Polyaniline offers a promissing possibility to make electrically conducting polymer blends with tailorable surface and bulk conductivities. The matrix polymer can be a thermoplast or a thermo- set. Different commonly used polymer processing methods are applicable to the blends; e.g. injection moulding, film blowing, compression moulding and fiber spinning. Also commonly used thermoset resins processings are possible. The key feature in making all this feasible is the co- solvent/plasticizer technology developed recently in the industry. Typically, the antistatic conduc- tivity level is reached in melt-processing with a polyaniline complex amount of 5 to 10 wt-% and in solution processing with 0.5 to 5 wt-% complex amounts. The maximum conductivity is in the range of 10 to 100 mS/cm for blends.

Self-assembled films of pyromellitic dianhydride oxydianiline (PMDA-ODA) were fabricated through the alternate adsorption of poly(amic acid) and various polycations including poly(allyl amine) (PAH), polyaniline (PAni), and the tetrahydrothiophene precursor of poly(p-phenylene vinylene) (PPV). In all cases, a linear build-up in thickness with increasing number of bilayers was observed with a high sensitivity of the average bilayer thickness to the ionic strength of the poly(amic acid) solution. By controlling the ionic strength of the PAA solution, the bilayer thickness could be varied from 10 to 100 Å, depending on the polycation used. Examination of the self-assembled films of poly(amic acid) and PAni showed that a conductivity of 0.5 S/cm could be achieved prior to conversion of the polyimide, but that the conductivity was drastically reduced when either the ionic strength of the poly(amic acid) solution was increased or when the poly(amic acid) was converted to polyimide. The self-assembly of poly(amic acid) with precursor PPV demonstrated that it was possible to produce a film which can be self-assembled as two ionic precursor polymers and then thermally converted into a film composed of two non- ionic polymers. Advancing sessile water drop contact angle measurements revealed that very hydrophobic surfaces can be generated upon conversion of the PAA/precursor PPV films.

We investigate the dynamics of photoexcitations in thiophene-based copolymers by site-selective and time-resolved photoluminescence spectroscopies. We attribute the large Stokes-shift observed between the absorption and luminescence peaks to spectral relaxation of excitons within an inhomogeneously broadened density of states. The non exponential decay of the photoluminescence intensity is explained through the interplay between spectral diffusion, thermally activated jumps and slow transfer to non nearest neighbour sites.

Polypyrrole films were electrogenerated and electrochemically compacted at high cathodic potentials on aluminium. Films removed from the electrode after polarization at -2000 mV show stable bulk conductivities of 10-6 S/cm for months. Planar structures metal/polymer/metal present rectifying properties. The presence of a thin oxidized surface layer having a higher conductivity than that of the bulk polymer can be deduced remaining reduced the polymer mass.

Silver Tetracyanoquinodimethane (AgTCNQ) is an organometallic semiconductingcompound with potential for use as an optical memory storage media due to its ability to exist intwo states. A laser Raman system has been proposed for this application as the two states havedistinct Raman vibrational peaks. However, the Raman spectra of bulk AgTCNQ films is veryweak and requires special measures to prevent laser-induced degradation and to ensure adequatesignal to noise ratios. In this paper, we report a synthesis AgTCNQ consisting of AgTCNQnanolayers grown around silver colloidal particles in both water and heptane with the use of theamphiphilic surfactants, AOT and SDS. The Raman scattering of such AgTCNQ systems hasbeen found to be strongly enhanced and far superior to that obtained on bulk AgTCNQ films.We believe that such a system represents a novel and advantageous way of detecting theswitching behavior of AgTCNQ (and other metal-TCNQ compounds) by laser, as Ramanresearch on metal-TCNQ systems has been stymied in the past by poor Raman signals andsusceptibility to laser-induced degradation.

The electronic transport mechanism for ion implanted and chemically doped polyanilinefilms was investigated through temperature dependent dc conductivity measurements over thetemperature range 1.8 – 300K. Chemically synthesized emeraldine base polyaniline free-standingfilms (∼40 µm thick) were irradiated by Ar ions at an energy of 90 keV and doses ranging from 1 ×1014 to 3 × 1017 cm-2 to an estimated thickness of 100 nm. Chemical modification of Polyanilinefilms consisted of doping with 1.0 M H2SO4.

Ion implantation and chemical doping were found to considerably increase the roomtemperature dc conductivity of polyaniline films reaching values up to 800 S cm-1and 8 S cm-1, respectively. Both ion irradiated and chemically doped polyaniline films exhibit p-type conduction.An increase in the irradiation dose increases the stability of the conducting layer compared tochemical doping. In both cases the samples are on the insulator side of the metal-insulatortransition, where cr(T) exhibits a common temperature dependent characteristic of the variablerange hopping (VRH) transport mechanism:σ(T) = σ (0) exp[ - (To / T)m ] (1)where m = 0.5 and To = 103 to 104K. The influence of electron-electron Coulomb the low temperature VRH of ion implanted and chemically doped polyanilCinoeu floilmmbs iisn tperreascetniotend

Time-resolved femtosecond pump and probe experiments were conducted on films and solutions of poly (para-phenylene)-type ladder-homopolymers featuring a high degree of intrachain order. We find photobleaching, stimulated emission and photoinduced absorption. The spectral separation of stimulated emission and photoinduced absorption makes this polymer a promising candidate for a solid state laser.

The synthesis and characterization of a 1,1′-binaphthyl based main chain chiral conjugated polymer, R-9, is described. The polymer is prepared from the palladium-catalyzed Suzuki coupling of an optically active binaphthyl molecule, (R)-2,2′-dihexyloxy-1,1′-binaphthyl-6,6′- diboronic acid, R-4 with 1,4-bis(p-bromostyryl)benzene (E:Z = 1:1.2), 8. The Suzuki coupling of 8 with 6-neopentyloxynaphthyl-2-boronic acid, 1 1, leads to the formation of a conjugated molecule 10. The structure of this molecule represents the repeat unit of R-9. The electronic absorption spectrum of 10 demonstrates that the degree of conjugation in the chiral conjugated polymer is almost the same as that of its repeat unit.

Conjugated, conducting pyrrole-based polymers were obtained by electropolymerization of 2,2′-spaced-dipyrroles in which the spacer was a vinylene, or a cyanovinylene, or an azo group. In every case, the bandgap of the polymers is considerably narrower than that of polypyrrole.

The anodic oxidative polymerization of alkyl functionalized 4H-cyclopenta[2, 1-b:3,4-b']- dithiophene (CPDT) followed by undoping provides soluble and processable materials. We used CP MAS and high resolution NMR to analyze the monomers and polymers with the aim of correlating their structural features and conductivity. T1 relaxation values in solution and solid state were compared. Information about the preferred conformations of the polymers (backbone, distances, torsional angles) was deduced using the Molecular Modeling approach. The conclusions were derived by combining the indications obtained from both the spectroscopic and computational methods.

Extensive gel permeation chromatography coupled with surface structure measurements clearly indicate that polyaniline (pani) base has a tendency to aggregate as a result of interchain hydrogen-bonding. The aggregation is present in the solid state powder; the extent of aggregation is found to be significantly dependent on the synthetic conditions. Pani base powders having a high degree of aggregation have significantly reduced solubility. The degree of aggregation of pani base in solution is found to be dependent on the solvent, concentration, and temperature. As the solvent becomes a better solvent for the base material, the less aggregated is the structure. Solvents which can strongly interact with the polymer disrupt the aggregation. In addition, salts such as LiCl which complex the polymer via a “pseudo-doping” process, also disrupt the internal pani hydrogen-bonding and deaggregate the polymer. As the polymer is deaggregated to different levels by a solvent or by LiCl, the individual chains can better be solvated and thus a conformational change also occurs. The chains adapt a more expanded coil type of conformation. The degree of expansion depends on the solvation power of the solvent. As the level of deaggregation and subsequent chain expansion increases, a significant red shift is observed in the λmaximum of the exciton absorbance and the surface structure of the polymer becomes smoother. It is found that the LiCl induced morphological changes results in increased conductivity upon doping pani base with a protonic acid.

Phthalocyanine and quinacridone pigments have been used in a variety of photovoltaic devices [1]. These pigments find utility as photoreceptors in xerography, photoelectrochemical devices and model solar cells [2]. They are of particular interest because of their high absorption in the visible region of the electromagnetic spectrum and their inherent chemical and thermal stability [3]. Asymmetric quinacridones demonstrate significant NLO properties. In recent years, devices based on quinacridones have shown great promise. In a few of these applications thin films of quinacridones, prepared by vacuum sublimation, are deposited onto electrode materials, however, in almost all other applications, the insoluble pigment is dispersed in a polymer binder at relatively high concentration [4]. Polymeric binders include polycarbonates and polyalkylmethacrylates [5].

Positron annihilation lifetime measurements are made in a series of polyaniline polymers with different chemical compositions and protonation ratios at room temperature. Two positron lifetimes are observed in these materials: one is assigned to annihilation in the bulk and the other to voids created due to protonation. A relationship between conductivities and positron annihilation probabilities is found.

We report a study of the optical and photoexcitation properties of a new polyalkylthiophene:poly[(3-pentyl-5-oxoazobenzene)thiophene]. UV-Vis absorption and emission, IR absorption, Raman scattering, indicate that the steric hindrance of the side chain induces some rotational disorder of the backbone but the π electron delocalization is not substantially differing from other polyalkylthiophenes. Long lived photoexcitations have been characterized by photoinduced absorption. The spectral features are intrinsic to the polyconjugated thiophene chain, even when the backbone and the azo chromophore are both photoexcited by UV light.

A new aggregated form of C60, believed to be “polymer”, was prepared through the reaction of C60 with iodine. First, C60 was reacted with iodine to give iodine-doped C60 with magnetic transition around 60 K. After removal of the doped iodine, the sample showed some of the characteristic properties common to the other “polymer” forms of C60. Finally, this “polymer” sample was found to show superconductivity after doping with various alkali-metals (K, Rb, Rb/Cs). Magnetic and/or superconducting properties of these C60 “polymer” are compared with monomer C60

The spectroscopic properties of the pyridine-based polymer poly(p-pyridyl vinylene p-phenylene vinylene) (PPyVPV) are examined. The emission of PPyVPV in solution has small intrinsic Stokes shift with some vibronic structure. In contrast, emission from thick film samples is featureless, with a strong redshift of ˜0.5 eV versus solution. We attribute these observations to the formation of aggregate states in film samples. Time-resolved photoluminescence measurements are in accord with the diffusion of excitons to the aggregate sites. Photoinduced absorption also originates from excitons in aggregate states.

Selectively excited room-temperature luminescence spectra are reported for thin films of poly(p-phenylene) (PPP) deposited onto quartz substrata. The spectra exhibit a localization threshold in the low-energy tail of the luminescence excitation band at vloc.= 22400 cm−1, 2200 cm−1 below the maximum of the excitation spectrum. Upon laser excitation at Vex < Vloc., the maximum Vem of the luminescence spectrum shifts linearly with Vex due to selective excitation of polymer segments. It was found that there exists the frequency range where the slope of the Vem vs Vex dependence is smaller than unity, which corresponds to our previous model calculations for the case of selective excitation of chromophores through broad phonon bands. At vex > vloc,, the luminescence spectrum is independent of Vex. This behavior can be explained if one assumes that upon excitation below the localization threshold the luminescence is related to polymer segments directly excited by laser, whereas upon exciting above the threshold the fast energy relaxation takes place from initially excited states to lower-lying states, from which uminescence occurs.

A tight binding, one dimensional, two-band model is used to investigate the formation and nonlinear optical properties of biexcitons in conjugated polymers. The full single and double electron-hole pair basis sets are explicitly considered for a Hamiltonian which includes an electron and hole transfer parameter (t) along with a truncated potential with only on-site (V0 ) and nearest neighbor (V1) Coulombic interactions. The biexciton phase space is determined to be a function of only two parameters α and βwhere α ≅V1/V0 and β ≅t/V0. Due to the truncated potential only a single biexciton eigenstate is formed in the region limited by 0.64 < α≤ 1 and 0 ≤ β< 0.33. The two-photon absorption spectra in the range 0 < hω < δ, where δ is the one photon gap, are found to contain at most two types of peaks: one arising from a biexciton and another due to a charge-transfer, single-exciton. The polymer limit is obtained and used to investigate polymers with large alternation such as polysilane.

A series of coordination compounds -macrocycle tetraaza derivatives with extended electronic conjugations- as molecular solids have been synthesized and analyzed by Raman spectroscopy. Their resistivity vs. temperature characteristics, measured in thin films, show three types of behavior: metallic, semiconductor and, in some cases, semiconductor with a transition to metallic below certain temperature. Room temperature Raman spectra were obtained in a FT-IR spectrometer and some stretching modes show different Raman shifts depending on the reactants. We relate these shifts with the degree of charge transfer between donor and acceptor radicals.

Conjugated polymers in general, and polythiophenes in particular have been attracting attention in the field of molecular electronics. Polythiophenes functionalized at the β- position with various groups have resulted in processable, conjugated polymeric systems with applications such as organic electrodes, photorefractive materials, electro-luminescent devices, among others. We report the synthesis of a thiophene copolymer with alkyl and chiral amino acid substituents at the β- position. We have synthesized a solution processable poly[3-octylthiophene-co-(N-1-carboxyl, 2- (4-hydroxy-3-nitrophenyl)ethyl)-3-thiophene acetamide] with 3-nitro-L-Tyrosine as the chiral amino acid side chain. The UV-Visible and optical rotatory dispersion spectra of the new copolymer are discussed.