writer：Huan Chang & Yan Liu & Mei Shi & Zhaotie Liu & Zhongwen Liu & Jinqiang Jiang
keywords：Amphiphilic polymer . Micelles . Coumarin . Reversible photo-dimerization . Hydrophobic association
source：期刊
specific source：Colloid Polym Sci DOI 10.1007/s00396-014-3474-7
Issue time：2014年

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 aqueoussolution. 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 irradiationat 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 ofirradiation cycles, indicating a wavy closeness of coumarin pendants within polymer micelles during the reversible photodimerization cycles.