Smart Nanofibers from Combined Living Radical Polymerization, “Click Chemistry”, and Electrospinning

A simple method for preparing solvent-resistant nanofibers with a thermal-sensitive surface has been developed by the combined technology of reversible addition-fragmentation chain-transfer (RAFT) polymerization, atom transfer radical polymerization (ATRP), electrospinning, and “click chemistry”. Initially, well-defined block copolymers of 4-vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA) (PVBC-b-PGMA) were prepared via RAFT polymerization. Electrospinning of PVBC-b-PGMA from a solution in tetrahydrofuran gave rise to fibers with diameters in the range of 0.4−1.5 μm. Exposure to a solution of sodium azide (NaN3) not only affords nanofibers with azido groups on the surface but also leads to a cross-linking structure in the nanofibers. One more step of “click chemistry” between the PVBC-b-PGMA nanofibers with azido groups on the surface (PVBC-b-PGMA−N3) and alkyne-terminated polymers of N-isopropylacrylamide (NIPAM) (PNIPAMAT), which were prepared by ATRP, allows the preparation of a PVBC-b-PGMA nanofiber with thermal-sensitive PNIPAM brushes on the surface (PVBC-b-PGMA-g-PNIPAM). PVBC-b-PGMA-g-PNIPAM nanofibers exhibit a good resistance to solvents and thermal-responsive character to the environment, having a hydrophobic surface at 45 °C (water contact angle ∼140°) and having a hydrophilic surface at 20 °C (water contact angle ∼30°).