Azobenzene Molecules Switching Assemblies of Ploy(N-isopropylacrylamide)in Ionic Liquid
Azobenzene-based materials have attracted much attention because of their reversible light controlled assemblies of polymers.Here,different structural and widely commercialized azobenzene-based compounds(azobenzene(AZO),p-hydroxyazobenzene(AZO-OH),p-aminoazobenzene(AZO-NH2)and dimethyl yellow(AZO-N(CH3)2)were used as photomolecular trigger to control assemblies of poly(N-isopropylacrylamide)(PNIPAm)in 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide([C2mim][NTf2])ionic liquid and investigate the effect of different end-groups on the phase behavior of PNIPAm self-assembly.The results show that the photo-induced isomerization of azobenzene small molecules could effectively affect the phase transition of PNIPAm in[C2mim][NTf2]ionic liquid.Meanwhile,various terminal groups attached on azobenzene moieties have little effect on the phase transition temperatures and phase transition interval of PNIPAm.Combined with the in situ FT-IR,the interaction between PNIPAm and ionic liquids was enhanced by UV irradiation,which inhibits the inter-aggregation between PNIPAm side chains,which promote the"solvation"effect under UV illumination conditions and a lower phase transition temperature could be obtained.