Jean-Yves Bergeron

Synthesis and characterization of novel aromatic polyesters derived from thiophenes

Abstract Novel aromatic polyesters have been synthesized by solution condensation reactions between hydroquinone and 3,4-disubstituted 2,5-thiophenedicarbonyl chlorides. The introduction of phenyl substituents in these poly( p -phenylene 3,4-disubstituted 2,5-thiophendicarboxylate)s did not enhance the fusibility nor the solubility of the resulting material when compared to the unsubstituted parent polyester. The presence of ethyl groups led to the formation of an insoluble semicrystalline aromatic polyester with a melting transition at 304°C. Poly( p -phenylene 3-methyl-4-propyl-2,5-thiophenedicarboxylate) was found to be soluble in chloroform and exhibited a melting transition at 242°C. All these polyesters are stable up to 350–400°C. However, in contrast to the unsubstituted parent polymer, all these aromatic polyesters did not show any evidence of liquid crystallinity in the melt. On the basis of theoretical calculations, this behaviour can be related to the ca. 143° core angle of 3,4-disubstituted thiophenes.

Solution and solid-state electrochemistry of soluble substituted polythiophenes

Abstract Poly(3-octylthiophene) (PT8), poly(3-tetradecylthiophene) (PT14) and poly[(3-octyloxy)-4-methylthiophene] (POMT) have been analyzed by cyclic voltammetry in solution and as precast films. All polymers show in both conditions at least two distinct oxidation processes separated by ca. 200 mV. Moreover, although these polymers have a non-planar conformation when in solution and a coplanar structure when in the solid state, these conformational differences are not detected in their respective cyclic voltammograms. It is then assumed that the dissolved polymers may adopt a coplanar conformation in the vicinity of the electrode.

Langmuir-Blodgett processing of conjugated polymers

Abstract Stable monolayers of poly(2-decyloxyaniline) and poly(1,1,1,2,2,3,3,4,4,5,5,6,6,-tridecafluorononylthiophene) have been obtained at an air-water interface. In both cases the presence of alkoxy or fluorinated substituents has improved the stability of these polymeric monolayers compared with their respective alkyl analogues. Successful transfer of multilayers of poly(2-decyloxyaniline) has been achieved, while only a monolayer of the fluorinated polythiophene could be obtained on silanized glass slides. A monolayer of the latter polymer has revealed similar thermochromic properties to those observed with a spin-coated film, indicating that the interchain interactions are not the dominant factor in these thermally induced optical effects.