Web Release Date: January 31,
Nanoscale Thin Film Ordering Produced by Channel Formation in the
Inclusion Complex of 
-Cyclodextrin with a Polyurethane Composed
of Polyethylene Oxide and Hexamethylene
and
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK, and H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
Received July 4, 2007
Revised Manuscript Received December 18, 2007
Abstract:
A polyurethane consisting of six blocks of polyethylene glycol and five blocks of hexamethylene
diisocyanate was synthesized. The influence of the addition of -cyclodextrin (-CyD) on the lower critical
solution temperature behavior of the polyurethane was investigated by "cloud point" measurements, and the
dependence of the phase state (solution, suspension, and gel) of -CyD/polyurethane mixtures on the concentration
of the two components was determined. The results suggest that the polyurethane forms inclusion complexes
with -CyD and that close to the maximum number of -CyDs was included. The associative constant of the
-CyD/polyurethane inclusion complex was determined by 1H NMR shift titration using a modified Benesi-Hildebrand equation, and the complex was characterized in the solid state by 13C cross polarization/magic angle
spinning NMR and X-ray diffraction. These studies showed that the complexes adopted a channel-like structure.
Finally, the morphology of -CyD/polyurethane complexes in the solid state was visualized by scanning electron
microscopy and atomic force microscopy (AFM). AFM images of the inclusion complexes spun-cast on to silicon
reveal the existence of ordered domains with heights commensurate with the existence of tetra- and higher-order
-CyD channels. The height quanta of these well-ordered, discrete plateaus point to the dominating influence of
the size of the polyethylene glycol blocks within the polyurethane and suggest a route to the production of controlled
subnanometer structured surfaces.
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