Abstract:
We present a new hypothesis and supporting experimental evidence about the essential role played by small
impurities of dicarboxystilbene in the process of UV treatment of PET films irradiated with swift heavy ions
(SHI). This treatment both forms highly selective membranes with permeability values comparable to natural
ones (the track-UV technique) and sharply accelerates the etching of latent tracks in membrane production (the
track-etching technique). We hypothesize (1) that these high permeability value is due to the presence of a
molecular motor of an Archimedes screw type in the central part of the latent track formed by photoinduced
trans-cis isomerization of dicarboxystilbene molecules that are anchored in helical conformations in the latent
track; and (2) that the acceleration of etching rates is due to the preferential accumulation of phenanthrene-type
molecules in the central part of the latent track due to the existence of a cyclization channel for photoexcited
molecules of cis-dicarboxystilbene. In the presence of alkali solution, phenanthrene molecules release electrons
which behave as strong anions in aqueous solution, catalyzing alkaline hydrolysis of PET molecules in the central
part of the track. We present experimental observations of photoinduced changes in transmission light intensity
after track-UV light treatment of both pristine and SHI irradiated PET films that confirm the presence of trans-cis
isomerization of dicarboxystilbene molecules and show their contribution to the formation of new helical con
formations in SHI irradiated PET films during the light treatment.
