Polycondensation via direct arylation of tetrafluorobenzene or octafluorobiphenyl was investigated for the synthesis of π-conjugated polymers consisting of fluorinated arylene units. The optimization of reaction conditions revealed that a combination of Pd(OAc)2 and P t Bu2Me-HBF4 is the most efficient catalytic system for the polycondensation reactions. The polycondensation reactions produced four types of π-conjugated polymers having low highest occupied molecular orbital (HOMO) levels due to the strong electron-withdrawing nature of the fluorine substituents. Owing to the low HOMO levels, the synthesized polymers served as an efficient hole-blocking layer (HBL) in OLEDs.

Light-induced electron spin resonance (LESR) measurements have been performed on the composites of regioregular polythiophene derivatives and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in order to study the recombination kinetics of photogenerated charge carriers. We adopt two regioregular polymers with different side chains; head-to-tail poly(3-hexylthiophene) (RR-P3HT) and head-to-head poly(3-dodecynylthiophene-2,5-diyl) [HH-P3(C≡CDec)Th]. In both systems, two LESR signals due to positive polarons on the polymer (g∼2.002) and fullerene radical anions (g∼2.000) have been observed. Quadrimolecular recombination (QR) kinetics, previously reported for RR-P3HT/C60 composites, where two positive polarons and two radical anions recombine simultaneously, has been confirmed in both systems by the observation of Iex0.25 dependence of the LESR intensity on the excitation light intensity (Iex) and the decay curve of the LESR intensity. This process implies the formation of doubly-charged states such as bipolarons or polaron pairs on the polymer to attract two radical anions. Temperature dependence of the QR rate constant, γ, in both systems has exhibited a crossover of the transport mechanism from low temperature tunneling to high temperature hopping process, as in the case of RR-P3HT/C60 composites. In the RR-P3HT/PCBM composites, γ has exhibited marked dependencies on the PCBM concentration or annealing, which may be related to the change of the crystallinity of the phase-separated polymer and fullerene domains as well as their interface structures, affecting the carrier mobilities or the trap states at the interface. Associated change of the molecular orientation of RR-P3HT crystalline domains with the lamellar structure has been further confirmed from the anisotropic LESR signals of the cast films on the substrates, exhibiting a qualitative agreement with the reported x-ray or optical analyses. In the HH-P3(C≡CDec)Th/PCBM composite, γ has been smaller than those in the RR-P3HT/PCBM composites, reflecting the difference of local structures due to the different molecular structure. Furthermore, the hyperfine-determined LESR linewidth of the positive polaron has exhibited a smaller value than those in the RR-P3HT composite, implying the larger extension of the polaron wave function on the polymer chain, which is consistent with the highly coplanar structure of this polymer.

Self-assembly of polythiophenes with C≡CR (R = alkyl, phenyl, etc.) side chains has been investigated. Seven new polymers consisting of head-to-head and tail-to-tail 2,2¤-bithiophenes with C≡CR side chains were synthesized. The new polymers include alternating copolymers between bithiophenes with C≡Calkyl side chains and thiophene and those between bithiophenes with C≡Calkyl side chains and 2,2¤-bithiophene. The polythiophene main chain is considered to be coplanar because of the absence of steric repulsion between the main chain and the C≡CR side chain. Single-crystal X-ray crystallography and DFT calculations indicated that the head-to-head-and tail-to-tail-2,2¤-bithiophenes with C≡CR side chains were coplanar. The polythiophenes with C≡CR side chains showed a strong tendency to selfassemble, and assumed edge-on alignment and side-on alignment on the surface of substrates. Self-assembly caused a decrease in the ³³* transition energy of the polymers by 0.30.4 eV. A copolymer of thiophene and dialkoxy-pphenylene showed analogous self-assembly. The polythiophenes with C≡CR side chains showed piezochromism, with a decrease in the ³³* transition energy by about 0.2 eV at 10 GPa. Head-to-head-P3(C≡CDec)Th with a C≡Cdecyl side chain gave a larger optical third-order nonlinear susceptibility » (3) than regio-regular poly(3-hexylthiophene)s.Electronic and optical functionalities of ³-conjugated polymers and molecules with large ³-electron systems are attracting interest.13 It is recognized that the electronic and optical functionalities of ³-conjugated polymers and molecules are affected by molecular assembly of the polymer and molecule. The synthesis (particularly organometallic synthesis 4,5a ) of regio-regular head-to-tail poly(3-alkylthiophene-2,5-diyl), HT-P3RTh (Chart 1), by McCullough and other research groups 4,5 initiated active studies of the molecular assembly of ³-conjugated polymers and its effects on the functionalities of the polymers.17 HT-P3RTh shows a higher mobility 6 of positive carrier, a larger third-order nonlinear optical susceptibility, » (3) , 7f and a larger Faraday rotation 7g than those of regiorandom poly(3-alkylthiophene-2,5-diyl), rand-P3RTh, and these results have been associated with molecular assembly of HT-P3RTh in the solid phase. Recently it has been reported that various ³-conjugated polythiophenes, such as those with Th(R)(³)Th(R) repeating units, also assume similar ³-stacked molecular assemblies (Chart 2). 811 McCulloch and coworkers synthesized such polythiophenes with fused thiophene units as the central (³) unit, 9 and the resulting polymer showed a large hole mobility of about 1 cm 2 V ¹1 s ¹1 , which is comparable to that of amorphous silicon. Although HT-P3RTh provides basic and important information about the molecular assembly of ³-conjugated polymers, some factors remain unclear.The UVvis absorption peak of HT-P3RTh shifts to a longer wavelength when ³-stacked molecular assemblies are formed in the solid. The shift is thought to originate from the following two fac...

A new π‐conjugated polymer consisting of isothianaphthene and bis(dodecyloxy)‐p‐phenylene units has been prepared by Pd‐catalyzed organometallic polycondensation. X‐ray diffraction analysis indicates that the polymer assumes an interdigitation‐type self‐assembled packing structure in the solid state and aligns on the surface of a platinum plate, with the dodecyloxy side chain oriented toward the surface of the platinum plate. The polymer undergoes facile electrochemical doping as well as chemical doping with iodine and NOBF4. BF 4−‐doped polymer is also considered to assume an interdigitation‐type packing structure in the solid state. Electrical conductivities of the chemically doped polymer are also reported.

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