Eur. Phys. J. E 5, 207-219
Hydrodynamic-flow-driven phase evolution in a polymer blend film modified by diblock copolymers
J. Rysz1, H. Ermer2, A. Budkowski1, A. Bernasik3, J. Lekki4, G. Juengst2, R. Brenn2, K. Kowalski3, J. Camra3, M. Lekka4 and J. Jedlinski31 Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Kraków, Poland
2 Fakultät für Physik, Universität Freiburg, H.-Herder-Str. 3, 79104 Freiburg i. Br., Germany
3 Surface Spectroscopy Laboratory, University of Mining and Metallurgy, Mickiewicza 39, 30-059 Kraków, Poland and Joint Centre for Chemical Analysis and Structural Research, Jagellonian University, Reymonta 23, 30-059 Kraków, Poland
4 Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Kraków, Poland
ufbudkow@cyf-kr.edu.pl
(Received 15 March 2000 and Received in final form 9 February 2001)
Abstract
We have studied surface-directed phase separation in thin films of
deuterated polystyrene and poly(bromostyrene) (with 22.7% of monomers
brominated) using 3He nuclear reaction analysis, dynamic secondary
ion mass spectroscopy and atomic force microscopy combined with preferential
dissolution. The crossover from competing to neutral surfaces of the
critical blend film (cast onto Au) was commenced: polyisoprene-polystyrene
diblock copolymers were added and segregated to both surfaces reducing in a
tuneable manner the effective interactions. Two main stages of phase
evolution are characterised by i) the growth of two surface layers and by
ii) the transition from the four-layer to the final bilayer morphology.
For increasing copolymer content the kinetics of the first stage is hardly
affected but the amplitude of composition oscillations is reduced indicating
more fragmented inner layers. As a result, a faster mass flow to the surfaces
and an earlier completion of the second stage were observed. The
hydrodynamic flow mechanism, driving both stages, is evidenced by nearly
linear growth of the surface layer and by mass flow channels extending from
the surface layer into the bulk. The final bilayer structure, formed even
for the surfaces covered by strongly overlapped copolymers, is indicative of
long-range (antisymmetric) surface forces.
64.75.+g - Solubility, segregation, and mixing; phase separation.
68.55.-a - Thin film structure and morphology.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001