Abstract:
Atom transfer radical polymerization is utilized to synthesize an amphiphilic photoresponsive
triblock copolymer poly(trifl uorostilbene methacrylate)- b -polystyrene- b -polyethylene oxide
(PTFS- b -PSt- b -PEO). Adding water into tetrahydrofuran solution of PTFS- b -PSt- b -PEO results in
the formation of spherical vesicular aggregates brought about as a result of the association of
the water insoluble TFS and St blocks. UV irradiation of the colloidal solution causes trans–cis
isomerization of the TFS units which result in morphological transition of the spherical vesicular
aggregates to rod-like particles. This morphological transition is studied using dynamic
light scattering, scanning electron microscopy, atomic force microscopy, transmission electron
microscopy, and UV–vis and fl uorescence spectroscopy. The trans -stilbene units have almost
zero dipole moment whereas the corresponding cis -form has a defi nite dipole moment. This
polarity difference associated with structural change is expected to be the main reason for the
structural transformation of the aggregates. It is also found
that PTFS- b -PSt- b -PEO aggregates have the ability of trapping
organic dyes inside their hydrophobic cavity thereby
making them water soluble. Subsequently the encapsulated
dye can be partially released upon UV irradiation.
