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

• Published in: Macromolecules Vol. 38; no. 19; pp. 7957 - 7966
• Main Authors: Wiesbrock, Frank, Hoogenboom, Richard, Leenen, Mark, van Nispen, Sjoerd F. G. M, van der Loop, Michel, Abeln, Caroline H, van den Berg, Antje M. J, Schubert, Ulrich S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 20.09.2005
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Cationic copolymerization; Substituent effect; Ethyleneimine derivative polymer; Ring opening polymerization; Living polymer; Cationic polymerization; Experimental study; Solution polymerization; Thermal stability; Preparation; Diblock copolymer; Microwave irradiation; Ethyleneimine derivative copolymer; Ring opening copolymerization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma050437x

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).