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

The silicon-based memory materials as the leading sector of the traditional microelectronic device, while the properties and economic factors limits the shrink of its dimensions, could not meet the demand of the prospective market any more. There are many charming qualities for polymeric materials such as high flexibility and processability. Furthermore, polymeric materials can be processed into three-dimensional?3D? structures composing of layer-by-layer arrangements at low costs, which makes fabrication of high-density memory devices economically possible, so they has been a research hotspot. Aromatic polyimides?PIs? are now widely used in photoelectric information storage by via of its high and low temperature resistance, low dielectric constant, flexibility and easy film ability. The research of memory characteristics of polyimides with new molecular structures is currently popular in the field of aromatic polymers.Two series of aromatic diamines were designed and synthesized base on carbazole and fluorenone. Diamines obtained were characterized by ¹H NMR, ¹³C NMR, FT-IR and elemental analysis. Two series of novel organosoluble aromatic polyimides were successfully synthesized by using of diamines obtained reacting with dianhydrides such as pyromelitic dianhydride?PMDA? and 2,2',3,3'-biphenyl tetracarboxylic dianhydride?BPDA?. These polyimides were characterized by ultraviolet visible, fluorescence, thermal gravimetric analysis, different scanning calorimetry, cyclic voltammetry, elemental 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. The electrical switching characteristics of sandwich structured memory devices based on the prepared polyimides have also been investigated, including the switching type, retention time, switching cycle performance.The main research work of this paper is as follows:1. 9-?2?-bromobenzyl?-9H-carbazole-3,6-diamine was synthesized by using carbazole as the starting material. A series of new aromatic diamines were synthesized by reacting 9-?2?-bromobenzyl?-9H-carbazole-3,6-diamine with kinds of arylboronic acid. The characterizations of these diamines and related intermediates were carried out by means of FT-IR, ¹H NMR, ¹³C NMR and elemental analysis.2. 2-bromo-9,9?-di?4-aminophenyl?fluorene was synthesized by using fluorenone via bromination and necleophilic substitution reaction. A series of new aromatic diamines were synthesized by reacting 2-bromo-9,9?-di?4-aminophenyl?fluorene with kinds of arylboronic acid. The characterizations of these diamines and related intermediates were characterized by means of FT-IR, ¹H NMR, ¹³C NMR and elemental analysis.3. Two series of new polyimides were synthesized from twelve new aromatic diamines with two aromatic dianhydrides by a two-step polycondensation method. All polyimides show preferable thermal properties. The temperatures of 5 % gravimetric losses of the polyimides reach over 350 °C under nitrogen. The residual yields at 900 °C for all the polymers are above 60 wt%. The polymers exhibit perfect solubility and optical property due to introduction of asymmetric diamine monomers.4. The synthetic polyimides were prepared into ITO/PI/Al storage devices, then to explore the storage performance of different polymer and its threshold voltage.