Eur. Phys. J. E 5, 451-464 (2001)
Partitioning of a heterotelechelic polystyrene to separate interfaces of thin films
L.R. Hutchings1, R.W. Richards1, R.L. Thompson1, D.G. Bucknall2 and A.S. Clough31 Interdisciplinary Research Centre in Polymer Science and Technology, University of Durham, Durham, DH1 3LE, UK
2 ISIS Science Division, Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QZ, UK
3 Department of Physics, School of Physics and Chemistry, University of Surrey, Guildford, Surrey GU2 5XH, UK
r.w.richards@durham.ac.uk
(Received 12 October 2000 and Received in final form 27 March 2001 )
Abstract
Heterotelechelic deuteropolystyrenes have been synthesised with a tertiary amine
functionality at one end and a fluorocarbon group at the other end of the polymer chain. A layer
of this polymer, circa 120 Åthick, has been attached to the surface of a silicon substrate and
subsequently covered with a much thicker layer of hydrogenous polystyrene. The combination
has then been annealed at 413 K under vacuum for defined times and the subsequent distribution
of the deutero heterotelechelic polymer determined using nuclear reaction analysis and neutron
reflectometry. The influences of annealing time, molecular weight and thickness of the
hydrogenous polymer have been examined. Nuclear reaction analysis showed that an excess of
the heterotelechelic polymer formed at both interfaces with a larger excess remaining at the
substrate-polymer interface. When the molecular weight of the hydrogenous polymer is lower
than that of the deuteropolymer, the deutero layer is initially swollen by the hydrogenous polymer
but the thickness then decreases as deutero polymer becomes detached from the silicon substrate
and an additional excess layer is eventually formed at the vacuum-polymer surface. When the
molecular weight of the hydrogenous polymer is higher, there is an initial shrinkage of the
deuteropolymer layer, but the original thickness (~ radius of gyration of the deuteropolymer) is
regained on prolonged annealing. There is no evidence for bridging between the two interfaces
by the heterotelechelic polymer. After five days annealing the volume fraction distribution of the
deuteropolymer at the silicon substrate was well described by a self-consistent field model where
the only adjustable parameter was the sticking energy of the tertiary amine group to the silicon
substrate for which a value of
was obtained. Comparison of the dependence of the
equilibrium layer thickness of the deuteropolymer on the equilibrium grafting density at the
silicon surface with the predictions of scaling theory for brush-like polymer layers suggested that
the grafted molecules were in the ideal, unperturbed brush region.
61.41.+e - Polymers, elastomers, and plastics.
61.12.Ha - Neutron reflectometry.
61.18.Bn - Atom, molecule, and ion scattering.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
