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The soluble polythiophenes functionalized with a non-linear optical chromophore were prepared using copolymerization. The microstructure and the composition of the copolymers was determined through nuclear magnetic resonance spectroscopy. Two different types of solvent effects were identified. The first effect was on the conformation of the thiophene backbone and the other was on the electronic transition energy of the azobenzene unit.

A series of thiophenic monomers functionalized with different chromophoric groups have been optically characterized in view of preparation of polymeric films for second-order nonlinear optics and electrooptics. In order to investigate the optical behaviour inside a solid host matrix, the molecules have been physically dispersed in poly(methylmethacrylate) (PMMA) films and poled through high-temperature corona-poling for characterization through in situ second harmonic generation and ex situ angle-resolved spectroscopy. The values of dipole moment μ and optical hyperpolarizability β have been estimated inside the host matrix and related to the molecular structure. For one of the chromophores the long-term reorientation dynamics has been monitored in order to investigate the stability and the interaction with the polymeric environment. © 2001 Elsevier Science B.V.

The solvatochromic behavior of chloroform solutions of poly(3-decyl-2,5-thienylene), poly[3-(10-hydroxydecyl)-2,5-thienylene] and their copolymers was studied by the addition of the non-solvent methanol. A reversed chromic transformation was found associated with the content of the hydroxyalkyl substituent. This anomalous effect was investigated using a number of non-solvents, in particular aliphatic alcohols from methanol up to decanol. In the case of a chloroform/methanol mixture, which gives the maximum anomalous effect, the effect produced by temperature variation was also examined. An explanation based on a molecular approach was attempted.

The chromic behaviour of a soluble ω-hydroxydecyl 3-substituted polythiophene has been investigated by UV-VIS spectroscopy in different solvent/non-solvent mixtures over a wide range of low temperatures. Some interesting new effects have been observed that is the first case of a reversal of the solvatochromic transformation in substituted polythiopenes and a concentration effect in dilute pure solvent solutions. A molecular approach based on solvent-polymer interactions has been adopted to study the conformational chromic transformation of the polymer. © 2001 Elsevier Science B.V.

An alternating methoxyhexylthiophene–thiophene copolymer was synthesized from 3-(6-methoxyhexyl)-2,2′-bithiophene and studied chiefly by means of optical absorption and nuclear magnetic resonance spectroscopy. The results were compared with those of the previously obtained poly[3-(6-methoxyhexyl)-2,5-thienylene]. The differences in the UV-Vis spectra of the two polymers in pure solvents, solvent/non-solvent mixtures and in films are discussed on the basis of the microstructure and the steric hindrance along the backbone. NMR spectroscopy revealed copolymer configuration to be regiorandom with a slight prevalence of head-to-head and tail-to-tail junctions.

Copolymerizations at various feed ratios between azo-dye-substituted thiophenes and 3-hexylthiophene under FeCl3-based oxidative conditions have been conducted. It is shown that when the molecular structure of the dye is properly designed, completely soluble copolymers, with molecular weigths ranging around 104 as Mn and dye-substituted monomer content up to 50% in a molar ratio, may be prepared, as well as a completely soluble homopolymer. In addition, the so-obtained polymers evidenced excellent filmability from a variety of solvents. The dye-substituted monomer content of the soluble copolymers has been assessed by 1H NMR analysis via a convenient choice of the reference signals. In the completely soluble copolymers the dye-substituted monomer content is well correlated to the feed within a range between 0 and 75% of dye-substituted unit in the feed, which corresponds to a 0-50% range in the copolymer composition, still conserving satisfactory molecular weights. Following these observations and analyzing the characteristics of the polymers, a lower reactivity of the dye-functionalized unit toward 3-hexylthiophene was evidenced in the used reaction conditions, and some hypotheses on this finding are presented.

Azobenzene-substituted polythiophenes were prepared by copolymerization of 3-alkylthiophenes functionalized with an azo-chromophore and 3-alkylthiophenes as plastifying comonomers to improve solubility. Monomers with different oligomethylenic spacer and alkylic chain lengths were synthesized and copolymerized via FeCl3 oxidative polymerization. Polymer soluble fractions were characterized by 1H and 13C NMR, FTIR, UV–Vis spectroscopy, and GPC, DSC and TGA. Second-order non-linear optical properties were measured by the second harmonic generation technique.

The poly(3-hexanoyloxyethyl-2,5-thienylene) was studied by means of mono-and bidimensional nuclear magnetic resonance spectroscopy. The regiochemistry of the polymer is assigned on the basis of the 13C chemical shifts, which are easily obtained through inverse detection experiments, utilizing a triad-based model. © 1997 Elsevier Science Ltd. All rights reserved.

For the purpose of preparing materials for nonlinear optics applications, a 3-ethylthiophene bearing an NLO-active chromophoric group as a substituent at the end of the ethylic chain was copolymerized with 3-hexylthiophene. Different FeCl3-based oxidative polymerization conditions in solvents such as CH3NO2 and CCl4 and their effects on the copolymers characteristics and solubility in CHCl3 (i.e., the copolymer's soluble fraction) were examined. This work allowed to achieve a satisfactory chloroform-soluble fraction of the copolymer, still containing a notable amount of NLO-active group, and to tune to some extent the main characteristics of the copolymer; moreover, the behavior of the monomers−solvent−oxidant system was investigated.

Ester-functionalized poly(3-alkylthienylene)s were obtained by chemical oxidation with FeCl3. Substituents with both different total length and different distance of the ester group from the thiophene ring were examined. The main reaction solvent studied was chloroform which gave polymers with high molecular weight and incomplete conversion of the monomer. Some polymers were synthesized with a new procedure involving the precipitation of FeCl3 from a saturated nitromethane solution by a tetrachloride solution of the monomer. In this way, lower molecular weights and complete monomer conversion were obtained. The effect of different substituent groups on the polymer microstructure was examined using 1H NMR spectroscopy. With both polymerization procedures, the regioregularity and absorption maximum in the visible spectrum increase with increasing length of the oligomethylenic spacer between thiophene ring and ester group.

The electrical conductivity, σ, of different samples of SbCl5-doped thianthrenic polymers is found to vary from 10−6 to 10−3 S · cm−1. The relationship between conductivity and dopant concentration is examined for one representative sample and a transition from an insulator to a semiconductive regime is observed near a dopant/repeating unit mole ratio of 0.06, above which σ tends to saturate. A detailed infrared analysis of the doped polymers, essentially based on a comparison with the pristine (undoped) polymers and the thianthrene-SbCl5 (1:1) complex as a model compound, is reported. A first tentative assignment of the IR spectrum of this complex is made. Additional absorptions are observed near 1120 and 1080 cm−1 and are common features of all the doped thianthrenic polymers. The new peaks, which increase with dopant concentration, seem to be intrinsic vibrations of the polymer chains in the doped material and are referred to stretching modes of CSC groups enhanced by complexation. Another characteristic absorption around 340–325 cm−1, due to SbCl stretching modes of the dopant species, is discussed.

A comparison between a thianthrenic polymer and the parent poly(p-phenylene sulfide) is presented on the basis of electrical and infrared properties. Evidence that the polyheterocycle has a higher conductivity after doping with different amounts of SbCl5 is reported. In this doped polymer significant spectral modifications are also observed, mostly around 1100 cm−1. On the contrary the spectral profile of poly(p-phenylene sulfide) remains nearly unchanged at all doping concentrations.

Synthetic methods for the functionalization of alkylthiophenes with stilbenic and azobenzenic chromophores were successfully explored starting from 3-(ω-bromoalkyl)thiophenes as the main intermediates. The incorporation of the chromophores was achieved through ethereal and aminic linkages obtained by nucleophilic substitution under different experimental conditions. These methods permitted to synthesize a number of alkylthiophenic monomers functionalized at the end of the side chain with second-order non-linear optical chromophores. Some of the new monomers were chemically polymerized. © 2002 Elsevier Science B.V. All rights reserved.

Full Paper: Functionalized second-order nonlinear optical (NLO) thiopene copolymers were synthesized. Two elegant syntheses based on the post-functionalization of polymeric precursors obtained by oxidative polymerization were developed, leading to copolymers that proved to be fully soluble in common organic solvents. The new materials were characterized by NMR, FT-IR, and UV-vis spectroscopies, gel permeation chromotography (GPC), and thermogravimetric analysis (TGA). Moreover, the NLO activity of the new materials, as determined by corona poling alignment and second harmonic generation (SHG) measurements, showed a good agreement between the second-order NLO coefficient and the chromophore concentration.

The paper discusses a systematic study of the UV - Vis spectral profiles of poly[3-(10-hydroxydecyl)-2,5-thienylene] during its solvatochromic transformation in different solvent/non-solvent mixtures. A simulation of the overlapped spectra of the two chromophores (A less and B more conjugated) of the polymer is made through the resolution of their pure forms by means of vibronic progressions of log_normal curves. The increment of the absolute intensity observed in the transformation has been determined and related to the increment of the transition moment; its value strongly supports the hypothesis that the solvatochromic transition consists in a doubling of A chromophores. Estimation of the average length of B chromophores has made it possible to evaluate the oscillator strength in the different solvent mixtures, the Franck-Condon factor and the Huang-Rhys parameter in relation to the intensity distribution of the vibronic structure. © 2002 Elsevier Science B.V. All rights reserved.

A method of synthesis leading to poly(3-alkylthiophene)s with two different functional groups in the side chain, one of which is an NLO-active chromophore, has been developed. This method, based on the post-functionalization of a reactive homopolymeric precursor, permits to prepare different polyfunctional polymers that are fully soluble in the most commonly used organic solvents. The procedure is very easy to perform, cost-effective, highly versatile and reproducible.

Poly(3-hexanoyloxyethyl-2,5-thienylene) has been chemically synthesized with FeCl3 in both nitromethane and chloroform using different conditions. A complete homopolymeric structure is obtained in chloroform as confirmed mainly by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The homopolymer shows a higher molar mass by gelpermeation chromatography and a higher thermal stability under nitrogen by thermogravimetry. The microstructure of the polymeric chains has been investigated by NMR and a low regioregularity, independent from the polymerization conditions, is found. The electronic spectra suggest low conjugation lengths. The conductivities of the oxidized polymers, ca. 10–3 S cm–1, are reported.

Polycondensation du diodure (hydroxy-2 methyl-5 trimethyl ammoniummethyl) benzyltrimethylammonium, dans le DMSO, entre 60 et 80°C, avec des bisamines secondaires

A number of azomethines derived from aromatic diamines and pyrrole or tiophene aldehydes have been prepared and subsequently doped with iodine: these CT complexes show very low conductivities comparable with those of iodine doped pyrrole and N,N′-dipyrrylmethane

Two samples of poly [3-(6-methoxyhexyl)-2,5-thienylene] with a slight difference in regioregularity and a greater difference in molecular weights were obtained by chemical oxidation with FeCl3. The solvatochromism of the two polymers was investigated in mixtures of various solvents (dioxane, dimethylpropyleneurea, methylene chloride, tetrahydrofuran, chloroform and toluene) with different non-solvent (methanol) molar fractions, at constant polymer concentration and temperature. Some solvent/non-solvent couples were able to distinguish between the two samples, giving a different solvatochromic effect. This can be considered a very useful tool to characterize polymers with configurational and molecular weight differences. © 1997 Elsevier Science S.A.

The preparation of a hexanoyloxydecyl 3-substituted polythiophene and its conversion to the corresponding hydroxydecyl polymer, soluble in common organic solvents, is described. Solvatochromic and thermochromic effects of the two polymers were investigated by UV-vis spectroscopy in pure solvent and in solvent/nonsolvent solutions. A very different response was found depending on the type of functional group. The carboxylate polymer requires the synergy of both nonsolvent and low temperature for a strong chromic effect comparable to that of the hydroxy polymer to be observed. A possible explanation of this behavior is discussed. © 1998 John Wiley & Sons, Ltd.