- 1 - The original publication is available at http://onlinelibrary.wiley.com/doi/10.1002/marc.201200046 Enhanced Selectivity for the Hydrolysis of Block Copoly(2-oxazoline)s in Ethanol-Water Resulting in Linear Poly(ethylene imine) Copolymers Huub P. C. van Kuringen, Victor R. de la Rosa, Martin W. M. Fijten, Johan P. A. Heuts, Richard Hoogenboom* ––––––––– H. P. C. van Kuringen, Johan P. A. Heuts, Martin W. M. Fijten Laboratory of Polymer Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600, MB, Eindhoven, The Netherlands H. P. C. van Kuringen, Victor R. de la Rosa, Richard Hoogenboom Supramolecular Chemistry Group, Department of Organic Chemistry, Ghent University, Krijgslaan 281 S4, 9000 Ghent, Belgium E-mail: richard.hoogenboom@ugent.be ––––––––– The ability of merging the properties of poly(2-oxazoline)s and poly(ethylene imine) is of high interest for various biomedical applications, including gene delivery, biosensors and switchable surfaces and nanoparticles. Moreover, the diverse end group functionality attainable in the CROP of 2-oxazolines, highly extends the application potential of such copolymers. In the present research, a methodology for the controlled and selective hydrolysis of (co)poly(2-oxazoline)s is developed in an ethanol-water solvent mixture, opening the path towards a wide range of block poly(2-oxazoline-co-ethylene imine) (POx-PEI) copolymers with tunable properties. The unexpected influence of the selected ethanol- water binary solvent mixture on the hydrolysis kinetics and selectivity is highlighted in the pursue of well defined POx-PEI block-copolymers.