Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. The levels of birefringence signal are found to depend an the polarization angle between the pump beam and the prob...Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. The levels of birefringence signal are found to depend an the polarization angle between the pump beam and the probe beam, and on the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described by known biexponential equations. The rate constants and the amplitudes associated with the growth process of the photoinduced birefringence are observed to display a linear dependence with the pump beam intensity. A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the bans and cis isomers of azobenzene groups and the local polymer segments. The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.展开更多
Fluid viscosity is ubiquitous property and is of practical importance in intelligent fluids,industrial lubrication,and pipeline fluid transportation.Recently,there has been a surging interest in viscosity regulation.H...Fluid viscosity is ubiquitous property and is of practical importance in intelligent fluids,industrial lubrication,and pipeline fluid transportation.Recently,there has been a surging interest in viscosity regulation.Here,we have developed a group of photorheological fluids by utilizing azobenzene polymers with a light-induced microstructure transformation.In this work,a photosensitive polymer with 4,4'-bis-hydroxyazobenzene as the main chain was designed and synthesized as a pivotal functional material.The sufficiently large structural difference under ultraviolet and near-infrared light makes it possible to regulate the viscosity of a polyethylene glycol solution.The viscosity of the photosensitive rheological fluids under ultraviolet light radiation is found to be up to 45.1%higher than that under near-infrared light radiation.To explore this intelligent lubricating technology,the friction regulation of ceramic sliding bearings was investigated utilizing photosensitive rheological fluids.Reversible friction regulation with a ratio of up to 3.77 has been achieved by the alternative irradiation of near-infrared and ultraviolet light,which can be attributed to the differences in mechanical properties and molecular structures under ultraviolet and near-infrared light according to both simulations and experiments.Such photorheological fluids will have promising applications in controllable lubrication,intelligent rheological fluids,and photosensitive dampers.展开更多
The preparation of monodisperse azobenzene(Azo)polymer microspheres by dispersion polymerization was reported.The photo-induced fusion of Azo polymer microspheres was successfully achieved during the process of revers...The preparation of monodisperse azobenzene(Azo)polymer microspheres by dispersion polymerization was reported.The photo-induced fusion of Azo polymer microspheres was successfully achieved during the process of reversible trans-cistrans photoisomerization of Azo units,and induced various unique“microsphere molecular”clusters or“microsphere polymers”.Encouraged by this interesting phenomenon,microsphere clusters of different topological structures were stabilized by the in situ acetal cross-linking chemistry.The photo-induced fusion polymerization of monodisperse polymer microspheres provides a new strategy for designing photo-responsive clusters and allows for control over the mechanical properties of microspheres with high spatiotemporal resolution.展开更多
Electro-optic （EO） effect and thermo-optic （TO） effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of...Electro-optic （EO） effect and thermo-optic （TO） effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of EO fluorinated polyimide films with side-chain azobenzene chromophore were measured by attenuated- total-reflection （ATR） technique at different temperatures with TE- and TM-polarized lights, respectively. It is found that the absolute values of TO coefficients increase with the increments of both chromophore concentration and film thickness, but the polarization dependence of TO coefficients increases with the increment of chromophore concentration and decreases with the increment of film thickness.展开更多
基金This work was supported by the National Natural Science Foundation of China (No. 19604015) and Guangdong Provincial Natural Science Foundation (No. 980279 and 980346).
文摘Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. The levels of birefringence signal are found to depend an the polarization angle between the pump beam and the probe beam, and on the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described by known biexponential equations. The rate constants and the amplitudes associated with the growth process of the photoinduced birefringence are observed to display a linear dependence with the pump beam intensity. A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the bans and cis isomers of azobenzene groups and the local polymer segments. The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51922058 and 51527901).
文摘Fluid viscosity is ubiquitous property and is of practical importance in intelligent fluids,industrial lubrication,and pipeline fluid transportation.Recently,there has been a surging interest in viscosity regulation.Here,we have developed a group of photorheological fluids by utilizing azobenzene polymers with a light-induced microstructure transformation.In this work,a photosensitive polymer with 4,4'-bis-hydroxyazobenzene as the main chain was designed and synthesized as a pivotal functional material.The sufficiently large structural difference under ultraviolet and near-infrared light makes it possible to regulate the viscosity of a polyethylene glycol solution.The viscosity of the photosensitive rheological fluids under ultraviolet light radiation is found to be up to 45.1%higher than that under near-infrared light radiation.To explore this intelligent lubricating technology,the friction regulation of ceramic sliding bearings was investigated utilizing photosensitive rheological fluids.Reversible friction regulation with a ratio of up to 3.77 has been achieved by the alternative irradiation of near-infrared and ultraviolet light,which can be attributed to the differences in mechanical properties and molecular structures under ultraviolet and near-infrared light according to both simulations and experiments.Such photorheological fluids will have promising applications in controllable lubrication,intelligent rheological fluids,and photosensitive dampers.
基金National Nature Science Foundation of China,Grant/Award Numbers:92056111,21971180China Postdoctoral Science Foundation,Grant/Award Number:2022M722312。
文摘The preparation of monodisperse azobenzene(Azo)polymer microspheres by dispersion polymerization was reported.The photo-induced fusion of Azo polymer microspheres was successfully achieved during the process of reversible trans-cistrans photoisomerization of Azo units,and induced various unique“microsphere molecular”clusters or“microsphere polymers”.Encouraged by this interesting phenomenon,microsphere clusters of different topological structures were stabilized by the in situ acetal cross-linking chemistry.The photo-induced fusion polymerization of monodisperse polymer microspheres provides a new strategy for designing photo-responsive clusters and allows for control over the mechanical properties of microspheres with high spatiotemporal resolution.
文摘Electro-optic （EO） effect and thermo-optic （TO） effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of EO fluorinated polyimide films with side-chain azobenzene chromophore were measured by attenuated- total-reflection （ATR） technique at different temperatures with TE- and TM-polarized lights, respectively. It is found that the absolute values of TO coefficients increase with the increments of both chromophore concentration and film thickness, but the polarization dependence of TO coefficients increases with the increment of chromophore concentration and decreases with the increment of film thickness.
