Yusong Wang

Synthesis and characterization of water-soluble multiwalled carbon nanotubes grafted by a thermoresponsive polymer

Water-soluble multiwalled carbon nanotubes (MWNTs) with temperature-responsive shells were successfully prepared by grafting poly (N-isopropylacrylamide) (PNIPAM) from the sidewalls of MWNTs, via surface reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized MWNTs as the chain transfer agent. Thermogravimetric analysis (TGA) measurements showed that the weight composition of the as-grown PNIPAM polymers on the MWNTs can be well controlled by the feed ratio (in weight) of NIPAM to RAFT agent functionalized MWNTs (MWNT-SC(S)Ph). The MWNT-g-PNIPAM has good solubility in water, chloroform, and tetrahydrofuran (THF). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images also showed that the MWNT-g-PNIPAM was dispersed individually and eventually bonded with the polymer layer by surface RAFT polymerization. The PNIPAM shell is very sensitive to a change of temperature. This method could find potential applications by grafting other functional polymer chains onto MWNTs.

Fabrication of silver/cross-linked poly(vinyl alcohol) cable-like nanostructures under γ-ray irradiation

Ag/cross-linked poly(vinyl alcohol) (PVA) cable-like nanostructures were synthesized with control in an aqueous solution of a hydrolysable amphiphilic block polymer, poly(vinyl acetone) (PVKA) (ketalization degree DH = 0.533) under γ-ray irradiation, via one-step in situ reduction of Ag+ and cross-linking of alcohol units. In the present approach, we try to control the speed of the cross-linking reaction of PVA chains (alcohol units), which are yielded from the hydrolysed PVKA, utilizing the low hydrolysis rate of the PVKA in dilute acidic solution.

One-step functionalization of multi-walled carbon nanotubes with Ag/polymer under γ-ray irradiation.

We reported an easy strategy of using γ-ray irradiation to functionalize multi-walled carbon nanotubes (MWCNTs) without the use of aggressive acid treatment, all in a single processing step. In this paper, we tried to decorate MWCNTs with Ag nanoparticles relying on covalently bonded polymers, via one-step covalent grafting of the polymer to the surface of MWCNTs, and simultaneous reducing of Ag(+) ions to Ag which are then efficiently anchored onto the MWCNTs. Herein, the polymer involved was the commercially available polymer poly(vinyl alcohol) (PVA) and two of its derivatives, polyvinylacetone with ketalization degree D(H) = 0.22 and 0.53. It is envisioned that this simple but efficient method could be extended to fabricate other CNT-based hybrids for both theoretical study and applications in biological and technological fields.

Functionalized carbon nanotubes with polystyrene-block-poly (N -isopropylacrylamide) by in situ RAFT polymerization

A fascinating nano-object, amphiphilic polymer brushes with a hard core of multiwalled carbon nanotubes (MWNTs) and a relatively soft shell of polystyrene-block-poly (N-isopropylacrylamide) (PS-b-PNIPAM), was easily constructed by in situ surface reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene followed by N-isopropylacrylamide on the modified convex surfaces of MWNTs (MWNT-PS). The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by Fourier-transform infrared (FTIR) spectrometry, nuclear magnetic resonance (NMR) spectrometry, thermogravimetric analysis (TGA) and Raman spectroscopic analysis. The MWNT-PS-b-PNIPAM that was produced has a PNIPAM block, which is very sensitive to temperature. Such a complex nano-object could open a door to the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structures and tailor-made properties.

In situ formation of Ag flowerlike and dendritic nanostructures in aqueous solution and hydrolysis of an amphiphilic block copolymer

Silver flowerlike and dendritic nanostructures were synthesized in an aqueous solution of a hydrolysable amphiphilic block copolymer polyvinylacetone (PVKA) via in situ reduction of Ag(+) and hydrolysis of PVKA at room temperature. Compared with a previous result, the complete hydrolysis time of PVKA is greatly shortened in this process.

Controlled synthesis of novel 3D dendritic Bi2S3 /cross-linked poly(vinyl alcohol) nanocomposites

Novel spherical three-dimensional (3D) dendritic Bi2S3 /cross-linked poly(vinyl alcohol) (PVA) nanocomposites were successfully synthesized in aqueous solution of amphiphilic polyvinylacetone (PVKA) (ketalization degree DH = 0.549), via one-step in situ decomposition of the complex [Bi(Tu)x]3+ under γ-ray irradiation, utilizing the controllable hydrolysis property of PVKA in acidic solution. Herein, PVA chains are obtained from the hydrolysed PVKA. These uniform 3D spherical nanocomposites have a structure similar to that found in the natural lotus leaf, where every microscale papilla on the leaf surface is covered by nanoscale papillae.

Novel dendritic nanostructures: self-assemblies of nanoparticles of poly(vinyl alcohol) coated Ag and/or Cu2O

Novel dendritic nanostructures, which are actually self-assemblies of nanoparticles of poly(vinyl alcohol) (PVA) coated Ag and/or Cu2O, were controllably synthesized in an aqueous solution of amphiphilic polyvinylacetone (PVKA) (DH = 0.549), via a one-step in situ reduction of Ag+ and Cu2+ under γ-ray irradiation, using the low hydrolysis rate of the PVKA in the dilute acidic solution. Subsequently, the hydrolysis of PVKA yields PVA chains.

pH-Responsive cagelike porous polymer microspheres prepared via consecutive RAFT polymerization induced by γ-ray radiation

Although RAFT polymerization in a homogeneous system has been widely studied, RAFT mediated polymerization on a solid–liquid surface has rarely been mentioned. In this work, a two-step consecutive RAFT polymerization of methyl methacrylate (MMA) and acrylic acid (AA) on the sulfonated polystyrene (SPS) microspheres dispersed in water was achieved under γ-ray radiation. As a result, poly(acrylic acid) (PAA)-grafted cagelike porous SPS/PMMA microspheres with distinct pH-responsive release properties have been fabricated. The RAFT mediated polymerization on the surface of porous microspheres has been discussed in detail based on the 1H NMR spectra combined with the 2D 1H–13C heteronuclear singular quantum correlation (HSQC) spectra. This work not only enriches the mechanism of heterogeneous surficial RAFT polymerization, but also indicates that γ-ray radiation induced RAFT mediated polymerization on a solid–liquid surface should be a practical technique for the fabrication of porous materials with subtle controllable surface properties.

Synthesis and characterization of CO2-sensitive temperature-responsive catalytic poly(ionic liquid) microgels

We report a class of poly(anionic liquid) microgels that are sensitive to carbon dioxide (CO2). Such microgels have been synthesized from free radical precipitation polymerization of tetrabutylphosphonium 4-styrenesulfonate, 1-vinyl-1H-imidazole and the crosslinker N,N′-methylenebisacrylamide. Upon bubbling with N2, these microgels can undergo reversible volume phase transition in response to a change in temperature, showing a lower critical solution temperature (LCST) in water, but showing an upper critical solution temperature (UCST) in dimethylacetamide, such that the temperature-responsive volume phase transition behavior can be readily tuned over a significant wide range in a mixture of water/dimethylacetamide by varying the mol ratio of the two solvents, resulting in a phase diagram displaying a co-solvency phase separation phenomenon; however, upon bubbling with CO2, they obey LCST-type volume phase transition behavior in both water, dimethylacetamide, and water/dimethylacetamide mixtures. Moreover, these microgels behave as catalysts in a model cycloaddition of CO2 to 1,2-epoxybutane in dimethylacetamide under atmospheric pressure (1 atm CO2) and display merits of both homogeneous (considerable high efficient catalytic activity) and heterogeneous (excellent recyclability) catalysis. With both the responsive and catalytic properties harnessed on the same object, the microgels react to external stimuli and allow catalytic properties to be altered accordingly to a certain extent in a non-monotonous way, making it possible to boost the reaction at a relatively lower temperature (e.g., ca. 50 °C) while maintaining considerable catalytic activity.

Formation and Characteristics of Acrylonitrile/Urea Inclusion Compound

The formation process and composition of the acrylonitrile/urea inclusion compounds (AN/UIC) with different aging times and AN/urea molar feed ratios are studied by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). It is suggested that DSC can determine the guest/host ratio and the heat of decomposition. Meanwhile, the guest/host ratio and heat of decomposition are obtained, which are 1.17 and 5361.53 J/mol, respectively. It is suggested AN molecules included in urea canal lattice may be packed flat against each other. It is found that the formation of AN/UIC depends on the aging time. XRD results reveal that once AN molecules enter urea lattice, AN/UIC are formed, which possess the final structure. When AN molecules are sufficient, the length of AN molecular arrays in urea canals increases as aging time prolonging until urea tunnels are saturated by AN.