Preparation And Properties Of Functional Polyimide Containing Pyridine Ring

Polyimide(PI),as a kind of special polymer materials with high heat stability,is one of the key materials for the development of high-tech industries in China.It is widely used in high-tech fields such as microelectronics and aviation industry etc.However,the traditional PI is insoluble and difficult to process,which restricts its further development and application.At present,high-performance PI products and technologies are still monopolized by foreign enterprises.Thus,the development of multifunctional PI with excellent solubility has always been an important research topic in the field of polymer materials.Pyridine ring has a rigid structure similar to benzene ring and a protonated nitrogen atom,which is helpful to promote the solubility of PI and ensure its high thermal stability.In this paper,soluble transparent PI and soluble photosensitive PI were synthesized based on the structure design of pyridine ring diamine monomer,and the solubility,optical properties,thermal properties and hydrophobic properties of the prepared polymers were investigated and discussed.Details are as follows:(1)Using p-nitroacetophenone and p-fluorobenzaldehyde as raw materials,a diamine monomer 4-(4-fluoro)Phenyl-2,6-bis4-(amino phenyl)pyridine(BAFP),whose structure contains pyridine ring and fluorine atom,was synthesized by improved Chichibabin cyclization reaction and Sn Cl₂/HCl reduction system.Then,using BAFP,4,6-diaminoresorcinol hydrochloride(DAR)and 4,4'-oxydiphthalic anhydride(ODPA)as raw materials,five kinds of soluble transparent PIs with pyridine ring,fluorine atom,hydroxyl group and ether bond were synthesized by chemical imidization.The results show that the series of PIs had good solubility and could be completely dissolved in common high-boiling organic solvents at 25?;the PI films had light color and high transparency,the transmittances of most films could reach 80%at 450 nm.In the nitrogen atmosphere,the temperatures of 10%weight loss of the polymers could be as high as 536?,maintaining high thermal properties.And most of the films showed certain hydrophobicity(the contact angle could reach 72°,and the water absorption was as low as 0.29%).(2)Two kinds of fluorinated polyimides PI-6 and PI-7 containing hydroxyl groups were synthesized by copolymerization of BAFP,DAR and 4,4'-(hexafluoroisopropyl)phthalic anhydride(6FDA)with the feed ratio of 1:4:5 and 2:3:5.Then,two soluble photosensitive polyimides PSPI-A and PSPI-B containing pyridine ring and hexafluoro isopropyl group were prepared by introducing methyl acrylate groups into the polyimide side chains by acylating hydroxyl groups.The results show that all the four polymers showed excellent solubility in common organic solvents in high and low boiling points at 25?.The transmittances of the films at 450 nm were above 90%,showing high transparency.And the four kinds of polymers all kept good thermal properties.Among them,in the nitrogen atmosphere,the temperatures of 10%weight loss of the two PSPIs were above 370?,and the temperature of 10%weight loss of fluorinated PIs could reach up to 540?.The films also showed good hydrophobicity(all contact angles were above 73°,the water absorption was as low as 0.21%).In addition,the prepared PSPI films could be photocrosslinked after UV exposure,and the conversion rate of double bonds could reach 68.3%,showing good photosensitivity.