Jean-Pierre Lère-Porte

Highly Conjugated Poly(thiophene)s − Synthesis of Regioregular 3-Alkylthiophene Polymers and 3-Alkylthiophene/Thiophene Copolymers

Tributyltin derivatives of 2-bromo-3-octylthiophene and 5-bromo-4-octyl-2,2′-bi(thiophene) have been selectively prepared. Condensation reactions in the presence of Pd2(dba)3(CHCl3)/4 PPh3 led to high yields (ca. 90%) of regioregular poly(3-octylthiophene) (Mw = 21.4 ×xa0104, Mw/Mn = 1.48) and poly[4-octylbi(thiophene)] (Mw = 3.8 ×xa0104, Mw/Mn = 1.1). The regioregularity of the head-to-tail (HT) coupling has been determined by 1H NMR, which showed HT > 95% for poly(3-octylthiophene) and HT > 90% for the new poly[4-octylbi(thiophene)]. The conjugation properties of these materials have been characterized by FT-IR and UV/Vis spectroscopy. Compared to the corresponding random polymers, the absorption maxima of the new regular polymers are shifted to higher wavelengths (λmax = 448 and 466xa0nm, respectively). The mean conjugation length increases with increasing regioregularity of the coupling and with fewer substituents along the conjugated chain. The electroactive properties of the materials have also been studied. The new poly[4-octylbi(thiophene)] shows an oxidation peak at a low potential, and, compared to poly(3-octylthiophene), a reduction peak is also observed at a lower potential indicating a higher electron affinity. Both polymers exhibit reversible blue-red electrochromic behavior associated with the reversible redox properties.

Synthesis, orientation and optical properties of thiophene–dialkoxyphenylene copolymers

A (thienylene–dialkoxyphenylene) copolymer has been prepared by using an organometallic condensation reaction between a bis(stannyl)thiophene reagent and a substituted dibromobenzene derivative in the presence of a palladium catalyst. The grafting of 2-butoxyethoxy substituents gave the polymer a good solubility in most organic solvents. Moreover, owing to the presence of polar dialkoxy chains along the conjugated skeleton, a material with excellent glass adhesion properties was obtained. It allows the formation of homogeneous thin films coatings. The material is highly fluorescent (Φsol = 0.9, λsol = 520xa0nm). The polymer was ordered by coating on an oriented Teflon deposit on a glass support and exhibited polarized fluorescence. On the other hand, the material presented a stable reversible blue–red electrochromism associated with a redox transfer at a low potential value (0.5xa0V vs. SCE). Moreover, the electrochromic properties of this material are preserved even in an aqueous electrolytic medium (LiClO4–H2O). The copolymer with enhanced optical properties compares quite favorably to polythiophene and has good potential for the elaboration of optical devices; for example it seems to be a good candidate for the preparation of electroluminescent diodes with polarized emission.

A chiral polymer with alternating conjugated segments and (1R,2R)-1,2-diaminocyclohexane as a unit with C2 symmetry

A chiral conjugated polymer was prepared via the palladium catalysed coupling reaction between 1,4-di-ynyl-2,5-dialkoxybenzene and a bis-5-bromothienyl derivative of (1R,2R)-1,2-diaminocyclohexane as a chiral unit with C2 symmetry and a unit with complexing properties. The resulting chiral polymer of which its backbone consists of alternating conjugated segments and chiral complexing units, showed intense luminescence properties and was used as a ligand in the rhodium-catalysed hydride transfer reduction.

Comparison of fluorescence and QCM technologies: Example of explosives detection with a π-conjugated thin film

A pi-conjugated compound was synthesized as a sensitive material for explosives detection. The detection of vapors of 2,4-dinitrotoluene was demonstrated with quartz crystal microbalance (QCM) and fluorescence transduction methods. The fluorescence intensity monitoring shows a higher sensitivity and selectivity than the monitoring of the QCM frequency. Both methods appear to be synergic when used simultaneously as the sensor helps to discriminate interferent vapors from nitroaromatics.

Synthesis and ionochromic properties of chelating conjugated polymers

Two types of conjugated copolymers functionalized by chelating subunits were prepared using the palladium catalysed coupling reaction of a dihalogenated substrate containing a coordinating unit and a bis(tributylstannyl) conjugated reagent. The ionochromic properties of the polymers containing crown ethers or bipyridine were studied.

A thienylene-phenylene copolymer with di(ethylene oxide) side chains and its use in light emitting diodes

Abstract A thienylene-dialkoxyphenylene copolymer was prepared by condensation between a bis-stannylthiophene reagent and a substituted dibromobenzene derivative in the presence of a palladium catalyst. Owing to the presence of 2-(2-butoxy-ethoxy)-ethoxy polar side chains the polymer was soluble in most organic solvents and exhibited excellent glass adhesion properties. It allowed the formation of homogeneous thin films on indium tin oxide (ITO) by spin coating. The electrochemical and optical properties of thin films of the material have been studied. The calculated band gap derived from cyclic voltammetry data (2.21xa0eV) is in good agreement with the one calculated from the UV–VIS spectrum edge ( 2.15xa0eV). A single layer light emitting diode (LED) was fabricated in the configuration of ITO/polymer/Al. Electroluminescent maximum was recorded at 600xa0nm corresponding to a red orange emission. The diode exhibited an operating voltage at ca. 5xa0V and a high current rectification ratio (3×10 3 ).

Silyl substitution as an aid in polymerization reactions: oxidative coupling of silylthiophene, a route to highly conjugated polythiophene

Abstract Raman spectroscopic and photoluminescence studies have shown that the oxidative polymerization of silyl thiophene monomers leads to highly conjugated polythiophene. Soluble high molecular weight polymers have been obtained by use of silylated monomers. The role of silicon is suggested to involve the stabilization of intermediate cationic species.

New chiral π-conjugated polymers based on a (1R,2R)-diiminocyclohexane chiral unit with weak interchain π stacking

New chiral pi-conjugated polymers consisting of alternating conjugated segments and (1R,2R)-diiminocyclohexane units with C2 symmetry were prepared by a palladium-catalyzed coupling reaction, they exhibited very high specific optical rotations ([alpha] up to -3000 degrees) and strong Cotton effects ([theta] 10(6) deg cm2 mol-1).

Synthesis and optical properties of (thienylene)–[1,6-dithienylhexa-1,3,5-trienylene] copolymers

Two [thiophene–1,6-dithienylhexa-1,3,5-triene] copolymers were prepared by a palladium catalysed coupling reaction of a dibromothiophene derivative and a bis(tributylstannyl) derivative of a 1,6-dithienylhexa-1,3,5-triene unit. The electrochromism and the photoluminescence properties of the highly conjugated polymers were studied. In the solid state the polymers have strong photoluminescence bands at 2.0xa0eV for 9 and 1.95xa0eV for 8. Polymer 8 seems particularly promising for use as a red-light emitting diode, and the two polymers 8 and 9 exhibit red–pale blue electrochromism that makes them suitable for fabricating new devices.

REACTIVITY OF SILYL MONOMERS FOR THE OXIDATIVE POLYMERIZATION OF PHENYLENE UNITS

Abstract Oxidative coupling of silyl monomers containing phenylene units was performed electrochemically and chemically using FeCl3 as oxidant. 2,5-Trimethylsilyl-1,4-dihexoxybenzene led to poly (2,5-dihexoxyparaphenylene) with a degree of polymerization higher than the one obtained upon oxdative coupling of non silyl monomers. The coupling reaction was however moderately improved in the case of 3,6-bis-dimethylsilyl(N-n-butylcarbazole). The role of the silyl substituents during the oxidative polymerization is dicussed.