Three‐Component Supramolecular System with Multistimuli‐Responsive Properties in Water |
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| Authors: | Bin Wang Dr Hua‐Ji Liu Xiao‐Bin Fu Prof?Dr Yefeng Yao Prof?Dr Yu Chen |
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| Affiliation: | 1. Department of Chemistry, School of Sciences, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, P. R. China;2. Department of Physics, Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, P. R. China |
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| 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 1H and 2D ROESY 1H 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. |
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| Keywords: | light-responsive polymers supramolecular complexes thermoresponsive |
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