title: Three-Component Supramolecular System with Multistimuli-Responsive Properties in Water.
abstract: Hyperbranched polyethylenimine terminated with isobutyramide groups (HPEI-IBAm), 4-(phenylazo)benzoic acid (PABA), and α-cyclodextrin (α-CD) were assembled together at pH≈7 to form the three-component supramolecular complexes that were verified by (1) H and 2D ROESY (1) H NMR spectroscopy. UV/Vis spectrometric titration experiments showed that the content of α-CD in the three-component complexes was less than the feed amount and it was difficult for all the PABA units in the complexes to further form complexes with α-CD. The obtained three-component supramolecular complexes exhibited thermoresponsive properties in water. Increasing the α-CD concentration led to a sharp increase in the cloud point temperature (Tcp ) at the beginning, but after the [α-CD]/[PABA] ratio was in the region of 1.3-1.6, the Tcp increased gradually When the concentration of α-CD was low, a higher concentration of PABA led to a lower Tcp , however, the opposite was observed when the concentration of α-CD was high. For the three-component complex, increasing the α-CD concentration at pH≈7 or at pH≈9 led to different Tcp temperatures. In the low α-CD concentration range, adjusting the pH from ≈7-≈9 resulted in an increase in the Tcp , similar but not so pronounced as that of the two-component system of HPEI-IBAm/[PABA]. When the concentration of α-CD was high, adjusting the pH from ≈7-≈9 decreased the Tcp ; this observation is different to that of the two-component system of HPEI-IBAm/[PABA]. Reversible trans-to-cis photoisomerization of azobenzene units in the complexes occurred, following irradiation with UV or visible light. Trans-to-cis isomerization of azobenzene units decreased the Tcp . However, this result differed to that of the two-component system of HPEI-IBAm/PABA.
authors.affiliation: Department of Chemistry, School of Sciences, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Wei Jin Road 92, Tianjin, 300072, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Chemistry, School of Sciences, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Wei Jin Road 92, Tianjin, 300072, P. R. China. liuhuaji@tju.edu.cn.
authors.forename: Hua-Ji
authors.initials: HJ
authors.lastname: Liu
authors.affiliation: Department of Physics, Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, North Zhongshan Road 3663, Shanghai, 200062, P. R. China.
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Fu
authors.affiliation: Department of Physics, Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, North Zhongshan Road 3663, Shanghai, 200062, P. R. China.
authors.forename: Yefeng
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Department of Chemistry, School of Sciences, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Wei Jin Road 92, Tianjin, 300072, P. R. China. chenyu@tju.edu.cn.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
keywords: light-responsive; polymers; supramolecular complexes; thermoresponsive