Zheng Deng

Non-covalent dispersion of multi-walled carbon nanotubes in aqueous solution with hyperbranched polyethylene-g-poly(methacrylic acid)

Carbon nanotubes (CNTs) have great potential applications in biomedical materials. However, the poor solubility of CNTs in water hinders their practical applications. Thus, an amphiphilic hyperbranched polyethylene-g-poly(methacrylic acid) (HBPE-g-PMAA) was synthesized to improve the solubility of multi-walled carbon nanotubes (MWCNTs) in water. The HBPE segment provided the CH–π interactions between HBPE and MWCNTs, while the PMAA segment gave the de-bundled MWCNTs good solubility and stability. In this way, the bundled MWCNTs were found to be dispersed efficiently into individual nanotubes by the HBPE-g-PMAA. The dispersing efficiency of MWCNTs was evaluated by TGA, TEM, SEM and AFM. The maximum concentration of MWCNTs was found to be 135 mg L−1. Hence, the HBPE-g-PMAA was an efficient amphiphilic polymer-based dispersant for dispersion of MWCNTs in water, and might find potential application in biomedical systems and devices.

Synthesis of ferrocenyl hyper-branched polyethylene for non-covalent dispersion of multi-walled carbon nanotubes and fabrication of flexible carbon nanotubes-based conductive films

Ferrocenyl hyper-branched polyethylene (HBPE-g-PFcEMA) was synthesized by chain-walking polymerization followed by atom transfer radical polymerization, and then characterized by 1H NMR and GPC. HBPE-g-PFcEMA was subsequently employed to disperse multi-walled carbon nanotubes (MWCNTs) in CHCl3. It was found that the MWCNTs were efficiently dispersed by HBPE-g-PFcEMA at a concentration of 150.4 mg L−1. The dispersibility of the MWCNTs in the presence of HBPE-g-PFcEMA was evaluated by TEM and SEM. The π–π stacking interactions between the MWCNTs and HBPE-g-PFcEMA were confirmed by UV-vis spectroscopy. Fabrication of the flexible conductive film by spin-coating the MWCNTs/HBPE-g-PFcEMA dispersion on a PET substrate was explored. The resultant conductive film showed good conductivity (conductivity = 943.4 S cm−1). Furthermore, its good conductivity was retained even after being twisted or bent. Thus, the conductive film might find its potential application in flexible electronics.

Noncovalent dispersion of multi-walled carbon nanotubes with poly(tert-butyl methacrylate) modified hyperbranched polyethylene for flexible conductive films

Carbon nanotubes (CNTs) have been extensively utilized in flexible electronics. However, further applications of CNTs are limited by their poor solubility in solvents. To overcome this obstacle, poly(tert-butyl methacrylate) modified hyperbranched polyethylene (HBPE-g-PtBMA) was employed. The HBPE core was designed to endow HBPE-g-PtBMA with a hyperbranched structure while the methyl groups of poly(tert-butyl methacrylate) provide CH–π interactions between HBPE-g-PtBMA and CNTs. Besides, the relative high melting endotherm of PtBMA segments enabled HBPE-g-PtBMA with feasibility to fabricate practical HBPE-g-PtBMA/MWCNTs conductive films. The bundled MWCNTs were found to be dispersed efficiently by HBPE-g-PtBMA into individual tubes with a maximum concentration of 455 mg L−1. Furthermore, fabrication of a conductive film by spin-coating the stable MWCNTs dispersion onto the PET substrate was explored. The conductive film was found to have good conductivity (13.14 S cm−1) and flexibility, which might have potential applications in flexible electronics.

Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

Summary The topic of stimuli-responsive nanocarriers for loading guest molecules is dynamic. It has been widely studied in applications including drug controlled release, smart sensing, catalysis, and modeling. In this paper, a graft copolymer (hyperbranched polystyrene)-g-poly[2-(dimethylamino)ethyl methacrylate] (HBPS-g-PDMAEMA) was synthesized and characterized by 1H NMR and GPC. It was observed that the star-like HBPS-g-PDMAEMA formed aggregates in aqueous solution. The influence of polymer concentration, ionic strength and pH value on the aggregates in aqueous solution was investigated by using UV–vis spectroscopy and DLS analysis. The results showed that size of aggregates was affected by a corresponding stimulus. In addition, the loading ability of HBPS-g-PDMAEMA aggregates was investigated by using pyrene or Nile red as the model guest molecules by using UV–vis and fluorescence spectroscopy. The results showed that HBPS-g-PDMAEMA aggregates were capable to encapsulate small hydrophobic molecules. These newly prepared HBPS-g-PDMAEMA nanocarriers might be used in, e.g., medicine or catalysis.