Solvent Dependency in the Synthesis of Multiblock and Cyclic Poly(2-oxazoline)s

• Published in: Macromolecules 2021-06, Vol.54 (12), p.5549-5556
• Main Authors: Drain, B. A, Beyer, V. P, Cattoz, B, Becer, C. R
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.1c00529

Multiblock copolymers as well as cyclic polymers exhibit unique physical properties and are being utilized in various applications. However, the synthesis of such polymers is quite challenging because there is a delicate balance in achieving either structure. Here, we report a surprising solvent dependence on the cyclization and step-growth reactions of poly­(2-alkyl 2-oxazoline)­s. Additionally, other important parameters such as catalyst concentration, polymer concentration, and temperature were investigated, and their influences on the obtained ratio between step-growth and cyclization polymers are discussed. Step growth of a telechelic poly­(2-ethyl 2-oxazoline) macromonomer yielded a multiblock polymer containing, on average, eight repeating units. Moreover, reaction conditions in order to favor cyclization over step-growth polymerization were optimized for poly­(2-fatty acid-2-oxazoline). Finally, using the optimized conditions, an up to 80:20 cyclization/step-growth polymer mixture was obtained at a relatively high polymer concentration (50 mg/mL).