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Side-chain Length (side-chain + length)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk Heterojunctions

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Abay Gadisa
Abstract The morphological, bipolar charge-carrier transport, and photovoltaic characteristics of poly(3-alkylthiophene) (P3AT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side-chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3-butylthiophene) (P3BT, m,=,4), poly(3-pentylthiophene) (P3PT, m,=,5), and poly(3-hexylthiophene) (P3HT, m,=,6). Solar cells with these blends deliver similar order of photo-current yield (exceeding 10,mA cm,2) irrespective of side-chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole-only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field-effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells. [source]

Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) Nanofibers

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Wibren D. Oosterbaan
Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source]

Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk Heterojunctions

Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains via metal-free anionic polymerization "grafting from" technique

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010
Junpeng Zhao
Abstract Thermoresponsive brush copolymers with poly(propylene oxide- ran -ethylene oxide) side chains were synthesized via a "grafting from" technique. Poly(p -hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal-free anionic ring-opening polymerization, with the phosphazene base (t -BuP4) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side-chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step-by-step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush-like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320,2328, 2010 [source]

Synthesis and characterization of aromatic polyamides containing alkylphthalimido pendent groups

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002
E. Ferrero
Abstract A series of polyisophthalamides containing pendent phthalimido groups and flexible side spacers were prepared from four novel diacids and three commercial aromatic diamines. These polyamides were prepared in high yields and with high molecular weights by direct polycondensation with triphenyl phosphite and pyridine as condensing agents. The weight-average and number-average molecular weights, measured by gel permeation chromatography, were 70,000,137,000 and 47,000,86,000 g/mol, respectively. The novel polyamides were amorphous and readily soluble and showed glass-transition temperatures of 150,240 °C, as measured by differential scanning calorimetry. Thermogravimetric analysis showed that the 10% weight-loss temperatures in nitrogen were 355,430 °C, a significant improvement in thermal stability having been observed with the increase in the side-chain length. A theoretical quantum mechanical study was successfully carried out to explain these results. Flexible and tough films, cast from polymer solutions, showed tensile strengths of 50,125 MPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3711,3724, 2002 [source]

Effect of side-chain length of succinic anhydride on coefficient of thermal expansion behavior of epoxy resins

POLYMER INTERNATIONAL, Issue 11 2006
Fan-Long Jin
Abstract The effect of an alkenyl side-chain of succinic anhydride (SA) on the thermal behavior and the coefficient of thermal expansion (CTE) of diglycidylether of bisphenol A (DGEBA) epoxy resins was studied. The number of carbons in the side-chain of SA was varied from 6 to 14 and N,N -Dimethylbenzylamine was used as an accelerator. As a result, the reactivity of SA with epoxide groups was decreased on increasing the length of the alkenyl side-chain of SA. The thermal stabilities of cured DGEBA/SA samples were approximately constant with varying alkenyl side-chain of SA. Also, the CTE of the systems was increased as the length of the alkenyl side-chain of SA increased. This could be attributed to the increased motion of the chain segments in the epoxy network structure induced by the longer alkenyl side-chain of SA. The effect of amount anhydride, thermoplastics, and fillers on the CTE of the epoxy resins was also discussed. Copyright © 2006 Society of Chemical Industry [source]

Relaxation of arterial smooth muscle: A new function of a water-soluble degradation product of coenzyme Q (ubiquinone)

BIOFACTORS, Issue 1-4 2003
R. Bindu
Abstract Treatment of coenzyme Q with ozone yielded a degradation product having unmodified ring that retained its spectral characteristics and a truncated side-chain that made it water-soluble. This derivative, but not the intact lipid-quinone, showed relaxation of phenylephrine-contracted rat arterial rings. This effect offers an explanation for the known hypotensive action of exogenous coenzyme Q regardless of its side-chain length. [source]

How comb-type poly(maleic acid alkylamide- co -,-olefin) assemble in waxy oils and improve flowing ability

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Jun Xu
Abstract Wax deposition in pipelines restricts flow and even leads to plugging during oil transportation. This paper aims to improve the flowing ability of cold waxy oils using comb-type copolymers to interact with main components of waxy oil: long-chain n -paraffins and asphaltenes. A series of comb-type poly(maleic acid alkylamide- co -,-olefin) (MAC) with different side-chain lengths were synthesized by copolymerization of ,-olefin and maleic anhydride followed by amidation with alkylamine. Their effects on the rheological property (yield stress) and crystallization behaviors of both model waxy oils and crude oils were observed by rheology, differential scanning calorimetry (DSC), and optical microscopy. MACs reduced the yield stress of oils and the crystal size of long-chain n -paraffins, and improved the flowing ability of oils at 0 °C significantly. The MACs either self-assemble to nucleate the crystallization of long-chain n -paraffins or co-crystallize with them by the nonpolar side chains and inhibit the growth of paraffin crystals by the layer of the polar parts, while the carboxyl and amide groups interact with polar aromatic asphaltenes to prevent their aggregation upon cooling. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]