Contact
    Start Publications Differences between Tethered Polyelectrolyte Chains on Bare ...
    ←  Publication Finder
    Attension

    Differences between Tethered Polyelectrolyte Chains on Bare Mica and Hydrophobically Modified Mica

    Year: 2006

    Journal: Langmuir, 2006, 22 (9), pp 4084–4091, 20111221

    Authors: Feng Li, Marc Balastre, Phillip Schorr, J.-F. Argillier, Jinchuan Yang, Jimmy W. Mays, and Matthew Tirrell

    Organizations: Department of Chemical Engineering and the Materials Research Laboratory, University of California at Santa Barbara, Santa Barbara, California 93106, Institut Français du Pétrole, 1-4 Avenue Du Bois Préau, 92582 Rueil Malmaison Cedex, France, Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, and Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

    This study investigates the structures of layers of amphiphilic diblock copolymers of poly(t-butyl styrene)−poly(styrene sulfonate) (PtBS−PSS) adsorbed on both the bare mica surface (hydrophilic) and an octadecyltriethoxysilane (OTE)-modified mica surface (hydrophobic). When the surface is rendered hydrophobic, the nonsoluble block exhibits stronger interaction with the surface and higher adsorbed masses are achieved. Interaction forces between two such adsorbed layers on both substrates were measured using the surface forces apparatus. The effect of salt concentration (Cs) and molecular weight (N) on the height of the self-assembled layers (L0) was examined in each case. The resulting scaling relationship is in good agreement with predictions of the brush model, L0  N1.0 in the low-salt limit and L0N-1  (Cs/σ)-0.32 in the salted regime, when adsorption takes place onto the hydrophobized mica surface. For adsorption on the bare mica surface, L0N-0.7  Cs-0.17 agrees with the scaling prediction of the sparse tethering model. The results suggest that, on the hydrophilic bare mica surface, the adsorbed amount is not high enough to form a brush structure and only very little intermolecular stretching of the tethered chains occurs; in contrast, the presence of the hydrophobic OTE layer increases the tethering density such that the polyelectrolyte chains adopt a brush conformation.