Colloidal polyaniline has been prepared in acidic aqueous media by a modified chemical polymerization of aniline in the presence of a tailor-made polymeric surfactant. The surfactant which acts as a steric stabilizer used in this study is derivatized poly(vinyl alcohol-co-vinyl acetate). This surfactant contains pendant aniline units which participate in the aniline polymerization, resulting in the formation of sterically-stabilized polyaniline particles which have a non-spherical “rice-grain” morphology.

It is shown that this novel form of polyaniline is more processable than the bulk powder that is normally obtained from a conventional chemical synthesis. The solid-state conductivity of solution-cast films or compressed pellets of these dispersions is surprisingly high (⋍ 1 S/cm), despite the presence of the insulating outer layer of chemically-grafted stabilizer.

Intercalative polymerization of aniline, pyrrole and 2,2’-bithiophene in vanadium oxide xerogels results in electrically conductive novel materials which are composed of alternating monolayers of metal-oxide and conductive polymers. The driving force for this intercalation is redox chemistry. The conductivity type in these materials is a function of the polymer/V2O5 xerogel ratio. Low ratios result in xerogel-based charge transport, while high ratios favor polymer-based charge transport properties. Chemical, spectroscopic and electrical data on the intercalative polymerization products of aniline, pyrrole and 2,2’-bithiophene with V2O5 xerogels are presented.

A preliminary physical study of the soluble part of emeraldine is presented. The electrical and magnetic properties of this low weight material are very similar of those of the pristine emeraldine salt. These results emphazise the possible role of short chain species in the conduction mechanism of polyaniline. In order to clarify this point, previous magnetic investigations on insoluble emeraldine salts are revisited. It appears that the fit of the magnetic susceptibility temperature dependence of polyaniline with a Curie law plus a Pauli term might not be justified at low temperature. A T−α law with a ≈ 0.75 gives a better fit suggesting a behavior similar to the one found in Random Exchange Heisenberg Antiferromagnetic Chain (REHAC)

Polyaniline is an interesting electrochromic material because its color can be changed from clear to green, to blue, and to purple by electrochemical oxidation[1]. The structural transformations associated with these color changes are shown in Scheme I. One of the possible applications for polyaniline is to use it as the active material in electrochromic windows.

Water content as well as conductivity have been measured as a function of water vapour pressure on polyaniline and poly-N-methylaniline samples. It is shown that i) absorption is governed by the acid protons of the polymers and ii) enhancement of conductivity needs the existence of protonated imines. It is concluded that moisture favours conductivity through an increase of the interchain transfers.

Poly(o-toluidine) and poly(m-toluidine) in base form have been characterized by infrared and lH NMR spectroscopy. Assignments of the proton NMR signals have been facilitated by the use of model compounds. The distinction between benzenoid and quinoid methyl resonances in the NMR permits a semi-quantitative estimation of the oxidation states of the polytoluidines. Infrared studies are consistent with a polyaniline-type backbone having pendant methyl groups. Field desorption mass spectrometry (FD-MS) was employed for estimation of the molecular weight of poly(o-toluidine). Gel-permeation chromatography of the same sample showed a bimodal elution pattern, suggesting that the FD-MS technique detects only the lower molecular weight fraction of the polymer. Despite this inherent limitation, FD-MS yields the interesting information that the polymer contains chains of both odd and even numbers of repeat units, necessitating the coexistence of different oxidation states in the base form of the polymer.

The improvement of the processibility and mechanical properties of poly-aniline (PAn) by processing a concentrated sulfuric acid solution of the mixture of chemically prepared conductive PAn powders and poly(p-phenylene-terephthalamide) (PPTA) in different weight ratios are presented.

The concentrated sulfuric acid solution of PAn and PPTA were processed to films and threads, they are liquid crystalline conductive polymer composites, the electrical conductivities of the composites are between 10−4 -10−1 s/cm.

PAn enhanced the tensile strength of PPTA, but does not effect the elongation. The morphology of the PPTA/PAn composite surfaces are fiberlike texture.

Polyaniline (PANI) films were grown on 304 L steel and studied by FTIR spectrometry. The spectra of the films formed carry evidence for quinonic/aromatic alternating structure involving head-to-tail coupling. The coupling is quite independent of the thickness of the polymeric layer. The quinonic/aromatic ratio can be varied when the film is subjected to further dedoping treatments (electrochemical reduction or KOH immersion).

The electrical properties of Langmuir-Blodgett films of conducting polypyrrole were investigated in an effort to illucidate the molecular architecture of these multilayer films and determine the mechanism of conduction. Values of the dielectric constant and transverse conductivity recorded as a function of frequency were determined from electrical measurements performed on devices made with the conductive polymer. The highly anisotropic nature of the conductivity as well as the frequency dependence demonstrated by both the conductivity and dielectric constant provide evidence for a highly ordered molecular structure in which the conductive and insulative components of the multilayer film form an organized, layered structure. Even greater control of the electrical and structural properties has been achieved through the fabrication of a thin film superlattice in which the conducting polymer and an insulating derivative were deposited as alternating bilayers. The properties of the superlattice were close to those predicted for an inhomogeneous, mixed media.

A series of aromatic polymers and copolymers have been investigated that contain a combination of 2,5-thienylene and 1,4-phenylene linkages. l,4-Bis-(2-thienyl)phenylene monomers have been prepared with a variety of substituents on the 2,5-phenylene positions. Subsequent oxidative polymerization of these monomers, both chemically and electrochemically, yield a family of polymers containing a thiophene-phenylene-thiophene repeat unit. Theoretical modeling, using both PRDDO and ab initio methods, has been used to correlate the thiophene-phenylene torsional angles with band gaps. In addition, polymer band structure has been investigated using the Extended Hiickel method.

Polyazines, -[N=CH-CH=N]x-, are environmentally stable conjugated polymers that can be doped with iodine into an electrically conductive state. These polymers are prepared by the condensation of glyoxal and glyoxal di-hydrazone with acid catalysis. IR spectra of the undoped polymers, independent of the synthetic conditions, exhibit a broad band centered around 3240 cm−1 indicative of the presence of OH groups in the polymer. Solid state NMR spectra show that the OH groups are covalently bound to the polymer chain so that the polymer chain has a number of defect and/or cross-linking sites present. The polymer can be doped with iodine into a poorly conducting state. Iodine doping introduces one new vibrational band into the IR spectra at 1490 cm−1, associated with a bipolaronic charge carrier.

Oxidative doping of individual thiophene oligomers nT (n = 3 to 6) with FeC13 in dilute CH2Cl2 solution generates the corresponding radical cations (polarons) nT+.. as evidenced by in-situ visible/near infrared absorption and electron spin resonance spectroscopies. The nT+. species in solution progressively precipitate as conducting (0′300K = 10−1−10−2 S/cm) and strongly paraaagnetic radical cation salts (g = 2.003, ΔHPP ∼ 4–8 G). The conductivity of the 6T+. salt is weakly temperature dependent, with an activation energy of 32 meV above 100 K and a tendency to level Dff at lower temperatures. In the case of the sexithienyl radical 6T+., further doping results in the quantitative conversion into the dication 6T++ (bipolaron).

The photoluminescence (PL) and optically detected magnetic resonance (ODMR) spectra of poly(3-hexylthiophene) in solutions of CCl4, toluene, and CH2Cl2, and films cast from these solutions, are described and discussed. In solution, the PL yield is 7%, and increases with increasing temperature. In oxygen-free, protected films cast from these solutions, the room-temperature yield is ∼0.7%, the spectra is red shifted by ∼0.5eV, and strong peaks at 1.52, 1.69, and 1.86eV appear. In films and CH2Cl2 solutions, the ODMR is resolvable into narrow and broad components, and its intensity ΔL/L is ∼5 × l0−5 at room temperature. A strong photoinduced oxidation process quenches the PL upon exposure to O2 but not water, at a rate possibly limited by O2 diffusion.

Helical conformations of polymers occur due to a variety of factors, some of which are electronic in origin. We briefly review the situations in which there is an electronic driving force towards a helix including a case that might be called a helical Peierls distortion. Energetics and geometries of helical conformations of polythiophene and polypyrrole are also analyzed.

We report Raman scattering measurements on poly-3-heptylthiophene and poly-3-undecylthiophenes both on resonance and preresonance conditions. We have studied different samples as solutions ,solution cast films and electrosynthetized as grown films. Our results indicate that the vibrational frequency of the mode which is strongly coupled to the π - π* electronic transition is sensible to “small” torsions between thiophenes rings , which do not necessarly interrupt completely the conjugation path.

We report studies of transport properties of thin films of undoped poly(3-hexylthiophene) (P3HT) fabricated by spinning a polymer solution onto oxidised silicon or glass. The film thicknesseswere on the order of 1000 Å. We studied magnetoresistance, the effect of magnetic field on field effect mobility and Hall effect.

Transverse magnetoresistance was measured on films on glass. A positive anomalous magnetoresistance with a saturation value of about 0.1 % was found. Transverse magnetoresistance was also studied by measuring the change of a field effect mobility with magnetic field. This measurement was performed using the field effect transistor structure. An initial mobility of 6.5 × 10−5 cm2/Vs was reduced by about 15 % in a transverse magnetic field.

We also carried out Hall effect measurements on films on glass using a Van der Pauw contact configuration. The measured Hall mobility was 2.17 × 10−5 cm2/Vs. Finally we measured the temperature dependence of the Hall mobility and found it follow the exp(T-l/4) law of variable range hopping.

We show by calculations for a chain of stage-1 (16.7%) potassium-doped (CH)x that the metallic state is obtained by adding to the Su-Schrieffer-Heeger Hamiltonian the Coulomb potential of the doping ions and solitons on other chains. Good agreement with the measured Pauli susceptibility is obtained. Adding interchain coupling is found to lead to essentially the same density of states.

Using exact finite-size diagonalizations of extended Peierls-Hubbard Hamiltonians for systems of up to 15 sites, we study the excited state spectra of models for the finite oligomer analogs of trans– and cis– polyacetylene. We use a novel “phase randomization” technique and a variety of other methods to extract maximal information from these small systems. For several electron-phonon couplings in the expected range, we discuss the extent to which we are able to find consistent values of the Hubbard on-site (U) and nearest-neighbor (V) correlation parameters such that the band gap, the 2 1Ag state, optical phonon frequency, and the optical absorptions for charged and neutral solitons and dimers occur in the experimentally expected ranges. Our results suggest that these correlation parameters are in the intermediate coupling regime (U ⋍ 2.5t0), beyond the range of perturbation theory.

Metal-Insulator-Semiconductor (MIS) and MISFET structures constructed with polyacetylene prepared by the Durham precursor route provide convenient systems for the investigation of charge storage and transport in this polymer. The charge accumulation layer is particularly easy to form, and is of particular interest because charge is introduced into the polymer without compensation by chemical dopants. Charge is stored in soliton-like excitations of the chain, and we are able to characterise these from optical measurements of their electronic excitations. We find that the nature of the soliton-like states is very sensitive to the structure of the polyacetylene at the interface between the insulator and polyacetylene, and we report here the properties of devices formed with various organic polymers as the insulator layers which we contrast with those formed with silicon dioxide.

Photoproduction and photodepletion of stable charged defects in trans-polyacetylene were observed, at low temperatures, by monitoring the IR signature of these defects: absorptions at 1368, 1289, 640 cm−1 (1053, 600 cm−1 for (CD)x). These absorptions could be observed at long times (two to several hundred minutes) after photolysis, only when the sample was protected from photolysis by the probe beam, by blocking v > 2,300 cm−1.

The location of these absorptions and the temperature dependence of their intensities were similar to those of previously observed photoinduced defects reported to have much shorter lifetimes (τ - ms). The stable defects reported here can be produced at much lower photolysis energies (v > 5,000 cm−1) than transient-photoinduced defects (v > 9,000 cm−1). A mechanism for the photoproduction of stable defects, involving a two-photon process catalyzed by existing neutral defects, is proposed to explain this low onset.

The slow decay of these defects observed when the sample is kept in the dark is attributed to photoinduced depletion by blackbody irradiation. This process was slow enough to allow the wavelength dependence of photodepletion (observed at 2,800 < v < 8,000 cm−1) to be studied. The photodepletion was fastest near 4,500 cm−1, suggesting that the defects possess an electronic absorption (with a peak near 4,500 cm−1) similar to that observed directly for the transient-photoinduced defects.