Study On Molecular Orbital Energy And Its Properties Of Flexible,Colorless And Transparent Polyimide Film Materials

With the rapid development of electronic information,flexible electronic material has become one of the most active research directions in recent years.And the flexible and colorless polyimide based material is one of the key materials.Polyimide film coloration has been one of the important factors affecting its application on flexible display devices and flexible solar cells.The strength of the intramolecular charge transfer interaction determined by the coloration and chemical structure of the polyimide film is dependent on the film preparation conditions(curing temperature,monomer purity,solvent residue,etc.).This paper mainly studies the intramolecular and intermolecular charge transfer effects theoretically,and preferably prepares the monomers of the flexible colorless polyimide film.After experimental verification,a high quality flexible colorless transparent polyimide film is obtained.This paper mainly studies on the following three aspects:(1)Geometry optimization and frontier molecular orbital calculation of diamine and dianhydride monomers and derived polyimide polymer models are conducted,in which density functional theory(DFT)method B3 LYP function model combined with a 6-31 G basis set is used.Respective ground state energy,dihedral angle,HOMO,LUMO molecular orbital energy and corresponding bandgap values are obtained,and the influence of charge transfer(CT)between monomer and polyimide molecules on light transmission is investigated from both molecular structure and electronic structure.(2)The HOMO and LUMO energy levels of diamine and dianhydride monomers are measured by electrochemical cyclic voltammetry method,and the electronic structure of the monomers is further investigated.At the same time,the derivatized polyimide film is prepared and the effects of different curing temperatures on the coloration of the film are explored.(3)The optical properties of the polyimide film are measured by an ultraviolet absorption spectrometer,the thermal stability of the polyimide film is measured by a thermogravimetric analyzer,and the mechanical properties of the polyimide film are measured by a film tension meter.And the effects of geometry and electronic structures on various properties are further discussed and summarized.