Controlling Phase Transition Behavior of Thermally Responsive Metal Affinity Hydrogels:  A Molecular Design Approach

Abstract

A molecular design approach is used to develop thermally responsive metal affinity hydrogels of N-isopropylacrylamide which can retain the nature of the overall volumetric response of the base gels and provide highly specific affinity separation. The synthesis of a novel iminodiacetic acid monomer to obtain metal affinity hydrogels with the right hydrophobic/hydrophilic balance is described and compared to a grafting technique presented in an earlier study. Copolymerization of this monomer with N-isopropylacrylamide and detailed characterization of both materials by various spectroscopic and elemental analysis techniques are presented. Preliminary experiments on the equilibrium swelling and critical analysis of the phase transition of the N-isopropylacrylamide gels incorporated with these novel metal affinity groups indicate that these gels retain the phase transition behavior of the base gels.

Polymer‐Based Stimuli‐Responsive Recyclable Catalytic Systems for Organic Synthesis

“…Subsequently, the same group34 reported the incorporation of Au nanoparticles with different sizes within a porous, chelating and responsive hydrogel of poly( N ‐isopropylacrylamide)‐ co ‐poly[2‐methacrylic acid 3‐(bis‐carboxymethylamino)‐2‐hydroxypropyl ester] (PNIPAM‐ co ‐PMACHE) for catalytic aerobic oxidation of alcohol 3 ( Scheme ). The resultant composite was thermoresponsive, which could reversibly deswell/swell at the volume‐phase‐transition temperature (VPTT)35 similar as the hydrogel itself. The studies on catalytic aerobic alcohol oxidation showed that the catalytic activity of the thermoresponsive composite was strongly dependent on the size of the encapsulated Au nanoparticles and the catalyst had satisfactory performance because the reactant of alcohol 3 was highly concentrated within hydrogel matrix through the reversible deswelling.…”