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In this study, carbonaceous nanomaterials (Activated Carbon (AC), Graphene Oxide (GO) and Porous Graphene Oxide (PGO)) were synthesized and attached to Fe3O4 magnetic powder for the effective removal of synthetic Methyl Orange (MO). AC and GO were successfully conjugated with Fe3O4 whilst PGO was not due to its surface functional groups. The morphology and chemical structure of the Fe3O4/Carbon nanocomposites were characterized by the N2 adsorption, Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM). Batch adsorption experiments were performed and showed significant removal efficiency of 90% at the first ten minutes for Fe3O4/AC nanocomposite. Analysis of adsorption equilibrium revealed that AC/Fe3O4 is well fitted with Langmuir model, a homogeneous adsorption having an adsorption capacity of 270 mg/g. The GO/Fe3O4 can fit with both Langmuir and Freundlich models indicating multilayer adsorption on the surface of the adsorbent with an adsorption capacity of 81.9 mg/g. In the case of adsorption kinetics, both adsorbents follow the pseudo second order kinetics model showing high F?2 values. Both adsorbents demonstrated advantageous superparamagnetic properties for their easy recovery from aqueous solutions and prospective applications to toxic removal in water and wastewater.

In this study, carbonaceous nanomaterials (Activated Carbon (AC), Graphene Oxide (GO) and Porous Graphene Oxide (PGO)) were synthesized and attached to Fe₃O₄ magnetic powder for the effective removal of synthetic Methyl Orange (MO). AC and GO were successfully conjugated with Fe₃O₄ whilst PGO was not due to its surface functional groups. The morphology and chemical structure of the Fe₃O₄/Carbon nanocomposites were characterized by the N₂ adsorption, Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM). Batch adsorption experiments were performed and showed significant removal efficiency of 90% at the first ten minutes for Fe₃O₄/AC nanocomposite. Analysis of adsorption equilibrium revealed that AC/Fe₃O₄ is well fitted with Langmuir model, a homogeneous adsorption having an adsorption capacity of 270 mg/g. The GO/Fe₃O₄ can fit with both Langmuir and Freundlich models indicating multilayer adsorption on the surface of the adsorbent with an adsorption capacity of 81.9 mg/g. In the case of adsorption kinetics, both adsorbents follow the pseudo second order kinetics model showing high F?² values. Both adsorbents demonstrated advantageous superparamagnetic properties for their easy recovery from aqueous solutions and prospective applications to toxic removal in water and wastewater.

The magnetic Fe3O4/activated carbon nanocomposites with high surface area were synthetized as recoverable adsorbents by chemical binding of Fe3O4 nanoparticles on activated carbon (AC) powders. The component AC and Fe3O4 in this nanocomposite possesses amorphous non-graphitic structure and cubic crystal structure, respectively. All composite samples presented superparamagnetic properties. The saturation magnetization of Fe3O4/AC nanocomposites was significantly lower than that of bare Fe3O4 particles, indicating that Fe3O4 particles were truly attached on AC surface. The microstructure image indicated that the Fe3O4 particles were uniformly dispersed on AC surface and thus maintained high specific surface area. The adsorption capacity of methyl orange (MO) at 30 °C slightly decreased from 384 mg/g on AC powders to 324 mg/g on Fe3O4/AC nanocomposites, which was reduced by 15% after magnetic fabrication. It was found that MO adsorption on Fe3O4/AC nanocomposites followed the pseudo-second order kinetic model and the isotherms could be described by the Langmuir model. The easy recovery of magnetic adsorbents from aqueous solution demonstrated their application potential to remove toxic pollutants in water and wastewater treatment.

Carbon dots (C-dots)/Fe3O4 nanocomposite powders were synthesized by bottom-up procedures at 140 °C with different reaction times ( $t = 0$ –18 h), to study the photocatalytic activity under visible light and recyclable ability in wastewater treatment. The results from vibrating sample magnetometer, X-ray diffraction, and Fourier transform infrared spectra indicated that C-dots were gradually attached on Fe3O4 nanoparticles with the increase of t, and C-dots/Fe3O4 nanocomposite powders were obtained. The microstructure images confirmed that magnetic Fe3O4 nanoparticles were surrounded by C-dots. The C-dots/Fe3O4 nanocomposite powders presented photocatalytic ability in visible light ( $\lambda > 420$ nm). In this paper, higher extent of degradation was addressed in a larger amount of C-dots on Fe3O4 nanoparticles surface. Methylene blue (MB) concentration can be decreased by 83% within 30 min exposing time. The C-dots/Fe3O4 nanocomposite powders exhibited good degradation ability for MB under visible light and could be easily recycled by applied magnetic field after photodegradation.

Monodispersed magnetite nanoparticles were obtained by investigating the different synthesis parameters of the solvothermal method. The morphology and chemical structure of the Fe3O4 nanoparticles were characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Dynamic Light Scattering (DLS) and Vibrating sample magnetometer (VSM). Results indicated that without the addition of water, it forms the minor phase of iron instead of magnetite. Furthermore, the size of nanoparticles is tunable in the range of 117.7 to 217.6 nm by changing the amounts of water, PSSMA and NaOH. The amount of PSSMA restricts the growth of the nanoparticles and narrow the size distribution and a hydrophilic surface was obtained. Synthesized magnetite nanoparticles were successfully conjugated with carbon dots. The resulting nanoparticles exhibited good fluorescence characteristics. Cytotoxicity tests confirmed that nanoparticles are non-toxic. Both magnetite and C-dots/Fe3O4 nanoparticles are good potential candidates for biomedical applications specifically for bioimaging and biosensing in the future.

Composite films consisting of polypyrrole (PPy) and graphene oxide (GO) were electrochemically synthesized by electrooxidation of 0.1 M pyrrole in aqueous solution containing appropriate amounts of GO. Simultaneous chronoamperometric growth profiles and frequency changes on a quartz crystal microbalance showed that the anionic GO was incorporated in the growing GO/PPy composite to maintain its electrical neutrality. Subsequently, the GO was reduced electrochemically to form a reduced GO/PPy (RGO/PPy) composite by cyclic voltammetry. Specific capacitances estimated from galvanostatic discharge curves in 1 M H2SO4 at a current density of 1 A g−1 indicated that values for the RGO/PPy composite were larger than those of a pristine PPy film and the GO/PPy composite. In the case of 6 mg mL−1 GO for the preparation of GO/PPy, a high specific capacitance of 424 F g−1 obtained at the electrochemically prepared RGO/PPy composite indicated its potential for use as an electrode material for supercapacitors.

Graphene oxide (GO) prepared by the modified Hummers method is used as a support in the formation of a Pt/GO nanocomposite electrocatalyst by microwave-polyol synthesis. The effects of microwave reaction times on particle size, dispersion, and electrocatalytic performance of Pt nanoparticles are studied using wide-angle X-ray diffractometery, Raman spectroscopy, transmission electron microscopy and three-electrode electrochemical measurements. The results indicate that Pt nanoparticles nucleation and growth occur, and the particles are uniformly deposited on the GO nanosheets within a short time. The maximum electrochemical active surface area 85.71 m 2 g −1 for a Pt/GO reaction time of 5 min, is a result of the deposition of a dense dispersion of small Pt particles. The highest methanol oxidation peak current density, I f , of 0.59 A mg −1 occurs for a Pt/GO reaction time of 10 min and is due to the formation of interconnecting Pt particles clusters. This novel Pt/GO nanocomposite electrocatalyst with high electrocatalytic activities has the potential for use as an anode material in fuel cells.

The hysteresis phenomenon in a polymer thin film transistor (PTFT) with either poly(3-hexylthiophene), poly(3-dodecylthiophene), or poly[2-methoxy- 5-(2-ethylhexyloxy)-1,4-phenylene vinylene] is investigated over a wide range of temperatures, and found to be generated by the delay in main chain ring distortion with an applied electric field. In the temperature range for side chain relaxation, main chain motion induced by side chain motion already starts such that polarization of the main chain by the applied electric field is permitted but in a limited extent and is not in phase with the variation in electric field. In the main chain relaxation temperature range, the extent of segmental motion increases, which leads to the main chain being more realignable by the applied electric field and thus a reduced hysteresis. After main chain relaxation is complete, the ring can distort more freely and chain segments are able to realign in phase with the applied electric field, which leads to a leveling off of the hysteresis. This investigation shows for first time that the chain relaxation in conjugated polymers is the origin of the hysteresis in PTFT devices.

Graphene was cast on basal and edge plane pyrolytic graphite electrodes for electrochemical applications. The morphology of the resulting graphene modified electrode was investigated by atomic force microscopy. In cyclic voltammetric responses, both anodic and cathodic peak currents varied linearly with the square root of scan rates over the range of 25–600 mV in 0.1 M KCl containing 5 mM Fe(CN)64- at graphene modified basal and edge plane pyrolytic graphite electrodes, which suggests a diffusion-controlled process. The graphene modified basal and edge plane pyrolytic graphite electrodes exhibited the abilities to lower the electrooxidation potentials of β-nicotinamide adenine dinucleotide and hydrogen peroxide in comparison with bare basal and edge plane pyrolytic graphite electrodes. The electrocatalytic behavior obtained at the graphene modified basal and edge plane pyrolytic graphite electrodes may led to new applications in electroanalysis. Keywords: Graphene, Edge plane pyrolytic graphite, Electrocatalysis, NADH, Hydrogen peroxide

The thermal degradation behaviors of biodegradable poly(3-hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)-modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain-scission process of cyclic β-elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The Ea value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008

X-ray diffraction method and differential scanning calorimetry analysis have been used to investigate the nonisothermal crystallization of poly(3-hydroxybutyrate) (PHB)/poly(ethylene glycol) phosphonates (PEOPAs)-modified layered double hydroxide (PMLDH) nanocomposites. Effects of cooling rates and PMLDH contents on the nonisothermal crystallization behavior of PHB were explored. These results show that the addition of 2 wt % PMLDH into PHB caused heterogeneous nucleation increasing the crystallization rate and reducing the activation energy. By adding PMLDH into the PHB probably hinder the transport ability of the molecule chains and result in a decreasing crystallity of PHB, thus increasing the activation energy. The correlation among melting behavior, apparent crystallite size, and paracrystalline distortion of PHB/PMLDH nanocomposites has been also discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 995–1002, 2007

A pyrene photoluminescent layer is coated on the front side of a dye-sensitized solar cell to enhance the power conversion efficiency. The power conversion efficiency of the dye-sensitized solar cell coated with a pyrene photoluminescent layer improves from 9.12 ± 0.06% to 10.30 ± 0.11% (an improvement of 12.94%).

The biodegradable polymers, poly(3-hydroxybutyrate) (PHB), have attracted more attention due to its renewable resources, thermoplastic and outstanding physical and mechanical properties close to those of isotactic polypropylene [1]. A new promising class of inorganic layered material, layered double hydroxides (LDH), has been considered as emerging host-guest materials [2]. PHB/LDH nanocomposites were prepared by mixing PHB and PEOPA-modified LDH (PMLDH) in chloroform solution [3]. Both X-ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PEOPA-modified LDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter and polarized optical microscopy. Mechanical properties of the fabricated nanocomposites measured by dynamic mechanical analysis (DMA) show significant improvements in the storage modulus when compared to that of neat PHB.

This study describes the synthesis of doped polyaniline in its emeraldine salt form (PANI-ES) with carboxylic groups containing multi-walled carbon nanotubes (c-MWNTs) via in situ polymerization. Both Raman and FTIR spectra indicate that carboxylic acid groups formed at both ends and on the sidewalls of the MWNTs. Based on the π–π* electron interaction between aniline monomers and MWNT and hydrogen bonding interaction between the amino groups of aniline monomers and the carboxylic acid group of c-MWNT, aniline molecules were adsorbed and polymerized on the surface of MWNTs. Structural analysis using FESEM and HRTEM showed that PANI-ES/c-MWNT composites are core (c-MWNT)-shell (doped-PANI-ES) tubular structures with diameters of several tens to hundreds of nanometers, depending on the PANI content. The conductivities of these PANI-ES/c-MWNT composites are 50–70% higher than those of PANI without MWNT.

A semirigid conjugated polyaniline (PANI) was complexed with a ω-methoxy poly(ethylene oxide) phosphate (PEOPA) through ionic bonding to yield a supramolecular hairy rod polymer comprised of an ionic PANI backbone and nonionic PEO side chains. The strong backbone−side chain repulsion resulted in a microphase-separated lamellar morphology consisting of alternating ionic and nonionic layers irrespective of the binding fraction. The thickness of the PEO layer increased with increasing binding fraction due to the smaller interfacial area per PEO chain at higher binding fraction which resulted in its higher stretching normal to the lamellar interface. The complex exhibited an order−disorder transition near 225 °C driven by deprotonation. The conformational rigidity of PANI backbone coupled with the strong backbone−side chain bonding strongly retarded the crystallization kinetics and the crystallizability of the PEO side chains in the complexes.

All solid-state poly(ethylene oxide) (PEO) nanocomposite electrolytes were made containing nanoscale fillers of layered double hydroxides (LDHs). Two kinds of LDHs with different surface states were prepared by aqueous co-precipitation method. The LDHs were added into PEO matrix to study the structures, conductivities and ionic transport properties of nanocomposite electrolytes. The structures of LDHs were characterized by infrared spectra, thermogravimetric analysis and wide-angle X-ray diffraction. With enhanced compatibility of LDH sheets by oligo(ethylene oxide) surface modification, the PEO/OMLDH nanocomposite electrolyte exhibits an amorphous morphology and an enhancement of conductivity by three orders of magnitude as compared to pure PEO electrolyte. The lithium ion transference number T Li + of PEO/LDH nanocomposite electrolyte measured with a value of 0.42 is two times higher than the one of pure PEO electrolyte, which can be attributed to the Lewis acid–base interaction between surface states of metal hydroxides and counter anions of lithium salts.

Fractionation during crystallization of heterodisperse homopolymers is a well-known phenomenon that originates from the mixing gap in the crystalline state of chain molecules differing sufficiently in length. Under thermodynamic equilibrium conditions, a binary mixture of homologous chain molecules with large disparity in molecular weights solidifies to form two solid phases. Under nonequilibrium conditions, however, solid solutions may form at relatively low solidification temperatures where the crystallization proceeds so rapidly that the cross-diffusion of the molecules, which is an essential step in the fractionation, is impeded.1 Recently, much attention has been paid to crystalline-amorphous diblock copolymers (C-b-A) and their blends with homopolymer A because their self-assembled structures provide interesting templates to explore the crystallization behavior of polymer chains confined in nanoscale space once C block forms microdomains in the melt state.2-5 In this study, we will deal with the blends of two chemically identical C-b-A with different chain lengths, i.e., CR-b-Aâ/Cγ-b-Aδ with the subscript representing the degree of polymerization. Though the binary blends of diblock copolymers have received considerable theoretical and experimental interests due to richness of their phase behavior, most of the works have been carried out on systems with all amorphous blocks.6-12 Introduction of a crystallizable block into this type of system is expected to create more complex phase behavior than normally has been observed for their amorphous counterparts. A very important question which arises naturally is whether CR and Cγ blocks originally mixed within the microdomains in the melt would cocrystallize or phase segregate into their own crystalline lamellar structures. In this study, we intend to demonstrate that cocrystallization leading to a solid solution occurs over a broad range of undercooling in the lamellae-forming blends of a nearly symmetric C-b-A with an asymmetric counterpart, while the corresponding homopolymer blends with similar molecular weight and compositions exhibit phasesegregated crystallization. In contrast to the kinetically trapped solid solution formed in homopolymer system, the cocrystallization of CR and Cγ blocks may be driven thermodynamically by the tendency of Aâ and Aδ blocks to remain intimately mixed.

The oligo(ethylene oxide) modified layered double hydroxide (LDH) prepared by template method was added as a nanoscale nucleating agent into poly(ethylene oxide) (PEO) to form PEO/OLDH nanocomposite electrolytes. The effects of OLDH addition on morphology and conductivities of nanocomposite electrolytes were studied using wide-angle X-ray diffractometer, polarized optical microscopy, differential scanning calorimetry and ionic conductivity measurement. The results show that the exfoliated morphology of nanocomposites is formed due to the surface modification of LDH layers with PEO matrix compatible oligo(ethylene oxide)s. The nanoscale dispersed OLDH layers inhibit the crystal growth of PEO crystallites and result in a plenty amount of intercrystalline grain boundary within PEO/OLDH nanocomposites. The ionic conductivities of nanocomposite electrolytes are enhanced by three orders of magnitude compared to the pure PEO polymer electrolytes at ambient temperature. It can be attributed to the ease transport of Li + along intercrystalline amorphous phase. This novel nanocomposite electrolytes system with high conductivities will be benefited to fabricate the thin-film type of Li-polymer secondary battery.

The photophysics, including radiative and nonradiative quantum yields and decay rates, of regioregular poly-(3-dodecylthiophene) (P3DT) in benzene were studied by means of UV-visible spectroscopy, photoluminescence spectroscopy, photothermal beam deflection (PBD), photoacoustic calorimetry (PAC), and time-resolved photoluminescence spectroscopy. We observe the fluorescence quantum efficiency to be 0.30 ′ 0.01 and the internal conversion (from S 1 to S 0 ) quantum yield of 0.59 ′ 0.02 as well as the intersystem crossing (from S 1 to T 1 ) quantum yield of 0.11 ′ 0.01. By measuring the fluorescence lifetime of ca. 490 ps, we estimate a radiative lifetime of 1.64 ns for the singlet excitons and nonradiative decay rate constants of k i c = 1.21 ns - 1 and k i s c = 0.22 ns - 1 for internal conversion and intersystem crossing, respectively. The nature and photophysics of triplet states in poly(3-dodecylthiophene) are well characterized using PBD and PAC, and the result suggests that internal conversion plays a major role in energy depletion.

All solid-state poly(ethylene oxide) (PEO) nanocomposite electrolytes were made containing nanoscale fillers of layered double hydroxides (LDHs). Two kinds of oligo(ethylene oxide) modified LDHs were prepared by template method, and added into PEO/LiClO4 matrix (with EO/Li molar ratio of 8) to study the effect on the ionic conductivity of PEO/LDH nanocomposite electrolytes. The structures of the modified LDHs were characterized by infrared spectra, thermogravimetric analysis and wide-angle X-ray diffraction. The results show that the oligo(ethylene oxide) with phosphonate anion can be effectively intercalated into the gallery region of LDHs and formed as an organic-inorganic hybrid (PLDH). With enhanced compatibility of LDH sheets by oligo(ethylene oxide) surface modification, the PEO/PLDH nanocomposite exhibits fully exfoliation morphology. The well dispersed LDH layers in PEO/LiClO4/PLDH nanocomposite electrolytes rendering the formation of amorphous phase, results in an enhancement of ionic conductivity by three orders of magnitude compared to the pure PEO/LiClO4 polymer electrolyte. This novel nanocomposite electrolytes system with high ionic conductivity will be benefited to fabricate the thin-film type of Li-polymer secondary battery.

X-ray diffraction methods and DSC thermal analysis have been used to investigate the structural change of nylon 6/clay nanocomposites. Nylon 6/clay has been prepared by the intercalation of e-caprolactam and then exfoliating the layered synthetic saponite by subsequent polymerization. Both X-ray diffraction data and DSC results indicate the presence of polymorphism in nylon 6 as well as in nylon 6/clay nanocomposites. This polymorphic behavior is dependent on the cooling rate of nylon 6/clay nanocomposites from the melt and on the content of synthetic saponite in nylon 6/clay nanocomposites. The quenching from the melt induces the crystallization into the γ crystalline form. The addition of synthetic saponite may increase the crystallization rate ot the α crystalline form at lower synthetic saponite content and promote the heterophase nucleation of γ crystalline form at hgher synthetic saponite contetn. The effect of thermal annealing on the crystalline structures of nylon 6/clay nanocomposites in the range between T g ant T m is also discussed.

For neutral poly(3-alkylthiophene)s (P3ATs), the electric modulus formalism of dielectric relaxation measurement together with the use of nonexponential decay function can be applied to describe the behavior of conductivity relaxation and carrier transport. The charge mobilities of neutral P3ATs calculated from conductivity relaxation with the use of the defect-diffusion model are in agreement with the data from field-effect transistor measurement. The temperature dependence of charge mobility exhibits a local maximum right after the end of glass transition region, which can be attributed to the transition of soft conformons in the disordered phase to localized conformons. The charge mobilities and activation energies of mobilities for P3ATs are dependent on conjugation length and volume fraction of conducting units. © 1994 John Wiley & Sons, Inc.

Measurements on polyaniline using dielectric analysis (DEA, −50°C to 240°C, 0,4 Hz to 105 Hz), differential scanning calorimetry (DSC, 30°C to 240°C) and infrared spectroscopy (IR) after heat treatment from 25°C to 300°C are carried out. After conversion of DEA results to complex electric modulus, the conductivity relaxation time distribution can be obtained, which remains unchanged for temperatures below 160°C and becomes narrower in the temperature range from 180°C to 240°C due to the occurrence of crosslinking reactions, as is confirmed by the exothermic behavior above 160°C and by the decrease of the relative intensity of quinoid absorption with respect to that of the aromatic ring. The crosslinking reaction causes a decrease in dc conductivity, a narrowing in conductivity relaxation time distribution and an increase in activation energies for conductivity and conductivity relaxation.

Conductivity relaxation of neutral poly(3-hexylthiophene) is analyzed based on temperature and frequency dependence of its electric conductivity and electric modulus. The frequency dependence of the electric modulus is well fitted by the nonexponential decay function, exp[−(t/τp)β], with fractional exponent β (0

For neutral poly(3-hexylthiophene) (P3HT), the electric modulus formalism of dielectric relaxation measurement together with the use of non-exponential decay function can be applied to describe the behavior of conductivity relaxation. The charge mobility of neutral P3HT calculated from conductivity relaxation frequency with the use of the defect-diffusion model is in agreement with the data from field-effect transistor measurement. The temperature dependence of charge mobility exhibits a local maximum right after the end of glass transition region, which can be attributed to the transition of soft conformons in the disordered phase to localized conformons.

The conductivity relaxation behavior of neutral poly(3-alkylthiophene)s (P3ATs) with the alkyl side chain having carbon numbers 4, 6, 8, and 12 is investigated on the basis of dielectric rexation measurements at -100 to 180 o C and 0.4-10 5 Hz after conversion to complex electric modulus formalism. It is found that the conductivity relaxation time distribution can be represented by the nonexponential decay function, φ(t)= exp(-t/τ p ) β involving a relaxation time distribution parameter β and a characteristic relaxation time τ p as in the case of vitreous ionic inorganic conducting materials

The conductivity relaxation of poly(3-alkylthiophene)s (P3ATs) is analyzed by use of electric modulus analysis together with non-exponential decay function to investigate intrinsic conduction mechanism of neutral P3ATs. A correlation with the thermal transitions from dynamic mechanical analysis and UV-Vis spectroscopy is attempted. It is found that conductivity relaxation behavior is highly related to the molecular motion. The side chain motion has no significant effect on the charge transport. While in the glass transition and rubbery region, relaxation time distribution becomes broadened with temperature. As the coplanar subchains in the ordered region melt, the conjugation length decreases and its distribution (and therefore relaxation time distribution) becomes narrower. The intrinsic conduction mechanism of neutral P3AT is determined by thermal activated hopping of charge carriers over energy barrier resulting from conformational defects such as soft or localized conformons.

Photoresponsive conductivities of copolymers of 3-hexylthiophene and azobenzene-modified 3-hexylthiophene prepared by chemical oxidation with FeCl3 were measured by placing a thin film (40 μm thick) in between an ITO glass and a disk-like Cu electrode. Upon irradiation of UV-light (γ=365 nm) (100 W Hg-lamp), conductivities of the copolymersincrease by a factor of 0.1 to 1.5 depending on the amount of the azobenzene moiety within 5 min to maxima and, upon turning off the light, return to original levels within the same period of time. Reversibility of the photoresponsive conductivity is excellent. It is found that the increase in conductivity upon irradiation is not due to a variation in interchain distance resulting from trans-cis isomerization in the azobenzene-moiety. This phenomenon can be attributed mainly to a generation of photoexcited hopping sites in the azobenzene moiety.

Poly(3-ether substituted thiophene)s are prepared from chemical oxidation with FeCl3 and have the structures: where (i) X  H; Y  (OC 7 H 15 ) 1 , (O(CH 2 ) 2 OC 4 H 9 ) 2 , (O(CH 2 )O(CH 2 )OCH 3 ) 3 ; (ii) X  CH 3 ; Y  (OC 7 H 15 ) 4 , (O(CH 2 ) 2 OC 4 H 9 ) 5 ; (iii) X  H; Y  (CH 2 OC 6 H 13 ) 6 ; (iv) X  H; Y  ((CH 2 ) 2 OC 5 H 11 ) 7 . The polymers of type (i) are crosslinked; only their oligomers are soluble. The polymer of type (iii) can not be obtained from its monomer by the present chemical method, since its monomer contains an allylic oxygen, which is easy to be attacked. The polymers of type (ii) and (iv) are soluble and have high molecular weight. FeCl3-doped polymer 7 at the doping level 0.04 is soluble and can be cast into flexible free standing film with a conductivity of 10−4S /cm. Those with an oxygen atom in the repeated unit of the side chain (polymers 4 and 7) have lower conjugation length in solution and solid forms in comparison with poly(3-octylthiophene) (P3OT) and have no appreciable thermochromism. The oxidation potential of polymer 7 is 1.0 V/SCE which is comparable with that of P3OT (1.01 V/SCE). Polymer 5, which has two oxygen atoms in the repeated unit, has higher conjugation length (λmax=535 nm) and lower oxidation potential (0.6 V/SCE) compared to P3OT (λmax = 500 nm, 1.01 V/SCE).

Dielectric relaxation (−90°C to 120°C, 0,4 Hz to 105 Hz) and ultraviolet-visible (UV/Vis) spectroscopic (−100°C to 200°C) measurements for poly(3-octylthiophene) were carried out. A correlation of complex electric moduli, which were converted from dielectric measurements, with thermal transitions from UV/Vis and dynamic mechanical analysis indicates (i) no significant effect of side-chain motion on charge transport; (ii) in the glass transition and rubbery regions relaxation time distribution becomes broadened with temperature; (iii) as the coplanar subchains in the order region melt, the relaxation time distribution becomes more narrow.