Fluorinated Triphenylamine Structure And Triphenyl Substituted Pyridine Ring Structure Polyimide Materials

The emerging of semiconductor package,state-of-art display and 5G communication drive the rapid development of polyimide materials in the field of microelectronics fabrication.Although traditional polyimide films own exellent mechanical and thermal properties,they are expected to have improvement in specific performances to keep up with the increasing requirement in some industries.For example,in the current semiconductor display industry,PI as an important substrate materiral in main screen,are requires to have specified thermal stability and low thermal expansion coefficient.In flexible display and folding screen,PIs are required for excellent mechanical properties to withstand multiple bending.Camera under screen requires high transparency of PI films.In memory storage device,PIs are required to have suitable HOMO energy level for good hole transporting in the function of memory storage.In high frequency telecommunication of 5G era,how to reduce power passipation and signal transmission loss remain main tasks facing PCB panel industry.The performance tailoring of PIs are usually achieved by structural design.Herein,this thesis focuses on the studies of functional design of polyimides and“strcture-properties”corelation of the synthesized PIs,which includes the two following research parts:In the first part,two novel fluorinated triphenylamine diamine monomers,3,4,5-trifluoro-4’,4’’-dinitrotriphenylamineand2,5-bis（trifluoromethyl）-4,4’-dinitrotriphenylamine,were synthesized by cesium fluoride-mediated N-arylation of 3,4,5-trifluoroaniline and 2,5-bis（trifluoromethyl）aniline with p-fluoronitrobenzene,respectively,followed by palladium catalyzed hydrazine hydrate reduction.Eight novel triphenylamine-type aromatic polyimides were obtained by the synthesized diamines monomer condenstion with four aromatic dianhydrides.Thermal imidization with programmed heating offers flexible and strong films of PIs containing triphenylamine unit fluorinated with C-F bond and trifluoromethyl,respectively.Both series of films show excellent tensile properties,hydrophobic properties and thermal properties,with tensile strength reaching 122.08MPa,T₅ greater than 500 ^oC,T₁₀ reaching 583 ^oC,water contact angle 80^o-98.2^o.The cyclic voltammograms of the two series of films on indium oxide（ITO）coated glass substrates showed reversible electrochemical oxidation process.The trifluoromethylated series showed higher oxidation potential due to the introduction of greater electron-withdrawing effect of trifluoromethyl group than fluorine atom.The higher HOMO level of trifluoromethylated series indicates that PIs can be used as a potential hole transporting material.In the second part,employing biomass aromatic small molecule eugenol,which has similar structure to vanillin but greater rigid,thermal resistant polymer materials were synthesized with the undervalued molecule.Diamine（DHPA）containing diohenylpyridine structure was synthesized starting from eugenol via Chichibabin pyridine synthesis reaction,and was copolymerized with diamine（ODA）in a certain proportion toward the dianhydride（ODPA）to prepare six films with toughness and transparency.The copolyimide films showed excellent thermal stability due to the rigid triphenylpyridine ring unit,plus the substituting methoxy and polar hydroxyl groups to increase rotation hindrence.When DHPA molar ratio was 20%,the film showed the highest weight loss temperature as T_d10 reached 543 ^oC,which was 10.7%higher than that of the prestine PI₀（ODPA-ODA）.60%molar ratio of DHPA gave highest hydrophobicity as water contact angle reached maximum value of 93.7^o,which was 44%higher than that of the PI₀.The solubility of the copolyimide films improved with the increasing DHPA,meanwhile,the mechanical properties of copolyimide films maintained with the similar strength those of PI₀ when molar ratio of DHPA was under 30%,and the tensile modulus was almost unaffected.Generally,the comprehensive performance of the copolyimide films can be optimized by properly adjusting the diamine ratio,in a view to devolop more competant heat-resistant substrate material for adventing microelectronics.