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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 411049
Title PMMA highlights the layering transition of PDMS in Langmuir films
Author(s) Bernardini, C.; Stoyanov, S.D.; Cohen Stuart, M.A.; Arnaudov, L.N.; Leermakers, F.A.M.
Source Langmuir 27 (2011)6. - ISSN 0743-7463 - p. 2501 - 2508.
DOI http://dx.doi.org/10.1021/la104285z
Department(s) Physical Chemistry and Colloid Science
VLAG
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) air-water-interface - molecular layers - polymer-films - surface - poly(dimethylsiloxane) - methacrylate - ellipsometry - behavior - spread
Abstract We report a system consisting of a mixed Langmuir monolayer, made of water-insoluble, spreadable, fluid-like polymers polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) with a minority P(DMS-b-MMA) copolymer. We have performed both Langmuir trough pressure/area isotherm measurements and Brewster angle microscopy (BAM) observations and complement the experiments with molecularly detailed self-consistent field (SCF) calculations. PDMS undergoes a layering transition that is difficult to detect by BAM. Addition of PMMA gives contrast in BAM, now showing a two-phase system: if this would consist of separate two-dimensional (2D) PMMA and PDMS phases, a PDMS-PMMA diblock should accumulate at the phase boundary. However, the diblock copolymer of PDMS-PMMA failed to show the expected “lineactant” behavior, i.e., failed to accumulate at the phase boundary. The calculations point to a nontrivial arrangement of the polymer chains at the interface: in mixtures of the two homopolymers, in a rather wide composition ratio, we find a vertical (with respect to the air/water interfacial plane) configuration, with PMMA sitting preferably at the PDMS/water interface of the thicker PDMS film, during the PDMS layering phase transition. This also explains why the diblock copolymer is not a lineactant. Both PMMA and P(DMS-b-MMA) are depleted from the thin-thick PDMS film interface, and the line tension between the phases is, consequently, increased, in the binary mixtures as well as in the ternary ones
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