Alkyl polythiophenes

R.E. Gill, G.G. Malliaras, J. Wildeman, and G. Hadziioannou, Tuning of photo- and electroluminescence in alkylated polythiophenes with well-defined regioregularity, Adv. Mater., 6 132-135, 1994. 

Electrochemically prepared alkylated polythiophenes have been investigated by Gamier and coworkers.90 91 When comparing polythiophene and monosubstituted polyalkylthiophenes, these workers found an increase in crystallinity of the substituted thiophenes in comparison to the unsubstituted poly thiophene. The degree of crystallinity was low (5%), but the crystal structure was assigned to a hexagonal cell... 

Polymerization of TOT, TTOTT and TTTOTTT leads to polymers characterized by the presence of one nonaromatic thienyl-5, S-dioxide moiety every two, four and six aromatic thienyl units. Table 4.2 shows that the oxidation potentials of the polymers (1.10, 1.08 and 0.98 V vs SCE, respectively) vary within a much smaller range than that of the corresponding oligomers and that they are comparable to those of polythiophene and alkylated polythiophenes. For example, poly(3,4-dimethyl)- and poly(3,4-diethyl)thiophenes have oxidation peak potentials of 1.00 and 1.10 V vs SCE, respectively [34]. Also, the range of variation of the reduction potentials is narrow (—1.20, —1.34 and —1.35 V vs SCE), but all the values are... 

Wallndfer et al. [963] investigated various anellated and alkylated polythiophenes [(polyisothianaphthene (PITN), polyison-aphthothiophene (PINT), poly(3-octylthiophene) (POT)] prepared by electropolymerization with resonance Raman spectroscopy at various laser wavelengths. " The spectrum of POT is dominated by a strong luminescence (which is related to some of the possible appUcations of this material). The main peak is around 1460 cm ... 

Doping these alkyl thiophenes with fluorescent dyes is reported to enhance the device efficiency and the frequency of emission is found to be dependent on regularity of the side chains on the polymers. Fig. 16. Alkylated polythiophenes were reported by Hadziioannou et al. [105] who found a correlation between emission maxima and the inverse number of alkylated thiophenes between two consecutive head-to-head coupled dyads. 

The conductive properties of alkylated polythiophenes are known to be unstable, particularly at elevated temperatures. The mechanism of thermal undoping has been associated with thermal mobility. Consequently, various workers have considered synthesis of random copolymers (e.g., thiophene and 3-octylthiophene), with well-distributed octyl side groups leaving space around the main chains to accommodate dopants. 

Polythiophenes with substituents other than alkyl groups at the 3 position have been prepared by the polymerization of substituted monomers. Many of these polymers have been substituted alkylthiophenes (8) where example side chains are (R =) —(86—89), —OCH (68), —NHC(0) (CH2) qCH (6 )) —0502(0112)30112 (90). Ohiral side chains have also been employed (91,92). Poly(3-alkoxythiophenes) (9) (93—95) and... 

Polythiophene [78] is a promising material for certain future electronic applications, due to its relatively high stability and processability in the substituted form [79-81]. Upon substitution, with e.g. alkyl side-chains [79, 80], polythiophene exhibit properties such as solvalochromism [82] and thermochromism [83]. Presently, a large variety of substituted polythiophenes with various band gaps exists (for example see Ref. [81 ]). 

M. Pomerantz, H. Yang, and Y. Cheng, Poly(alkyl thiophene-3-carboxylates). Synthesis and characterization of polythiophenes with a carbonyl group directly attached to the ring, Macromolecules, 28 5706-5708, 1995. 

M. Berggren, G. Gustaffson, O. Inganas, M.R. Andersson, O. Wennerstrom, and T. Hjertberg, Thermal control of near-infrared and visible electroluminescence in alkyl-phenyl substituted polythiophenes, Appl. Phys. Lett., 65 1489-1491, 1994. 

Whereas in solution the photoluminescence efficiency (Of) of poly(3-alkylthiophenes) (PATs) is 3(Mf)%, it drastically drops to 1-4% and lower in the solid state due to the increased contribution of nonradiative decay via interchain interactions and ISC caused by the heavy-atom effect of sulfur (97MM4608). Optoelectronic devices of this type of compounds have been studied (98SCI(280)1741 06SM(156)1241). Fibers of poly(3-hex-ylthiophene) for photovoltaic applications have been described (07MI1377). Poly(3-octylthiophene) showed a TTA band at 800 nm (96JPC15309). The photophysical properties of some alkyl and aryl polythiophenes have been studied (03JCP(118)1550). The absorption maximum of poly(3-octylthiophene) is at 438 nm, while the fluorescence was... 

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