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Abstract Soluble conjugated polymers based on 3,5‐didecanyldithieno3,2‐ b :2′,3′‐ d thiophene—single‐bond ( 1 ), double‐bond ( 2 ), and triple‐bond linked ( 3 )—were synthesized by palladium(0)‐catalyzed Stille coupling reaction and oxidation polymerization. The thermal, absorption, emission, and electrochemical properties of these polymers were examined; the effect of the link pattern was studied. All polymers exhibit decomposition temperatures over 295 °C and glass‐transition temperatures in the range of 137–202 °C. The absorption spectra of 1 , 2 , and 3 in thin films exhibit absorption maxima at 381, 584, and 444 nm, respectively. Polymer 1 exhibits intense green emission located at 510 nm in film, whereas polymers 2 and 3 are nonemissive both in solution and in film due to H‐aggregate. Cyclic voltammograms of polymers 1 , 2 , and 3 display irreversible oxidation waves with onset oxidation potentials at 1.73, 0.78, and 1.03 V versus Ag + /Ag, respectively. Theory calculation on model compounds suggests that the dihedral angle decreases in the order of 1 > 3 > 2 . On reducing the dihedral angle, the polymer exhibits a longer absorption maximum, a smaller bandgap, a less oxidizing potential and fluorescence quench, due to more coplanar and more π‐electron delocalized backbone structure. Polymer solar cells were fabricated based on the blend of polymer 2 and methanofullerene 6,6‐phenyl C61‐butyric acid methyl ester (PCBM). The power conversion efficiency of 0.45% was achieved under AM 1.5, 100 mW cm −2 using polymer 2 :PCBM (1:2, w / w ) as active layer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2843–2852, 2009
Zhang et al. (2009) studied this question.