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Adsorption of hydrophilic‐hydrophobic block copolymers on silica from aqueous solutions
Author(s) -
Sikka Mohan,
Schneider Jim,
Tirrell Matthew,
Amiel Catherine
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.199509801102
Subject(s) - adsorption , copolymer , aqueous solution , polyelectrolyte , chemical engineering , polymer chemistry , sulfonate , styrene , ellipsometry , materials science , chemistry , polymer , sodium , organic chemistry , nanotechnology , thin film , engineering
Adsorption of a water‐soluble diblock copolymer, poly( t ‐butylstyrene)‐sodium poly(styrene sulfonate) (PtBS‐NaPSS), on silica surfaces in aqueous solutions was studied using ellipsometry and atomic‐force microscopy (AFM). Molar masses of 87 000 and 160 000 g/mol were used. The block copolymers used were compositionally asymmetric, with large, hydrophilic, PSS blocks and small, hydrophobic, PtBS blocks. Adsorption could not be observed in pure water without added salt. When the NaCl concentration was increased to 1 mol/L, adsorption could be readily observed. The measured adsorbed amount at long times was significantly larger for the 87 000 diblock compared with that for a polyelectrolyte homopolymer of comparable molecular size, demonstrating the role played by the uncharged block in anchoring the diblock at the solid surface. The kinetics of adsorption showed a two‐stage process, an initial diffusion‐limited stage, followed by a slower buildup of surface coverage in a brush‐limited stage. The number density of molecules at the surface was smaller for the higher molecular weight species, in agreement with simple scaling arguments.