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Staff Publications

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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 446004
Title (Quasi-) 2D aggregation of polystyrene-b-dextran at the air-water interface
Author(s) Bosker, W.T.E.; Cohen Stuart, M.A.; Norde, W.
Source Langmuir 29 (2013)8. - ISSN 0743-7463 - p. 2667 - 2675.
DOI https://doi.org/10.1021/la304797r
Department(s) Physical Chemistry and Colloid Science
VLAG
Publication type Refereed Article in a scientific journal
Publication year 2013
Keyword(s) diblock copolymer monolayers - surface micelle formation - block polyelectrolytes - air/water interface - molecular-dynamics - solid-state - behavior - brushes - polymers - spectroscopy
Abstract Polystyrene-b-dextran (PS-b-Dextran) copolymers can be used to prepare dextran brushes at solid surfaces, applying Langmuir–Blodgett deposition. When recording the interfacial pressure versus area isotherms of a PS-b-Dextran monolayer, time-dependent hysteresis was observed upon compression and expansion. We argue that this is due to (quasi-) 2D aggregation of the copolymer at the air–water surface, with three contributions. First, at large area per molecule, a zero surface pressure is measured; we ascribe this to self-assembly of block copolymers into surface micelles. At intermediate area we identify a second regime (“desorption regime”) where aggregation into large patches occurs due to van der Waals attraction between PS blocks. At high surface pressure (“brush regime”) we observe hysteretic behavior attributed to H-bonding between dextran chains. When compared to hysteresis of other amphiphilic diblock copolymers (also containing PS, e.g., polystyrene-b-poly(ethylene oxide)) a general criterion can be formulated concerning the extent of hysteresis: when the hydrophobic (PS) block is of equal size as (or bigger than) the hydrophilic block, the hysteresis is maximal. The (quasi-) 2D aggregation of PS-b-Dextran has significant implications for the preparation of dextran brushes at solid surfaces using Langmuir–Blodgett deposition. For each grafting density the monolayer needs to relax, up to several hours, prior to transfer.
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