Microwave-assisted cationic ring-opening polymerization of 2-oxazolines: A powerful method for the synthesis of amphiphilic triblock copolymers

We report on the first successful example of the preparation of triblock copolymers via a cationic ring-opening polymerization procedure. A library of 30 triblock copolymers was prepared from 2-methyl-, 2-ethyl-, 2-nonyl-, and 2-phenyl-2-oxazoline in a single-mode microwave reactor. The polymers exhibited narrow molecular weight distributions and showed only minor deviations from the targeted monomer ratio of 33:33:33. The glass-transition temperature of the triblock copolymers spanned the range from 50 to 100 degrees C depending on the incorporated monomers. The micellization behavior was investigated for some amphiphilic triblock copoly(2-oxazoline)s containing two hydrophilic and one hydrophobic blocks. The size of the micelles was larger when the hydrophobic block is located at one end of the triblock copoly(2-oxazoline) s, as measured by atomic force microscopy and dynamic light scattering.