Planar Poly(p-phenylene) Derivatives. Ladder Formation for Maximization of Extended Conjugation
SOUTH CAROLINA UNIV COLUMBIA
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Described is the synthesis of ladder polymers with a polyp-phenylene PPP backbone. The main PPP backbone was synthesized via palladium-catalyzed coupling of an arylbisboronic ester with an aryldibromide. Imine bridges, formed by exposure of the polymer to trifluoroacetic acid or HC1, are used to force the consecutive units into planarity. The bridging units are sp2 hybridized thus allowing for greater pi-electron flow between the consecutive phenyl units by lowering the band gap between the hydroquinoidal and the quinoidal forms of the phenylene backbone. Upon planarization, bathochromic shifts of 210-240 nm occur for the n-dodecyl substituted polymer. The optical spectra of the planar systems are compared to that of the parent nonplanarized polymers, oligop-phenylenes, PPP, and other near-planar PPP derivatives. When the bridges are n-dodecyl substituted, the fully planar structures can be made into flexible free standing films.
- Organic Chemistry
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy