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

Abstract

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 microm. Exposure to a solution of sodium azide (NaN(3)) 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) (PNIPAM(AT)), 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 degrees C (water contact angle approximately 140 degrees) and having a hydrophilic surface at 20 degrees C (water contact angle approximately 30 degrees).

Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled Radical Polymerization

“…Polymer brush growth from electrospun fibers has typically been achieved using ATRP polymerization of a variety of different monomers. In most approaches that are directed towards biomedical applications, the initiating group is incorporated as a post electrospinning modification before polymerization has been undertaken 17, 18, 19, 20, 21, 22. Our strategy offers significant advantages to this by incorporating the initiator as an end‐group to the polymer prior to electrospinning to allow precise control over the spatial position of the functional groups without disrupting the fiber architecture.…”

Temperature-responsive electrospun nanofibers for ‘on–off’ switchable release of dextran

“…an amine or a thiol) and a vinyl group [42]. Nowadays, 'click chemistry', typified by the condensation reaction between an azido group and a triple bond, is extensively used because the reactions occur at low temperatures, give high yields and are tolerant to various media as they can be carried out in the presence of oxygen and even in water [43,44]. In the case of NIPAAm-based NFs, however, post-crosslinking has to be carried out under dry conditions because these NFs dissolve not only in aqueous media but also in various organic solvents.…”

The Design of Temperature-Responsive Nanofiber Meshes for Cell Storage Applications

“…functional nanofibers with core-shell structure prepared through coaxial electrospinning extend the applications of nanofibers to drug delivery [18]. Except for functional nanofibers fabricated from electrospinning with the combined installations mentioned above, nanofibers with "smart" or "stimuli-responsive" surfaces are of great interest for such applications as "on-off" switchable control of permeability, wettability, and/or swelling/deswelling behavior [19]. Because the electrospun fibers have a much larger external surface area, the meshes or mats electrospun from smart polymers display much quicker response times than the corresponding bulk materials such as hydrogels.…”