In this study,a novel waterborne polyurethane(WPU)with azobenzene-containing(azo-containing)pendant groups was synthesized by isophorone diisocyanate,long-chain diol of polycaprolactone,2-ethyl-2-methyl-butanoic acid(...In this study,a novel waterborne polyurethane(WPU)with azobenzene-containing(azo-containing)pendant groups was synthesized by isophorone diisocyanate,long-chain diol of polycaprolactone,2-ethyl-2-methyl-butanoic acid(2,2-dimethylolpropionic acid),10-(4-(phenyldiazenyl)phenoxy)decyl-3-hydroxy-2-(hydroxymethyl)-2-methylpropanoate,and N,N-diethyl-ethanamine(triethylamine).Moreover,the influence of ultraviolet and visible(UV-Vis)light irradiation on the viscoelasticity of azo-containing WPU film in terms of the reversible trans-cis photoisomerization of azo-containing pendant groups was investigated by UV-Vis light spectroscopy,atomic force microscopy,and dynamic thermomechanical analysis.The results revealed that the adhesion of azo-containing WPU with single crystal silicon atomic force microscope probe was about 13 n N when irradiated by 450 nm Vis light for 60 s at 25°C.Subsequently,the adhesion increased to 82 n N after irradiation with 365 nm UV light for 60 s at 25°C.In addition,the azo-containing WPU presented a photo-induced reversible transition of tensile modulus and tanδin the range from about 2 MPa to 22 MPa and 6000 to 0.35 with UV-Vis light cyclic irradiation for 120 s at 25°C,respectively.展开更多
Herein we demonstrate crystallization-driven self-assembly ofisotactic polystyrene （iPS） with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of iPS...Herein we demonstrate crystallization-driven self-assembly ofisotactic polystyrene （iPS） with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of iPS aggregates in N, N-dimethylformamide （DMF）. The formation and morphology switching of the self-assembled aggregates of iPS are investigated by means of dynamic light scattering （DLS）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC） and wide angle X-ray diffraction （WXRD）. The results reveal that cooling DMF solution of iPS promotes iPS chains to self-assemble into spherical aggregates with a gelled core cross-linked by microcrystals, which is surrounded by solvent-swollen corona. Furthermore, crystallization induces the deformation of iPS aggregates from spherical to plate-like or nest-like.展开更多
基金financially supported by the Guangzhou Science and Technology Plan Project (No. 201607010348)
文摘In this study,a novel waterborne polyurethane(WPU)with azobenzene-containing(azo-containing)pendant groups was synthesized by isophorone diisocyanate,long-chain diol of polycaprolactone,2-ethyl-2-methyl-butanoic acid(2,2-dimethylolpropionic acid),10-(4-(phenyldiazenyl)phenoxy)decyl-3-hydroxy-2-(hydroxymethyl)-2-methylpropanoate,and N,N-diethyl-ethanamine(triethylamine).Moreover,the influence of ultraviolet and visible(UV-Vis)light irradiation on the viscoelasticity of azo-containing WPU film in terms of the reversible trans-cis photoisomerization of azo-containing pendant groups was investigated by UV-Vis light spectroscopy,atomic force microscopy,and dynamic thermomechanical analysis.The results revealed that the adhesion of azo-containing WPU with single crystal silicon atomic force microscope probe was about 13 n N when irradiated by 450 nm Vis light for 60 s at 25°C.Subsequently,the adhesion increased to 82 n N after irradiation with 365 nm UV light for 60 s at 25°C.In addition,the azo-containing WPU presented a photo-induced reversible transition of tensile modulus and tanδin the range from about 2 MPa to 22 MPa and 6000 to 0.35 with UV-Vis light cyclic irradiation for 120 s at 25°C,respectively.
基金financially supported by the National Natural Science Foundation of China(Nos.21174167 and 20974123)the Guangdong Province Higher School Science and Technology Innovation Key Project and the Natural Science Foundation of Guangdong Province(No.S2013030013474)
文摘Herein we demonstrate crystallization-driven self-assembly ofisotactic polystyrene （iPS） with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of iPS aggregates in N, N-dimethylformamide （DMF）. The formation and morphology switching of the self-assembled aggregates of iPS are investigated by means of dynamic light scattering （DLS）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC） and wide angle X-ray diffraction （WXRD）. The results reveal that cooling DMF solution of iPS promotes iPS chains to self-assemble into spherical aggregates with a gelled core cross-linked by microcrystals, which is surrounded by solvent-swollen corona. Furthermore, crystallization induces the deformation of iPS aggregates from spherical to plate-like or nest-like.
