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Influence of Confinement on the Chain Conformation of Cyclic Poly(N‑isopropylacrylamide)
Version 2 2015-12-17, 11:09
Version 1 2015-11-23, 19:46
journal contribution
posted on 2015-12-17, 11:09 authored by David Magerl, Martine Philipp, Ezzeldin Metwalli, Philipp Gutfreund, Xing-Ping Qiu, Françoise
M. Winnik, Peter Müller-BuschbaumIn thin and ultrathin supported films,
the conformations of flexible
linear polymer chains might be considerably confined, in particular,
for film thicknesses smaller than a few times the radius of gyration.
For ring polymers in solution or in melt, the radii of gyration are
significantly reduced as compared to those of their linear counterparts.
We study here the influence of geometrical confinement on the chain
conformation of cyclic PNIPAM in silicon-supported films. Measurements
are performed by grazing incidence small angle neutron scattering
(GISANS). For all films, the component of the radius of gyration parallel
to the substrate, Rgc∥, is significantly
higher than the unperturbed Rgc determined
under theta solvent or melt conditions. We attribute this effect to
a preferential selection of stretched PNIPAM ring conformations in
thin films and a preferential orientation of macromolecules parallel
to the film interfaces with the substrate and air.