Study On Synthesis And Properties Of Semiaromatic Polyamides Containing Pyridine Ring In Main Chain

Pyridine ring,as a kind of important aromatic heterocyclic structure,can significantly improve the solubility,thermal resistance and mechanical properties of polymers.Herein,pyridine ring are mainly used to modify aromatic polyamide and aromatic polyimide structure,which can improve their processing performance and mechanical performance and expand polymers' application in electromagnetics,organic ligand synthesis,catalysis and other fields.Until now,only complicate monomers containing pyridine ring are studied in detail,while aromatic homopolyamides based on pyridine ring and the effect of this kind heterocyclic ring on the properties of aromatic polyamides have not been reported yet,which is crucial for theunderstanding of the single chain behavior and multichain aggregation behavior of aromatic polyamides.Therefore,it is important to synthesizeand study the new homopolyamides containing single pyridine heterocyclic structures as constitutional unit.In this paper,based on the widely used in electrical products,automobile industry of the semi aromatic polyamide as the break through point,we synthesized new semi-aromatic polyamides containing single pyridine ring in the main chain.The semi-aromatic polyamides structures were confirmed by FT-IR,elementary analysis,¹H-NMR and ¹³C-NMR,and their solubility,thermal property,mechanical property,aggregate structures were investigated and discussed all-sided.Based on the characteristics of the synthesis of heterocyclic semi-aromatic polyamide,a new template method for preparing nanomaterials by in-situ polymerization was proposed.A series of novel semi-aromatic polyamides containing 2,5-pyridine ring in the main chain,such as poly?tetramethylene 2,5-pyridine dicroboxamide??PA4Py?,poly?hexamethylene 2,5-pyridine dicroboxamide??PA6Py?,poly?decame-thylene 2,5-pyridine dicroboxamide??PAlOPy?,poly?dodecamethylene 2,5-pyridine dicroboxamide??PA 12Py?were successfully synthesized through a three-step procedure:salt formation,prepolymerization and solid-state polymerization.The aqueous salifying system was explored,and the optimum conditions of salifying process were determined.The parameters such as pre-polymerization temperature,pre-polymerization time and solid-state polymerization were also studied and optimized.The performance of the semi-aromatic polyamides containing 2,5-pyridine ring in main chain was characterized,the results showed that the series of semi-aromatic polyamide has excellent thermal performance,5%heat temperature?T5%?are above 400?,the polyamides exhibited good solubility in polar organic solvents,the preparation of aromatic polyamide films has good mechanical properties and low water absorption.Taken 2,5-pyridine dicarboxylic acid,terephthalic acid and diamine as the starting materials,a semi-aromatic copolymer PAlOT/lOPy was synthesized by salt,prepolymerization and solid phase polymerization.The resulted indicated that copolyamide films with excellent thermal and mechanical properties,their tensile strength was 71-82MPa,and the elongation at break was 5-10%.A noval semi-aromatic polyamide PA6PI containing 2,6-pyridine heterocyclic ring in main chain was synthesized through "one step polymerization" between 2,6-pyridine dicarboxylic acid and 1,6-hexamethylenediamine.The structure of PA6PI was confirmed by FT-IR,NMR and elemental analysis.The results show that PA6PI exhibited good solubility in polar organic solvents,PA6PI film has good thermal stability and mechanical properties,5%thermal degradation temperature?T₅%?of up to 400?,the maximum temperature is 470??T_max?degradation rate,and the transmittance can reach 90%in the visible light range.In this paper,taken semi-aromatic amide salt containing pyridine ring and nanoparticle precursor as raw materials,a new route was proposed to fabricate nanoparticlesis through the coordination function and situ polymerization.The method based on semi-aromatic polyamide PA6Py template matrix,uniform nanoparticles coated by condensation polymerization in the polymer matrix,then calcination,polymer matrix and the carbide strip,the final preparation of uniform particle size of nanoparticles.The average diameter of ?-Al₂O₃ and anatase TiO₂ nanoparticles is 10.1 nm and 12 nm,respectively.When the mole ratio of nanoparticle precursor and amide salt is expanded by 10 times,the diameter of nanoparticles will grow up to about 4 times.After the surface modification of?-Al₂O₃ and anatase TiO₂ with carboxyl terminated polystyrene and poly ethylene oxide,we obtain the colloidal ?-Al₂O₃ and anatase TiO₂ nanocrystals with core-shell structure,which effectively prevent the agglomeration of nanoparticles,improvethe surface activity,and lay foundation for it following application.