Gs. Smith et al., NEUTRON REFLECTIVITY STUDY OF ADSORBED DIBLOCK COPOLYMERS, Nuovo cimento della Societa italiana di fisica. D, Condensed matter,atomic, molecular and chemical physics, biophysics, 16(7), 1994, pp. 721-726
In this paper, we summarize our cumulative work on neutron reflectivit
y studies of polystyrene-poly(vinyl-2-pyridine) (PS-PW) and polystyren
epolyethylene oxide (PS-PEO) adsorbed at a quartz-solvent interface. D
euterated toluene was chosen as the solvent since it is a good solvent
for PS and a poor one for either of the other two blocks. In this cas
e, the polystyrene dangles into the solvent while the other block acts
as an anchor. The neutron reflectivity studies reveal that the form o
f the polymer density profile normal to the substrate may be varied fr
om an extended <<brush>> to a condensed mushroom conformation by manip
ulating the ratio of the molecular weights of the two blocks. In addit
ion, we present new data on the PS-PEO system in a poor solvent, deute
rated cyclohexane, under conditions of shear flow in Poiseuille geomet
ry. We find that when the PS-PEO diblock is absorbed from cyclohexane
and is allowed to relax, the PS chain takes on a <<mushroom>> conforma
tion. However, when the shear is applied, the layer shear thickens due
to the PS chains extending to nearly twice their original lengths.