Fractal structure of fullerite

Золотухин, И. В.; Yanchenko, L. I.; Belonogov, E. K.

doi:10.1134/1.567707

Cited by 9 publications

(8 citation statements)

References 2 publications

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“…The transmission electron microscopy observations by Kropka et al indicate aggregates on the order of 10-20 nm for a C 60 concentration, Ϸ 0.01, and similar clusters are even obtained by casting C 60 solutions onto a substrate without any polymer. 37 Large scale particle clustering also provides an obvious source of the structural disorder responsible for the suppression of BCP ordering. Currently, we are attempting to image the fullerene clusters in our BCP samples.…”

Section: Discussionmentioning

confidence: 99%

Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive

Zhao

Hashimoto

Douglas

2009

The Journal of Chemical Physics

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Thermal fluctuations in block copolymer (BCP) materials characteristically drive the ordering phase transition order from second to first order by the well known Brazovskii mechanism and there have been many observations of jumps in x-ray and neutron scattering intensity data at the order-disorder transition (ODT) that signal this phenomenon. However, the existence of quenched disorder can either destroy the ODT or restore the second-order nature of this type of phase transition. The present work considers how the dispersion of C(60) ("buckyballs"), which is prone to clustering in polymeric media, into poly(styrene)-block-poly(isoprene) to see how this nanoparticle additive alters the qualitative character of the BCP ordering. Small angle x-ray scattering indicates that a small amount (approximately = 1 mass %) of C(60) causes the BCP to remain disordered over a wide temperature range so that a phase transition no longer exists. This phenomenon offers both technological problems and opportunities.

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Section: Discussionmentioning

confidence: 99%

Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive

Zhao

Hashimoto

Douglas

2009

The Journal of Chemical Physics

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“…The existence of hole pinning and hole size polydispersity imply that the filler particles are firmly fixed to the solid substrate and thus a strong interaction between the nanoparticle and the substrate. It is also likely that the interparticle interaction must be reasonably attractive in order to form fractal aggregate structures at the solid substrate 22 [Fullurenes can form fractal (dynamic) clusters in solution even under equilibrium conditions in nonpolar solvents such as benzene. 25 ] Neutron reflection measurements confirmed that the fullerene particles segregate to the solid substrate in the PS films.…”

Section: Discussionmentioning

confidence: 99%

Suppression of Dewetting in Nanoparticle-Filled Polymer Films

et al. 2000

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The perturbing influence of nanosize filler particles on the dewetting of spun-cast polymer films is investigated. Previous studies have shown that spun-cast films of unentangled polystyrene (PS) and polybutadiene (PB) dewet acid-cleaned silicon wafers when the films are annealed above their bulk glass transition temperature T g. It is also known that "impurity" particles tend to promote dewetting in thin polymer films. Here we demonstrate that the addition of a small amount of C60 fullerene nanoparticles to the spin-casting polymer solution leads to an inhibition of dewetting in thin (L < 100 nm) PS and PB films cast on both acid-cleaned and carbon-coated silicon wafer substrates. Neutron reflection measurements indicate that this effect is associated with the formation of a diffuse fullerene layer near the solid substrate. Evidently, the immobilized fullerene particles form an enrichment layer at the solid boundary and "pin" the contact line of the growing dewetted ("dry") regions so that hole growth in the filled films becomes arrested at a scale which diminishes with increasing filler concentration. Above a relative fillerpolymer mass fraction of 1%, we no longer observe hole formation by atomic force microscopy on the time scales of our measurements (typically on the order of hours), suggesting the existence of a critical filler surface coverage for the suppression of dewetting. The roughness of the fullerene layer probably also contributes to the modification of the surface wetting properties through a change in the surface energy of the substrate, as suggested by recent measurements on substrates "roughened" by other means such as irradiation of polymer film substrates, grafting of polymer chains, etc.

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“…5g), with a structure reminiscent of bundles with a rami-ed internal structure. Large ($100 mm) fractal fullerite C 60 structures from toluene can be obtained under specic slow evaporation conditions, 37 suggesting that the slow evaporation and a higher viscosity of PS/toluene drop cast solutions yield these 'tumbleweed' structures. Directional assembly of C 60 in solution with rod-like (and other) features, 38,39 and for polymer/ colloid mixtures 40 have been observed previously.…”

Section: Drying Timescales and Lm Thicknessmentioning

confidence: 99%

Polymer fullerene solution phase behaviour and film formation pathways

Dattani

Cabral

2015

Soft Matter

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We report the phase behaviour of polymer/fullerene/solvent ternary mixtures and its consequence for the morphology of the resulting composite thin films. We focus particularly on solutions of polystyrene (PS), C60 fullerene and toluene, which are examined by static and dynamic light scattering, and films obtained from various solution ages and thermal annealing conditions, using atomic force and light microscopy. Unexpectedly, the solution phase behaviour below the polymer overlap concentration, c*, is found to be described by a simple excluded volume argument (occupied by the polymer chains) and the neat C60/solvent miscibility. Scaling consistent with full exclusion is found when the miscibility of the fullerene in the solvent is much lower than that of the polymer, giving way to partial exclusion with more soluble fullerenes (phenyl-C61-butyric acid methyl ester, PCBM) and a less asymmetric solvent (chlorobenzene), employed in photovoltaic devices. Spun cast and drop cast films were prepared from PS/C60/toluene solutions across the phase diagram to yield an identical PS/C60 composition and film thickness, resulting in qualitatively different morphologies in agreement with our measured solution phase boundaries. Our findings are relevant to the solution processing of polymer/fullerene composites (including organic photovoltaic devices), which generally require effective solubilisation of fullerene derivatives and polymer pairs in this concentration range, and the design of well-defined thin film morphologies.

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Fractal structure of fullerite

Cited by 9 publications

References 2 publications

Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive

Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive

Suppression of Dewetting in Nanoparticle-Filled Polymer Films

Polymer fullerene solution phase behaviour and film formation pathways

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