Poly(γ-benzyl-L-glutamate)-functionalized single-walled carbon nanotubes from surface-initiated ring-opening polymerizations of N-carboxylanhydride

Abstract

Single-walled carbon nanotubes (SWCNTs) have been functionalized with poly(γ-benzyl-L-glutamate) (PBLG) by ring-opening polymerizations of γ-benzyl-L-glutamic acid-based N-carboxylanhydrides (NCA-BLG) using amino-functionalized SWCNTs (SWCNT-NH2) as initiators. The SWCNT functionalization has been verified by FTIR spectroscopy and transmission electron microscopy. The FTIR study reveals that surface-attached PBLGs adopt random-coil conformations in contrast to the physically absorbed or bulk PBLGs, which exhibit α-helical conformations. Raman spectroscopic analysis reveals a significant alteration of the electronic structure of SWCNTs as a result of PBLG functionalization. The PBLG-functionalized SWCNTs (SWCNT-PBLG) exhibit enhanced solubility in DMF. Stable DMF solutions of SWCNT-PBLG/PBLG with a maximum SWCNTs concentration of 259 mg L−1 can be readily obtained. SWCNT-PBLG/PBLG solid composites have been characterized by differential scanning calorimetry, thermogravimetric analysis, wide/small-angle X-ray scattering (W/SAXS), scanning electron microscopy, and polarized optical microscopy for their thermal or morphological properties. Microfibers containing SWCNT-PBLG and PBLG can also be prepared via electrospinning. WAXS characterization reveals that SWCNTs are evenly distributed among PBLG rods in solution and in the solid state where PBLGs form a short-range nematic phase interspersed with amorphous domains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2340–2350, 2010