π-conjugation and conformation in a semiconducting polymer: small angle x-ray scattering study

Choudhury, Paramita Kar; Bagchi, Debjani; Menon, Reghu

doi:10.1088/0953-8984/21/19/195801

Cited by 12 publications

(15 citation statements)

References 21 publications

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“…In this work, conformation of multiwall carbon nanotube (MWNT) suspensions in aqueous solution of conducting polymer polyethylene dioxythiophene -polystyrene sulfonic acid (PEDOT-PSS) is studied using small angle X-ray scattering (SAXS) technique. Small angle X-ray scattering (SAXS) studies in polymeric systems have already shown that the local nanoscale morphology at various length scales can be probed to show the correlation among conformation and assembly of chains [9][10][11]. Our results show rigid-rod characteristics of nanotubes held in a meshwork in the polymer solution; the polymer globules close to the CNTs are extended and tend to aggregate onto the nanotube walls partially "coating" them.…”

Section: Introductionmentioning

confidence: 69%

Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites

Choudhury

Ramaprabhu

Ramesh

et al. 2011

J. Phys.: Condens. Matter

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The strikingly different charge transport behaviours in nanocomposites of multiwall carbon nanotubes (MWNTs) and conducting polymer polyethylenedioxythiophene-polystyrene-sulfonic-acid (PEDOT-PSS) at low temperatures are explained by probing their conformational properties using small-angle x-ray scattering (SAXS). The SAXS studies indicate the assembly of elongated PEDOT-PSS globules on the walls of nanotubes, coating them partially, thereby limiting the interaction between the nanotubes in the polymer matrix. This results in a charge transport governed mainly by small polarons in the conducting polymer despite the presence of metallic MWNTs. At T > 4 K, hopping of the charge carriers following one-dimensional variable range hopping is evident which also gives rise to a positive magnetoresistance (MR) with an enhanced localization length (∼5 nm) due to the presence of MWNTs. However, at T < 4 K, the observation of an unconventional positive temperature coefficient of resistivity is attributed to small polaron tunnelling. The exceptionally large negative MR observed in this temperature regime is conjectured to be due to the presence of quasi-1D MWNTs that can aid in lowering the tunnelling barrier across the nanotube-polymer boundary resulting in large delocalization.

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Section: Introductionmentioning

confidence: 69%

Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites

Choudhury

Ramaprabhu

Ramesh

et al. 2011

J. Phys.: Condens. Matter

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“…1,6 The SAXS data for MEH-PPV in dilute solutions of xylene (aromatic, non-polar) and THF (aliphatic, polar), have shown that the tendency to form aggregates increases in former solvent than in case of the latter, since non-aromatic and polar solvents like THF prefer solvating the side groups of MEH-PPV, while aromatic and non-polar solvents like xylene solvate the polymer backbone that give rise to different conformations. 28 Moreover, the small-angle neutron scattering (SANS) study in different solutions of MEH-PPV has shown the aggregation of chain segments to form nanoscale disc-like domains. 8 Many interesting solvent dependent optical as well as electrical properties have been observed in conjugated polymers, 6 which have been understood in detail with the help of our SAXS measurements in PEDOT-PSS solutions, and also compared to the conductivity measurements as described below.…”

Section: Resultsmentioning

confidence: 99%

Modified conformation and physical properties in conducting polymers due to varying conjugation and solvent interactions

et al. 2011

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Small angle X-ray scattering (SAXS) studies in poly[2-methoxy-5-(2 ' -ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with varying conjugation, and polyethylene dioxythiophene complexed with polystyrene sulfonate (PEDOT-PSS) in different solvents have shown the important role of -electron conjugation and solvent-chain interactions in controlling the chain conformation and assembly. In MEH-PPV, by increasing the extent of conjugation from 30 to 100 %, the persistence length (l p ) increases from 20 to 66 Å. Moreover, a pronounced second peak in the pair distribution function has been observed in fully conjugated chain, at larger length scales. This feature indicates that the chain segments tend to self-assemble as the conjugation along the chain increases. In case of PEDOT-PSS, the chains undergo solvent induced expansion and enhanced chain organization. The clusters formed by chains are better correlated in dimethyl sulfoxide (DMSO) solution than water, as observed in the scattered intensity profiles. The values of radius of gyration and the exponent (water: 2.6, DMSO: 2.31) of * Electronic address: s_paramita@physics.iisc.ernet.in Fax: +91-80-2360 2602 Tel: +91-80-2293 2859power-law decay, obtained from the unified scattering function (Beaucage) analysis, give evidence for chain expansion from compact (in water) to extended coil in DMSO solutions, which is consistent with the Kratky plot analysis. The mechanism of this transition and the increase in dc conductivity of PEDOT-PSS in DMSO solution are discussed. The onset frequency for the increase in ac conduction as well as its temperature dependence probes the extent of connectivity in PEDOT-PSS system. The enhanced charge transport in PEDOT-PSS in DMSO is attributed to the extended chain conformation as observed in SAXS results.

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“…To clarify this hypothesis, the persistence length of PMm in dilute solutions was evaluated based on the Kratky plot. 60−64 For the semiflexible chains of the rigid segments in a dilute solution, the SAXS intensity profile, I(q), can be divided into three characteristic regions: 60 in the low q region, I(q) presents Gaussian curve character that is related to the dimension of the chain (radius of gyration can be estimated from the Guinier plot 60,61 ). On the other hand, in the high q region, I(q) is approximately proportional to q −1 and related to the interference within the localized linear sections of the chain (i.e., segments).…”

Section: Resultsmentioning

confidence: 99%

“…The higher critical concentrations of the PM m series are similar to those observed for hydroxypropyl cellulose (critical conc., 40–50 wt %) , and can be reasonably explained by the semiflexible character of the PM m backbones and much shorter persistence length (smaller axial ratio) than the rigid-rod α-helix polypeptides. To clarify this hypothesis, the persistence length of PM m in dilute solutions was evaluated based on the Kratky plot. − …”

Section: Results and Discussionmentioning

confidence: 99%

Spontaneous Chain Orientation of Aromatic Polyimides Evolved during Thermal Imidization from Shear-Oriented Glassy Liquid Crystalline Precursors

Tanaka¹,

Ando²,

Ishige³

2019

Macromolecules

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A series of poly(amic ester)s, PMm, based on pyromellitic acid derivatives with long n-alkylene side chains [−(CH2) m H], were synthesized to prepare low-temperature lyotropic liquid crystalline (LC) precursors for a fully aromatic rigid-rod polyimide (PI). Highly oriented LC precursor films (m > 8) were prepared by shearing at ambient temperature. Although the polydispersity of PMm was not controlled, the PMm solution exhibited a lyotropic smectic phase in which the main chains were parallel to the layer normal. After prebaking the lyotropic solution (70 °C), uniaxial orientation order parameter of the main chain was maintained at ∼0.5 during heating from 70 to 250 °C before imidization. Synchrotron radiation wide-angle X-ray diffraction and polarized Fourier transform infrared spectroscopy revealed that the orientation order spontaneously increased (0.5–0.9) during imidization (>270 °C), even for free-standing films. This unique phenomenon distinctly differs from the behavior of conventional amorphous precursors. In the present case, the rigid PI segments with longer persistence length spontaneously grow along the n-director of the LC matrix of the precursor to form highly oriented homogeneous PI films.

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π-conjugation and conformation in a semiconducting polymer: small angle x-ray scattering study

Cited by 12 publications

References 21 publications

Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites

Correlated conformation and charge transport in multiwall carbon nanotube-conducting polymer nanocomposites

Modified conformation and physical properties in conducting polymers due to varying conjugation and solvent interactions

Spontaneous Chain Orientation of Aromatic Polyimides Evolved during Thermal Imidization from Shear-Oriented Glassy Liquid Crystalline Precursors

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