Changjin Lee

Redox Cyclability of a Self‐Doped Polyaniline

Poly(4-anilino-1-butanesulfonic acid) sodium salt was synthesized from the electrochemical oxidation of 4-anilino-1-butanesulfonic acid sodium salt, which was readily obtained from aniline and 1,4-butane sultone. The resulting water-soluble polymer has shown much higher redox cyclability than unsubstituted polyaniline, which was demonstrated by an in situ spectroelectrochemical and a cyclic voltammetric study

The preparation of polypyrrole and polythiophene in the presence of ferrocene derivatives

Abstract Polypyrroles doped with electroactive materials such as ferrocenemonosulfonate, ferrocenedisulfonate, and poly(vinylferrocenesulfonate) were prepared and their electrochemical properties were studied. Polypyrrole doped with poly(vinylferrocenesulfonate) was examined for the rechargeable battery electrode material. A fairly high energy density (384 Wh/Kg) was obtained for the lithium/polypyrrole-poly(vinylferrocenesulfonate) battery. A facile release of ferrocenemonosulfonate from polypyrrole was observed during redox cycles whereas poly(vinylferrocenesulfonate) in the polypyrrole matrix was retained for more than hundreds of cycles. Combined with the smooth and uniform film forming property, polypyrrole doped with poly(vinylferrocenesulfonate) is a promising electrode material for the rechargeable battery.

Curing and optical properties of thin films prepared by vacuum deposition of acetylene containing triphenylamines

Mono- and triacetylene substituted triphenylamines were prepared and their vacuum deposited films were cured by UV irradiation and thermal treatment. FT-IR analysis indicated that triple bond was converted into double bond during curing. Thermal stability was improved after UV curing. Photo-patterning of the film can be achieved by UV irradiation through the photo mask followed by developing with chloroform. The vacuum deposited and polymerized acetylene containing triphenylamine was utilized as a hole-transporting layer of electroluminescence devices. The improved luminescent efficiency of the EL device was observed.

Electrochemical quartz crystal microbalance study of the self-assembled multilayered poly(aniline N-butansulfonate) film

Abstract Electrochemically active multilayers of self doped polyaniline films were prepared by the ionic interaction between poly(aniline N-butanesulfonate) (PANBUS) and polyethylene imine. Kinetic constant and free energy of the PANBUS adsorption were calculated to be 2.3/M·sec and -5.4 kcal/mole, respectively from the analysis of QCM. The prepared film showed the characteristic cyclic voltammogram of polyaniline and EQCM study of the multilayered film indicated that the mass change during oxidation and reduction was independent on the cations and anions of the used electrolytes.

Self-Assembled Film of Carboxylic Acid Substituted Poly(p-Phenylene Vinylene) Derivative and its Luminescence Properties

Abstract Carboxylic acid group pendent poly(p-phenylene vinylene) was synthesized and its layer-by-layer film with poly(ethylene imine) was fabricated by means of self assembly technique. The photoluminscence efficiency of the PPV-COOH in solution increases as increasing pH and the size of counter cation. The photoluminescent spectrum of the self-assembled PPV-COOH film is red shifted by ca. 10 nm compared to that of the casted film.

PREPARATION OF MEROCYANINE SALTS BY TREATMENT OF ACIDS ON SPIROPYRANS AND INVESTIGATION ON THEIR PHOTOCHROMIC BEHAVIORS

Merocyanine salts were prepared and their photochromic behavior investigated. The salts were prepared from a solution of spiropyrans in the presence of acids such as toluenesulfonic acid and dodecylbenzene sulfonic acid under irradiation of UV light and heat. The 1H NMR spectrum confirmed the chemical structure of the merocyanine salts. The salt showed an absorption peak at 422 nm, which was blue-shifted as compared with the absorption peak at 578 nm of the merocyanine form of spiropyran. The salt form was quite stable and virtually exhibited a negative photochromism. The salt showed better fatigue resistance than the spiropyran. The photoinduced refractive index change for the salt films by a prism coupler method was estimated to be as large as 0.0055.

Multilayer thin films of poly(3-[2-(carboxymethoxy)ethyl]thiophene) and its luminescence properties

We synthesized carboxylic acid group pendant poly(3-alkylthiophene) and prepared multilayer self-assembled films by the use of ionic interaction between charged molecules. The prepared multilayer thin films were optically transparent high quality films and showed emission maximum at 592 nm that was identical to the emission of the cast film. About 2.5 fold enhancement in emission efficiency was observed for the self-assembled film which indicated that less excimer quenching occurred. The light emitting devices were made from both multilayer film and cast film. The device made from the multilayer film had electroluminescence maximum at 602 nm which was shifted about 10 nm to the longer wavelength than that from the cast film.

Effect of curing temperature on pretilt angles of polyimide alignment layer

Poly(amic acid ester)and poly(amic ester)of polyimide precursors were prepared from the corresponding poly(amic acid)with controlling esterification ratio of the pendent carboxylic group. These three different precursors were examined for the generation of pretilt angle after curing at various temperatures. All three alignment layers generated maximum tilt angle when they were cured at the temperature approximately 20°C below the maximum imidization temperature. The results indicated that the proper stiffness of main chain and residual functional group in the alignment layer were important for the generation of high pretilt angle.

Measurement of Refractive Index and Thickness of Fluorinated Copolyimide Films by Spectroscopic Reflectometry

Abstract Various fluorinated copolyimide films were prepared on a Si wafer from copoly(amic acid) solution of pyromellitic dianhydride (PMDA) or bis(3,4-dicarboxyliphenyl)hexafluoropropane dianhydride (6FDA) and a diamine mixture of 4,4′-oxydianiline (ODA) and 2,2′-bis-(trifluoromethyl)benzidine (BTBz). Refractive index and thickness of polyimide films were measured by means of spectral reflectance measurement. A gradual increase of the refractive, index was observed in the course of imidization for PMDA series polyimides and almost no change or a slight decrease for 6FDA series polyimides. Film thickness decreased about 30% after imidization. The refractive indices of final polyimides depended on the fluorine content as well as the structure of the copolyimide.

UV Curing of Vacuum Deposited Ethynyl Triphenylamines

Abstract Mono-and tri-acetylene substituted triphenylamine were prepared and their vacuum deposited films were cured by UV. FT-IR analysis indicated that triple bond was converted into double bond during curing. Thermal stability was improved after UV curing and triacetylenyl triphenylamine had higher thermal stability than monoacetylenyl triphenylamine. The hole transporting property of the film was demonstrated by fabrication of electroluminescence devices.