Synthesis, Microwave‐Assisted Polymerization, and Polymer Properties of Fluorinated 2‐Phenyl‐2‐oxazolines: A Systematic Study

• Published in: Chemistry : a European journal 2008-11, Vol.14 (33), p.10396-10407
• Main Authors: Lobert, Matthias, Thijs, Hanneke M. L., Erdmenger, Tina, Eckardt, Rebecca, Ulbricht, Christoph, Hoogenboom, Richard, Schubert, Ulrich S.
• Format: Article
• Language: English
• Subjects: fluorine; oxazolines; polymerization; surface energy; thermal properties
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200800671

We present a detailed systematic study of the synthesis and ability of fluorinated 2‐phenyl‐2‐oxazolines to undergo polymerization. The synthesis of these compounds is based on a two‐step procedure that gives the desired 2‐oxazolines in moderate‐to‐good yields. All the compounds were fully characterized by IR and NMR (1H, 13C, and 19F) spectroscopy, mass spectrometry, and elemental analysis. The 2‐oxazolines were subsequently used as monomers for living cationic ring‐opening polymerization (CROP) with microwave irradiation as the heat source (T=140 °C), nitromethane as the solvent, and methyl tosylate as the initiator. The linear first‐order kinetic plots of the polymerizations accompanied by a linear increase of the molecular weight with conversion and low polydispersity index (PDI) values (generally below 1.30) indicate a living polymerization mechanism. The resulting polymerization rates reflect a strong sensitivity to the quantity of fluorine substituents in general and the presence or absence of ortho‐fluoro substituents of the phenyl ring in particular. All the polymers were isolated and characterized by size‐exclusion chromatography and MALDI‐TOF mass spectrometry. Finally, a detailed investigation of selected polymer properties was performed by using differential scanning calorimetry, thermogravimetric analysis, and contact‐angle measurements, thus resulting in structure–property relationships. Whereas the thermal properties of the polymers are mostly influenced by the presence of ortho‐fluoro substituents, the surface properties are mainly determined by the presence of para‐ and/or meta‐fluoro substituents. Given all the possibilities…︁ living cationic ring‐opening polymerization was performed on all possible fluorinated 2‐phenyl‐2‐oxazolines. Selected thermal properties and surface properties of the resulting polymers reveal structure–property relationships for the polymerization rates (kp), thermal properties, and the surface energies (SEs; see the picture).