THF-Functionalized Polyethers: Biosourced Monomers, Tunable Thermoresponsiveness, and Iron-Selective Adsorption

Biosourced polymers and aqueous thermoresponsive polymers have both received broad attention, but the two attributes are rarely merged. Here, furfural-derived alcohol and carboxylic acid are transformed into tetrahydrofuran(THF)-bearing epoxides, tetrahydrofurfuryl glycidyl ether (F 2 GE) and glycidyl 2-tetrahydrofuroate, by reacting with epichlorohydrin. Ring-opening polymerization catalyzed by an organic Lewis pair occurs in a highly selective manner, producing THF-functionalized polyethers with controlled molar mass (5.6–22.7 kg mol –1 ) and low dispersity (1.09–1.12). Nonbiosourced (tetrahydrofuran-3-yl)methyl glycidyl ether is also synthesized and polymerized for comparison. The polyethers exhibit high thermal stability, minimal cytotoxicity, and structure-dependent cloud point temperature ( T cp ) in water with polyF 2 GE showing the highest T cp (24.1–37.3 °C) at all concentrations (0.1–1.0 mg mL –1 ). Alkali metal halides exhibit variable “salting-in/-out” effects, with T cp increased by NaI, LiI, or LiBr and decreased by NaCl, NaBr, or KCl. Also interestingly, the THF functionalities allow polyF 2 GE to selectively adsorb Fe 3+ (95.3%) from an aqueous solution containing other ions (Ni 2+, Co 2+, and Mn 2+ ) above T cp .