179 results found
Gregory GL, Sulley GS, Carrodeguas LP, et al., 2020, Triblock polyester thermoplastic elastomers with semi-aromatic polymer end blocks by ring-opening copolymerization, CHEMICAL SCIENCE, Vol: 11, Pages: 6567-6581, ISSN: 2041-6520
Leung AHM, García-Trenco A, Phanopoulos A, et al., 2020, Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol, Journal of Materials Chemistry A, Vol: 8, Pages: 11282-11291, ISSN: 2050-7488
Doped-ZnO nanoparticles, capped with dioctylphosphinate ligands, are synthesised by the controlled hydrolysis of a mixture of organometallic precursors. Substitutional doping of the wurtzite ZnO nanoparticles with 5 mol% Mg(II), Al(III) and Cu(I) is achieved by the addition of sub-stoichiometric amounts of the appropriate dopant [(n-butyl)(sec-butyl)magnesium, triethylaluminium or mesitylcopper] to diethylzinc in the precursor mixture. After hydrolysis, the resulting colloidal nanoparticles (sizes of 2–3 nm) are characterised by powder X-ray crystallography, transmission electron microscopy, inductively-coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. A solution of the doped-ZnO nanoparticles and colloidal Cu(0) nanoparticles [M:ZnO : Cu = 1 : 1] are applied as catalysts for the hydrogenation of CO2 to methanol in a liquid-phase continuous flow stirred tank reactor [210 °C, 50 bar, CO2 : H2 = 1 : 3, 150 mL min−1, mesitylene, 20 h]. All the catalyst systems display higher rates of methanol production and better stability than a benchmark heterogeneous catalyst, Cu–ZnO–Al2O3 [480 μmol mmolmetal−1 h−1], with approximately twice the activity for the Al(III)-doped nanocatalyst. Despite outperforming the benchmark catalyst, Mg(II) doping is detrimental towards methanol production in comparison to undoped ZnO. X-Ray photoelectron spectroscopy and transmission electron microscopy analysis of the most active post-catalysis samples implicate the migration of Al(III) to the catalyst surface, and this surface enrichment is proposed to facilitate stabilisation of the catalytic ZnO/Cu interfaces.
Raman SK, Deacy AC, Carrodeguas LP, et al., 2020, Ti(IV)-Tris(phenolate) Catalyst Systems for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide, ORGANOMETALLICS, Vol: 39, Pages: 1619-1627, ISSN: 0276-7333
Sehmi SK, Lourenco C, Alkhuder K, et al., 2020, Antibacterial Surfaces with Activity against Antimicrobial Resistant Bacterial Pathogens and Endospores, ACS INFECTIOUS DISEASES, Vol: 6, Pages: 939-946, ISSN: 2373-8227
Deacy AC, Kilpatrick AFR, Regoutz A, et al., 2020, Understanding metal synergy in heterodinuclear catalysts for the copolymerization of CO2 and epoxides, NATURE CHEMISTRY, Vol: 12, Pages: 372-+, ISSN: 1755-4330
Sulley GS, Gregory GL, Chen TTD, et al., 2020, Switchable catalysis improves the properties of CO2-derived polymers: poly(cyclohexene carbonate-b-epsilon-decalactone-b-cyclohexene carbonate) adhesives, elastomers, and toughened plastics, Journal of the American Chemical Society, Vol: 142, Pages: 4367-4378, ISSN: 0002-7863
Carbon dioxide/epoxide copolymerization is an efficient way to add value to waste CO2 and to reduce pollution in polymer manufacturing. Using this process to make low molar mass polycarbonate polyols is a commercially relevant route to new thermosets and polyurethanes. In contrast, high molar mass polycarbonates, produced from CO2, generally under-deliver in terms of properties, and one of the most widely investigated, poly(cyclohexene carbonate), is limited by its low elongation at break and high brittleness. Here, a new catalytic polymerization process is reported that selectively and efficiently yields degradable ABA-block polymers, incorporating 6–23 wt % CO2. The polymers are synthesized using a new, highly active organometallic heterodinuclear Zn(II)/Mg(II) catalyst applied in a one-pot procedure together with biobased ε-decalactone, cyclohexene oxide, and carbon dioxide to make a series of poly(cyclohexene carbonate-b-decalactone-b-cyclohexene carbonate) [PCHC-PDL-PCHC]. The process is highly selective (CO2 selectivity >99% of theoretical value), allows for high monomer conversions (>90%), and yields polymers with predictable compositions, molar mass (from 38–71 kg mol–1), and forms dihydroxyl telechelic chains. These new materials improve upon the properties of poly(cyclohexene carbonate) and, specifically, they show good thermal stability (Td,5 ∼ 280 °C), high toughness (112 MJ m–3), and very high elongation at break (>900%). Materials properties are improved by precisely controlling both the quantity and location of carbon dioxide in the polymer chain. Preliminary studies show that polymers are stable in aqueous environments at room temperature over months, but they are rapidly degraded upon gentle heating in an acidic environment (60 °C, toluene, p-toluene sulfonic acid). The process is likely generally applicable to many other lactones, lactides, anhydrides, epoxides, and heterocumulenes and sets the s
Williams CK, Nozaki K, 2020, Metal Complexes for Catalytic Polymerizations, INORGANIC CHEMISTRY, Vol: 59, Pages: 957-959, ISSN: 0020-1669
Deacy AC, Durr CB, Williams CK, 2020, Heterodinuclear complexes featuring Zn(ii) and M = Al(iii), Ga(iii) or In(iii) for cyclohexene oxide and CO2 copolymerisation, DALTON TRANSACTIONS, Vol: 49, Pages: 223-231, ISSN: 1477-9226
Yi N, Chen TTD, Unruangsri J, et al., 2019, Orthogonal functionalization of alternating polyesters: selective patterning of (AB)(n) sequences, CHEMICAL SCIENCE, Vol: 10, Pages: 9974-9980, ISSN: 2041-6520
Raman SK, Raja R, Arnold PL, et al., 2019, Waste not, want not: CO2 (re)cycling into block polymers (vol 55, pg 7315, 2019), CHEMICAL COMMUNICATIONS, Vol: 55, Pages: 8190-8190, ISSN: 1359-7345
Raman SK, Raja R, Arnold PL, et al., 2019, Waste not, want not: CO2 (re)cycling into block polymers, CHEMICAL COMMUNICATIONS, Vol: 55, Pages: 7315-7318, ISSN: 1359-7345
Stosser T, Sulley GS, Gregory GL, et al., 2019, Easy access to oxygenated block polymers via switchable catalysis, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
Trott G, Garden JA, Williams CK, 2019, Heterodinuclear zinc and magnesium catalysts for epoxide/CO2 ring opening copolymerizations, CHEMICAL SCIENCE, Vol: 10, Pages: 4618-4627, ISSN: 2041-6520
Lim JYC, Yuntawattana N, Beer PD, et al., 2019, Isoselective Lactide Ring Opening Polymerisation using Rotaxane Catalysts, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 6007-6011, ISSN: 1433-7851
Pankhurst JR, Paul S, Zhu Y, et al., 2019, Polynuclear alkoxy-zinc complexes of bowl-shaped macrocycles and their use in the copolymerisation of cyclohexene oxide and CO2, DALTON TRANSACTIONS, Vol: 48, Pages: 4887-4893, ISSN: 1477-9226
Zhu Y, Poma A, Rizzello L, et al., 2019, Metabolically Active, Fully Hydrolysable Polymersomes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 4581-4586, ISSN: 1433-7851
Kennedy OW, White ER, Howkins A, et al., 2019, Mapping the origins of luminescence in ZnO nanowires by STEM-CL, Journal of Physical Chemistry Letters, Vol: 10, Pages: 386-392, ISSN: 1948-7185
In semiconductor nanowires, understanding both the sources of luminescence (excitonic recombination, defects, etc.) and the distribution of luminescent centers (be they uniformly distributed, or concentrated at structural defects or at the surface) is important for synthesis and applications. We develop scanning transmission electron microscopy-cathodoluminescence (STEM-CL) measurements, allowing the structure and cathodoluminescence (CL) of single ZnO nanowires to be mapped at high resolution. Using a CL pixel resolution of 10 nm, variations of the CL spectra within such nanowires in the direction perpendicular to the nanowire growth axis are identified for the first time. By comparing the local CL spectra with the bulk photoluminescence spectra, the CL spectral features are assigned to internal and surface defect structures. Hyperspectral CL maps are deconvolved to enable characteristic spectral features to be spatially correlated with structural features within single nanowires. We have used these maps to show that the spatial distribution of these defects correlates well with regions that show an increased rate of nonradiative transitions.
Stoesser T, Mulryan D, Williams CK, 2018, Switch Catalysis To Deliver Multi-Block Polyesters from Mixtures of Propene Oxide, Lactide, and Phthalic Anhydride, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 57, Pages: 16893-16897, ISSN: 1433-7851
Deacy AC, Durr CB, Garden JA, et al., 2018, Groups 1, 2 and Zn(II) Heterodinuclear Catalysts for Epoxide/CO2 Ring-Opening Copolymerization, INORGANIC CHEMISTRY, Vol: 57, Pages: 15575-15583, ISSN: 0020-1669
Durr CB, Williams CK, 2018, New Coordination Modes for Modified Schiff Base Ti(IV) Complexes and Their Control over Lactone Ring-Opening Polymerization Activity, INORGANIC CHEMISTRY, Vol: 57, Pages: 14240-14248, ISSN: 0020-1669
Regoutz A, Kerherve G, Villar-Garcia I, et al., 2018, The influence of oxygen on the surface interaction between CO2 and copper studied by ambient pressure X-ray photoelectron spectroscopy, SURFACE SCIENCE, Vol: 677, Pages: 121-127, ISSN: 0039-6028
Chen TTD, Zhu Y, Williams CK, 2018, Pentablock Copolymer from Tetracomponent Monomer Mixture Using a Switchable Dizinc Catalyst, MACROMOLECULES, Vol: 51, Pages: 5346-5351, ISSN: 0024-9297
Thevenon A, Cyriac A, Myers D, et al., 2018, Indium Catalysts for Low-Pressure CO2/Epoxide Ring-Opening Copolymerization: Evidence for a Mononuclear Mechanism?, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 140, Pages: 6893-6903, ISSN: 0002-7863
Stoesser T, Williams CK, 2018, Selective Polymerization Catalysis from Monomer Mixtures: Using a Commercial Cr-Salen Catalyst To Access ABA Block Polyesters, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 57, Pages: 6337-6341, ISSN: 1433-7851
Zhu Y, Radlauer MR, Schneiderman DK, et al., 2018, Multiblock polyesters demonstrating high elasticity and shape memory effects, Macromolecules, Vol: 51, Pages: 2466-2475, ISSN: 0024-9297
Polyester block polymers containing polylactide have garnered significant attention as renewable, degradable alternatives to traditional elastomers. However, the low glass transition of the PLA blocks limits the upper-use temperatures of the resulting elastomers. To improve the thermal performance, we explore a series of multiblock polyesters composed of poly(ε-decalactone) (PDL) and poly(cyclohexene phthalate) (PCHPE). These materials are prepared using switchable polymerization catalysis followed by chain extension. The strategy involves (i) alternating ring-opening copolymerization (ROCOP) of cyclohexene oxide and phthalic anhydride, (ii) ε-decalactone ring-opening polymerization (ROP), and (iii) diisocyanate coupling of the telechelic triblocks to increase molar mass. The resulting multiblock polyesters are amorphous, and the blocks are phase separated; glass transition temperatures are ∼−45 and 100 °C. They show thermal resistance to mass loss with Td5% ∼ 285 °C and higher upper use temperatures compared to alternative aliphatic polyesters. The nanoscale phase behavior and correlated mechanical properties are highly sensitive to the block composition. The sample containing PCHPE = 26 wt % behaves as a thermoplastic elastomer with high elongation at break (εb > 2450%), moderate tensile strength (σb = 12 MPa), and low residual strain (εr ∼ 4%). It shows elastomeric behavior from −20 to 100 °C and has a processing temperature range of ∼170 °C. At higher PCHPE content (59 wt %), the material has shape memory character with high strain fixation (250%) and recovery (96%) over multiple (25) recovery cycles. The multiblock polyesters are straightforward to prepare, and the methods presented here can be extended to produce a wide range of new materials using a other epoxides, anhydrides, and lactones. This first report on the thermal and mechanical properties highlights the significant
Leung AHM, Pike SD, Clancy AJ, et al., 2018, Layered zinc hydroxide monolayers by hydrolysis of organozincs, CHEMICAL SCIENCE, Vol: 9, Pages: 2135-2146, ISSN: 2041-6520
2D inorganic materials and their exfoliated counterparts are both of fundamental interest and relevant for applications including catalysis, electronics and sensing. Here, a new bottom-up synthesis route is used to prepare functionalised nanoplatelets, in apolar organic solvents, via the hydrolysis of organometallic reagents; the products can be prepared in high yield, at room temperature. In particular, a series of layered zinc hydroxides, coordinated by aliphatic carboxylate ligands, were produced by the hydrolysis of diethyl zinc and zinc carboxylate mixtures, optimally at a molar ratio of [COOR]/[Zn] = 0.6. Layered zinc hydroxides coordinated by oleate ligands form high concentration solutions of isolated monolayers (3 nm thick x ∼ 26 nm) in apolar organic solvents (up to 23 mg mL−1 in toluene), as confirmed by both atomic force and transmission electron microscopies of deposited species. The high solubility of the product allows the synthetic pathway to be monitored directly in situ through 1H NMR spectroscopy. The high solubility also provides a route to solution deposition of active functional materials, as illustrated by the formation of nanoporous films of optically transparent porous zinc oxide (1 μm thickness) after annealing at 500 °C. This new organometallic route to 2D materials obviates common complications of top-down exfoliation syntheses, including sonochemical-degradation and low yields of aggregated polydispersed layers, and may potentially be extended to a wide range of systems.
Stosser T, Chen TTD, Zhu Y, et al., 2018, 'Switch' catalysis: from monomer mixtures to sequence-controlled block copolymers, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 376, ISSN: 1364-503X
Garcia-Trenco A, Regoutz A, White ER, et al., 2018, PdIn intermetallic nanoparticles for the hydrogenation of CO2 to methanol, Applied Catalysis B: Environmental, Vol: 220, Pages: 9-18, ISSN: 0926-3373
Direct hydrogenation of CO2 to methanol could offer significant environmental benefits, if efficient catalysts can be developed. Here, bimetallic Pd-In nanoparticles show good performance as catalysts for this reaction. Unsupported nanoparticles are synthesised by the thermal decomposition of Pd(acetate)2 and In(acetate)3 precursors in a high boiling point solvent (squalane), followed by reduction using dilute H2 gas (210 °C). Adjusting the ratio of the two metallic precursors allow access to 5–10 nm nanoparticles with different phase compositions, including metallic Pd(0), In2O3 and intermetallic PdIn. Liquid phase methanol synthesis experiments (50 bar, 210 °C, H2:CO2 = 3:1) identify the intermetallic PdIn nanoparticles as the most efficient. The catalysts exhibit around 70% higher methanol rates (normalised to the overall molar metal content) compared to the conventional heterogeneous Cu/ZnO/Al2O3 catalyst (900 and 540 μmol mmolPdInorCuZnAl−1 h−1, respectively). In addition, the optimum Pd/In catalyst shows an improved methanol selectivity over the whole temperature range studied (190–270 °C), reaching >80% selectivity at 270 °C, compared to only 45% for the reference Cu/ZnO/Al2O3 catalyst. Experiments showed an improvement in stability; the methanol production rate declined by 20% after 120 h run for the optimum PdIn-based compared with 30% for the Cu/ZnO/Al2O3 catalyst (after 25 h). The optimum catalyst consists of ∼8 nm nanoparticles comprising a surface In-enriched PdIn intermetallic phase as characterised by XRD, HR-TEM, STEM-EDX and XPS. Post-catalysis analysis of the optimum catalyst shows that the same PdIn bimetallic phase is retained with only a slight increase in the nanoparticle size.
Stosser T, Li C, Unruangsri J, et al., 2017, Bio-derived polymers for coating applications: comparing poly(limonene carbonate) and poly (cyclohexadiene carbonate), POLYMER CHEMISTRY, Vol: 8, Pages: 6099-6105, ISSN: 1759-9954
Myers D, Witt T, Cyriac A, et al., 2017, Ring opening polymerization of macrolactones: high conversions and activities using an yttrium catalyst, POLYMER CHEMISTRY, Vol: 8, Pages: 5780-5785, ISSN: 1759-9954
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