Novel template-less synthesis of polycyanoacrylate nanofibers

Polymer nanofibers are 1D nanostructures that are gathering significant interest because of their potential applications in a wide variety of fields such as biomedicine, separation, electronics and sensor materials. They are also fascinating structures because in some cases they posses unique properties arising from the preferential arrangement of the polymer chains parallel to the fibers axes. Challenges that synthesis techniques for polymer nanofibers face are scalability and control during fabrication. An alternate to current common approaches such as electrospinning and templated-synthesis of polymer nanofibers, is template-less synthesis of polymer nanofibers during polymerization. This approach offers the advantage of bottom-up fabrication and the potential for large scale synthesis. Herein results from an investigation using this approach for poly (ethyl 2-cyanoacrylate) [PECA] nanofiber formation are reported.;This technique is also extended to demonstrate growth of PECA nanofibers on silane-modified glass slides with varying fiber densities depending upon ECA (monomer) wettability of the glass surface. These results showcase the ability of control over placement of the fibers using this template-less synthesis approach.;Finally two examples of exercising control during synthesis of polymer nanofibers are provided. In the first case by controlling conditions during polymerization, termination steps are varied to create polymer nanofibers with different molecular weights. In the second case, random copolymer nanofibers of ethyl 2-cyanoacrylate and methyl 2-cyanoacrylate are formed by introducing both monomers simultaneously during nanofiber synthesis.;The template-less growth of PECA nanofibers is first demonstrated using the initiators present in human fingerprint residue via vapor phase polymerization of the monomer under conditions of high humidity. Studies showed that anionic initiators like the Cl- ion present in fingerprint residues is responsible for fiber formation whereas other anions such as OH - results in the formation of a polymer film under the same conditions of polymerization. Insights into individual initiator effects reveal a classification of the initiators to explain the basis for the morphology of the polymer obtained (1D fiber or 2D film). The classification based on the Hard Soft Acid Base principle implies that for faster initiation (achieved by harder anions) a polymer film is obtained versus polymer nanofibers that are obtained for slower initiation (achieved by softer anions). This suggests that for faster initiation two dimensional growth of the polymer occurs versus one dimensional growth for slower initiation rates leading to fiber formation.