Imperial College London

PROFESSOR CHARLOTTE K. WILLIAMS

Faculty of Natural SciencesDepartment of Chemistry

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 5790c.k.williams Website

 
 
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Location

 

317 RCS1ChemistrySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

189 results found

Diment WT, Stosser T, Kerr RWF, Phanopoulos A, Durr CB, Williams CKet al., 2021, Ortho-vanillin derived Al(iii) and Co(iii) catalyst systems for switchable catalysis using epsilon-decalactone, phthalic anhydride and cyclohexene oxide, CATALYSIS SCIENCE & TECHNOLOGY, Vol: 11, Pages: 1737-1745, ISSN: 2044-4753

Journal article

Kerr RWF, Ewing PMDA, Raman SK, Smith AD, Williams CK, Arnold PLet al., 2021, Ultrarapid Cerium(III)-NHC Catalysts for High Molar Mass Cyclic Polylactide, ACS CATALYSIS, Vol: 11, Pages: 1563-1569, ISSN: 2155-5435

Journal article

Carrodeguas LP, Chen TTD, Gregory GL, Sulley GS, Williams CKet al., 2020, High elasticity, chemically recyclable, thermoplastics from bio-based monomers: carbon dioxide, limonene oxide and epsilon-decalactone, GREEN CHEMISTRY, Vol: 22, Pages: 8298-8307, ISSN: 1463-9262

Journal article

Deacy AC, Moreby E, Phanopoulos A, Williams CKet al., 2020, Co(III)/Alkali-Metal(I) heterodinuclear catalysts for the ring-opening copolymerization of CO2 and propylene oxide., Journal of the American Chemical Society, Vol: 142, Pages: 19150-19160, ISSN: 0002-7863

The ring-opening copolymerization of carbon dioxide and propene oxide is a useful means to valorize waste into commercially attractive poly(propylene carbonate) (PPC) polyols. The reaction is limited by low catalytic activities, poor tolerance to a large excess of chain transfer agent, and tendency to form byproducts. Here, a series of new catalysts are reported that comprise heterodinuclear Co(III)/M(I) macrocyclic complexes (where M(I) = Group 1 metal). These catalysts show highly efficient production of PPC polyols, outstanding yields (turnover numbers), quantitative carbon dioxide uptake (>99%), and high selectivity for polyol formation (>95%). The most active, a Co(III)/K(I) complex, shows a turnover frequency of 800 h-1 at low catalyst loading (0.025 mol %, 70 °C, 30 bar CO2). The copolymerizations are well controlled and produce hydroxyl telechelic PPC with predictable molar masses and narrow dispersity (Đ < 1.15). The polymerization kinetics show a second order rate law, first order in both propylene oxide and catalyst concentrations, and zeroth order in CO2 pressure. An Eyring analysis, examining the effect of temperature on the propagation rate coefficient (kp), reveals the transition state barrier for polycarbonate formation: ΔG‡ = +92.6 ± 2.5 kJ mol-1. The Co(III)/K(I) catalyst is also highly active and selective in copolymerizations of other epoxides with carbon dioxide.

Journal article

Yuntawattana N, McGuire TM, Durr CB, Buchard A, Williams CKet al., 2020, Indium phosphasalen catalysts showing high isoselectivity and activity in racemic lactide and lactone ring opening polymerizations, CATALYSIS SCIENCE & TECHNOLOGY, Vol: 10, Pages: 7226-7239, ISSN: 2044-4753

Journal article

Chen TTD, Carrodeguas LP, Sulley GS, Gregory GL, Williams CKet al., 2020, Bio-based and Degradable Block Polyester Pressure-Sensitive Adhesives, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 23450-23455, ISSN: 1433-7851

Journal article

Gregory GL, Sulley GS, Carrodeguas LP, Chen TTD, Santmarti A, Terrill NJ, Lee K-Y, Williams CKet 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

Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-alt-phthalate)-b-poly(ε-decalactone)-b-poly(cyclohexene-alt-phthalate) {PE–PDL–PE}. The synthesis is accomplished using a zinc(II)/magnesium(II) catalyst, in a one-pot procedure where ε-decalactone ring-opening polymerization yielding dihydroxyl telechelic poly(ε-decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85–98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (fhard = 0.4) and variable molar masses 40–100 kg mol−1; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol−1) and variable hard-block volume fractions (0.12 < fhard < 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼−51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (fhard < 0.4 and N > 1300) with linear stress–strain relationships, high ultimate tensile strengths (σb = 1–5 MPa), very high elongations at break (&ep

Journal article

Pasta M, Armstrong D, Brown ZL, Bu J, Castell MR, Chen P, Cocks A, Corr SA, Cussen EJ, Darnbrough E, Deshpande V, Doerrer C, Dyer MS, El-Shinawi H, Fleck N, Grant P, Gregory GL, Grovenor C, Hardwick LJ, Irvine JTS, Lee HJ, Li G, Liberti E, McClelland I, Monroe C, Nellist PD, Shearing PR, Shoko E, Song W, Jolly DS, Thomas C, Turrell SJ, Vestli M, Williams CK, Zhou Y, Bruce PGet al., 2020, 2020 roadmap on solid-state batteries, JOURNAL OF PHYSICS-ENERGY, Vol: 2, ISSN: 2515-7655

Journal article

Leung AHM, García-Trenco A, Phanopoulos A, Regoutz A, Schuster ME, Pike SD, Shaffer MSP, Williams CKet 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.

Journal article

Raman SK, Deacy AC, Carrodeguas LP, Reis N, Kerr RWF, Phanopoulos A, Morton S, Davidson MG, Williams CKet 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

Titanium(IV) complexes of amino-tris(phenolate) ligands (LTiX, X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium chloride (PPNCl) are active catalyst systems for the ring-opening copolymerization of carbon dioxide and cyclohexene oxide. They show moderate activity, with turnover frequency values of ∼60 h–1 (0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their absolute performances are lower than those of the most active Ti(IV) catalyst systems. The reactions proceed with linear evolution of polycarbonate (PCHC) molar mass with epoxide conversion, consistent with controlled polymerizations, and evolve bimodal molar mass distributions of PCHC (up to Mn = 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl, allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized using single-crystal X-ray diffraction techniques. The anionic titanium complex [LTi(OR)Cl]− is proposed as a model for the propagating alkoxide intermediates in the catalytic cycle.

Journal article

Sehmi SK, Lourenco C, Alkhuder K, Pike SD, Noimark S, Williams CK, Shaffer MSP, Parkin IP, MacRobert AJ, Allan Eet al., 2020, Antibacterial surfaces with activity against antimicrobial resistant bacterial pathogens and endospores, ACS Infectious Diseases, Vol: 6, Pages: 939-946, ISSN: 2373-8227

Hospital-acquired bacterial infections are a significant burden on healthcare systems worldwide causing an increased duration of hospital stays and prolonged patient suffering. We show that polyurethane containing crystal violet (CV) and 3–4 nm zinc oxide nanoparticles (ZnO NPs) possesses excellent bactericidal activity against hospital-acquired pathogens including multidrug resistant Escherichia coli (E. coli), Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), and even highly resistant endospores of Clostridioides (Clostridium) difficile. Importantly, we used clinical isolates of bacterial strains, a protocol to mimic the environmental conditions of a real exposure in the healthcare setting, and low light intensity equivalent to that encountered in UK hospitals (∼500 lux). Our data shows that ZnO NPs enhance the photobactericidal activity of CV under low intensity light even with short exposure times, and we show that this involves both Type I and Type II photochemical pathways. Interestingly, polyurethane containing ZnO NPs alone showed significant bactericidal activity in the dark against one strain of E. coli, indicating that the NPs possess both light-activated synergistic activity with CV and inherent bactericidal activity that is independent of light. These new antibacterial polymers are potentially useful in healthcare facilties to reduce the transmission of pathogens between people and the environment.

Journal article

Deacy AC, Kilpatrick AFR, Regoutz A, Williams CKet al., 2020, Understanding metal synergy in heterodinuclear catalysts for the copolymerization of CO2 and epoxides, NATURE CHEMISTRY, Vol: 12, Pages: 372-+, ISSN: 1755-4330

Journal article

Sulley GS, Gregory GL, Chen TTD, Carrodeguas LP, Trott G, Santmarti A, Lee K-Y, Terrill NJ, Williams CKet 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

Journal article

Williams CK, Nozaki K, 2020, Metal Complexes for Catalytic Polymerizations, INORGANIC CHEMISTRY, Vol: 59, Pages: 957-959, ISSN: 0020-1669

Journal article

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

Journal article

Yi N, Chen TTD, Unruangsri J, Zhu Y, Williams CKet al., 2019, Orthogonal functionalization of alternating polyesters: selective patterning of (AB)(n) sequences, CHEMICAL SCIENCE, Vol: 10, Pages: 9974-9980, ISSN: 2041-6520

Journal article

Hepburn C, Adlen E, Beddington J, Carter EA, Fuss S, Mac Dowell N, Minx JC, Smith P, Williams CKet al., 2019, The technological and economic prospects for CO2 utilization and removal, Nature, Vol: 575, Pages: 87-97, ISSN: 0028-0836

The capture and use of carbon dioxide to create valuable products might lower the net costs of reducing emissions or removing carbon dioxide from the atmosphere. Here we review ten pathways for the utilization of carbon dioxide. Pathways that involve chemicals, fuels and microalgae might reduce emissions of carbon dioxide but have limited potential for its removal, whereas pathways that involve construction materials can both utilize and remove carbon dioxide. Land-based pathways can increase agricultural output and remove carbon dioxide. Our assessment suggests that each pathway could scale to over 0.5 gigatonnes of carbon dioxide utilization annually. However, barriers to implementation remain substantial and resource constraints prevent the simultaneous deployment of all pathways.

Journal article

Raman SK, Raja R, Arnold PL, Davidson MG, Williams CKet 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

Journal article

Raman SK, Raja R, Arnold PL, Davidson MG, Williams CKet al., 2019, Waste not, want not: CO2 (re)cycling into block polymers, CHEMICAL COMMUNICATIONS, Vol: 55, Pages: 7315-7318, ISSN: 1359-7345

Journal article

Stosser T, Sulley GS, Gregory GL, Williams CKet al., 2019, Easy access to oxygenated block polymers via switchable catalysis, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723

Journal article

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

Journal article

Lim JYC, Yuntawattana N, Beer PD, Williams CKet al., 2019, Isoselective Lactide Ring Opening Polymerisation using [2]Rotaxane Catalysts, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 6007-6011, ISSN: 1433-7851

Journal article

Pankhurst JR, Paul S, Zhu Y, Williams CK, Love JBet 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

Journal article

Zhu Y, Poma A, Rizzello L, Gouveia VM, Ruiz-Perez L, Battaglia G, Williams CKet al., 2019, Metabolically Active, Fully Hydrolysable Polymersomes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 4581-4586, ISSN: 1433-7851

Journal article

Kennedy OW, White ER, Howkins A, Williams CK, Boyd IW, Warburton PA, Shaffer MSPet 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.

Journal article

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

Journal article

Deacy AC, Durr CB, Garden JA, White AJP, Williams CKet 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

Journal article

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

Journal article

Regoutz A, Kerherve G, Villar-Garcia I, Williams CK, Payne DJet 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

Journal article

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

Journal article

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