A library of 4 chain-extended homo- and 12 diblock copoly(2-oxazoline)s was prepared from 2-methyl-, 2-ethyl-, 2-nonyl-, and 2-phenyl-2-oxazoline within less than a day (total net reaction time). The living cationic ring-opening polymerization was initiated by methyl tosylate and performed in acetonitrile at 140 °C in a single-mode microwave reactor. A total number of 100 (50 + 50) monomer units was incorporated into the respective polymer chains; the thus-obtained 16 polymers exhibited narrow average molecular weight distributions (PDI <1.30). All compounds were stable up to temperatures of (at least) 300 °C. The subsequent determination of the glass-transition temperatures and the specific heats revealed a significant influence of the type of substituents attached to the polymers' backbones: the glass-transition temperature as well as the corresponding specific heat increased with an increasing rigidity of the substituents in the polymer (phenyl/methyl vs nonyl/ethyl).
Wiesbrock, F. D., Hoogenboom, R., Leenen, M. A. M., Nispen, van, S. F. G. M., Loop, van der, M., Abeln, C. H., Berg, van den, A. M. J., & Schubert, U. S. (2005). Microwave-Assisted Synthesis of a 42-Membered Library of Diblock Copoly(2-oxazoline)s and Chain-Extended Homo Poly(2-oxazoline)s and Their Thermal Characterization. Macromolecules, 38(19), 7957-7966. https://doi.org/10.1021/ma050437x