Abstract
Covalently functionalized multi-walled carbon nanotubes (MWNTs) were prepared by grafting well-defined thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click reactions. First, azide-terminated poly(N-isopropylacrylamide) (N3-PNIPAM) was synthesized by reversible addition fragmentation chain-transfer (RAFT) polymerization, and then the N3-PNIPAM moiety was connected onto MWNTs by click chemistry. The products were characterized by means of FT-IR, TGA and TEM. The results show that the modification of MWNTs is very successful and MWNTs functionalized by N3-PNIPAM (MWNTs-PNIPAM) have good solubility and stability in water. TEM images show the functionalized MWNTs are dispersed individually, indicating that the bundles of original MWNTs are separated into individual tubes by surface modification with polymer chains. These MWNTs modified with PNIPAM represent a potential nano-material for preparation of hydrophilic composite materials.
Highlights
Carbon nanotubes (CNTs) [1] have attracted extensive industrial and academic attention thanks to their exciting potential applications in sensors [2], nanocomposites [3], molecular devices [4] or advanced materials with electronic properties [5]
As illustrated in Scheme 1, azide-decorated PNIPAM, namely N3-PNIPAM, was prepared through reversible addition fragmentation chain-transfer (RAFT) polymerization, and multi-walled carbon nanotubes (MWNTs) were covered with alkyne groups; the MWNTs modified with PNIPAM were obtained through coupling reaction via click chemistry
MWNTs-COOH were treated with thionyl chloride and reacted with excess propargyl alcohol to obtain MWNTs-alk where the alkyne groups should be connected on the surface
Summary
Carbon nanotubes (CNTs) [1] have attracted extensive industrial and academic attention thanks to their exciting potential applications in sensors [2], nanocomposites [3], molecular devices [4] or advanced materials with electronic properties [5] Their inherent insolubility in most organic and aqueous solvents, together with the poor chemical and biological compatibility of CNTs, are the major limitations to the solution-phase manipulation and processability of these structures, greatly hindering the wide application of CNTs in practical use [6]. The copper-catalyzed azide-alkyne cycloaddition (click chemistry) discovered by Sharpless has been widely employed and confirmed to be highly efficient [25,26,27,28] It would be very convenient and effective to graft polymer chains to CNTs by using such a coupling reaction. The azide-terminated polymer was coupled and MWNTs were functionalized via Cu(I)-catalyzed 1,3-dipolar cycloaddition
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