Meiran Xie

Synthesis and Properties of a Novel Cycloaliphatic Epoxide

The novel cycloaliphatic epoxide 3,4-epoxycyclohexylmethyl-2′,3′-epoxycyclohexyl ether (II) containing an unsymmetrical epoxycyclohexyl moiety linked via an ether bond, and its precursor 3-cyclohexene-1-methyl-2′-cyclohexene ether (I) were synthesized. Their structure was confirmed by means of elemental analysis, FT-IR and 1H NMR spectroscopy. Compared with commercial epoxide ERL-4221, the newly synthesized epoxide II shows a higher epoxy value (0.85 eq/g) and lower viscosity (86 mpa·s/25°C). The cured product, based on epoxide II and curing agent hexahydro-4-methylphthalic anhydride (HMPA), showed higher glass transition temperature (162°C), higher storage modulus at the glass transition region (2.95 GPa), higher crosslinking density (1.60×10–3 mol/cm3) and a lower coefficient of thermal expansion (6.22×10–5/°C).

Robust hybrid nanostructures comprising gold and thiol-functionalized polymer nanoparticles: facile preparation, diverse morphologies and unique properties

Nanohybrids are generated via covalent integration of Au nanoparticles (NPs) with thiol-functionalized crosslinked polymer NPs. The polymer NPs have been readily prepared by the controlled intramolecular crosslinking of long-chain highly branched polymers through the thiol–ene reaction in dilute solution, and the thiol groups on polymer NPs can be introduced and tailored by alternating the cross linkers with various thiol functionalities, which facilitates the further fabricatation of nanohybrids with different loadings of Au NPs. The structures and optical properties of these nanostructures are characterized by elemental analysis, IR, NMR, XPS, XRD, and UV-vis measurements. The morphologies of nanostructures are investigated via dynamic light scattering, atom force microscopy, transmission electron microscopy, and cryogenic transmission electron microscopy. The results reveal that the crosslinked polymer NPs have an average diameter of 45 nm, and Au NPs in the nanohybrids are isolated and distributed throughout the surface of the polymer NPs. When varying the concentrations, the hybrid nanostructures display diverse morphologies going through nanosphere, chainlike assembly and nanorod, accompanied with unique optical properties. Additionally, this type of hybrid nanostructure has high stability and recoverability in catalysis, and shows excellent efficiency for the reduction of nitro compounds.

Thermoresponsive AuNPs Stabilized by Pillararene-Containing Polymers

Pillararene-containing thermoresponsive polymers are synthesized via reversible addition-fragmentation chain transfer polymerization using pillararene derivatives as the effective chain transfer agents for the first time. These polymers can self-assemble into micelles and form vesicles after guest molecules are added. Furthermore, such functional polymers can be further applied to prepare hybrid gold nanoparticles, which integrate the thermoresponsivity of polymers and molecular recognition of pillararenes.

Novel amphiphilic and photo-responsive ABC 3-miktoarm star terpolymers: synthesis, self-assembly and photo-responsive behavior

Novel amphiphilic and photo-responsive ABC 3-miktoarm star terpolymers consisting of hydrophilic poly(ethylene glycol) monomethyl ether (MPEG), hydrophobic polystyrene (PS) and azobenzene-containing poly[6-(4-methoxy-azobenzene-4′-oxy) hexylmethacrylate] (PMMAZO) were synthesized by a combination of atom transfer radical polymerization (ATRP) and click chemistry. MPEG was first end-capped by an epoxide ring, which was opened by sodium azide for the preparation of the modified MPEG bearing reactive azide group and hydroxyl group (MPEG–(OH)(N3)). Click chemistry was then performed to conjugate α-alkynyl-ω-diethylamino-PS and MPEG–(OH)(N3) for the preparation of a block copolymer with reactive hydroxyl group at the junction point (MPEG(–OH)–b–PS), which was further esterified with 2-bromoisobutyryl bromide to prepare the macroinitiator with reactive bromo group at the central point (MPEG(–Br)–b–PS). Finally, an azobenzene-containing PMMAZO arm was introduced into the diblock copolymer by ATRP of 6-(4-methoxy-azobenzene-4′-oxy) hexylmethacrylate monomer (MMAZO) initiated with macroinitiator MPEG(–Br)–b–PS for the preparation of ABC 3-miktoarm star terpolymer (MPEG)(PS)(PMMAZO). The self-assembled morphologies of the star terpolymers in selective solvents changed from bowl-shaped structures to multibowl-shaped structures with the lengthening of the hydrophobic chains (PS or PMMAZO). Photo-responsive investigation showed that the different aggregation states had a great effect on the photo-induced isomerization behaviors. These results may provide guidelines for the design of effective photoresponsive anisotropic materials.

Promotion of Atom Transfer Radical Polymerization and Ring-Opening Metathesis Polymerization in Ionic Liquids

In the last decade, there has been an increasing interest in using ionic liquids as solvents for chemical reactions and polymerizations. This interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction or polymerization and the properties of products. Recent developments in ionic liquids as solvents for atom transfer radical polymerization, and ring-opening metathesis polymerization are described. The syntheses of ruthenium-based complexes bearing PEG ligand and ionic liquids moieties and their utilizations as precatalysts for metathesis polymerizations are also summarized.

A bridge-like polymer synthesized by tandem metathesis cyclopolymerization and acyclic diene metathesis polymerization

A facile synthesis of a novel bridge-like polymer was accomplished by the combined procedures of metathesis cyclopolymerization (MCP) and acyclic diene metathesis (ADMET) polymerization. A telechelic double-stranded polyacetylene (PA) with two terminal alkenyl groups was firstly prepared through the third generation Grubbs’ catalyst-mediated chain terminating MCP of bis(1,6-heptadiyne), containing a perylene bisimide (PBI) segment, in the presence of 1,4-bis(10-undecenyloxy)-cis-2-butene. A symmetrical triolefinic ether acted as the functional terminating agent, and was then utilized as the macromonomer in subsequent ADMET polymerization to yield the resultant bridge-like polymer, consisting of the nonconjugated polyolefin backbone and the separated pier-like double-stranded PA. The molecular weight of the product increased (25.2–122.4 kDa) as the reaction time was prolonged, and there was a relatively broad polydispersity index (PDI = 1.41–1.75). The bridge-like polymer can assemble into an ordered ladder-like architecture and a fence-like ribbon morphology, and displays excellent thermal stability, with a Td of above 300 °C and a high Tg between 175 and 189 °C, which is important for applications in devices.

Synthesis and conductivity of hyperbranched poly(triazolium)s with various end-capping groups

A series of novel hyperbranched poly(triazolium)s with different terminal groups were synthesized by alkylation and anion exchange reactions of the corresponding hyperbranched poly(triazole)s, which were obtained from an AB2-type monomer via Cu(I)-catalyzed azide–alkyne cycloaddition polymerization. The hyperbranched poly(triazolium)s showed high thermal stability with decomposition temperatures of 328–361 °C, and good flexibility, with glass transition temperatures (Tg) ranging from −6.2 to −14.9 °C. Among them, an oligo(ethylene glycol)-terminated hyperbranched poly(triazolium) presented the lowest Tg of −14.9 °C, the highest ionic conductivity (7.70 × 10−6 S cm−1 at 30 °C and 1.02 × 10−3 S cm−1 at 110 °C) and a wide electrochemical stability window of 6.0 V. Therefore, these hyperbranched poly(triazolium)s could act as new electrolyte materials.

Precisely designed perylene bisimide-substituted polyethylene with a high glass transition temperature and an ordered architecture

Acyclic diene metathesis polymerization of a structurally symmetrical perylene bisimide (PBI)-containing α,ω-diene has been performed, yielding an unsaturated polymer with increased molecular weight (Mn = 21.2–87.6 kDa) and decreased polydispersity index (PDI = 2.31–1.76) as the reaction time was prolonged. The subsequent hydrogenation of the as-synthesized polymer was readily accomplished, affording the desired polyethylene (PE) with a saturated backbone and precisely repeating substituted bulky PBI branches. This PBI-substituted PE derivative displayed high glass transition temperatures (Tg = 51.8–75.8 °C), a relatively wide range of light absorption (λ = 230–590 nm), and a highly ordered architecture, which should facilitate electron mobility and be suitable for utilization in optoelectronic devices. It can therefore serve as a superior model for simple construction of functional PE polymers with precisely repeating bulky branches and a soluble PBI polymer with an ordered architecture.

Formation and decomposition of a Ca2PbO4-modified phase in the Bi1.6Pb0.4Sr2Ca2Cu3Ox compound

Abstract The stability of the Pb-doped BPSCCO 2223 phase was studied by in situ resistivity,. XRD analysis electron probe microanalysis. It was found that annealing the BPSCCO 2223 phase at high temperature (700°C) under ambient oxygen will incur precipitation of a Ca 2 PbO 4 -modified impurity phase, and the impurity phase would be decomposed upon annealing in nitrogen atmosphere. The precipitation of the Ca 2 PbO 4 -modified phase has a positive influence on the T c of the 2223 material as a result of adjustment in the composition of the 2223 phase and a negative influence on the weak link between the superconducting grains. Two other impurity phases, Ca 2 CuO 3 and SrCaCu 3 O x , were also reported, and a metastable (Bi, Pb) Sr 2 Ca 2 Cu 3 O x phase was observed.

Hyperbranched poly(triazole) with thermal and metal ion dual stimuli-responsiveness

Oligo(ethylene glycol)-terminated hyperbranched poly(triazole) (hb-PTA-OEG) with thermal and metal ion dual stimuli-responsiveness was synthesized by Cu(I)-catalyzed azide–alkyne cycloaddition polymerization, which possessed a high molecular weight (Mn = 203 kDa) and good thermal properties (Td = 367 °C, Tg = −14.1 °C). Importantly, hb-PTA-OEG exhibited a relatively low cloud point (CP) temperature ranging from 34.4 to 31.1 °C as the concentration was increased from 0.02 to 2.0 wt%. Simultaneously, hb-PTA-OEG has the ability to coordinate with various metal ions, and the type of metal ions influenced the CP of hb-PTA-OEG solution to some extent as a result of their different association strengths with the polymer, particularly, Ag+ ion showed a conspicuous contribution to increasing the CP among the several selected ions. As a result, hb-PTA-OEG can act as an absorber of metal ions, and the selective absorption of Ag+ ion could be reached by tuning temperature.