68 research outputs found
Self-Consistent Field study of Polyelectrolyte Brushes
We formulate a self-consistent field theory for polyelectrolyte brushes in
the presence of counterions. We numerically solve the self-consistent field
equations and study the monomer density profile, the distribution of
counterions, and the total charge distribution. We study the scaling relations
for the brush height and compare them to the prediction of other theories. We
find a weak dependence of the brush height on the grafting density.We fit the
counterion distribution outside the brush by the Gouy-Chapman solution for a
virtual charged wall. We calculate the amount of counterions outside the brush
and find that it saturates as the charge of the polyelectrolytes increases
CRITERES DE CHOIX DES MATERIAUX DES DENTS PROTHETIQUES SUR LA PERENNITE DE L'OCCLUSION EN PROTHESE AMOVIBLE COMPLETE BIMAXILLAIRE
PARIS7-Odontologie (751062104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
CONTRIBUTION A L'ETUDE DE L'ETAT DENTAIRE DANS LA MARINE DE GUERRE A L'EPOQUE NAPOLEONIENNE
PARIS7-Odontologie (751062104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
CONTRIBUTION DE LA MORPHOLOGIE DENTAIRE A L'ETUDE DE LA PALEOANTHROPOLOGIE
PARIS7-Odontologie (751062104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Differences between Tethered Polyelectrolyte Chains on Bare Mica and Hydrophobically Modified Mica
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
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