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Weiche Materie Vortrag: Fr., 10:00–10:20 F-V47
Multilevel structures formed by partially crystalline polymers in solution:
from fundamentals to applications - a combined USANS, focusing-SANS
and conventional SANS study
Aurel Radulescu 1 , Dietmar Schwahn 1 , Michael Monkenbusch 1 , Emmanuel
Kentzinger 1 , Lewis J. Fetters 2 , Dieter Richter 1
1 Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich – 2 School
of Chemical and Biomolecular Engineering, Cornell University, Ithaca NY 14853-1301,
USA
Under wintry conditions, middle distillate fuels can clog the filters by precipitating
large waxy crystals and thereby prevent engine operations. The copolymers consisting
of crystalline and amorphous segments can interact favorably with waxes (long-chain
CnH2n+2 alkanes or simply Cn) and modify the crystal morphology to smaller units.
The wax-copolymer interaction in solution is rather complex and is not yet fully understood.
Because the morphology of the common wax-copolymer aggregates strongly
depends on the precipitation temperatures of both components, a good knowledge of
the copolymer self-assembling behavior in solution is required first of all. Therefore,
these copolymers are also of much interest in basic research. Several polymer architectures
with a combination of crystalline and amorphous sequences have been studied
for determination of their self-assembly and wax crystal modification properties.
We report here the case of the poly(ethylene-butene) random copolymers and syndiotactic-polypropylene
-block-poly(ethylene-co-propylene) diblock copolymers. Their
self-assembling or common aggregation with waxes yields in hydrocarbon solutions
complex morphologies with characteristic lengths covering four orders of magnitude,
from 10 µm to 1 nm. These morphologies evolving either separately or as hierarchical
multilevel structures could be fully analysed by three small-angle neutron scattering
techniques namely, the conventional pin-hole SANS, the focusing-mirror SANS and
the double-crystal diffractometry (USANS) covering a Q range from 3x10 −5 - 0.2 ˚A −1 .
Microscopy techniques have been complementarily used in order to visualize the morphologies
formed.