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Bimodal crystallization at polymer–fullerene interfaces

DOI: 10.1039/C4CP04253K DOI Help

Authors: Dyfrig Môn (Swansea University) , Anthony Higgins (Swansea University) , David James (Swansea University) , Mark Hampton (Cardiff University) , J. Emyr Macdonald (Cardiff University) , Michael B. Ward (University of Leeds) , Philipp Gutfreund (Institut Laue-Langevin) , Samuele Lilliu (Cardiff University) , Jonathan Rawle (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics , VOL 17 (3) , PAGES 2216 - 2227

State: Published (Approved)
Published: November 2014

Open Access Open Access

Abstract: The growth-kinetics of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) crystals, on two different length-scales, is shown to be controlled by the thickness of the polymer layer within a PCBM–polymer bilayer. Using a model amorphous polymer we present evidence, from in situ optical microscopy and grazing-incidence X-ray diffraction (GIXD), that an increased growth-rate of nanoscale crystals impedes the growth of micron-sized, needle-like PCBM crystals. A combination of neutron reflectivity and GIXD measurements, also allows us to observe the establishment of a liquid–liquid equilibrium composition-profile between the PCBM layer and a polymer-rich layer, before crystallization occurs. While the interfacial composition-profile is independent of polymer-film-thickness, the growth-rate of nanoscale PCBM crystals is significantly larger for thinner polymer films. A similar thickness-dependent behavior is observed for different molecular weights of entangled polymer. We suggest that the behavior may be related to enhanced local-polymer-chain-mobility in nanocomposite thin-films.

Subject Areas: Energy, Materials, Physics

Instruments: I07-Surface & interface diffraction