We report the synthesis, optical and electrochemical details, and properties of copolymers P1 − P3 consisting of alternate hole-transporting 1,4-bis(hexyloxy)-2,5-distyrylbenzene (HDB) and electron-transporting 4-(4-(hexyloxy)phenyl)-3,5-diphenyl- 4H-1,2,4-triazole (EDT) or 2,5-diphenyl-1,3,4-oxadiazole (EDO) segments linked via an ether spacer or a twisted σ-bond (biphenyl). These copolymers are soluble in common organic solvents such as chloroform, NMP, and 1,1,2,2-tetrachloroethane and exhibit good thermal stability with decomposition temperatures higher than 375 °C. P1 − P3 show efficient energy transfer from EDT or EDO to EDO fluorophores when photoexcited. Optical and electrochemical properties of P1 − P3 are also investigated in detail by comparing with P4 and P5 containing similar chromophores. From the cyclic voltammograms the onset oxidation and reduction potentials for isolated P1 and conjugated P2 are comparable, indicating that the effect of the twisted σ-bond in P2 is similar to that of the ether spacer in P1. The optimized geometries of P2 and P3 show that the torsion angle between HDB and EDT or EDO are 83.6° or 89.6°, respectively, based on MNDO semiempirical calculations. The large torsion angle in P2 and P3 significantly limits delocalization of charges between hole- and electron-transporting segments. Accordingly, in P2 and P3 the oxidation and reduction starts at the hole- and the electron-transporting, respectively, like those in isolated P1. The HOMO and LUMO energy levels of P1, P2, and P3, estimated from electrochemical data, are −5.16, −5.12, and −5.19 eV and −3.35, −3.38, and −3.23 eV, respectively. Single-layer light-emitting diodes (Al/P1 − P3/ITO) have been successfully fabricated, and they reveal blue or yellow electroluminescence.

Four novel poly(aryl ether)s (P1–P4) consisting of alternate isolated electron‐transporting (3,3″′‐bis‐trifluoromethyl‐p‐quaterphenyl for P1, P3 or 3,3″′‐dicyano‐p‐quaterphenyl for P2, P4) and hole‐transporting fluorophores [N‐(2‐ethylhexyl)‐3,6‐bis(styryl)carbazole for P1, P2 or 9,9‐dihexyl‐2,7‐bis(styryl)fluorene for P3, P4] were synthesized and characterized. These poly(aryl ether)s can be dissolved in organic solvents and exhibited good thermal stability with 5% weight‐loss temperature above 500 °C in nitrogen atmosphere. The photoluminescent (PL) spectra of the films of these polymers showed maximum peaks at around 442–452 nm. The PL spectral results revealed that the emission of polymers was dominated by the fluorophores with longer emissive wavelength via the energy transfer from p‐quaterphenyl to 3,6‐bis(styryl)carbazole or 2,7‐bis(styryl)fluorene segments. Therefore, the p‐quaterphenyl segments function only as the electron‐transporting/hole‐blocking units in these polymers, and the other segments are the emissive centers and hole‐transporting units. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels of these polymers were measured by cyclic voltammetry. The electron‐donating nitrogen atom on carbazole resulted in the higher HOMO energy levels of P1 and P2 than those of P3 and P4. The single‐layer light‐emitting diodes (LED) of Al/poly(aryl ether)s (P1–P4)/ITO glass were fabricated. P1, P2, and P4 revealed blue electroluminescence, but P3 emitted yellow light as a result of the excimer emission. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2215–2224, 2002

The optical-absorption study of synthetic pyrite FeS2 single crystals prepared by the chemical-vapor-transport method is reported over a temperature range from 4.2 to 300 K. At lower temperatures several features which occur below the absorption edge are superposed on the absorption curve. The origin of the sharpest peak is identified as the transition between the top of valence band and Cr3+ trapping center through comparison of the results with that of the low-temperature photoconductivity and the photoelectron paramagnetic resonance measurements. The nature of other weaker features is discussed. The existence of these features prevents the determination of the band gap of FeS2 by fitting the optical-absorption data to the form of (αhν)∝(hν−E0)n. Therefore, the energy gap of FeS2 at low temperatures is estimated by adding the thermal ionization energy of the shallow acceptor states to the photoionization energy between the (SCl)2− states and the bottom of the conduction band. The band gap of various temperatures is determined and its temperature dependence is analyzed by an empirical expression proposed by O’Donnell and Chen [Appl. Phys. Lett. 58, 2924 (1991)]. The parameters that describe the temperature dependence of Eg of the material are evaluated and discussed.

Two, novel copoly(aryl ether)s (P1 and P2) consisting of alternate, isolated electron‐ and hole‐transporting fluorophores were synthesized and characterized. Furthermore, we investigated the optical, photoluminescent (PL), and electrochemical properties of copoly(aryl ether)s P1–P5. The PL spectra of these polymers in film states showed maximum peaks around 420–498 nm. However, compared with the PL spectra of corresponding model compounds M1–M5, the emissions of P1 and P2 were compositions of the two isolated fluorophores, and that of P3 was dominated by the fluorophores with a longer emissive wavelength via the energy transfer. The formation of an interchain interaction in P4 and P5 was also observed. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of these copolymers were measured by cyclic voltammetry. Both the electron and hole affinities could be enhanced simultaneously because of the introduction of isolated hole‐transporting naphthalene (or fluorene) and electron‐transporting bis‐1,3,4‐oxadiazole segments. The single‐layer devices (Al/polymer/indium tin oxide) of P1, P2, and P4 revealed blue or blue‐green electroluminescence, but that of P3 emitted yellow light because of the excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 883–893, 2004

Phenolic resin (PF)/montmorillonite (MMT) nanocomposites have been successfully prepared using intercalative polymerization of resole-type phenolic resins in montmorillonites modified by octadecylamine (C18), benzyldimethylhexadecylammonium chloride (B2MH), benzyltriethylammonium chloride (B3E), and benzyldimethylphenylammonium chloride (B2MP). X-ray diffraction measurements and transmission electron microscope observations showed that clay platelets were partially exfoliated or intercalated after complete curing of the phenolic resins. The cured nanocomposites were named as modifier-MP (MP means montmorillonite-phenolic resin), for example, B3E-MP. Thermogravimetric analysis showed that thermal decomposition temperatures (T d s) of the cured nanocomposites B2MP-MP (826 K), B3E-MP (794 K), and B2MH-MP (783 K) were much higher than those of C18-MP (768 K) and cured phenolic resin (737 K). Therefore, thermal stability of the nanocomposites depends mainly on the chemical structure of the organic modifiers. B2MP-MP possesses the highest T d since B2MP contains both benzyl and phenyl groups, followed with B3E-MP and B2MH-MP whose modifiers contain only one benzyl group. This is attributable to favorable interaction between phenolic resin and organic modifiers containing benzene rings.