The water-soluble amphiphilic random copolymer
of P(DMA-co-VBC) with coumarin pendants has been designed
to investigate the photo-induced dynamic association
of coumarin pendants within polymer micelles in aqueous
solution. Methods of absorption and emission spectra, solution
transmittance, dynamic light scattering (DLS), and atomic
force microscope (AFM) were applied. It was found that
P(DMA-co-VBC) can form polymer micelles in aqueous
solution. The time-dependent photo-dimerization degree
(PD) of polymer micelles upon different intensity irradiations
of 320 nm light showed saturating behaviors with an intensityindependent
value of the maximum photo-dimerization extent,
while the maximum photo-cleavage extent of coumarin
dimers declined with the increasing intensity of 254 nm irradiation
at used conditions. Furthermore, a significant emission
band at 445 nm (I2) evidently emerged as against the disappearance
of emission band at 385 nm (I1) during the photodimerization,
and the time-dependent I2/I1 ratios of polymer
aqueous solution upon alternative irradiations of 320 and
254 nm light showed a wave-like increase as a function of
irradiation cycles, indicating a wavy closeness of coumarin
pendants within polymer micelles during the reversible photodimerization
cycles.
