| As the most abundant natural polymers and renewable materials,cellulose has always received much attention duo to the advantages of its biocompatible and biodegradable,etc.In this thesis,azobenzene functionalized hydroxypropyl cellulose(Azo-HPC)was synthesized via the esterification of N-(4-phenylazophenyl)succinamic acid(Azo-COOH)and hydroxypropyl cellulose(HPC)at room temperature with DCC/DMAP as catalyst.The degree of substitution of azobenzene moieties(DSAzo)of the resultant Azo-HPC increases with the increase in reaction time and the feeding ratio of Azo-COOH and HPC(in weight).The resulting Azo-HPC was characterized by FT-IR,1H-NMR and TGA.Photoinduced isomerization of the Azo-HPC was investigated in THF,and the Azo-HPCs show the reversible cis-trans conformation transition upon intervals UV and visible light irradiation.The photosensitivity of the Azo-HPC films was characterized by UV-vis spectra.The surface morphology and the contact angle of the films were investigated by atomic force microscope(AFM)and contact angle meter,respectively.The contact angle of the Azo-HPC is mainly depends on the surface polarity the films,which correlates with photoisomerization of the azobenzene moieties of Azo-HPCs.The variation of the water contact angle of the films depends on DSAzo and the thickness of the films.A higher DSAzo and more thick film lead to a larger variation of the water contact angle during the UV and visible light irradiation.A UV source with the wavelength closer to trans-to-cis isomerization absorption peak(355 nm)leads to a faster trans-cis transition rate of the photoisomerization.The self-assembly behavior of Azo-HPC in the selective solvent of water was investigated by using transmission lectron microscopy(TEM),scanning electron microcopy(SEM)and dynamic light scattering(DLS).It was found that Azo-HPC can self-assemble into spherical micelles with core-shell structure.The micellar size increases with the increase in polymer concentration. |
