Hongbiao Chen

Preparation and characterization of maleic anhydride-functionalized syndiotactic polystyrene

Abstract The free radical-induced grafting of maleic anhydride (MA) onto syndiotactic polystyrene (sPS) has been accomplished in the solution process by using 1,1,2-trichloroethane as solvent and dicumyl peroxide as free radical initiator. The amount of MA grafted on sPS was evaluated by a titration method. Grafted products separated from the reaction mixture were purified and analyzed. Fourier transform infrared spectroscopy and 1 H NMR studies indicate that MA attaches to the sPS in the form of single succinic anhydride rings as well as short oligomers. The results obtained by GPC analysis suggest that the degradation and chain extension reaction do not occur under the reaction conditions. Moreover, the crystallization behavior of MA-functionalized sPS was also studied by means of differential scanning calorimetry. It was found that the crystallization behavior of the grafted polymer exhibited somewhat differences in comparison to the neat sPS. The MA-functionalized sPS crystallizes at higher rate than the unmodified polymer, on the other hand, the degree of crystallinity ( X c ) are lowered by the presence of the MA grafts.

Colorimetric fluorescent cyanide chemodosimeter based on triphenylimidazole derivative.

In this paper, we demonstrated a highly selective colorimetric chemodosimeter for cyanide anion detection. This chemodosimeter having a triphenylimidazole group as a fluorescent signal unit and a dicyano-vinyl group as a reaction unit was synthesized by the Knoevenagel condensation of 4-(4,5-diphenyl-1H-imidazol-2-yl)benzaldehyde with malononitrile in a reasonable yield. The probe exhibited an intramolecular charge transfer (ICT) absorption band at 420 nm and emission band at 620 nm, respectively. Upon the addition of cyanide anion, the probe displayed a blue-shifted spectrum and loss in color due to the disruption of conjugation. With the aid of the fluorescence spectrometer, the chemodosimeter exhibited a detection limit of 0.11 μM (S/N=3). Interferences from other common anions associated with cyanide anion analysis were effectively inhibited.

Redox- and pH-responsive polymer gels with reversible sol–gel transitions and self-healing properties

Covalent dynamic gels based on reversible acylhydrazone and disulfide bonds were prepared by crosslinking of benzhydrazide-containing poly(triazole) (PTB) with a novel disulfide-containing dialdehyde (C2) in DMF at ambient temperature. The PTB was synthesized by the metal- and solvent-free click polymerization of diazide and dialkyne monomers followed by treatment with hydrazine hydrate. The as-fabricated polymer gels exhibited both redox and pH stimuli-responsive behaviours. Analysis of the composition-property relationships of these polymer gels, specifically considering the effects of catalysts, molar ratio of benzhydrazide to aldehyde groups (–NH2/–CHO), and gelator concentrations on rheological properties, were performed. Additionally, the gel revealed interesting self-healing properties through acylhydrazone exchange and/or disulfide exchange reactions. Employing this dynamic character, it is possible to regenerate the used gel, and thus it has the potential to perform in a range of dynamic or bioresponsive applications.

FREE RADICAL COPOLYMERIZATION OF N-PHENYLMALEIMIDE WITH CYCLOHEXENE

Radical copolymerization of cyclohexene (M1) with N-phenylmaleimide (M2) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator in various solvents at 50°C. The copolymerization of cyclohexene with N-phenylmaleimide in chloroform and dioxane proceeded in a homogeneous system to give an alternating copolymer over a wide range of the comonomer composition in the feed. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was a maximum at about 65 mol% of N-phenylmaleimide in the feed. A solvent effect on the Rp and the reactivity ratio was investigated in this copolymerization system, i.e., copolymerization in benzene produced a higher Rp than that in chloroform and in dioxane, while in chloroform produced a higher alternating tendency compared with those in benzene and in dioxane (r1=0, r2=0.012 in chloroform; r1=0, r2=0.081 in benzene and r1=0, r2=0.073 in dioxane). The copolymer was characterized by 1H-NMR spectrum.

Porous N-Doped Carbon Prepared from Triazine-Based Polypyrrole Network: A Highly Efficient Metal-Free Catalyst for Oxygen Reduction Reaction in Alkaline Electrolytes

Metal-free N-doped carbon (NC) materials have been regarded as one of the most promising catalysts for the oxygen reduction reaction (ORR) in alkaline media because of their outstanding ORR catalytic activity, high stability, and good methanol tolerance. Up to now, only a small minority of such catalysts have been synthesized from triazine-based polymeric networks. Herein, we report the synthesis of such NC catalyst by directly pyrolyzing a nitrogen-rich, triazine-based polypyrrole network (TPN). The TPN is fabricated by oxidative polymerization of 2,4,6-tripyrrol-1,3,5-triazine monomer using TfOH as the protonating agent and benzoyl peroxide as the oxidizing agent. The obtained NC-900 (pyrolyzed at 900 °C) catalyst exhibits excellent ORR activity in alkaline media with a high ORR onset potential (0.972 V vs RHE), a large kinetic-limiting current density (15.66 mA cm-2 at 0.60 V), and good MeOH tolerance and durability. The as-synthesized NC-900 material is a potential candidate as a highly active, stable, and low-cost ORR catalyst for alkaline fuel cells.

A highly sensitive and reversible chemosensor for Hg2+ detection based on porphyrin‐thymine conjugates

In this study, we demonstrated a highly sensitive, selective, and reversible chemosensor for Hg2+ determination. This chemosensor was synthesized by direct condensation of thymin‐1‐ylacetic acid with zinc tetraaminoporphyrin, which has a porphyrin core as the fluorophore and four thymine (T) moieties as the specific interaction sites for Hg2+. The probe (4T‐ZnP) exhibited split Soret bands with a small peak at 408 nm and a strong band at 429 nm in a dimethylformamide/H2O (7/3, v/v) mixed solvent as well as a strong emission band at 614 nm. Upon the addition of Hg2+, the probe displayed strong fluorescence quenching due to the formation of T‐Hg2+‐T complexes. With the aid of the fluorescence spectrometer, the chemosensor in the dimethylformamide/H2O (7/3, v/v) mixed solvent (0.3 μM) exhibited a detection limit of 6.7 nM. Interferences from other common cations, such as Co2+, K+, Sn2+, Zn2+, Cu2+, Ni2+, Mn2+, Na+, Ca2+, Mg2+, Pb2+, and Cd2+, associated with Hg2+ analysis were effectively inhibited. Copyright

Synthesis and Self-Assembly of β-Cyclodextrin Terminated DMA/NIPAM Diblock Copolymers

A series of β-cyclodextrin (β-CD) terminated diblock copolymers has been prepared via click reaction. The Huisgen cycloaddition between alkyne decorated copolymer and azide functionalized β-CD was performed in organic solvent in the presence of a Cu(I) catalyst, resulting in the formation of β-CD terminated diblock copolymers, which contain thermally responsive poly(N-isopropylacrylamide) (PNIPAM) block and hydrophilic poly(N,N-dimethylacrylamide) (PDMA) block. Using dynamic light scattering and fluorescence spectroscopy measurements, it is demonstrated that these β-CD functionalized block copolymers are capable of reversibly forming micelles in response to changes in solution temperature and that the critical micelle concentration, micellar size, and transition temperature are dependent on both the NIPAM block length and the polymer functionalization.

Self-assembly of sodium 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoate into ultralong microbelts

In this study, a self-assembly technique is developed to fabricate ultralong microbelts of sodium 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoate (SDB). The as-prepared SDB microbelts have a belt-like structure with a rectangular cross section. All of the obtained microbelts under the optimum conditions have a relatively uniform size of about 5 μm in width, 2 μm in thickness, and approximately 5 mm in length. Particularly, the length of the SDB microbelts can be readily controlled by adjusting the SDB concentration as well as the aging temperature. In addition, the optical and electrical properties of the as-prepared microbelts are also investigated. These results should be significant in triarylimidazole derivatives crystallization and their potential application in optoelectronic devices.

Polymer-assisted fabrication of crystalline rectangular microtubes of triphenylimidazole derivatives

In this study, a self-assembly technique assisted with thermoresponsive diblock copolymer poly(N,N-dimethylacrylamide)-b-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) is developed to fabricate crystalline microtubes of 2-(4′-((4′-vinylbenzyl)oxyl)phenyl)-4,5-diphenylimidazole (VPD). The as-prepared VPD microtubes are identified to have a hollow tubular structure with a rectangular cross section. All the obtained microtubes under optimal conditions have a uniform size of 220 nm in diameter, 20 nm in wall thickness, and 4.5 μm in length. Additionally, the length of the VPD microtubes can be readily controlled by adjusting the concentration of VPD. Furthermore, the VPD microtubes exhibit interesting size-dependent optical properties, of which the UV-vis absorption band shows an obvious red shift compared to that of the monomer. These results should be significant in triphenylimidazole derivative crystallization and their potential applications in optoelectronic devices.

A Porous Organic Poly(triphenylimidazole) Decorated with Palladium Nanoparticles for the Cyanation of Aryl Iodides

A new porous organic poly(triphenylimidazole), PTPI-Me, was prepared through a Yamamoto self-coupling reaction of 2,4,5-tris-(4-bromophenyl)-1-methyl-1H-imidazole (TPI-Me) in the presence of bis(1,5-cyclooctadiene)nickel(0). The polymer was subsequently decorated with Pd nanoparticles (NPs) to afford a heterogeneous cyanation catalyst, Pd@PTPI-Me. Pd NPs with an average diameter of 2.7 nm were grown within the PTPI-Me framework, owing to the coordination of the imidazole rings to the Pd species. The resultant Pd@PTPI-Me catalyst, with a Pd loading of 0.13 mmol g-1 , exhibited superior catalytic activity for the cyanation of aryl iodides. More importantly, the heterogeneous catalyst was also readily recycled and displayed negligible deactivation after five cycles.