The adsorption of the nonionic surfactant C10E4 from solutions in D2O to a
polymethylmethacrylate (PMMA) and a polystyrene (PS) surface is studied by
neutron reflectometry in the concentration range from 0.1 to 4.5 c.m.c. at
289.15 K, corresponding to a temperature ca. 1 K below the lower critical s
olution temperature of the C10E4 + D2O system. Polymer films of uniform thi
ckness (140 to 300 Angstrom) were obtained by spin-coating of silicon wafer
s. While non-tempered polymer films show some swelling (<5%) in D2O, anneal
ed films are non-swelling and stable in the aqueous surfactant solutions. A
dsorption of C10E4 on the PMMA surface leads to a layer of 21<plus/minus>2
Angstrom thickness and surfactant volume fraction phi (s) = 0.63 +/-0.08 ov
er the entire concentration range (0.33-4.50 c.m.c.), and experiments above
the c.m.c. show that the absorption of the surfactant on PMMA is reversibl
e. On the more hydrophobic PS substrate an adsorption layer of 11 +/-2 Angs
trom thickness and surfactant volume fraction phi (s) = 0.53 +/-0.08 is fou
nd at the lowest experimental concentration (0.1 c.m.c.). As the surfactant
concentration is gradually increased, the thickness of the adsorbed layer
grows to 40 +/-3 Angstrom at 1.20 c.m.c., with a nearly constant surfactant
volume fraction in the layer (phi (s) = 0.75 +/-0.03) above a concentratio
n of 0.2 c.m.c. Experiments above the c.m.c. reveal that a surfactant layer
of 18 +/-2 Angstrom thickness is adsorbed irreversibly to the PS surface.