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Vesicle‐to‐Rod Transition of Polymer Aggregates upon Irradiation
Author(s) -
Me Sajith,
Ongungal Rahul M.,
Das Suresh
Publication year - 2015
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201500262
Subject(s) - dynamic light scattering , polystyrene , polymer chemistry , polymer , polymerization , transmission electron microscopy , glass transition , chemistry , copolymer , small angle x ray scattering , materials science , chemical engineering , atom transfer radical polymerization , photochemistry , nanoparticle , scattering , nanotechnology , organic chemistry , optics , physics , engineering
Atom transfer radical polymerization is utilized to synthesize an amphiphilic photoresponsive triblock copolymer poly(trifluorostilbene 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 fluorescence spectroscopy. The trans ‐stilbene units have almost zero dipole moment whereas the corresponding cis ‐form has a definite 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.