54. Morphology and Photophysical Properties of Phenyleneethynylene Oligomers. C.Z.Zhou, T.X.Liu, T.T.Lin, X.H.Zhang, Z.K.Chen. Polymer, 46(24), 10952-10959, 2005.
The influence of annealing on the morphologies and optical properties of phenyleneethynylene pentamer films has been investigated by
using optical microscopy, UV–vis spectroscopy, steady-state and time-resolved photoluminescence (PL). The optical microscopy study shows
that the grainy morphology of crystallites with irregular shapes and sizes of the spincoated oligomer films reorganize into well-ordered single
crystal-like laths or bamboo-like structures upon melt-crystallization or annealing. The crystalline features of the annealed films were
simulated and modeled through molecular mechanics (MM) and molecular dynamics (MD) and further measured by X-ray diffraction. These
studies revealed that the molecular backbones form lamellar and interdigitated conformations. Investigation of optical properties of the
thermally treated films indicated that aggregates and excimers dominate excitation/emission processes due to molecular closely packing upon
annealing, which are evidenced by the broadening, structureless absorption and luminescence spectra, as well as longer lifetime of PL
dynamics.