Figure 3. Schematic illustration of fabrication of (a) individual spherical porous polymers from solid spherical nanoparticle templates, (b) tubular porous polymers from tubular porous templates, such as AAO, and (c) ordered macroporous polymers from colloidal crystal templates.

A unified approach to covalently functionalize graphene nanosheets based on nitrene chemistry is reported. This strategy is simple and efficient, allowing various functional moieties (e.g., hydroxyl, carboxyl, amino, bromine, long alkyl chain, etc.) and polymers (e.g., poly(ethylene glycol), polystryene) to covalently and stably anchor on graphene to produce single-layer functionalized graphene from graphene oxide in a one-step reaction. The structure and morphology of nanosheets are characterized using microscopy (AFM, SEM, TEM), spectroscopy (FTIR, XPS, Raman), thermal gravimetric analysis (TGA), and X-ray diffraction (XRD) measurements. The resulting functionalized graphene nanosheets are electrically conductive, readily dispersible in solvents and easily processable, making them promising candidates for further modification and applications such as nanohybrids, and polymer composites, etc. The presented work provides a general methodology to prepare individually dispersed graphene nanosheets with various functionalizations and properties, paving the way for the synthesis and applications of functionalized graphene materials.

The amazing properties of graphene are triggering extensive interests of both scientists and engineers, whereas how to fully utilize the unique attributes of graphene to construct novel graphene-based composites with tailor-made, integrated functions remains to be a challenge. Here, we report a facile approach to multifunctional iron oxide nanoparticle-attached graphene nanosheets (graphene@Fe(3)O(4)) which show the integrated properties of strong supraparamagnetism, electrical conductivity, highly chemical reactivity, good solubility, and excellent processability. The synthesis method is efficient, scalable, green, and controllable and has the feature of reduction of graphene oxide and formation of Fe(3)O(4) nanoparticles in one step. When the feed ratios are adjusted, the average diameter of Fe(3)O(4) nanoparticles (1.2-6.3 nm), the coverage density of Fe(3)O(4) nanoparticles on graphene nanosheets (5.3-57.9%), and the saturated magnetization of graphene@Fe(3)O(4) (0.5-44.1 emu/g) can be controlled readily. Because of the good solubility of the as-prepared graphene@Fe(3)O(4), highly flexible and multifunctional films composed of polyurethane and a high content of graphene@Fe(3)O(4) (up to 60 wt %) were fabricated by the solution-processing technique. The graphene@Fe(3)O(4) hybrid sheets showed electrical conductivity of 0.7 S/m and can be aligned into a layered-stacking pattern in an external magnetic field. The versatile graphene@Fe(3)O(4) nanosheets hold great promise in a wide range of fields, including magnetic resonance imaging, electromagnetic interference shielding, microwave absorbing, and so forth.

Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) with ppm amount of Cu catalyst was successfully developed in water. For the first time, Cu catalyst concentrations of 100 ppm and lower were used in aqueous media to prepare well-defined macromolecules. Polymers of oligo(ethylene oxide) methyl ether acrylate were synthesized with low dispersity (M w /M n = 1.15−1.28) using 20−100 ppm of an active CuBr/tris(pyridin-2-ylmethyl)amine-based catalyst in the presence of excess bromide anions. This technique was used to synthesize a thermoresponsive block copolymer of poly(oligo(ethylene oxide) methyl ether methacrylate)-b-poly(oligo(ethylene oxide) methyl ether acrylate). The methacrylic block had a lower critical solution temperature (LCST = 77 ± 2 °C) below that of the acrylic block. The hydrodynamic diameter of ca. 10 nm at temperatures below the LCST is consistent with free polymer chains in solution, and the diameter of ca. 30 nm above the LCST is consistent with a micellar structure. The aqueous ICAR ATRP technique was also used to successfully synthesize a well-defined bioconjugate by growing poly(oligo(ethylene oxide) acrylate) from a bovine serum albumin (BSA) protein functionalized with ca. 30 ATRP initiating sites.

Poly(ionic liquid)s (PILs) are an important class of technologically relevant materials. However, characterization of well-defined polyionic materials remains a challenge. Herein, we have developed a simple and versatile gel permeation chromatography (GPC) methodology for molecular weight (MW) characterization of PILs with a variety of anions. PILs with narrow MW distributions were synthesized via atom transfer radical polymerization, and the MWs obtained from GPC were further confirmed via nuclear magnetic resonance end group analysis.

A facile, green, low cost and efficient one-step technology to synthesize highly dispersible functional single-walled and multiwalled carbon nanotubes (f-SWNTs and f-MWNTs) up to supergrams is reported. Large-scale (up to hundreds of grams) synthesis of functional azides was developed at first, and various reactive groups (i.e., -OH, -NH 2 , -COOH, and -Br) were then introduced onto the convex surfaces of CNTs in merely one reaction of nitrene addition under a relatively mild condition without causing significant damage to nanotubes. The contents of the functional moieties can be easily controlled by adjusting the feed ratio of the azide compounds to CNTs. In order to demonstrate the reactivity and functions of the immobilized organic moieties, different chemical reactions, including surface-initiated polymerizations, amidation, and reduction of metal ions, were performed on the functional CNTs, affording various CNT-polymer and CNT-Pt nanohybrids. The resulting materials were characterized by various measurements, such as TGA, Raman, XPS, FTIR, NMR, XRD, SEM, TEM, and HRTEM. The presented one-step methodology opens the avenue for industrial production of functional CNTs.

Several polymeric materials were prepared for reversible CO 2 capture. These materials contain quaternary ammonium ions and hydroxide counter ions, including polymers grafted from carbon black, crosslinked porous polymers templated by ordered colloidal crystals, and high internal phase emulsion systems. The porous polymers displayed an order of magnitude improvement in the kinetics of the absorption and desorption processes and a significant improvement in the swing sizes compared to a commercially available material with similar functional groups. This work suggests a new direction for the design of porous polymeric materials for CO 2 air capture.

The covalent functionalization of multiwalled carbon nanotubes (MWNTs) by layer-by-layer (LbL) click chemistry is reported. The clickable polymers of poly(2-azidoethyl methacrylate) and poly(propargyl methacrylate) were synthesized at first by atom transfer radical polymerization (ATRP) of 2-azidoethyl methacrylate and reverse addition-fragmentation chain transfer (RAFT) polymerization of propargyl methacrylate, respectively. The two polymers were then alternately coated on alkyne-modified multiwalled carbon nanotubes using Cu(I)-catalyzed click reaction of Huisgen 1,3-dipolar cycloaddition between azides and alkynes. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements confirm that the quantity and thickness of the clicked polymer shell on MWNTs can be well controlled by adjusting the cycles or numbers of click reaction and the polymer shell is uniform and even. X-ray photoelectron spectroscopy (XPS) and Fourier tranform infrared (FTIR) measurements showed that there were still a great amount of residual azido groups on the surfaces of the functionalized MWNTs after clicking three layers of polymers. Furthermore, alkyne-modified rhodamine B and monoalkyne-terminated polystyrene were subsequently used to functionalize the clickable polymer grafted MWNTs, giving rise to fluorescent carbon nanotubes (CNTs) and CNT-based polystyrene brushes, respectively. It demonstrates that the residual azido groups on the surfaces of MWNTs are available for further click reaction with various functional molecules.