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With the progress of organic electronics, materials possessing various functionalities are attracting much attention. Here we have synthesized a novel photo-alignment polymer composed of a conjugated carbazole main-chain and a coumarin side-chain through nickel(0)-mediated polymerization. Carbazole is a well-known hole transporting material and coumarin is also famous for its good photo-alignment properties. The photochemical reactivity of thecoumarin side-chain was monitored by UV-vis spectroscopy and the liquid crystal (LC) photo-alignment direction of the polymer film was proved to be perpendicular to the polarization direction of the irradiated UV light. the highest occupied molecular orbital (HOMO) level of the polymer, measured from both cyclic voltammetry and photoelectron spectroscopy, was -5.32 eV. Organic light-emitting diodes (OLEDs) of the configuration [ITO/polymer/NPB/Alq 3 /LiF/Al] showed a higher efficiency (2.17%) and brightness (14000 cd.m -2 ) than a control device due to enhanced charge balance.

Poly[(oxy-4,4′-octafluorobiphenyloxy)-1,4-phenylenevinylene-2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene-1,4-phenylene], POFB-MEH-PPV, poly[(oxy-4,4′-octafluorobiphenyloxy)-1,4-phenylenevinylene-9,9-dihexyl-2,7-fluorenediylvinylene-1,4-phenylene], POFB-PF, and poly[(oxy-4,4′-octafluorobiphenyloxy)-1,4-phenylenevinylene-N-ethylhexyl-3,6-carbazolevinylene-1,4-phenylene], POFB-PK, were synthesized by the well-known Wittig condensation polymerization. We incorporated the high electron affinity (octafluorobiphenyl) and hole-transporting (carbazole, fluorene, and dialkoxyphenyl) units into the conjugated main chain. The conjugation lengths are limited to the blue-emission region by ether linkage. The resulting polymers were completely soluble in common organic solvents such as chloroform, 1,2-dichloroethane, and cyclohexanone, and exhibited good thermal stability up to 300°C. The synthesized polymers showed UV-visible absorbance and photoluminescence (PL) in the ranges of 350–385 nm and 460–490 nm, respectively. The fluorene or carbazole containing POFB-PF and POFB-PK showed blue photoluminescence peaks at 470 and 460 nm, respectively. The single-layer light-emitting diode was fabricated in a configuration of ITO (indium-tin oxide)/polymer/Al. Electroluminescence (EL) emission of POFB-PF and POFB-PK were shown at 475 and 458 nm, respectively, corresponding to the pure blue emissions. And, a dialkoxyphenyl containing POFB-MEH-PPV showed greenish blue light at 494 nm. But, LED devices from synthesized polymers showed poor device performance and high turn on voltage. So, we fabricated light-emitting diodes (LEDs) from blend polymers composed of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and POFB-MEH-PPV (POFB-PF or POFB-PK) as the emitting layers. The EL emission maxima of each blend polymers were in the range of 573–591 nm, which indicates that the emission is mainly due to MEH-PPV and POFB-MEH-PPV (POFB-PF or POFB-PK) contributes to the enhancement of the luminescence. And each blend polymers exhibited higher EL quantum efficiency compared with MEH-PPV at the same current density.

Poly[2-(5-cyclohexylmethoxypentyloxy)-5-methoxy-1,4-phenylenevinylene] (PMCYHPV) was synthesized through dehydrohalogenation polymerization. This polymer shows good solubility in common organic solvents. The absorption and photoluminescence (PL) emission maxima of PMCYHPV are 497 nm and 590 nm, respectively. The electroluminescence (EL) properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and PMCYHPV were studied by means of the EL spectra, current-voltage characteristics, and EL power-current characteristics. The measured relative EL quantum efficiency of PMCYHPV is about 6 times higher than that of MEH-PPV. The EL enhancement of PMCYHPV originates from the reduction of non-radiative decay of excitons caused by better separation of the polymer chains due to the rigid cyclohexyl side group. Furthermore, we found that the PL quantum efficiency of PMCYHPV is 15% higher than that of MEH-PPV.

We have demonstrated a novel approach to achieve a stable second-order NLO polymer by incorporating NLO moieties into a processable epoxy polymer and hardening with crosslinkable sol-gel technique. The crosslinked polymer showed high nonlinearity (d 33 = 41 pm/V) and better thermal stability compared to the prepolymer, which maintained its nonlinearity up to 100°C without significant loss of NLO activity.

Poly{oxy-4,4'-octafluorobiphenylyleneoxy-1,4-phenylenevinylene(3-trimethylsilyl-1,4-phenylene)vinylene-1,4-phenylene (PFSi) was synthesized and characterized to investigate its thermal, optical, electrical and xerographic properties. An LED (light emitting device) using PFSi as the light emitting layer exhibits maximum emission for blue light, but a high turn-on voltage. The origin of the low device performance was examined by investigating the photoconducting behavior. PFSi shows a high photoconductivity in the presence of electron acceptors such as 5-nitroanthranilonitrile (SNAN), and the photoconductivity of PFSi is improved by introducing charge transport materials such as triphenylamine (TPA).

Two types of new polyurethanes with a highly NLO active chromophore, 2-[4-[4-[bis(2-hydroxyethyl)amino]phenylazo]benzylidene]malonitrile (HAPM), in the polymer side chain were synthesized (PU1-DCN and PU2-DCN) and characterized. The diisocyanate components of the polymers are 2,4-tolylene diisocyanate and 3,3'-dimethoxybiphenyl-4,4'-ylene diisocyanate. The molecular weights of PUI-DCN and PU2-DCN were determined to be M w = 23 000 (M w /M n = 2.19) and M w = 22000 (M w /M n = 2.34), respectively. The final products are readily soluble in polar aprotic organic solvents, like tetrahydrofuran, N,N-dimethyl-formamide, cyclohexanone, etc. Good optical quality films were obtained by spin coating. The glass transition temperatures of both polymers were found to be 158-159°C. They showed no melting points in the DSC curves, suggesting an amorphous phase. It was found that the electro-optic coefficient of PU 1-DCN was r 33 = 62.7 pm. V -1 at 633 nm wavelength. The macroscopic second-order hyperpolarizability at 1064 nm wavelength was determined to be x (2) = 136 pm. V -1 for PU1-DCN and x (2) = 120 pm. V -1 for PU2-DCN.

Poly(2-methoxy-5-trimethylsilyl-1,4-phenylenevinylene) (PMTSPV) was prepared as thin film via the water-soluble precursor route, and its electrical and optical properties were studied. The conductivity values of drawn (L/L 0 ) = 7) and undrawn FeCl 3 -doped PMTSPV films were 0.1 and 0.5 S.cm -1 , respectively. The electroluminescence device was fabricated with PMTSPV as an emitting layer, and ITO and aluminium as hole-injection and electron-injecting electrodes, respectively. The threshold voltage of the device was about 4 V, and the emission maximum was at about 560 nm, with quantum efficiency of 2 x 10 -4 % (emitted photons per electron), which corresponds to yellow light emission. The X (3) for the PMTSPV film was investigated by using the third-harmonic generation method at 1907 nm fundamental wavelength, and found to be 1.0 x 10 -11 esu.

Poly(1,4-phenylenevinylene) (PPV) and its derivatives are readily processable and thermally stable polyconjugated polymers. Since PPV contains phenylene units, its structure can be easily altered and modified in the electronic structure. Moreover, PPV and the derivatives are easily prepared via water-soluble or organic-soluble precursor polymers. Various PPVs substituted with electron-donating or -withdrawing groups were synthesized and their third-order optical nonlinearities were investigated by third-harmonic generation method or degenerate four-wave mixing technique. When phenylene rings carry two alkoxy electron-donating groups, the substituted PPVs show third-order nonlinear optical properties up to an χ (3) value of about 10 -9 esu. In order to obtain polymeric materials having high optical quality, PPV and silica alkoxide can be mixed successfully by sol-gel processing without any phase separation or precipitation. This unusual organic-inorganic hybrid shows a great advantage in the photonics applications.

Electron donor and acceptor substituted poly(2-methoxy-5-methylsulfinyl- 1,4-phenylenevinylene) (PMMSPV) and a series of copolymers containing 1,4-phenylenevinylene (PV) units were synthesized via the water-soluble precursor pathway and cast into films. The electrical conductivity of FeCl 3 -doped PMMSPV was 1.5 x 10 -4 S. cm -1 and the copolymers showed conductivities in the range of 10 -4 ∼ 10 -1 S. cm -1 depending on the copolymer compositions. The second-order nonlinear optical coefficient of PMMSPV was obtained with second harmonic generation method. The measured d 33 value was 1.5 pm/V and gave no decay at 100°C over 40 d.

Poly(2,5-dipropargyloxy-1,4-phenylenevinylene) (PDPPV) and its copolymers were prepared as thin films via the organic-soluble and water-soluble precursor routes. Elimination and crosslinking reactions could be controlled by the temperature. Crosslinked PDPPV is stable up to 450°C. The conductivity values of undrawn and drawn FeCl 3 -doped PDPPV films are 5.0 x 10 -2 and 2.0 x 10 -1 S.cm -1 , respectively. The third-order nonlinear optical susceptibility, χ (3) for the PDPPV film was investigated by degenerate four-wave mixing (DFWM) technique at 602 nm wavelength, and found to be 2.3 x 10 -10 esu.