Poly(2s-Butynes-1,4s-Diyl)S as Precursors to Novel Substituted Polyacetylenes
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NOVEL SUBSTITUTED POLYACETYLENES STEVEN K. POLLACK, ASHEBIR FISEHA Department of Chemistry and the Polymer Science and Engineering Program, Howard University, Washington, DC 20059, [email protected] ABSTRACT Thermally-induced polymerization of 1,4-diphenyl-1,2,3-butatriene affords poly(1,4-diphenyl2-butyne-1,4-diyl) as a soluble high molecular weight material. Structure is characterized by 13C and vibrational spectroscopy. When treated with base, this material rearranges to a soluble red poly(acetylene) with a unique substitution pattern. INTRODUCTION The polymerization of simple butatrienes has long frustrated spectroscopists in their attempts to isolate and study the free monomeric molecule[ 1-6]. Carothers observed this phenomenon and obtained a patent on the potential use of butatriene as a reactive monomer, not understanding the nature of the polymer formed[7]. Recently, we have been studying the structure and potential applications of butatrienes as monomers in addition polymerization[8-10]. In reviewing of the literature concerning 1,2,3-butatriene, there were reports that in some situations, the normally white solid formed from its polymerization would convert to a yellow, blue or even black material[l]. This intrigued us as it implied the formation of a conjugated system. Based on our previous and ongoing studies, 1,2,3-butatrienes polymerize in the presence or absence of freeradical initiators via a 1,4 addition to produce a poly(2-butyne-1,4-diyl) structure. R R R R R
R
l
1R
For the case R=H, this creates a polymer which is formally (CA-),. This is isomeric with the conjugated polymer poly(acetylene). We reasoned that the formation of colored materials could be due to rearrangement of the unconjugated, acetylene containing system to the thermodynamically more stable conjugated polyene. If one could design the butatriene monomer appropriately, such a rearrangement of the resulting substituted poly(2-butyne-1,4-diyl) could lead to conjugated polymers with unique electronic and physical properties. In this paper, we report on a first example of such a rearrangement.
725 Mat. Res. Soc. Symp. Proc. Vol. 488 © 1998 Materials Research Society
EXPERIMENT Unless otherwise noted reagents were used as received. All solvents were purified using standard procedures. Melting points were obtained using a Fisher-Johns melting point apparatus and are reported uncorrected. NMR data was obtained on a General Electric QE-300 FT-NMR system equipped with a TecmagTM data system and were referenced either to an internal TMS standard or to solvent peaks. ESR spectra were obtained both in the solid state and in solution in chloroform using a Bruker ER 2000-SRC spectrometer operating at 9.74 GHz at an RF power of 10 mW, modulation frequency of 100 Khz and a field modulation intensity 2.8 G. UV spectra were obtained using a Perkin Lambda 2 spectrometer. Fluorescence spectra were obtained using a Spex Fluorimax-2 spectrofluorimeter. Synthesis 1,4-Diphenyl-2-butyn-l,4-ol[1 1, 12] Under a dry nitrogen atmosphere, 1.57g (16mmo
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