A Simple Method to Grow Polymer Nanofibers from Superglue
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0948-B02-04
A Simple Method to Grow Polymer Nanofibers from Superglue Pratik Mankidy1, Ramakrishnan Rajagopalan2, Carlo Pantano2, and Henry Foley1 1 Chemical Engineering, Penn State University, 166 Fenske Lab., Penn State University, University Park, PA, 16802 2 Materials Research Institute, Penn State University, University Park, PA, 16802
ABSTRACT A novel template-less method for polymerization of ethyl 2-cyanoacrylate to form an intrinsically nanofibrous polymer is investigated. Effect of the anionic initiator used for polymerization is examined to explain the mechanism of formation of nanofibers or film of polymer. A suitable classification of the initiators is established based on the Hard Soft Acid Base principle to explain the mechanism. Infrared analysis, SEM and Gel permeation chromatography is utilized for characterization of the different polymer samples. INTRODUCTION There is little question that nanomaterials are becoming major contenders not only in the development of new technologies but also in replacing current ones in medicine, electronics, textiles, and separations to name a few1. Polymer nanofibers/nanowires, a subset of these nanomaterials are currently made by various top down and bottom-up approaches. These include utilizing nanosized pores of a membrane as a mould or templated in-situ growth of structures in these pores2, electrospinning3 of polymer nanofibers and phase separation techniques4. In our recent work5, we were successful in employing a new and novel bottom-up approach for the fabrication of polymer nanofibers. This technique was illustrated by the fabrication of SuperGlueÆ (ethyl-2-cyanoacrylate) nanofibers. The method does not require any template and is carried out under relatively easier conditions than the other approaches of fabrication. Herein we report the effect of different initiators on the growth of the poly (ethyl 2-cyanoacrylate) [PECA] nanofibers. THEORY Ethyl 2-Cyanoacrylate (ECA) undergoes rapid anionic polymerization initiated by a suitable nucleophile (Nu-). Polymerization proceeds by successive addition of monomer units to the living carbanion end of the polymer chain as shown in Scheme 16.
Nu-
H C H
C N Nu
C C O OC2H5
H C H
C N C C O OC2H5
H C H
C N
n
C
Nu
C O OC2H5
H C H
C N C O OC2H5
ECA monomer INITIATION
H C H
C
PROPAGATION
Scheme 1: Ethyl 2-cyanoacrylate initiation and propagation steps
n
C N C C O OC2H5
Initiators for the polymerization range from covalent bases such as ammonia and pyridine to ions such as chloride, acetate, sulfate, phosphate and even water. As ions are initiators this polymerization is used in forensic science as a method to develop latent fingerprints at crime scenes7. The monomer vapor exposed to the fingerprint polymerizes on the ridges of the ionic salts laden fingerprint residue. This process called fuming is sometimes enhanced by exposing the fingerprint residue to a humid atmosphere first. Water serves in two ways; as an initiator for polymerization and to solvate the ions present in the finger print resi
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