Oriented Thin Films from Soluble Polythiophenes

The degree of orientation of thin films of eight different
polymeric structures, belonging to the class of soluble
polyalkylthiophenes (PATs) has been studied. Thin films
of the polymers, obtained by spin coating onto glass
substrates, were oriented by means of the rubbing
technique. The degree of orientation is related to the
regioregularity of the system: highly regioregular polymers
can be oriented, while regiorandom materials are
not oriented. The degree of orientation can be improved
by thermal annealing of the oriented films. As a result of
annealing, which was performed at different temperatures
according to the thermal behavior of the polymers,
it was possible to increase the polarization ratio for
poly(3-decylthiophene) up to 12–13 as detected from
the UV-vis spectra in polarized light. Moreover in the
investigated PATs, both the key role of molecular weight
and its distribution for achieving a high orientation
degree has been assessed.