Sheng-Huei Hsiao

Highly stable anodic green electrochromic aromatic polyamides: synthesis and electrochromic properties

A 4-methoxy-substituted triphenylamine containing the aromatic diamine, 4,4′-diamino-4″-methoxytriphenylamine (2), was synthesized by the caesium fluoride-mediated condensation of p-anisidine with 4-fluoronitrobenzene, followed by palladium-catalyzed hydrazine reduction of the dinitro intermediate. A series of new polyamides with pendent 4-methoxy-substituted triphenylamine (TPA) units having inherent viscosities of 0.27–1.39 dL g−1 were prepared via the direct phosphorylation polycondensation of various dicarboxylic acids and the diamine (2). All the polymers were readily soluble in many organic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N,N-dimethylacetamide (DMAc), and could be solution-cast into tough and flexible polymer films. These aromatic polyamides had useful levels of thermal stability associated with their relatively high softening temperature (242–282 °C), 10% weight-loss temperatures in excess of 470 °C, and char yields at 800 °C in nitrogen higher than 60%. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium-tin oxide (ITO)-coated glass substrate exhibited reversible oxidation at 0.73–0.79 V versus Ag/AgCl in acetonitrile solution, and revealed excellent stability of electrochromic characteristics with a color change from colorless to green at applied potentials ranging from 0.00 to 1.05 V. These anodically polymeric electrochromic materials not only showed excellent reversible electrochromic stability with good green coloration efficiency (CE = 374 cm2 C−1) but also exhibited high contrast of optical transmittance change (ΔT %) up to 85% at 787 nm and 30% at 391 nm. After over 1000 cyclic switches, the polymer films still exhibited excellent stability of electrochromic characteristics.

Structure–property study of polyimides derived from PMDA and BPDA dianhydrides with structurally different diamines

Abstract A series of aromatic diamines were polymerized with two aromatic dianhydrides, pyromellitic dianhydride and 3,3′,4,4′-biphenyltetracarboxylic dianhydride, and the resulting poly(amic acid)s were thermally cyclodehydrated to aromatic polyimides. The polyimides were characterized by determining the glass transition temperatures (Tg), thermal stability, coefficients of thermal expansion, and wide-angle X-ray diffraction. Structure–property relationships are elucidated and discussed in terms of the structural fragments in the polymer chain. The PMDA-based polyimides generally revealed a higher Tg than the corresponding BPDA-based analogues. Generally, the dilution of the imide content by the insertion of oxyphenylene segments into the diamines significantly reduced the Tg. The introduction of m- or o-phenylene units into the polymer backbone usually resulted in a decrease in Tg. The attachment of pendant groups on the backbone may lead to decreased or increased Tgs, depending on the structure of pendant groups. As evidenced by X-ray diffraction, the polyimides derived from rigid, rod-like diamines or the diamines having two or three p-oxyphenylene showed a higher crystalline tendency. The presence of aliphatic pendant groups slightly reduced the thermal stability of the polyimides. The other structural changes did not show a dramatic influence on the thermal stability. Some polyimides obtained from p- or m-phenylenediamine had low thermal expansion coefficients below 2×10 −5 ° C−1.

Novel high-Tg poly(amine-imide)s bearing pendent n-phenylcarbazole units : synthesis and photophysical, electrochemical and electrochromic properties

A new carbazole-derived, triphenylamine-containing aromatic diamine monomer, 4,4′-diamino-4″-N-carbazolyltriphenylamine, was successfully synthesized by the caesium fluoride-mediated condensation of N-(4-aminophenyl)carbazole with 4-fluoronitrobenzene, followed by palladium-catalyzed hydrazine reduction. A series of novel poly(amine-imide)s 6a–6g with pendent N-phenylcarbazole units having inherent viscosities of 0.17–0.56 dL g−1 were prepared from the newly synthesized diamine monomer and seven commercially available tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical or thermal cyclodehydration. The polymers of the series were amorphous and most of them could afford flexible, transparent, and tough films with good mechanical properties. All the poly(amine-imide)s had useful levels of thermal stability associated with high glass-transition temperatures (303–371 °C), 10% weight-loss temperatures in excess of 543 °C, and char yields at 800 °C in nitrogen higher than 60%. The poly(amine-imide)s 6e–6g exhibited a UV-vis absorption maximum at around 300 nm in NMP solution. The poly(amine-imide) 6g derived from an aliphatic dianhydride was optically transparent in the visible region and fluoresced violet–blue at 403 nm in NMP with 4.54% quantum yield higher than the wholly aromatic 6e and 6f. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-imide) films on an indium-tin oxide (ITO)-coated glass substrate exhibited a reversible oxidation wave at 1.05 V and an additional irreversible oxidation wave at 1.39 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from neutral pale yellowish to green doped form at applied potentials ranging from 0.00 to 1.15 V.

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.

Organosoluble optically transparent poly(ether imide)s based on a tert‐butylhydroquinone bis(ether anhydride)

Full Paper: A novel bis(ether anhydride) monomer, 1,4-bis(3,4-dicarboxyphenoxy)-2-tert-butylbenzene dianhydride, was synthesized from the nitro displacement of 4-nitrophthalodinitrile by the phenoxide ion of tert-butylhydroquinone, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and dehydration of the resulting bis(ether diacid). A series of colorless and organosoluble poly(ether imide)s (PEIs) bearing pendent tert-butyl groups were prepared from the bis(ether anhydride) with various aromatic diamines via a conventional two-stage process that included ring-opening polyaddition to form the poly(amic acid)s followed by chemical or thermal cyclodehydration to the PEIs. The inherent viscosities of these PEIs are in the range of 0.70-1.44 dL/g. Most PEIs show excellent solubilities in amide polar solvents, m-cresol and chlorohydrocarbons. The glass transition temperatures (T g ) of these PEIs were recorded between 217-278°C, and the decomposition temperatures at 10% weight loss are all above 460°C in air or nitrogen atmosphere. Solvent-cast films have high tensile moduli and strengths. The PEIs obtained from long chain diamines exhibit high extension to break.

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.

Synthesis, luminescence and electrochromism of aromatic poly(amine–amide)s with pendent triphenylamine moieties

A new triphenylamine-containing aromatic dicarboxylic acid monomer, N,N-bis(4-carboxyphenyl)-N′,N′-diphenyl-1,4-phenylenediamine (2), was synthesized from the amination reaction between 4-aminotriphenylamine and 4-fluorobenzonitrile and subsequent alkaline hydrolysis of the dinitrile intermediate. A series of novel aromatic poly(amine–amide)s with triphenylamine units in the main chain and as the pendent group were prepared from the newly synthesized dicarboxylic acid and various aromatic diamines. These poly(amine–amide)s were amorphous and readily soluble in many organic solvents. All the polymers could be solution-cast into flexible films with good mechanical properties. They had excellent levels of thermal stability associated with high glass-transition temperatures (226–261 °C). These polymers exhibited strong UV–vis absorption bands at 350–365 nm in NMP solution. Their photoluminescence spectra showed maximum bands around 512–543 nm in the green region. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine–amide) 5a prepared from the dicarboxylic acid monomer 2 with a structurally similar diamine monomer N,N-bis(4-aminophenyl)-N′,N′-diphenyl-1,4-phenylenediamine (4a) exhibited four reversible oxidation redox couples in acetonitrile solution at E1/2 = 0.60, 0.80, 0.97 and 1.13 V, respectively. All the poly(amine–amide)s exhibited excellent reversibility of electrochromic characteristics by continuous five cyclic scans between 0.0 to 1.30 V, with a color change from the original pale yellowish neutral form to the green and then to blue oxidized forms.

Syntheses and properties of polyimides based on bis(p-aminophenoxy)biphenyls

Three biphenyl unit-containing diamines,4,4′-bis(p-aminophenoxy)biphenyl (IIIa), 2,2′-bis(p-aminophenoxy)biphenyl (IIIb), and 3,3′,5,5′-tetramethyl-4,4′-bis(p-aminophenoxy)biphenyl (IIIc), were prepared by the chlorodisplacement ofp-chloronitrobenzene with 4,4′-biphenol (Ia), 2,2′-biphenol (Ib), and 3,3′,5,5′-tetramethyl-4,4′-biphenol (Ic), respectively, giving the corresponding bis(nitrophenoxy) compounds IIa-c, followed by catalytic reduction with palladium (Pd) and hydrazine. Three series of polyimidesp-PI,o-PI, and Me-PI were prepared from diamines IIIa-c and aromatic tetracarboxylic dianhydrides via a two-stage procedure that included ring-opening polyaddition to give poly(amic acid)s followed by thermal cyclodehydration to polyimides. The resultant three series of poly(amic acid)s had inherent viscosities of 1.09–2.83, 0.78–1.93, and 1.55–3.09 dL/g, respectively. Almost all the poly(amic acid)s could be solution-cast and thermally converted into transparent, flexible, and tough polyimide films. All the polyimides were characterized by solubility, tensile test, wide-angle X-ray scattering measurements, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Effects of the structures of aromatic diamines and dianhydrides on the properties of polyimides were investigated.

Synthesis and characterization of new fluorene-based poly(ether imide)s

A novel bis(ether anhydride) monomer, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (4), was synthesized from the nitrodisplacement of 4-nitrophthalonitrile by the bisphenoxide ion of 9,9-bis(4-hydroxyphenyl)fluorene (1), followed by alkaline hydrolysis of the intermediate tetranitrile and dehydration of the resulting tetracarboxylic acid. A series of poly(ether imide)s bearing the fluorenylidene group were prepared from the bis(ether anhydride) 4 with various aromatic diamines 5a–i via a conventional two-stage process that included ring-opening polyaddition to form the poly(amic acid)s 6a–i followed by thermal cyclodehydration to the polyimides 7a–i. The intermediate poly(amic acid)s had inherent viscosities in the range of 0.39–1.57 dL/g and afforded flexible and tough films by solution-casting. Except for those derived from p-phenylenediamine, m-phenylenediamine, and benzidine, all other poly(amic acid) films could be thermally transformed into flexible and tough polyimide films. The glass transition temperatures (Tg) of these poly(ether imide)s were recorded between 238–306°C with the help of differential scanning calorimetry (DSC), and the softening temperatures (Ts) determined by thermomechanical analysis (TMA) stayed in the range of 231–301°C. Decomposition temperatures for 10% weight loss all occurred above 540°C in an air or a nitrogen atmosphere.

Ambipolar, multi-electrochromic polypyromellitimides and polynaphthalimides containing di(tert-butyl)-substituted bis(triarylamine) units

Four bis(triarylamine)-based polyimides were prepared from the polycondensation reactions of diamine monomers, N,N-bis(4-aminophenyl)-N′,N′-bis(4-tert-butylphenyl)-1,4-phenylenediamine (1) and 4,4′-diamino-4′′-(3,6-di-tert-butylcarbazol-9-yl)triphenylamine (1′), with pyromellitic dianhydride (PMDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), respectively. These polyimides showed high glass transition temperatures and high thermal stability. Cyclic voltammetry studies revealed that these polyimides were ambipolar; they showed well-defined and reversible redox couples during both p- and n-doping processes, together with multi-electrochromic behaviors and high contrast ratios in the visible and near-infrared regions. An all-plastic flexible electrochromic device (ECD) based on polypyromellitimide 3a was constructed and characterized. The device shows a maximum optical contrast (ΔT%) of 85% at 940 nm for green coloring and of 91% at 760 nm for deep blue coloring.