Studies On Synthesis And Properties Of Azobenzene Functionalized Hydroxypropyl Cellulose

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.