CONFORMATIONAL TRANSFORMATIONS IN CHIRAL POLYTHIOPHENE DERIVATES AGGREGATED IN
POLYMETHACRYLATE MATRICES: EXPERIMENTS AND MOLECULAR DYNAMICS SIMULATIONS:
Thomas Bjornholm (1), Witold Brostow (2), Kjeld Schaumburg (1),
Peter V. Shibaev (1,3,*), Vladimir Sinani (4), Rostislav Vinokur (3)
(1) Centre for Interdisciplinary Studies of Molecular Interactions (CIMSI), University of
Copenhagen, Fruebjergvej 3, DK-2100, Copenhagen Ø, Denmark
(2) Laboratory of Polymers
and Composites (LAPOM), Departments of Materials Science and Chemistry, University of North Texas, Denton, TX
76203-5310, USA
brostow@unt.edu
(3) Department of Physical Electronics, Moscow State University,
119899 Moscow, Russia
(4) Department of Chemistry, Moscow State University, 119899 Moscow, Russia
(*) Author for correspondence at ps@symbion.ki.ku.dk
ABSTRACT
Chiral derivates of poly(3-(S-3',7'-dimethyloctyl)thiophene) embedded in either poly(methyl methecrylate)
(PMMA) or poly(butyl methacrylate) (PBMA) were studied by polatization optical microscopy, UV absortion
and circular dichroism (CD) spectroscopy as well as simulated using the Molecular Dynamics Procedure.
CD spectra change on heating to mirror spectra; for PMMA-containing blends the changes in heating/cooling
cycles are reversible. The signs of CD spectra depend on free volume, the packing of side groups in
particular. Since in the melt there are no restrictions on the positions of the chiral groups, those
groups appear with equal probabilities at any location with respect to the thiophene ring. By contrast,
in clusters restrictions imposed by other alkyl chains result in positioning of chiral methyl groups
preferencially on the left or right sides of the thiophene rings. The consequence is the formation of
right or left twists in molecular backbones.
Maintained by Ricardo Simoes