Using light to tune thermo-responsive behavior and host-guest interactions in tegylated poly(azocalix[4]arene)s

Polymers consisting of azocalix[4]arenes in the main chain and tetraethylene glycol monomethyl ether chains in the lower rim of the calix[4]arene units have been prepared. The polymers undergo reversible photoisomerization between the trans and the cis forms, the extent of which depends on the solvent. A lower critical solution temperature (LCST) type behavior is observed for aqueous solutions of the polymers, which is strongly affected by the molar mass and concentration. More importantly, the same polymers exhibit an upper critical solution temperature (UCST) type transition in alcohols. It is shown that the temperature of the phase transition in alcohols decreases proportionally to the decrease in the trans content of the samples thus offering a unique possibility to reversibly tune the UCST behavior by adjusting the irradiation exposure time. An exciting photoassisted writing on solutions of the polymer in alcohols is demonstrated. Furthermore, the host-guest complex formation with a low molar mass guest is influenced by the photostationary state of the polymers.