Yi-Chun Kung

Solution-processable, high-Tg, ambipolar polyimide electrochromics bearing pyrenylamine units

Two new pyrenylamine-based polyimides were prepared from the polycondensation reaction of N,N-di(4-aminophenyl)-1-aminopyrene with pyromellitic dianhydride (PMDA) or 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). The polyimide derived from PMDA is soluble in hot N-methyl-2-pyrrolidone and can be solution-cast into a flexible and strong film. The polyimides showed high glass transition temperatures (Tg > 364 °C) and high thermal stability. Cyclic voltammetry studies revealed that these two polyimides were ambipolar; they showed well-defined and reversible redox couples during both p- and n-doping processes, together with multi-electrochromic behaviors. The polymer films also exhibited high coloration efficiency, high redox stability, and fast response time.

Fluorescent and electrochromic polyamides with pyrenylamine chromophore

A series of novel polyamides with a pyrenylamine chromophore in the backbone were prepared from a newly synthesized diamine monomer, N,N-di(4-aminophenyl)-1-aminopyrene, and various dicarboxylic acids via the phosphorylation polyamidation technique. These polyamides were readily soluble in many organic solvents and could be solution-cast into tough and amorphous films. They had useful levels of thermal stability with glass-transition temperatures in the range of 246–326 °C and 10% weight loss temperatures in excess of 500 °C. The dilute NMP solutions of these polyamides exhibited fluorescence maxima around 522–544 nm with quantum yields up to 30.2%. These polyamides also showed remarkable fluorescence solvatochromism in various solvents. The polymer films showed reversible electrochemical oxidation and reduction accompanied by strong color changes from the yellow neutral state to a purple oxidized state and to an orange reduced state. The anodically electrochromic films had high coloration efficiency (up to 172 cm2 C−1 at 834 nm) and good redox stability, which still retained a high electroactivity after long-term redox cycles.

Novel luminescent and electrochromic polyhydrazides and polyoxadiazoles bearing pyrenylamine moieties

New aromatic polyhydrazides bearing redox-active pyrenylamine unit were prepared from the polycondensation reactions of N,N-di(4-carboxyphenyl)-1-aminopyrene with terephthalic dihydrazide (TPH) and isophthalic dihydrazide (IPH), respectively, via the phosphorylation reaction. These two hydrazide polymers could be further cyclodehydrated into the corresponding oxadiazole polymers in the range of 300–400 °C in the solid state. The resulting poly(1,3,4-oxdiazole)s had high glass-transition temperatures (298–304 °C) and high thermal stability (10% weight-loss temperature in excess of 520 °C). The dilute solutions of all the hydrazide and oxadiazole polymers showed a medium to high fluorescence with emission maxima around 457–545 nm in the blue to yellowish-green region. The polymer films revealed one redox couples upon electrochemical oxidation, together with interesting electrochromic behaviors: color changes from pale yellow neutral state to pale green oxidized states. Additionally, cyclic voltammetry studies of the oxadiazole polymers also showed reduction processes accompanied by strong color changes from pale yellow to orange, red or deep blue due to the formation of radical anions of the oxadiazole and pyrene units.