Synthesis, Characterization and Properties of Conjugated Poly(1-Alkyl-2,5-Pyrrylene Vinylene)
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respectively [7-9]. Conducting polymer processibility has been obtained recently by the development of soluble precursor polymers yielding high quality materials which can be easily formed into films for poly(acetylene) [10], poly(p-phenylene vinylene) (PPV) [11,12] and poly(2,5-thienylene vinylene) [13]. The common backbone of these polymers is made up of aromatic rings bridged by vinylene linkages which not only reduce steric hindrance between backbone rings and groups attached to them, but also have a beneficial effect on electronic properties as evidenced by experimental and theoretical data on both poly(p-phenylene vinylenes) [7] and poly(thienylene vinylenes) [14]. 665 Mat. Res. Soc. Symp. Proc. Vol. 488 0 1998 Materials Research Society
Recently, theoretical calculations using the Valence-Effective Hamiltionian technique were performed on poly(pyrrylene vinylene), poly(3-methylpyrrylene vinylene) and poly(3-methoxy pyrrylene vinylene) [15]. These calculations predict that the electronic properties of poly(pyrrylene vinylene) remain almost unaffected upon methyl substitution, while a noticeable lowering by -A0.4 eV is obtained for the ionization potential and energy gap upon methoxy substitution. Recently, poly(pyrrylene vinylene) synthesized by the thermal elimination of methanol from the precursor polymer poly(1-methoxy-1,2-ethylenediyl-co-2,5-pyrrolylene) exhibited an electrical conductivity on the order of 6.9x107 S/cm [16].
/R
R=-lCH 3 (1)
R-(CH
-(CH 2 )5CH 3 (2) 2)1 1CH 3 (3)
In this paper, we report results for the conductivity and properties of poly(Nalkylpyrrylene vinylenes) (alkyl = methyl(l), hexyl(2), dodecyl(3)), synthesized by chemical means, in comparison with literature data for related polymers. EXPERIMENTAL H- and 13 CNMR spectra were obtained on a Bruker MSL 300 spectrometer. UV-VIS-NIR spectra were obtained on a Varian Cary 5E UV-VIS-NIR spectrometer. FT-IR spectra were recorded on a Digilab FTS-40 FT-IR spectrometer using powdered samples mixed with KBr. Elemental analyses were determined by Quantitative Technologies Inc. TGA and DSC were performed on a DuPont 951 and 910 thermal analysis system, respectively. Conductivity measurements were performed on a Keithley four-in-line probe apparatus. CV studies were carried out on an EG&G PAR Model 273 potentiostat/Galvanostat in a dry box under Ar. 1
Synthesis of Poly(1-methyl-2,5-pyrrylene vinylene)(1) To a solution of 4 equivalents(0.748 g) t-BuOK+ in 20 mL of THF under reflux was added a solution of 2 g (6.12 mmol) of 1-methyl-2,5-bis(phenylthiomethy)pyrrole in 2 mL of THF under nitrogen. Stirring was maintained for 24hr in a round bottomed flask until the light yellow solution turned purple in color. The polymer was separated and purified by repeated washing with hot water, methanol and then extracted (Soxhlet) with acetone for 24 hr. Drying under vacuum at room temperature gave the deep purple blue polymer 1. The overall yield was 75% (0.449 g). Anal. Calcd for C7H 7N: C, 79.95; H, 6.71; N, 13.32. Found: C, 74.75; H, 6.51; N, 10.22
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