Synthesis And Properties Of Polyamide Metal Complexes Based On Pyridine-transition Metal Ions Coordination

In recent years,there are more and more researches on polymer metal complexes（PMCs）,which benefit from their unique structure and properties.PMCs not only have the advantages of easy processing of polymer,strong structural design,various synthesis methods,controllable physical and chemical properties,but also have interesting photoelectric properties,catalytic ability and electromagnetic properties brought by metal compounds.It plays an important role in the application of smart materials,heavy metal ion adsorption,catalysis,polymer based magnetic ceramic precursor and other fields.Among them,the magnetic ceramics prepared from PMCs as polymer based ceramic precursors have the following advantages:lower ceramization temperature（<1000℃）,convenient processing,and various forming methods.In addition,PMCs possess controllable physical and chemical properties due to various synthesis methods.The key to the synthesis of PMC lies in the synthesis of chelating polymer ligand（CPL）.The simplest method to synthesize CPL is the synthesis of monomer with chelating fragments,and then the copolymerization of monomer to obtain polymer ligand.In addition,Aza-Michael addition is considered to be a simple,efficient and economically efficient strategy for synthesizing new structure.Thus,we synthesized pyridine-containing diester monomer（PYDE）via Aza-Michael addition.On this basis,different polyamide ligands containing pyridine groups were synthesized by bulk polycondensation method,and different transition metal salts were selected for complexation to prepare different polyamide metal complexes based on pyridine-transition metal coordination.The first chapter reviewed the background.The second chapter synthesized polyamide metal complexes and applied them as the precursors of magnetic ceramics.The third chapter selected bio-based monomers to prepare bio-based polyamide metal complexes,and focused on the change of the properties of transition metal ions before and after complexing,which provides a new simple and environmentally friendly synthesis way for new functional bio-based polyamide metal complexes.In the first chapter,the advantages,applications and synthetic modification methods of PMCs and polyamide metal complexes are reviewed,and the advantages of Michael addition in the synthesis of new molecular structures and polymer functionalization are introduced.Finally,the preparation methods and performance evaluation parameters of polymer-derived magnetic ceramics are summarized.In the second chapter,a new strategy was developed to prepare magnetoceramics through a bulk pyrolysis of novel Fe-containing polyamide preceramic precursors at low pyrolysis temperature.A series of novel polyamides with different chemical structures were synthesized by bulk Michael addition and polycondensation,and their structures were characterized fully.Polymer precursors（PPs）were prepared by direct melt blending polyamides and Fe Cl3,and polymer-derived ceramics（PDCs）were prepared via the pyrolysis of PPs.The polyamide structure with pendant pyridine groups in repeating units makes the Fe complexes uniformly dispersed in matrix.The relationship between magnetoceramic compositions and PP structures was investigated by TGA,XPS,XRD,FE-SEM,FE-TEM and VSM characterizations.Different chemical structures and Fe catalysis effect lead to different thermal decomposition processes of PPs.Increasing crystal-Fe content in PDCs contributes to higher magnetic properties.The morphology of crystal phases in PDCs relies on the structures of PPs and pyrolysis temperature.Different pyrolysis temperatures and chemical structures of PPs bring about different Fe crystal phases and carbon crystal state of nanosheets or nanofiber bundles.In the third chapter,we synthesized several bio-based polyoxamido-ureas（POA-Ps）with pendent pyridine groups through a bulk Aza-Michael addition and polycondensation method from flexible bio-based Priamine 1074 and dioxalamide diester（HDODE）.The POA-Ps were chelated with transition metal salts（Co Cl₂·6H₂O and Ni Cl₂·6H₂O）to prepare polyamide metal complex（POA-P-Ms,M is Co or Ni）.The structures of POA-Ps and intermediates were determined by FT-IR,¹H-NMR,ESI-MS,and GPC characterization methods.Subsequently,by DSC,TGA,DMA,XRD,water contact angle test,optical microscopy,SEM,and UV-Vis characterization methods,the changes of the structure and properties of the polyoxamide ligand before and after complexing with the transition metal salt were deeply investigated.The results show that POA-Ps and POA-P-Ms have excellent thermal stability,good thermal working and mechanical properties.Interestingly,POA-P-Ms crosslinked by transition metal and polyamide ligand not only have reproducibility,certain thermal repairing ability,but also have wide temperature range damping and solvatochromic properties.These properties of POA-P-Ms are closely related to the content of oxalamide structure in POA-Ps,the rigidity of polymer network and the type of metal ions that are complexed.In conclusion,we have developed a simple and environmentally friendly synthesis scheme of new bio-based polyamide metal complexes,which not only meets the requirements of the green and sustainable development of polymer materials,but also the functional characteristics of polyamide metal complexes.These merits make them expected to become a new polymer damping material and environmental stimulus responsing intelligent material.