ELECTROACTIVE AND PHOTOACTIVE ROD-COIL COPOLYMERS - DESIGN, SYNTHESIS, AND SUPRAMOLECULAR REGULATION OF PHOTOPHYSICAL PROPERTIES

Two series of electroactive and photoactive rod-coil copolymers have b een designed, synthesized, and investigated to explore a new structura l motif for organizing molecular and macromolecular materials at the s upramolecular structure level for enhanced functional and solid state photophysical properties. The rod-coil copolymers consisting of electr oactive and photoactive rodlike conjugated segments and inactive coill ike segments, exemplified by benzobisthiazole-co-decamethylenebenzobis thiazole) and enzobisthiazole-co-decamethylenebenzobisthiazole), have semiflexible (semirigid) chains whose flexibility (rigidity), folding, intermolecular interactions, and packing, and hence the solid state s upramolecular structure and photophysical properties of the materials, are regulated by copolymer composition. The molecular structure, chai n sequence lengths, and copolymer composition were determined by NMR ( H-1, C-13), FTIR, and W-vis spectra. The sequence length distribution of the conjugated rodlike segments predicted from the copolymerization statistics was in good agreement with the H-1 NMR results. It is show n that nanocomposites are formed at rod molar fractions of less than 0 .5 which also marks a dramatic change in the photophysical properties of the copolymers. The photoluminescence quantum yield varied with cop olymer composition, reaching over 6- and 7-fold enhancements compared to the ''bulk'' pure conjugated polymers. The photoluminescence peak o f the rod-coil copolymers varied from 486 to 640 nm which represents e mission colors that span the visible (blue to red) region.