| Electrochromism refers to a phenomenon that a material changes colors when the material takes place reversible redox reaction induced by applied voltage and its optical properties exhibit reversible changes in visible light region.The electrochromic materials are widely used in display devices,smart windows,glare free mirror,military camouflage et al,which will be the heat point in electrochromism on account of their facile molecular design,multi color changes,easy processing,low costs and so on.The rapid development of information technology demands the memory device to be non-volatile,high-density data storage and low cost.The fabrication and application of the traditional silicon-based memory device have met many difficulties.Polymer non-volatile memory devices,which not only overcome the disadvantage of silicon-based semiconductor device but also possess some advantages such as flexible,easy fabrication and light-weight,but most likely breaking through limitation of scaling difficulties,have become the active research topic in new non-volatile data storage technology.Polymer electrical memory materials exist different conductivity states at applied voltage,which will fulfill the need of ultra-high density and ultra-capacity data storage.So they are promising candidates for next generation non-volatile memories.The functional and soluble polyimides,due to their excellent thermal stability,chemical stability and film-developing ability,have been widely used in optoelectronic devices.In this dissertation,novel functional polyimdes with different substituents have been synthesized and characterized by FTIR,1H NMR and elemental analysis.The effects of the different structure on thermal stability,solubility,electrochemical,electrochromics and electrical switching properties were studied systematically.PIs were prepared through one step method by the polycondensation reaction of 2,2′-bis(4-amino-3-trifluoromethylthylphenoxy)biphenyl and 2,2′-bis(4-amino-3-meth-oxyphenoxy)biphenyl respectively,with various commercially available tetracarboxylic dianhydrides,respectively.These PIs showed well soluble in many polar organic solvents and excellent thermal stability.In the electrochromic applications,PIs with different dianhydrides moiety showed different colors,however,the color charge is not obvious when electron withdrawing groups existed in dianhydrides moiety.The diamine moiety has very little direct influence on the reduction of the PIs.These PIs with trifluoromethylthyl have lower reduction potential and higher electrochromic coloring efficiency.In memory devices applications,PI-a,PI-b,PI-c and PI-d exhibited nonvolatile and rewritable flash type memory characteristics,whereas,PI-e demonstrated write-once read many times(WORM)memory capability.The PIs containing-OCH3 group-based devices show lower threshold voltage,while containing-CF3 group-based memory devices exhibits a larger ON/OFF current ratio.Poly(amic acid-imide)s containing triphenylamine with different substituents were prepared by the polycondensation reactions of 4,4′-diamino-4′′-phenoxytriphenylamine,4,4′-diamino-4′′-methoxytriphenylamine,4,4′-diamino-4′′-fluorotriphenylamine,4,4’-damino-2’’,4’’-difluorotriphenylamine and 3,3’,4,4’-diphenylsulfonetetracarboxylic(DSDA)respectively by partial imidization at moderate temperatures.The electrochromic properties of these polymers were studied by two kinds of electrolyte solution which are acetonitrile solution containing tetrabutylammonium perchlorate(TBAP)or p-toluenesulfonic(TsOH).The results showed that coloration changed from a colorless neutral state to blue oxidized state in the electrochromic process.The electrochemical performance was different depending on different electrolytes.Compared to common TBAP as electrolyte solution,in TsOH electrolyte solution PAA-IM has good cycle stability and PAA-IM-F displays more excellent stability,higher coloration efficiency and larger contrast of optical transmittance change. |
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