Synthesis And Memory Characteristics Of Soluble Polyimides Based On Novel Aromatic Diamines

With the rapid development of information technology,electronic products move in the direction of miniaturization,intellectualization,generalization.Restricted by the limited size effect,the conventional silicon-based memory materials could not meet the demand of the prospective market.Developing a storage material of low cost,good performance and high stability has already become a focus of many researchers.Meanwhile,organic memory materials have attracted much attention by virtue of its charming qualities such as feasible manipulation of the structures during synthesis,high processability,three-dimensional(3D)accumulation ability and large data storage capacity.Wherein,functionalized polyimides(PIs)is now widely used in photoelectric information storage because of its easy film ability,heat resistance and low dielectric constant,etc.Exploring the relationship between the molecular structure of polyimide and storage performance has become one of the hotspots in the field of polymer material research.Two series of novel aromatic diamines were designed and synthesized using bis(4-methoxyphenyl)methanone and 3,5-dinitrobenzoyl chloride as the starting materials,respectively.The resulting diamines were characterized by 1HNMR,13 CNMR,FT-IR and elementary analysis.Two series of novel organosoluble aromatic polyimides were successfully synthesized by a conventional two-step procedure using diamines obtained polycondensation with dianhydrides such as Pyromelitic dianhydride(PMDA)and 2,2',3,3'-biphenyl tetracarboxylic dianhydride(BPDA).These polyimides were characterized by FT-IR,ultraviolet visible,fluorescence,differential scanning calorimetry,thermal gravimetric analysis,cyclic voltammetry,elementary analysis and so on.The HOMOs and LUMOs orbital energy level were calculated from DET at the gaussian 09 with the wb97XD/6-31G(D,P)basis set.Memory devices with the configuration of Al/polyimide/ITO were fabricated by means of conventional solution spin-coating to test its storage performance.The main research work of this paper are as follows:1.Bis(3-amino-5-bromo-4-methoxyphenyl)methanone was synthesized via nitration,bromination,reduction using bis(4-methoxyphenyl)methanone as the starting material.A series of of new aromatic diamines were synthesized by Suzuki coupling reaction using bis(3-amino-5-bromo-4-methoxyphenyl)methanone with kinds of arylboronic acid.The characterizations of these diamines and related intermediates were carried out by means of FT-IR,1H NMR,13 C NMR and elemental analysis methods.2.(4-bromophenyl)(3,5-diaminophenyl)methanone was synthesized via F-C acylation,reduction using 3,5-dinitrobenzoyl chloride as the starting material.A series of new aromatic diamines were synthesized by Suzuki coupling reaction using(4-bromophenyl)(3,5-diaminophenyl)methanone with kinds of arylboronic acid.The characterizations of these diamines and related intermediates were carried out by means of FT-IR,1H NMR,13 C NMR and elemental analysis methods.3.Two series of new polyimides,characterized by GPC,FT-IR and elemental analysis,were synthesized from nine new aromatic diamines with two aromatic dianhydrides by a two-step polycondensation method.The polyimides exhibited excellent organo-solubility and thermal stability with the temperature of 5 % gravimetric losses over 300? under nitrogen,while 10%gravimetric losses over 400?.The residual yields at 800? for all the polymers are around 60wt%.4.The PI films was formed through spin-coating onto the ITO glass substrate.Then,the Al top electrodes was formed by magnetron sputtering onto the polymer surface to achieve memory devices,some of which show high ON/OFF current ratios up to 104 and long retention times of104 s under ambient atmosphere without any encapsulation.No obvious fluctuation was observed in the current of the ON state and OFF state during the test,which means the devices were stable and could meet the requirement in the practical application.