Synthesis And Application Of Triarylimidazole-Containing Polymers

With the acceleration of industrialization,the emissions of heavy metals and the excessive use of fossil fuels have brought serious pollution to the earth's environment.Using cheap and high-performance materials to detect heavy metal ions and to replace fossil fuels for energy storage and conversion have become an important strategy to avoid environmental pollution.Triarylimidazole,as an important imidazole derivative,has been widely used in the fields of energy storage,optics,bio-medicine,and aerospace.Moreover,the triarylimidazole-modified polymers have not only retained their intrinsic properties but also have enhanced their thermal stability,solubility,and molecular designed.Based on the above characteristics,a series of triarylamidazole-containing polymers have been prepared and applied in Ag⁺fluorescent sensor and zinc-air batteries.The main contents of this thesis are as follows:(1)Preparation of triarylamidazole-containing polymers and the Ag⁺detection performance.Two novel benzoxazine monomers containing triphenylimidazole(TBZ)and triphenylimidazolium(MTBZ)moieties were synthesized from 2-(4-aminophenyl)-4,5-diphenyl-1h-imidazole by mannich condensation and methylation.The thermal ring-opening polymerization process of the two monomers was monitored by using ¹H NMR and GPC analyses,which demonstrated that such polymerizations proceeded through a rearrangement of ketal-type linkage in the main chain into mannich-type polymer along with the fast increasing in molecular weight.The structures of the triphenylimidazole-containing polybenzoxazines,PTBZ and PMTBZ,were verified by ¹H NMR and FT-IR spectroscopies,and the thermal and mechanical properties of such polybenzoxazines were investigated by TGA and DMA analyses.Owing to the good solubility of PMTBZ in common organic solvents,PMTBZ could be used as a chemodosimeter for the detection of Ag⁺through anion exchange between I^-anion in PMTBZ and acidic anion in Ag salts accompanying by forming Ag I precipitate,which exhibited high selectivity,good linearity in the Ag⁺concentration range of 0-20?M.Common cations such as Na⁺?Mg²⁺?Ni²⁺?Zn²⁺?Co²⁺?Ca²⁺?Mn²⁺did not interfere with the Ag⁺detection.(2)Preparation and ORR catalytic performance of N-doped carbon derived from cross-linked PTBZ.Hypercrosslinked polymer(namely CPTBZ)was synthesized by heterogeneous Friedel-Crafts cross-linking of PTBZ mentioned in the former chapter by using CCl₄as the dispersing and crosslinking agent and anhydrous Al Cl₃as the catalyst.The CPTBZ was then pyrolyzed at 900°C to give N-doped porous carbon(namely NDC-900).The as-fabricated NDC-900 catalyst was composed of aggregated,irregular-shaped nanoparticles with a high specific surface area(947.2 m²g^-1)and a porous structure.The N/O-doping levels were determined to be 3.39 at%and 4.74at%,respectively,in which N element was doped only in the form of pyridinic-N and graphitic-N with a relative content of 40.48%and 59.52%,respectively,as verified by XPS analysis.Based on above reasons,the NDC-900 catalyst exhibited a higher ORR activity than that of commercial Pt/C catalyst,the ORR onset potential(E₀),half-wave potential(E_1/2),and limiting current density(J_l)were determined to be 0.986 V,0.845V,and 5.66 m A cm^-2,respectively,in alkaline media.Moreover,NDC-900 catalyst can tolerate a high level of Me OH and CO at the selected potentials.In addition,the NDC-900-based Zn-air battery achieved a high power density of 131.4 m W cm^-2and a high specific capacity of 818.4 m Ah g^-1_Znat 5.0 m A cm^-2.(3)Preparation and Zn-air battery performance of Fe/Co/N-codoped carbon nanotube bifunctional electrocatalyst based on crosslinked triarylimidazole.Hyper-crosslinked polymer(namely CDIP)was synthesized by homogeneous Friedel-Crafts cross-linking of 2-(4,5-diphenyl-1h-imidazole-2-yl)-phenol(DIP)by using CHCl₃as the solvent/crosslinking agent and anhydrous Al Cl₃as catalyst.The Fe/Co/N-codoped carbon nanotube(namely Fe Co/N-CNT)bifunctional electrocatalyst was prepared by the co-coordination of CDIP with Co(NO₃)₂/Fe(NO₃)₃,followed by mixing with melamine template and then pyrolysis.In alkaline electrolyte,the Fe Co/N-CNT electrocatalyst exhibited a higher ORR activity(E₀=0.981 V,E_1/2=0.864 V)than that of Pt/C catalyst,together with an oxygen evolution reaction(OER)activity(E_j=10=1.620 V)that is comparable to Ir O₂catalyst.The reversible oxygen electrode index was determined to be 0.756 V,lower than that of Pt/C/Ir O₂composite catalyst.In addition,Zn-air battery assembled by using Fe Co/N-CNT air electrode delivered a high specific capacity of 779 m Ah g^-1_Znand a high power density of 144 m W cm^-2.Moreover,such a Zn-air battery could be repeatedly charged and discharged for 400 h at 5.0 m A cm^-2.(4)Preparation and Zn-air battery performance of Fe/Ni/N-codoped carbon nanosheets bifunctional catalyst based on triarylimidazole-containing polyaniline.Triarylimidazole-containing polyaniline(TPANI)oligmer was prepared by oxidative polymerization of 3-(4,5-diphenyl-1H-imidazol-2-yl)-phenylamine monomer by using ammonium sulfate as the oxidizing agent.The Fe/Ni/N-codoped graphene-like carbon nanosheets(namely Fe Ni/N-C-L)was prepared by the co-coordination of TPANI with Ni(NO₃)₂/Fe(NO₃)₃,followed by mixing with melamine template and then pyrolysis.In 0.1 M KOH electrolyte,the Fe Ni/N-C-L catalyst exhibited a higher ORR activity(E₀=0.975 V,E_1/2=0.850 V)than that of Pt/C catalyst,together with a higher OER activity(E_j=10=1.570 V)than that of Ir O₂catalyst.The reversible oxygen electrode index was as low as 0.720 V.Moreover,the catalytic contributions of Fe Ni alloy nanoparticles,M-N_xspecies(Fe-N_xand Ni-N_x),and N-C configurations(pyridinic-N and graphitic-N)to both ORR and OER were quantitatively estimated,in which the relative contributions to ORR were determined to be 2.94%,14.41%,and 82.65%,and to ORR were estimated to be 45.38%,35.85%,and 18.77%,respectively.These results indicated that the N-C configurations and M-N_xspecies are mainly responsible for the high ORR activity,whereas the ultrafine Fe Ni alloy nanoparticles and M-N_xspecies are essentially responsible for high OER activity of the Fe Ni/N-C-L catalyst.Based on above reasons,the Fe Ni/N-C-L-based primary Zn-air battery delivered both high peak power density(162 m W cm^-2)and high specific capacity(831 m Ah g^-1_Znat5.0 m A cm^-2).Importantly,the rechargeable Zn-air battery based on the Fe Ni/N-C-L catalyst could be repeatedly charged and discharged for 1100 h at 5.0 m A cm^-2.