Huijing Han

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.

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.

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.

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.

Photocrosslinkable Polynorbornene-based Block Copolymers with Enhanced Dielectric and Thermal Properties

Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (exo-PTNP-b-exo-PCONBI) were synthesized by ring-opening metathesis polymerization. The endo- or exo-PTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNP-b-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant (ε) of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low ε of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photocrosslinking, the polymer film has an increased ε of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 °C, and an enhanced decomposition temperature of 405 °C, compared to those of polymer films without irradiation.