Backbone‐Based LCST‐Type Hyperbranched Poly(oligo(ethylene glycol)) with CO2‐Reversible Iminoboronate Linkers

Abstract

AbstractDue to the very weak acidity of CO2 in water, the trigger of CO2 is always used to tune the physico‐chemical properties of polymeric materials through the protonation of organic bases rather than the hydrolysis of acid‐labile moieties contained in polymeric structures. Herein, a novel strategy of gas‐switchable lower critical solution temperature (LCST)‐type hyperbranched polymer of iminoboronate‐linked hyperbranched poly(oligo‐(ethylene glycol)) (IB‐hPOEG), by employing CO2‐acidolyzable iminoboronates as linkers and protonable tertiary amines as branch points, is presented. Upon alternative CO2 and N2, iminoboronates are partially reversibly hydrolyzed and tertiary amines are repeatedly protonated. This leads to a tunable thermo‐responsive behavior of IB‐hPOEG aqueous solution with a broad range of T cp at 28–78 °C intervals by varying the molar ratio of boronic acid, polymer concentration, or bubbling of CO2 and N2. This gas‐controllable LCST‐type hyperbranched polymer with CO2‐hydrolyzable iminoboronates is believed to have a promising potential for advanced biomedical and material applications such as drug delivery, gene transfection, functional coatings, etc.