Hsun-Tsing Lee

White-light emission from electroluminescence diode with polyaniline as the emitting layer

Abstract A light-emitting diode (LED) with emeraldine base polyaniline (PAn) as the emitting layer, indium—tin oxide coated glass plate as the hole injector and deposited aluminum (or magnesium) thin film as the electron injector was fabricated, which can emit nearly white light covering the full range of visible light (380–750 nm). It is found that the white light is emitted from the phase with reduced repeat units (amine form), while the phase with oxidized repeat units (quinoid form) has no contribution to the emitting light. The turn-on voltage for eye-observable light intensity is 13 and 6 V for the LEDs with aluminum and magnesium electrodes, respectively, at a thickness of the emitting layer of 800 A. The range of the electroluminescence (EL) spectrum covering the range 300–800 nm is much broader than that of the photoluminescence (PL) spectrum, 350–510 nm.

Structures and properties of the soluble polyanilines, N-alkylated emeraldine bases

Abstract The N-alkylated emeraldine bases (N-butyl, N-hexyl, N-octyl, N-decyl, N-dodecyl, and N-hexadecyl) are synthesized by incorporation of flexible alkyl chains onto the polyaniline (PAn) through an N-alkylation method with the emeraldine base. The solubility of PAn in common organic solvents is improved remarkably with the alkylation and the oxidation level is maintained at 40–50 mol% (close to that of the original emeraldine base, 50%) allowing for an adequate acid doping. When carbon number of the alkyl side chain is six or more, the polymers can be dissolved in common organic solvents (such as tetrahydrofuran, dichloromethane, and chloroform) even in the presence of a protonic organic acid as dopant, such as dodecylbenzene sulfonic acid (DDBSA) and camphor sulfonic acid (CSA), and free-standing films can be obtained by casting from the solutions. When the carbon number is 12, the polymer film is flexible. DDBSA-doped N-alkylated emeraldine salt films cast from polymer solutions in dichloromethane in the presence of the acid dopant have maximum conductivities in the range 10−2– 10−4 S/cm, being two to three orders of magnitude higher than those of the reported HClO4-doped poly(N-alkylaniline)s.

Polyaniline-acid dopant interaction in the presence of 1-methyl-2-pyrrolidone

Abstract For the thin solution film of polyaniline (PAn) and polyacrylic acid (PAA) in 1-methyl-2-pyrrolidone (NMP), the UV-Vis spectra indicate that PAn is not doped, but becomes doped when the same volume of water as that of NMP is added. This is due to the electrostatic interaction and hydrogen bonding between PAA and NMP, the hydrogen bonding between water and NMP, polarity of solvent and entropy of solvation. As a dynamic vacuum is applied, the water is removed first and PAn is dedoped; subsequently, as NMP is removed, PAn becomes doped with PAA.

Polyacrylic acid-doped polyaniline as p-type semiconductor in Schottky barrier electronic device

Abstract Large area (about 0.3∼1 cm 2 ) Schottky diodes with polyacrylic acid (PAA)-doped polyaniline (PAn) and undoped PAn as p-type semiconductors sandwiched in between aluminum (Al) and indium-tin oxide (ITO) prepared by casting technique exhibit a moderate rectifying behavior and low leakage current. The current rectification ratio of the diode after doping increases by 1-order raising from 30 at ±1.3 V to 433 at ±0.8 V; and the passing current density raises from 10 −5 A/cm 2 to 10 −2 A/cm 2 .

Synthesis of biodegradable polycaprolactone/polyurethane by curing with H2O

To prepare a pre-polymer in this study, the following materials were used: 4,4′-diphenylmethane diisocyanate, poly(ε-caprolactone) diol (PCL), and polytetramethylene ether glycol. The pre-polymer was then cured using H2O to form a new type of polyurethane (PU), PCL/H2O-PU. Fourier transform infrared analysis confirmed the successful synthesis of PCL/H2O-PU. Results from thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis showed that the thermal resistance and glass transition temperature of PCL/H2O-PU increased with the H2O and the hard segment content. Stress–strain curves for the PCL/H2O-PU specimens showed that with increasing H2O content, the tensile strength and Young’s modulus increased, but the elongation at break decreased. WAXD patterns indicated that with a higher H2O content, the polymer chains were in a more ordered arrangement, although the morphology was still amorphous. The degree of swelling in an aqueous ethanol solution and the hydrolytic degradation rate increased with the PCL content. Scanning electron microscopic images showed that during the degradation period, the original wrinkled surface of PCL/H2O-PU became smooth, and then cracks were formed. The cracks became more severe when the degradation was at a higher temperature.

Doping behavior of polyaniline film containing 1-methyl-2-pyrrolidone

Abstract The NH groups in polyaniline (PAn) can form hydrogen bonding with CO groups in 1-methyl-2-pyrrolidone (NMP), and the CO groups in NMP can also form hydrogen bonding with acid, leading to a decreased chance for NMP plasticized PAn to be doped by the acid. Thus, the interior part of the film is difficult to be doped due to this interaction and the diffusional resistance of dopants when immersed in acid solutions. However, doping PAn by mixing an acid (polymeric or monomeric) with PAn solution in NMP and then casting into a film is the best way to produce a PAn film with uniform doping.

Effects of different metals on the synthesis and properties of waterborne polyurethane composites containing pyridyl units

This study used dicyclohexylmethane 4,4-diisocyanate, polybutylene adipate, polyether-1,3-diol, and 2,6-pyridinedimethanol to synthesize a novel water-based polyurethane (WPU) that contained pyridyl units. To enhance the thermal, mechanical, swelling, and antimicrobial properties of the WPU, various metals (silver nitrate, copper acetate, cobalt acetate, and zinc acetate) were incorporated to form WPU/metal composites. In addition, the study investigated the effects of the metal types on the WPU properties. Fourier transform infrared spectroscopy was used to confirm the synthesis of the WPU containing pyridine. Atomic force microscopy illustrated that the added metals increased the WPU surface roughness. The contact angle and degree of swelling tests demonstrated that the added metal reduced the WPU hydrophilicity, and with the addition of other metal types, the hydrophobicity increased considerably. Thermal gravimetric analysis indicated that the initial decomposition temperature of the highest WPU thermal stability was attributed to zinc. In addition, the results of differential scanning calorimetry and dynamic mechanical analysis showed that adding a small amount of metal increased the hard and soft segment glass transition temperatures. A universal strength tester validated that the WPU mechanical properties varied with the different metal additives and that the WPU strength increased. However, the WPU toughness and ductility decreased with the addition of metals; silver provided the highest mechanical strength. An antimicrobial test indicated that silver enhanced the antimicrobial property. The moisture permeability and waterproof property of the WPU coating was also analyzed.

Synthesis and properties of novel biodegradable polyurethanes containing fluorinated aliphatic side chains

This study used 5H–octafluoropentanoylfluoride and 2-amino-2-methyl-1,3-propanediol to synthesize a novel fluoro chain extender 2,2,3,3,4,4,5,5-octafluoro-N-(1,3-dihydroxy-2-methylpropan-2-yl) pentanamide (ODMP). Furthermore, 4,4′-diphenylmethane diisocyanate served as the hard segment, polycaprolactone diol (PCL) served as the soft segment, and ODMP served as the chain extender in the novel synthesized polyurethanes (ODMP/PUs). Gel permeation chromatography revealed that the molecular weight of the ODMP/PUs increased when the ODMP content was increased. 1H and 19F nuclear magnetic resonance and Fourier transform infrared spectroscopy verified that the ODMP chain extenders were successfully synthesized and that the ODMP chain extenders were successfully incorporated into the backbone of the PUs. The interaction between the -NH (hydrogen bond) and CF2 groups in the ODMP/PUs became stronger when the ODMP content was increased. Thermal analysis revealed that the initial decomposition temperature of the ODMP/PUs decreased and the second decomposition temperature increased when the polymers’ ODMP content was increased. Higher ODMP content also resulted in the ODMP/PUs’ higher glass transition and dynamic glass transition temperatures and lower ODMP maximum stress and Young’s modulus, causing a lower elongation at break. ODMP/PUs with higher ODMP content exhibited more protrusions and more rugged surfaces. The chemical resistance of the ODMP/PUs increased when the fluorine content was increased. Scanning electron microscopy revealed that ODMP/PUs with higher PCL content exhibited higher levels of hydrolytic degradation. Finally, in vitro erythrocyte tests revealed that increasing the ODMP chain extender content reduced the average number of erythrocytes adhering to the surface of the PUs.

Synthesis and Characterization of the Luminescent Poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene]

A new soluble luminescent poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene] (DBDP-PPV) is prepared by the dehydrohalogenation of 1,4-bis(bromomethyl)-2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl) benzene (as monomer) in this study. The above monomer bearing decyloxy and 2′,5′-bis(decyloxy)phenyl substituents was prepared via such chemical reactions as alkylation, bromination, and Suzuki coupling reactions. The two asymmetric substituents on the phenylene ring make the DBDP-PPV soluble in organic solvents and eliminate the tolan-bis-benzyl (TBB) structure defects. The structure and properties of the DBDP-PPV are examined by 1H-NMR, FT-IR, UV/Vis, TGA, photoluminescence (PL), and electroluminescence (EL) analyses. The DBDP-PPV film exhibits a PL peak at 519 nm. With the DBDP-PPV acting as a light-emitting polymer, a device is fabricated with a sequential lamination of ITO/PEDOT/DBDP-PPV/Ca/Ag. The EL spectrum of the device shows a maximum emission at 507 nm. The turn on voltage of the device is about 15.6 V. Its maximum brightness is 4.67 cd/m2 at a voltage of 16.8 V.

In situ polymerisation and characteristic properties of the waterborne graphene oxide/poly(siloxane-urethane)s nanocomposites

In this study, waterborne graphene oxide/poly(siloxane-urethane)s (GO/SWPUs) nanocomposites were in situ synthesised. Therein, siloxane units facilitated the crosslinking of polyurethanes, and GO imparted the nanocomposites with special functions. With increasing GO content, the average particle size, viscosity, and ionic conductivity of the GO/SWPU dispersion increased, but the absolute value of the zeta potential decreased; this was due to ionic interactions between the COO−NH+(C2H5)3 ions of the SWPU and COO−H+ ions of the GO. The surface roughness of the GO/SWPU film was larger as GO content was higher, which was due to a strong interaction between the GO and SWPU phases. Increasing the GO content improved the thermal resistance, dynamic glass transition temperature, and tensile strength of the GO/SWPU film, but adding more than 0.1 wt% GO yielded unfavourable results. Thus, adding GO improved the thermal and mechanical properties of the GO/SWPU nanocomposites, but this improvement was observed only up to a certain GO concentration, possibly because of the agglutination of GO in SWPU. In addition, the surface and volumetric electrical resistivities of the GO/SWPU nanocomposites decreased when the GO content were increased.