Synthesis and Polymerization of Thiophene-Bearing 2-Oxazolines and 2-Oxazines.

Intrinsically conductive polymers have garnered a great deal of attention for use in medical and bioelectronic applications. Despite this, challenges associated with the mechanical stability, processability, and fabrication of conducting polymers have limited their utility. To circumvent these limitations, thiophene substituted 2-oxazolines (2Ox) and 2-oxazines (2Ozi) are introduced, which can be polymerized to form a thermally stable and potentially melt-processable polymers as precursors for conductive polymers. A series of such monomers are synthesized and yields above 50% are obtained for gram scale reactions. The monomers can subsequently be polymerized using standard cationic ring-opening methods to yield thiophene-bearing poly(2-oxazoline)s (POx) and poly(2-oxazine)s (POzi) with narrow to moderate dispersity. The polymers exhibit glass transition temperatures between 50 °C and 100 °C and thermal stability beyond 250 °C. Moreover, random copolymers can be produced by introducing aliphatic 2-oxazolines during polymer synthesis, which facilitates tailoring of the polymer properties and may enable new applications in melt extrusion printing or electrospinning of precursors for conducting polymer systems. Overall, a facile approach is described for the synthesis of thiophene-functionalized monomers and polymers, providing covalent integration of thiophenes that opens new avenues toward the generation of functional and stimuli-responsive biomaterials.