Hao Kong

Constructing amphiphilic polymer brushes on the convex surfaces of multi-walled carbon nanotubes by in situ atom transfer radical polymerization

A fascinating nanoobject, amphiphilic polymer brushes with a hard core of multi-walled carbon nanotubes (MWNTs) and a relatively soft shell of polystyrene-block-poly(acrylic acid) (PS-b-PAA), was easily constructed by in situ atom transfer radical polymerization (ATRP) of styrene followed by tert-butyl acrylate on the modified convex surfaces of MWNTs (MWNT-PS) followed by hydrolysis of the grafted poly(tert-butyl acrylate) (PtBA) blocks. The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by electron microscopy (TEM and SEM), nuclear magnetic resonance (NMR) spectrometry, and thermogravimetric analysis (TGA). The results showed that both styrene and acrylate types of ATRP-active vinyl monomers can be easily initiated and then propagated on the MWNT sidewalls via the in situ ATRP approach, and the length of the PtBA blocks increases with increasing tBA : MWNT-PS weight feed ratio. We believe that the breakthrough associated with formation of such a complex nanoobject would open a door for the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structure and tailor-made properties.

Facile and large-scale synthesis and characterization of carbon nanotube/silver nanocrystal nanohybrids

A facile and efficient aqueous phase-based strategy to synthesize carbon nanotube (CNT)/silver nanocrystal nanohybrids at room temperature is reported. In the presence of carboxyl group functionalized or poly(acrylic acid)-?(PAA-) grafted CNTs, silver nanoparticles were in situ generated from AgNO3 aqueous solution, without any additional reducing agent or irradiation treatment, and readily attached to the CNT convex surfaces, leading to the CNT/Ag nanohybrids. The produced silver nanoparticles were determined to be face-centred cubic silver nanocrystals by scanning transmission electron microscopy (STEM), electron diffraction (ED) and x-ray powder diffraction (XRD) analyses. Detailed experiments showed that this strategy can also be applied to different CNTs, including single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), multiwalled carbon nanotubes (MWNTs), and polymer-functionalized CNTs. The nanoparticle sizes can be controlled from 2?nm to 10?20?nm and the amount of metal deposited on CNT surfaces can be as high as 82 wt%. Furthermore, large-scale (10 g or more) CNT/Ag nanohybrids can be prepared via this approach without the decrease of efficiency and quality. This approach can also be extended to prepare Au single crystals by CNTs. The facile, efficient and large-scale availability of the nanohybrids makes their tremendous potential realizable and developable.

pH-responsive poly(2-diethylaminoethyl methacrylate)-functionalized multiwalled carbon nanotubes

Poly(2-diethylaminoethyl methacrylate) (PDEAEMA)-coated multiwalled carbon nanotubes (MWNT-PDEAEMA) were successfully prepared by MWNT-surface initiated atom transfer radical polymerization (ATRP). The obtained MWNT-PDEAEMA nanocylinders have a core of MWNT and a shell of PDEAEMA and this core-shell structure was confirmed by TEM observations. The UV-Vis and AFM measurements showed that the MWNT-PDEAEMA exhibited obvious pH sensitivity. The solubility of PDEAEMA-coated MWNT dramatically decreased when pH increased to ca. 7.0. Because of the giant molecular weight of the molecular hybrids and local high density of polymeric grafts linked onto MWNTs, the resulting MWNT-PDEAEMA nanocomposites are easier to aggregate, or more sensitive to pH, as compared with the neat PDEAEMA.

Controlled Functionalization of Carbon Nanotubes by in Situ Polymerization Strategy

The in situ ATRP (atom transfer radical polymerization) “grafting from” approach was successfully applied to graft covalently polymers such as poly(methyl methacrylate) (PMMA) and polystyrene (PS) onto the convex surface of multi‐walled carbon nanotubes (MWNTs). The thickness of the coated polymer layers can be conveniently controlled by the feed ratio of vinyl monomer to MWNT‐supported macroinitiators (MWNT‐Br). The resulting MWNT‐based polymer brushes were characterized and confirmed with FTIR, NMR, SEM, TEM, and TGA. Moreover, the approach has been extended to the copolymerization system, affording novel hybrid core‐shell nanoobjects with MWNT as the hard core and amphiphilic copolymers as the soft shell. The approach presented here may open an avenue for exploring and preparing novel carbon nanotubes‐based nanomaterials and molecular devices with tailor‐made structure, architecture, and properties.