KINETICS OF THE ADSORPTION OF A POLYSTYRENE-POLY(ETHYLENE OXIDE) BLOCK-COPOLYMER ON SILICA - A STUDY OF THE TIME-DEPENDENCE IN SURFACE SEGMENT INTERACTIONS/
Cp. Tripp et Ml. Hair, KINETICS OF THE ADSORPTION OF A POLYSTYRENE-POLY(ETHYLENE OXIDE) BLOCK-COPOLYMER ON SILICA - A STUDY OF THE TIME-DEPENDENCE IN SURFACE SEGMENT INTERACTIONS/, Langmuir, 12(16), 1996, pp. 3952-3956
The kinetic aspects of polymer adsorption on surfaces are important in
many practical applications. Usually, the dynamic conformational beha
vior of an adsorbed polymer is not measured directly but is interprete
d from changes in the thickness of the layer or in the adsorbed amount
. Infrared spectroscopy is now used to present direct evidence of the
dynamic behavior of segment/surface interactions. The time dependent b
ehavior of the segment/surface interactions of a PS-PEO (polystyrene-p
oly(ethylene oxide)) block copolymer adsorbed on silica particles is r
eported. Three distinct zones are identified. In the first region, the
polymer adsorbs on vacant sites on the surface and does not undergo a
ny rearrangement. The relative number of surface-anchored PEO and PS s
egments is dictated by the differential sticking enthalpies rather tha
n the geometric size of each block. In the second region, the surface
sites are fully covered and fresh polymer arriving at the surface is a
ccommodated by a rearrangement of the existing adsorbed polymer layer.
The more weakly attached PS segments are displaced by PEO units of th
e incoming chains. In a final stage, a slow rearrangement of the adsor
bed polymer layer occurs. The adsorbed PS segments are sacrificed for
additional adsorbed PEO segments, and the adsorbed layer tends toward
the brush conformation.