A series of 4-n-aIkyl-and 4,4-di-n-alkyl-substituted cyclopentadithiophenes (C"CPDT and (C")2CPDT, n = 1, 3,4,6,8, and 16) were synthesized and polymerized by anodic coupling in 0.1 TEAP + AN. Electrochemistry, IR and electronic spectroscopies, elemental analysis, and in situ conductivity indicate that the polymers are oxidized to the conductive state (0.5 anion per monomeric unit) in two steps and in a single step for poly[C"CPDT] and poly[(C")2CPDT], respectively. The polymers are highly conductive (80-300 S/cm for poly[C"CPDT] and 2-40 S/cm for poly[(C")2CPDT]) and soluble in CHCls (degree of polymerization = 10-40 for poly[Ci«CPDT] and for poly[(C4)2CPDT]). Absorption maxima, in the range 545-605 nm, are anomalously red shifted to 640 and 680 nm for poly[(C8)2CPDT] and poly[(Cie)2CPDT].

Hybrid materials of polymers and cadmium selenide nanocrystals (CdSe-NCs) were produced through a layer-by-layer deposition technique. Polymer series comprises sulfonic, phosphonic, and carboxylic acids; pyridine- and amine-based polymers; and some related bipolar amphiphiles, including a dithiol. Nonaqueous dispersions of amine- and oleate-capped CdSe-NCs with 3, 4, and 5 nm diameters were used. Polymers and CdSe-NCs are alternately deposited on indium-tin-oxide/glass surfaces. CdSe-NCs layers undergo a sharp and irreversible electroxidation process in acetonitrile corresponding to the passage of two electrons per CdSe unit. The multilayer build-up, monitored by UV−vis spectroscopy and cyclic voltammetry, shows an increase in the film absorbance and oxidation stripping charge proportional with the number of adsorbed CdSe layers and with the particle diameter. Layer formation rate by acids follows their acidity, with thiols being much slower than sulfonic, phosphonic, or carboxylic acids. The semiconductor properties of the multilayers were evidenced by photoluminescence (PL), photoelectrolchemical, and photoconduction analysis. Good PL was recorded in pyridine-, amine-, and carboxylate-based multilayers, PL quenching in sulfonate-, phosphonate-, and thiolate-based multilayers. PL quenching is accompanied by higher photoelectrochemical and photoconductivity responses.

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New low-gap thiophene-based regular copolymers are produced by anodic coupling of 3,4ethylenedioxythiophene-2,5-substituted thieno [3,4-b]pyrazine (TP), cyclopenta[2,1-b;3,4-b′]dithiophen-4-one (CO), and 4-dicyanomethylene-4H-cyclopenta [2,1-b;3,4-b′]dithiophene (CN). The copolymers are characterized by cyclic voltammetry, FTIR reflection-absorption and UV-vis spectroscopy, electrochemical quartz crystal microbalance analysis, and in situ pand n-conductivity measurement. The copolymers show low optical gaps (measured at the maximum absorption) and electrochemical gaps (measured from redox potentials) in the range 0.8-1.3 eV. The CN-based polymer displays the lowest reported electrochemical gap (0.8 V). Random copolymers of CO and 3,4-ethylenedioxythiophene (EDT) have also been produced and compared with the relevant regular copolymer. Copolymerization of CO with increasing amounts of EDT decreases the gap. From an analysis of redox potential as a function of EDT fraction, it is found that the gap is limited by the redox potentials of the individual homopolymers. Localization of n-doping carriers in the polythiophene chains is progressively increased by donor-acceptor alternation and then by copolymerization till the expected intrinsic conductivity is made completely p-type.

Carboxypentyl and carboxyhexyl bithiophenes and terthiophenes, in which the oligothiophene tail is either perpendicularly or linearly linked to the tethering carboxyalkyl chain, were adsorbed on ITO electrodes. The obtained stable monolayers are anodically oxidized in acetonitrile to produce polymer layers (storing a reversible charge of 15 μC cm-2) in the case of perpendicular adsorbates whereas linear bithiophene and terthiophene are able to couple only with oligothiophenes in solution. Electrochemical and UV−vis spectroscopic analysis indicate that the polymer layers are in fact constituted by thiophene hexamers. The adsorbed linear terthiophene may be coupled with the terthiophene itself in solution to produce a one-end surface-grafted sexithiophene monolayer (reversible charge 40 μC cm-2), whereas a two-end surface-grafted sexithiophene with the same coverage is produced by adsorption of the α-coupled terthiophene. The one-end and two-end grafted sexithiophene monolayers display different electrochemical and spectral patterns. Chronoamperometry and cyclic voltammetry show that the adsorbed linear bithiophene may be oxidatively coupled with 2,2‘-bithiophene in solution to produce surface-anchored polythiophene chains.

All‐plastic and flexible electrochromic devices will facilitate new technological applications, such as information display and storage, in the automotive industry (rear‐view mirrors) and in architecture (smart windows). Here the authors describe an all‐plastic and flexible solid‐state electrochromic device using two optically complementary conductive polymer blends deposited on ITO‐PET (indium tin oxide–poly(ethyleneterephthalate)), and a polymeric electrolyte. The device was constructed under atmospheric conditions and showed good optical characteristics.

Conjugated polymers (CPs) are interesting materials for preparing devices based on nanoscopic molecular architectures because they exhibit electrical, electronic, magnetic, and optical properties similar to those of metals or semiconductors while maintaining the flexibility and ease of processing of polymers. The production of well-defined mono- and multilayers of CPs on electrodes with nanometer-scale, one-dimensional resolution remains, however, an important challenge. In this Account, we describe the preparation and conductive properties of nanometer-sized CP molecular structures formed on electrode surfaces--namely, self-assembled monolayer (SAM), brush-type, and self-assembled multilayer CPs--and in combination with gold nanoparticles (AuNPs). We have electrochemically polymerized SAMs of carboxyalkyl-functionalized terthiophenes aligned either perpendicular or parallel to the electrode surface. Anodic coupling of various pyrrole- and thiophene-based monomers in solution with the oligothiophene-based SAMs produced brush-like films. Microcontact printing of these SAMs produced patterns that, after heterocoupling, exhibited large height enhancements, as measured using atomic force microscopy (AFM). We have employed layer-by-layer self-assembly of water-soluble polythiophene-based polyelectrolytes to form self-assembled multilayers. The combination of isostructural polycationic and polyanionic polythiophenes produced layers of chains aligned parallel to the substrate plane. These stable, robust, and dense layers formed with high regularity on the preformed monolayers, with minimal interchain penetration. Infrared reflection/adsorption spectroscopy and X-ray diffraction analyses revealed unprecedented degrees of order. Deposition of soluble polypyrroles produced molecular layers that, when analyzed using a gold-coated AFM tip, formed gold-polymer-gold junctions that were either ohmic or rectifying, depending of the layer sequence. We also describe the electronic conduction of model alpha,omega-capped sexithiophenes featuring a range of electron donor/acceptor units and lengths of additional conjugation. The sexithiophene cores exhibit redox-type conductivity, developing at the neutral/cation and cation/dication levels with values depending the nature of the substitution and the redox system. Extending the conjugation beyond the sexithiophene frame introduces further oxidation processes displaying enhanced conductivity. Finally, we discuss the ability of CP-based monolayers to coordinate AuNPs. Although thiophene- and pyrrole-based oligomers aggregate toluene-soluble AuNPs, alkyl substitution inhibits the aggregation process through steric restraint. Consequently, we investigated the interactions between AuNPs and polypyrrole or polythiophene monolayers, including those formed from star-shaped molecules. The hindered aggregation provided by alkyl substituents allowed us to adsorb thiol-functionalized oligothiophenes and oligopyrroles directly onto preformed AuNPs. Novel materials incorporating AuNPs of the same s...

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