Side Chain Influence on Electrochemical and Photovoltaic Properties of Yne-Containing Poly(phenylene vinylene)s

The electrochemical behaviour of four types of (phenylene ethynylene)-alt-(phenylene vinylene) hybrid polymers, 1, 2, 3, and 4 have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2, 3, and 4, the strong insulating nature of longer linear octadecyl or bulky branched 2-ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, Eg, between the electrochemical, E, and the optical, E, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, VOC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3:PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3 solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.

Macromolecular Rapid Communications, 2005, 26, 1389 - 1394

Influence of the Conjugation Pattern on the Photophysical Properties of Alkoxy-Substituted PE/PV Hybrid Polymers

Alkoxy-substituted phenylene-ethynylene (PE)/phenylene-vinylene (PV) hybrid polymers of general constitutional structure (-Ar-CC-Ar-CH=CH-)n (2), (-Ar-CC-Ar-CH=CH-Ar-CC-)n (3), and (-Ar-CC-Ar-CC-Ar-CH=CH-Ar-CH=CH-)n (4) have been synthesized and characterized. Comparisons of their photophysical properties in solution as well as in solid state (photoconductivity, absorption, emission, and electroluminescence) with those of their corresponding alkoxy-substituted poly(phenylene-ethynylene) (1) and poly(phenylene-vinylene) (5) have been carried out. Large octadecyloxy groups were selected as side chains in order to reduce the effect of - stacking interaction on the properties of the polymers in the solid state. This resulted in easy detection of photoconductivity and higher fluorescence quantum yields in solid state. The hybrid conjugation pattern in 4 is more favorable for photoconductivity than that in 2. A red shift of the absorption and emission spectra in solution is observed from 1 over 2b, 3, and 4 to 5. LED devices of ITO/PEDOT/polymer/Ca configuration have been fabricated with all compounds, except 2a. The phenylvinylene side groups in 3 not only give rise to a red shift of the solid-state photoluminescence spectrum and electroluminescence spectrum (relative to 2b) but also bring about a decrease of the turn-on voltage and improve the electroluminescence efficiency for more than 100 times.

Macromolecules, 36 (25), 9303 -9312, 2003.

Stereocontrolled Synthesis and Characterization of cis-Poly(arylenevinylene)s

A highly stereocontrolled synthesis of five kinds of cis-poly[(arylenevinylene)-alt-(2,5-dioctyloxy-1,4-phenylenevinylene)]s has been accomplished by Suzuki-Miyaura-type polycondensation [arylene = p-phenylene (3af), m-phenylene (3bf), 4,4'-biphenylene (3cf), 2,7-fluorenylene (3df), 9,9-dihexyl-2,7-fluorenylene (3ef)]. Reactions of (Z,Z)-bis(2-bromoethenyl)arenes (1a-e) with 2,5-dioctyloxybenzene-1,4-diboronic acid (2fx) in toluene in the presence of Pd(PPh3)4 catalyst, aqueous KOH base, and Bu4NBr as a phase-transfer catalyst at 80 C for 24 h form 3af-ef with number-average molecular weight (Mn) of 5700-9500 in 77-99% yields. The stereoregularity of vinylene linkages in the polymer backbone has been found at least 95%. The starting monomers (1a-e) were prepared in almost geometrically pure forms (99% cis), either by ruthenium-catalyzed hydrosilylation of diethynylarenes followed by bromodesilylation of the resulting bis(2-bromoethenyl)arenes or by addition of bromine to arenediacrylic acids followed by debrominative decarboxylation promoted by Et3N. MALDI-TOF-MS analysis of cis-3af has revealed the presence of two types of polymers having different end groups. Type I polymer bears (Z)-4-(2-bromoethenyl)phenyl and 2,5-dioctyloxyphenyl group at each end, whereas type II polymer has 2,5-dioctyloxyphenyl groups at both ends. Type I polymer is successfully converted to type II polymer by palladium-catalyzed reaction with 2,5-dioctyloxybenzeneboronic acid to obtain cis-poly[(p-phenylenevinylene)-alt-(2,5-dioctyloxy-1,4-phenylenevinylene)] in a single form.

Macromolecules, 39 (6), 2039 -2048, 2006. 10.1021/ma052183l

A Novel Bipolar Electroluminescent Poly(arylene ethynylene) Consisting of Carbazole and Diethynylthiophene Units

A novel bipolar conjugated copolymer poly[(2, 5-diethynylthienylene)-alt-co-(9-hexyl-3,6-carbazole)] (PCT) bearing electron-affinitive moiety of 2,5-diethynylthiophene and hole-transport moiety of carbazole was synthesized via a Pd-catalyzed coupling reaction. The polymer possesses a weight average molecular weight of 23 000 with a polydispersity index of 2.5. PCT exhibits good thermal stability with a glass-transition temperature of 103°C and an onset decomposition temperature of 338°C. The HOMO and LUMO energy levels of PCT were determined to be -5.36 and -2.46 eV, respectively, using cyclic voltammetry. Single-layer and multilayer light-emitting diodes emit yellow light (peak at 580 nm). Double-layer electroluminescent device with the structure of ITO/copper phthalocyanine/PCT/Ca/Ag has an external quantum efficiency of 0.01%, higher than that of three-layer device with the structure of ITO/copper phthalocyanine/PCT/Alq3/Al, indicating that the electron injection is the limiting factor for the performance of PCT in polymer light-emitting diodes.

Macromolecular Chemistry and Physics, 201, 202, Issue 11 , Pages 2341 - 2345

Synthesis of poly(fluorenevinylene-co-phenylenevinylene) by suzuki coupling

uzuki coupling modified by adding Ag2O instead of the Na2CO3 used in the original reaction protocol, was used as a synthetic tool for the synthesis of a copolymer in which 9,9-dialkylfluorene moieties were coupled to unsubstituted poly(p-phenylenevinylene) (PPV) units. The possibility of performing the polymerisations at moderate temperatures appears to be an advantage related to the use of Ag2O. The copolymer shows a [bar M ]w of 21 000 and [bar M ]w/[bar M ]n = 2.1 and is suitable for the construction of electroluminescent devices. Monolayer organic light-emitting diodes (OLEDs) have been built which emit greenish light.

Macromol. Chem. Phys. 2002, 203,1926-1930

Conjugated polymers for nonlinear optics. 1. Synthesis and properties of poly(aryleneethynylenevinylene)s

Rigid-rod conjugated poly(aryleneethynylenevinylene)s were prepared from diethynyl aromatic compounds containing alkoxy groups and trans,trans-1,4-bis(β-bromoviny ])benzene by palladium-catalyzed coupling reaction. Polymerizations were carried out in THF in the presence of Pd catalyst, CuI and diethyl amine and gave a series of poly(aryleneethynylenevinylene)s with weight average molecular weight up to 56,000. The characterization of polymers by IR, NMR, UV-Vis, thermogravimetry, DSC, optical microscopy and X-ray are reported. The polymers exhibited intense fluorescence in solution (THF) and absorption band shifted to longer wavelength in films of the polymers. Polymers with long alkoxy side chains showed good solubility in THF, CH2Cl2 and CHCl3.

Reactive and Functional Polymers, 1996, 30, 341-352

Stereocontrolled Synthesis and Optical Properties of All-cis Poly(phenylene vinylenes) (PPVs): A Method for Direct Patterning of PPVs

Geometrically pure, all-cis poly(phenylene vinylenes) (PPVs) are synthesized by Suzuki-Miyaura-type polycondensation of 2,5-dioctyloxy-1,4-benzenediboronic acid with (Z,Z)-bis(2-bromoethenyl)benzenes, which are prepared by ruthenium-catalyzed (Z)-selective double hydrosilylation of diethynylbenzenes, followed by bromodesilylation of the resulting (Z,Z)-bis(2-silylethenyl)benzenes with N-bromosuccinimide. The all-cis PPVs thus obtained undergo one-way photoisomerization to the corresponding trans-PPVs both in solution and in the solid. This phenomenon is applied to direct microscale patterning of PPVs onto a quartz substrate.

J. Am. Chem. Soc., 127 (12), 4350 -4353, 2005. 10.1021/ja042853n