Synthesis of new polymethyloxazoline hydrogels by the "macroinitiator" method

New polymethyloxazoline hydrogels are synthesized by the cationic ring-opening copolymerization of 2-methyl-2-oxazoline and 2,2′-tetramethylenebis(2-oxazoline), using random copolymers of chloromethylstyrene and methyl methacrylate, or of chloromethylstyrene and styrene as macroinitiators. The synthesis is carried out in benzonitrile at 110 °C in the presence of potassium iodide, which activates the chloromethyl group as initiating functionality. In general, the hydrogels are obtained very rapidly, with a yield of between 42 and 95 wt.-%. Besides its initiating function, the macroinitiator also provides the possibility of introducing heterogeneity into the hydrogel structure by forming rigid hydrophobic domains. The hydrogel structures were characterized by high-resolution magic angle spinning NMR spectroscopy, and their solvent absorption capacity was determined by swelling experiments in solvents of different polarity. The hydrogels showed a maximal swelling degree of 18 g of water and 40 g of methanol, respectively, per gram of the hydrogel.