Kinetic investigations on microwave-assisted statistical terpolymerizations of 2-oxazoline monomers

The microwave-assisted statistical terpolymerization of 2-oxazolines via a living cationic ring-opening polymerization mechanism is discussed. Kinetic investigations on the terpolymerizations of combinations of 2-methyl-2-oxazoline, 2-ethyl-2-oxazoline, 2-nonyl-2-oxazoline, and 2-phenyl-2-oxazoline were performed by heating separate polymerization mixtures for different predefined times. The resulting polymer solutions were analyzed by gas chromatography and size exclusion chromatography, demonstrating the living character of the statistical terpolymerizations. In addition, the monomer distribution throughout the polymer chains is discussed based on the linear first order kinetic plots of the separate monomers in the terpolymerizations. The observed differences in monomer distribution are expected to influence the polymer properties, which will be the focus of future investigations

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

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)