Modular ambient temperature functionalization of carbon nanotubes with stimuli-responsive polymer strands

Abstract

Cyclopentadienyl end-capped poly(N-isopropylacrylamide) (PNIPAM-Cp, M_n = 5400 g mol⁻¹, PDI = 1.13) was synthesized via a combination of RAFT (Reversible Addition–Fragmentation Chain Transfer) polymerization and modular conjugation (characterized via Nuclear Magnetic Resonance (NMR) as well as Electrospray Ionization-Mass Spectrometry (ESI-MS)), and reacted with untreated Single Walled Carbon Nanotubes (SWCNTs) as dienophiles in a Diels–Alder reaction with PNIPAM-Cp (diene) at ambient temperature in the absence of any catalyst. The obtained stimuli-responsive hybrid materials display thermo-responsive behaviour evidenced via UV-VIS-spectroscopy and Dynamic Light Scattering (DLS). The grafting density of the PNIPAM chains at the surface of the SWCNTs was determined via Thermogravimetric Analysis (TGA), Elemental Analysis (EA) and X-ray Photoelectron Spectroscopy (XPS), to be close to 0.0288 chains per nm².