and TGA.Moreover,PAN-g-PDMAEMA exhibited excellent self-assembly performance and could autonomously develop the spindle,spheres structure micelle in DMF/water mixture solvent.In the process of self-assembly,PAN acted as the backbone of the functional polymer brushes due to its hydrophobic group and PDMAEMA as the branch of the functional polymer brushes with its hydrophilic group.?2?Poly?acrylonitrile-g-ethylene alcohol??PAN-g-PEG?polymer brushes were efficiently synthesized by combination of Cu?0?-CRP,Mitsunobu reaction and Click Chemistry.Firstly,Cu?0?-CRP was employed to prepare well-controlled PAN with EBiB as initiator,TEMED as ligand and Cu?0?as catalyst.The GPC data indicated that the polymerization of AN accords with the first-order reaction kinetics.The molecular weight?M_n?and molecular weight distribution?M_w/M_n?of PAN possess well-controllability.Then,the tetrazole-containing PAN was prepared by the click reaction between PAN and NaN₃ with NH₄Cl as catalyst at 120 ^oC.Finally,PAN-g-PEG polymer brushes was prepared from tetrazole-containing PAN and poly?ethyl alcohol??PEG?using Mitsunobu reaction with triphenylphosphine?PPh₃?and diethyl azodicarboxylate?DEAD?.The polymer was further confirmed by GPC,FTIR spectrum,UV-Vis analyses,¹H NMR spectra and TGA.The SEM picture of PAN-g-PEG nanofiber show that the diameter was about 95 nm and PAN-g-PEG nanofiber possess a smooth surface.?3?The combination of Cu?0?-CRP,Mitsunobu reaction and PAN nitrile click chemistry was used to graft functional polymer on the surface of cellulose nanocrystals?CNC?.And the modified CNC as the stabilizer realized the RAFT-mediated Pickering emulsionpolymerizationofmethylmethacrylate?MMA?.Firstly,poly?acrylonitrile-r-butylacrylate??poly?AN-r-nBA??wassynthesizedby Cu?0?-mediated CRP with EBiB as initiator,TEMED as ligand.Under 120 ^oC conditions,poly?AN-r-nBA?was further modified via click chemistry stategy with NaN₃ to obtain poly?ethylene tetrazole-r-butyl acrylate??poly?VT-r-nBA??.Then,poly?VT-r-nBA?was grafted onto CNC through Mitsunobu reaction to achieve poly?VT-r-nBA?-g-CNC.Meanwhile,we investigate Pickering emulsion stabilized of CNC and poly?VT-r-nBA?-g-CNC by using RAFT polymerization with MMA as monomer,water-soluble potassium persulfate?KPS?as initiator and oil-soluble4-cyanopentanoic acid dithiobenzoate?CPADB?as chain transfer agent,respectively.The preparation of polymethyl methacrylate?PMMA?with controlled molecular weights and low M_w/M_n values were successfully synthesized by the Pickering emulsion.Furthermore,rheological analysis suggested that the prepared Pickering emulsion possessed good stability under the influence of strain,time,frequency and temperature,respectively.Furthermore,the recycling utilization of CNC and poly?VT-r-nBA?-g-CNC could be simply realized through centrifugal separation.