Mechanism insights in controlling host-guest (de)complexation by thermoresponsive polymer phase transitions
Résumé
The combination of (thermo)responsive polymers with supramolecular chemistry recently allowed the development of adaptative materials based on the reversible regulation of host-guest complexation. The properties of these artificial systems rely on their synthetic design, which requires a perfect understanding of the mechanisms triggering the thermo-induced decomplexation. Despite recent progress, the origins of this phenomenon are still not fully understood. To investigate the effect of phase separation mechanism and thermodynamics on the host-guest (de)complexation behavior, different naphthalene-functionalized (guest) thermoresponsive polymers, including lower critical solution temperature (LCST) and upper critical solution temperature (UCST) polymers, were prepared. The hostguest complexation of the polymers with cyclobis(paraquat-p-phenylene) (Blue Box) was investigated in water at different temperatures. Host-guest complexation was lost upon heating-induced hydrophobic phase separation of complexed guest-functionalized LCST-polymers, while, in contrast, the host-guest complex was retained upon cooling-induced hydrogen bond-driven phase separation of a complexed guest-functionalized UCST polymer. This comparative analysis showed that the mechanism behind the thermoresponsive polymer phase separation is a key factor that dominates the host-guest (de)complexation.
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