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Attachment assays of a Pseudomonas isolate to fused silica slides showed that treatment with DNaseI significantly inhibited cellular adsorption, which was restored upon DNA treatment. These assays confirmed the important role of extracellular DNA (eDNA) adsorption to a surface. To investigate the eDNA adsorption mechanism, single-molecule force spectroscopy (SMFS) was used to measure the adsorption of eDNA to silicon surfaces in the presence of different concentrations of sodium and calcium ions. SMFS reveals that the work of adhesion required to remove calcium-bound eDNA from the silicon oxide surface is substantially greater than that for sodium. Molecular dynamics simulations were also performed, and here, it was shown that the energy gain in eDNA adsorption to a silicon oxide surface in the presence of calcium ions is small and much less than that in the presence of sodium. The simulations show that the length scales involved in eDNA adsorption are less in the presence of sodium ions than those in the presence of calcium. In the presence of calcium, eDNA is pushed above the surface cations, whereas in the presence of sodium ions, short-range interactions with the surface dominate. Moreover, SMFS data show that increasing [Ca2+] from 1 to 10 mM increases the adsorption of the cations to the silicon oxide surface and consequently enhances the Stern layer, which in turn increases the length scale associated with eDNA adsorption.
Ana L. Morales-García; Rachel Walton; Jamie T. Blakeman; Steven A. Banwart; John H. Harding; Mark Geoghegan; Colin L. Freeman; Stephen A. Rolfe. The Role of Extracellular DNA in Microbial Attachment to Oxidized Silicon Surfaces in the Presence of Ca2+ and Na+. Langmuir 2021, 37, 9838 -9850.
AMA StyleAna L. Morales-García, Rachel Walton, Jamie T. Blakeman, Steven A. Banwart, John H. Harding, Mark Geoghegan, Colin L. Freeman, Stephen A. Rolfe. The Role of Extracellular DNA in Microbial Attachment to Oxidized Silicon Surfaces in the Presence of Ca2+ and Na+. Langmuir. 2021; 37 (32):9838-9850.
Chicago/Turabian StyleAna L. Morales-García; Rachel Walton; Jamie T. Blakeman; Steven A. Banwart; John H. Harding; Mark Geoghegan; Colin L. Freeman; Stephen A. Rolfe. 2021. "The Role of Extracellular DNA in Microbial Attachment to Oxidized Silicon Surfaces in the Presence of Ca2+ and Na+." Langmuir 37, no. 32: 9838-9850.
Neutron specular reflectometry (SR) and off-specular scattering (OSS) are nondestructive techniques which, through deuteration, give a high contrast even among chemically identical species and are therefore highly suitable for investigations of soft-matter thin films. Through a combination of these two techniques, the former yielding a density profile in the direction normal to the sample surface and the latter yielding a depth-resolved in-plane lateral structure, one can obtain quite detailed information on buried morphology on length scales ranging from the order of ångströms to ∼10 µm. This is illustrated via quantitative evaluation of data on SR and OSS collected in time-of-flight (ToF) measurements of a set of films composed of immiscible polymer layers, protonated poly(methyl methacrylate) and deuterated polystyrene, undergoing a decomposition process upon annealing. Joint SR and OSS data analysis was performed by the use of a quick and robust originally developed algorithm including a common absolute-scale normalization of both types of scattering, which are intricately linked, constraining the model to a high degree. This, particularly, makes it possible to distinguish readily between different dewetting scenarios driven either by the nucleation and growth of defects (holes, protrusions etc.) or by thermal fluctuations in the buried interface between layers. Finally, the 2D OSS maps of particular cases are presented in different spaces and qualitative differences are explained, allowing also the qualitative differentiation of the in-plane structure of long-range order, the correlated roughness and bulk defects by a simple inspection of the scattering maps prior to quantitative fits.
Aljoša Hafner; Philipp Gutfreund; Boris P. Toperverg; Andrew O. F. Jones; Johann P. de Silva; Andrew Wildes; Henry E. Fischer; Mark Geoghegan; Michele Sferrazza. Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces. Journal of Applied Crystallography 2021, 54, 924 -948.
AMA StyleAljoša Hafner, Philipp Gutfreund, Boris P. Toperverg, Andrew O. F. Jones, Johann P. de Silva, Andrew Wildes, Henry E. Fischer, Mark Geoghegan, Michele Sferrazza. Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces. Journal of Applied Crystallography. 2021; 54 (3):924-948.
Chicago/Turabian StyleAljoša Hafner; Philipp Gutfreund; Boris P. Toperverg; Andrew O. F. Jones; Johann P. de Silva; Andrew Wildes; Henry E. Fischer; Mark Geoghegan; Michele Sferrazza. 2021. "Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces." Journal of Applied Crystallography 54, no. 3: 924-948.
Specular and off-specular neutron reflectometry have been used in a combined approach to study thin polymer films. Our goal in this work is to illustrate the power of the off-specular scattering technique to probe the properties of the buried interface of immiscible polymer bilayers of deuterated polystyrene and protonated poly(methyl methacrylate) (h-PMMA). The diffuse scattering stemming from these systems is discussed in relation to thermal fluctuations at the polymer/polymer interface, providing a means to extract in-plane correlation lengths from buried interfaces. In addition the onset of hole formation in the top layer is evidenced by the diffuse scattering, not easily detectable by specular reflection alone.
Aljosa Hafner; Philipp Gutfreund; Boris Pa. Toperverg; Mark Geoghegan; Michele Sferrazza. 2D Reflectometry for the investigation of polymer interfaces: off-specular neutron scattering. Journal of Physics: Condensed Matter 2021, 33, 1 .
AMA StyleAljosa Hafner, Philipp Gutfreund, Boris Pa. Toperverg, Mark Geoghegan, Michele Sferrazza. 2D Reflectometry for the investigation of polymer interfaces: off-specular neutron scattering. Journal of Physics: Condensed Matter. 2021; 33 (36):1.
Chicago/Turabian StyleAljosa Hafner; Philipp Gutfreund; Boris Pa. Toperverg; Mark Geoghegan; Michele Sferrazza. 2021. "2D Reflectometry for the investigation of polymer interfaces: off-specular neutron scattering." Journal of Physics: Condensed Matter 33, no. 36: 1.
Fluorescence correlation spectroscopy was used to show that the temperature-dependent diffusion coefficient of poly(ethylene oxide) (PEO) adsorbed on polystyrene and different poly(alkyl methacrylate) (PAMA) films in aqueous solution exhibited a maximum close to (but below) the surface glass transition temperature, Tgs, of the film. This elevated diffusion was observed over a small range of temperatures below Tgs for these surfaces, and at other temperatures, the diffusion was similar to that on silicon, although the diffusion coefficient for PEO on polystyrene at temperatures above Tgs did not completely decrease to that on silicon, in contrast to the PAMA surfaces. It is concluded that the enhanced surface mobility of the films near the surface glass transition temperature induces conformational changes in the adsorbed PEO. The origin of this narrow and dramatic increase in diffusion coefficient is not clear, but it is proposed that it is caused by a coupling of a dominant capillary mode in the liquid surface layer with the polymer. Friction force microscopy experiments also demonstrate an unexpected increase in friction at the same temperature as the increase in diffusion coefficient.
Matthew Mears; Zhenyu J. Zhang; Ryan C. D. Jackson; Yuchen Si; Tigerlily J. B. Bradford; John M. Torkelson; Mark Geoghegan. Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films. The Journal of Chemical Physics 2021, 154, 164902 .
AMA StyleMatthew Mears, Zhenyu J. Zhang, Ryan C. D. Jackson, Yuchen Si, Tigerlily J. B. Bradford, John M. Torkelson, Mark Geoghegan. Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films. The Journal of Chemical Physics. 2021; 154 (16):164902.
Chicago/Turabian StyleMatthew Mears; Zhenyu J. Zhang; Ryan C. D. Jackson; Yuchen Si; Tigerlily J. B. Bradford; John M. Torkelson; Mark Geoghegan. 2021. "Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films." The Journal of Chemical Physics 154, no. 16: 164902.
The presence of excited-states and charge-separated species was identified through UV and visible laser pump and visible/near-infrared probe femtosecond transient absorption spectroscopy in spin coated films of poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles. Optical gain in the mesoparticle films is observed after excitation at both 400 and 610 nm. In the mesoparticle film, charge generation after UV excitation appears after around 50 ps, but little is observed after visible pump excitation. In the nanoparticle film, as for a uniform film of the pure polymer, charge formation was efficiently induced by UV excitation pump, while excitation of the low energetic absorption states (at 610 nm) induces in the nanoparticle film a large optical gain region reducing the charge formation efficiency. It is proposed that the different intermolecular interactions and molecular order within the nanoparticles and mesoparticles are responsible for their markedly different photophysical behavior. These results therefore demonstrate the possibility of a hitherto unexplored route to stimulated emission in a conjugated polymer that has relatively undemanding film preparation requirements.
Mark Geoghegan; Marta Mróz; Chiara Botta; Laurie Parrenin; Cyril Brochon; Eric Cloutet; Eleni Pavlopoulou; Georges Hadziioannou; Tersilla Virgili. Optical Gain in Semiconducting Polymer Nano and Mesoparticles. Molecules 2021, 26, 1138 .
AMA StyleMark Geoghegan, Marta Mróz, Chiara Botta, Laurie Parrenin, Cyril Brochon, Eric Cloutet, Eleni Pavlopoulou, Georges Hadziioannou, Tersilla Virgili. Optical Gain in Semiconducting Polymer Nano and Mesoparticles. Molecules. 2021; 26 (4):1138.
Chicago/Turabian StyleMark Geoghegan; Marta Mróz; Chiara Botta; Laurie Parrenin; Cyril Brochon; Eric Cloutet; Eleni Pavlopoulou; Georges Hadziioannou; Tersilla Virgili. 2021. "Optical Gain in Semiconducting Polymer Nano and Mesoparticles." Molecules 26, no. 4: 1138.
Polyelectrolyte adhesives, either poly[2-(dimethylamino)ethyl methacrylate] or poly(methacrylic acid), functionalized with a surface-active calix[4]resorcinarene were grafted onto silicon wafers. Adhesion studies on these grafted-to brushes using polyelectrolyte hydrogels of opposite charge showed that it is the calix[4]resorcinarene, rather than adsorption of polyelectrolyte monomers, that adheres the brush to the silicon substrate. The adhesion measured was similar to that measured using polymers grafted from the surface, and was stronger than a control layer of poly(vinyl acetate) under the same test conditions. The limiting factor was determined to be adhesive failure at the hydrogel-brush interface, rather than the brush-silicon interface. Therefore, the adhesion has not been adversely affected by changing from a grafted-from to a grafted-to brush, demonstrating the possibility of a one-pot approach to creating switchable adhesives.
William D. Seddon; Latifah AlFhaid; Alan D. F. Dunbar; Mark Geoghegan; Nicholas H. Williams. Adhesion of Grafted-to Polyelectrolyte Brushes Functionalized with Calix[4]resorcinarene and Deposited as a Monolayer. Langmuir 2020, 36, 13843 -13852.
AMA StyleWilliam D. Seddon, Latifah AlFhaid, Alan D. F. Dunbar, Mark Geoghegan, Nicholas H. Williams. Adhesion of Grafted-to Polyelectrolyte Brushes Functionalized with Calix[4]resorcinarene and Deposited as a Monolayer. Langmuir. 2020; 36 (46):13843-13852.
Chicago/Turabian StyleWilliam D. Seddon; Latifah AlFhaid; Alan D. F. Dunbar; Mark Geoghegan; Nicholas H. Williams. 2020. "Adhesion of Grafted-to Polyelectrolyte Brushes Functionalized with Calix[4]resorcinarene and Deposited as a Monolayer." Langmuir 36, no. 46: 13843-13852.
Force spectroscopy was used to measure the adhesion of Leishmania to synthetic mimics of galectins on the sand fly midgut.
Amy R. Hall; Jamie T. Blakeman; Ahmed M. Eissa; Paul Chapman; Ana L. Morales-García; Laura Stennett; Oihane Martin; Emilie Giraud; David H. Dockrell; Neil R. Cameron; Martin Wiese; Laith Yakob; Matthew E. Rogers; Mark Geoghegan. Glycan–glycan interactions determine Leishmania attachment to the midgut of permissive sand fly vectors. Chemical Science 2020, 11, 10973 -10983.
AMA StyleAmy R. Hall, Jamie T. Blakeman, Ahmed M. Eissa, Paul Chapman, Ana L. Morales-García, Laura Stennett, Oihane Martin, Emilie Giraud, David H. Dockrell, Neil R. Cameron, Martin Wiese, Laith Yakob, Matthew E. Rogers, Mark Geoghegan. Glycan–glycan interactions determine Leishmania attachment to the midgut of permissive sand fly vectors. Chemical Science. 2020; 11 (40):10973-10983.
Chicago/Turabian StyleAmy R. Hall; Jamie T. Blakeman; Ahmed M. Eissa; Paul Chapman; Ana L. Morales-García; Laura Stennett; Oihane Martin; Emilie Giraud; David H. Dockrell; Neil R. Cameron; Martin Wiese; Laith Yakob; Matthew E. Rogers; Mark Geoghegan. 2020. "Glycan–glycan interactions determine Leishmania attachment to the midgut of permissive sand fly vectors." Chemical Science 11, no. 40: 10973-10983.
The adhesion at the aqueous interface between a polyacid hydrogel and a grafted polycation layer (brush) is shown to be reversible on the addition of sodium chloride, which screens the charges on the gel and brush. Furthermore, it is shown that a double‐network (DN) hydrogel both exhibits adhesive failure and stronger adhesion with the brush than a simple poly(methacrylic acid) (PMAA) hydrogel, which undergoes cohesive failure on detachment. The adhesive force at the hydrogel–brush interface significantly increases after adding dilute salt solution (of 0.001 M). Once the concentration of salt solution is raised above 0.05 M, both the adhesive force and work done in detaching both single‐network and DN hydrogels from the brush surface are notably reduced. This result confirms that reversible adhesion between a hydrogel and polymer brush in salt solutions is possible, although a DN gel is required for adhesive failure.
Latifah AlFhaid; Nicholas Williams; Mark Geoghegan. Adhesion between oppositely charged polyelectrolytes in salt solution. Journal of Polymer Science 2020, 137, 1 .
AMA StyleLatifah AlFhaid, Nicholas Williams, Mark Geoghegan. Adhesion between oppositely charged polyelectrolytes in salt solution. Journal of Polymer Science. 2020; 137 (38):1.
Chicago/Turabian StyleLatifah AlFhaid; Nicholas Williams; Mark Geoghegan. 2020. "Adhesion between oppositely charged polyelectrolytes in salt solution." Journal of Polymer Science 137, no. 38: 1.
Dynamic single-molecule force spectroscopy was performed to monitor the unbinding of fibronectin with the proteoglycans syndecan-4 (SDC4) and decorin and to compare this with the unbinding characteristics of α 5 β 1-integrin. A single energy barrier was sufficient to describe the unbinding of both SDC4 and decorin from fibronectin, whereas two barriers were observed for the dissociation of α 5 β 1-integrin from fibronectin. The outer (high-affinity) barriers in the interactions of fibronectin with α 5 β 1-integrin and SDC4 are characterized by larger barrier heights and widths and slower dissociation rates than those of the inner (low-affinity) barriers in the interactions of fibronectin with α 5 β 1-integrin and decorin. These results indicate that SDC4 and (ultimately) α 5 β 1-integrin have the ability to withstand deformation in their interactions with fibronectin, whereas the decorin-fibronectin interaction is considerably more brittle.
Thomas M. Kennelly; Yiran Li; Yi Cao; Eva E. Qwarnstrom; Mark Geoghegan. Distinct Binding Interactions of α5β1-Integrin and Proteoglycans with Fibronectin. Biophysical Journal 2019, 117, 688 -695.
AMA StyleThomas M. Kennelly, Yiran Li, Yi Cao, Eva E. Qwarnstrom, Mark Geoghegan. Distinct Binding Interactions of α5β1-Integrin and Proteoglycans with Fibronectin. Biophysical Journal. 2019; 117 (4):688-695.
Chicago/Turabian StyleThomas M. Kennelly; Yiran Li; Yi Cao; Eva E. Qwarnstrom; Mark Geoghegan. 2019. "Distinct Binding Interactions of α5β1-Integrin and Proteoglycans with Fibronectin." Biophysical Journal 117, no. 4: 688-695.
The Flory-Huggins free energy of mixing is shown to be appropriate for the analysis of the temporal evolution of a ternary blend of polystyrene and poly(methyl methacrylate) during spin-coating from toluene using an in-situ light scattering technique. For the range of concentrations studied, both the onset of film instability and the observation of a scattering ring occur at the same toluene volume fraction. The success of Flory-Huggins theory indicates that polymer chains retain random walk characteristics during spin-coating. It is also concluded that the thermodynamics of phase separation during film formation is independent of the initial solvent concentration.
Youmna Mouhamad; Parvaneh Mokarian-Tabari; Richard A.L. Jones; Mark Geoghegan. Application of mean-field theory to the spin casting of polystyrene and poly(methyl methacrylate) blend films from toluene. Polymer 2019, 178, 121578 .
AMA StyleYoumna Mouhamad, Parvaneh Mokarian-Tabari, Richard A.L. Jones, Mark Geoghegan. Application of mean-field theory to the spin casting of polystyrene and poly(methyl methacrylate) blend films from toluene. Polymer. 2019; 178 ():121578.
Chicago/Turabian StyleYoumna Mouhamad; Parvaneh Mokarian-Tabari; Richard A.L. Jones; Mark Geoghegan. 2019. "Application of mean-field theory to the spin casting of polystyrene and poly(methyl methacrylate) blend films from toluene." Polymer 178, no. : 121578.
The photophysics of water and propan-1-ol suspensions of poly [N-9”-heptadecanyl-2,7-carbazole-alt−5,5-(4,7-di-2-thienyl-2′,1′,3′- benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles has been studied by ultrafast spectroscopy. High molar mass polymer (HMM > 20 kg/mol) forms nanoparticles with around 50 nm diameter via mini-emulsion post-polymerization, while low molar mass (LMM < 5 kg/mol) polymer prepared by dispersion polymerization results in particles with a diameter of almost one order of magnitude larger (450 ± 50 nm). In this study, the presence of excited-states and charge separated species was identified through UV pump and visible/near-infrared probe femtosecond transient absorption spectroscopy. A different behavior for the HMM nanoparticles has been identified compared to the LMM mesoparticles. The nanoparticles exhibit typical features of an energetically disordered conjugated polymer with a broad density of states, allowing for delayed spectral relaxation of excited states, while the mesoparticles show a J-aggregate-like behavior where interchain interactions are less efficient. Stimulated emission in the red-near infrared region has been found in the mesoparticles which indicates that they present a more energetically ordered system.
Tersilla Virgili; Chiara Botta; Marta M. Mróz; Laurie Parrenin; Cyril Brochon; Eric Cloutet; Eleni Pavlopoulou; Georges Hadziioannou; Mark Geoghegan. Size-Dependent Photophysical Behavior of Low Bandgap Semiconducting Polymer Particles. Frontiers in Chemistry 2019, 7, 409 .
AMA StyleTersilla Virgili, Chiara Botta, Marta M. Mróz, Laurie Parrenin, Cyril Brochon, Eric Cloutet, Eleni Pavlopoulou, Georges Hadziioannou, Mark Geoghegan. Size-Dependent Photophysical Behavior of Low Bandgap Semiconducting Polymer Particles. Frontiers in Chemistry. 2019; 7 ():409.
Chicago/Turabian StyleTersilla Virgili; Chiara Botta; Marta M. Mróz; Laurie Parrenin; Cyril Brochon; Eric Cloutet; Eleni Pavlopoulou; Georges Hadziioannou; Mark Geoghegan. 2019. "Size-Dependent Photophysical Behavior of Low Bandgap Semiconducting Polymer Particles." Frontiers in Chemistry 7, no. : 409.
Force spectroscopy was used to show that extracellular DNA (eDNA) has a pre-eminent structural role in a biofilm. The adhesive behavior of extracellular polymeric substances to poly(ethylene terephthalate), a model hydrophobic surface, was measured in response to their degradation by hydrolytic enzymes known for their biofilm dispersion potential: DNaseI, protease, cellulase, and mannanase. Only treatment with DNaseI significantly decreased the adhesive force of the model bacterium Micrococcus luteus with the surface, and furthermore this treatment almost completely eliminated any components of the biofilm maintaining the adhesion, establishing a key structural role for eDNA.
Jamie T. Blakeman; Ana L. Morales-García; Joy Mukherjee; Klaus Gori; Adam S. Hayward; Neil J. Lant; Mark Geoghegan. Extracellular DNA Provides Structural Integrity to a Micrococcus luteus Biofilm. Langmuir 2019, 35, 6468 -6475.
AMA StyleJamie T. Blakeman, Ana L. Morales-García, Joy Mukherjee, Klaus Gori, Adam S. Hayward, Neil J. Lant, Mark Geoghegan. Extracellular DNA Provides Structural Integrity to a Micrococcus luteus Biofilm. Langmuir. 2019; 35 (19):6468-6475.
Chicago/Turabian StyleJamie T. Blakeman; Ana L. Morales-García; Joy Mukherjee; Klaus Gori; Adam S. Hayward; Neil J. Lant; Mark Geoghegan. 2019. "Extracellular DNA Provides Structural Integrity to a Micrococcus luteus Biofilm." Langmuir 35, no. 19: 6468-6475.
A model system for the investigation of diffusional transport in compartmentalized nanosystems is described.
Christopher G. Clarkson; Alexander Johnson; Graham J. Leggett; Mark Geoghegan. Slow polymer diffusion on brush-patterned surfaces in aqueous solution. Nanoscale 2019, 11, 6052 -6061.
AMA StyleChristopher G. Clarkson, Alexander Johnson, Graham J. Leggett, Mark Geoghegan. Slow polymer diffusion on brush-patterned surfaces in aqueous solution. Nanoscale. 2019; 11 (13):6052-6061.
Chicago/Turabian StyleChristopher G. Clarkson; Alexander Johnson; Graham J. Leggett; Mark Geoghegan. 2019. "Slow polymer diffusion on brush-patterned surfaces in aqueous solution." Nanoscale 11, no. 13: 6052-6061.
Uniform onion micelles formed from up to ten nano-structured polymer layers were produced by the aqueous self-assembly of highly-branched copolymers.
Sarah L. Canning; Joseph M. F. Ferner; Natalie M. Mangham; Trevor J. Wear; Stuart W. Reynolds; Jonathan Morgan; J. Patrick A. Fairclough; Stephen M. King; Tom Swift; Mark Geoghegan; Stephen Rimmer. Highly-ordered onion micelles made from amphiphilic highly-branched copolymers. Polymer Chemistry 2018, 9, 5617 -5629.
AMA StyleSarah L. Canning, Joseph M. F. Ferner, Natalie M. Mangham, Trevor J. Wear, Stuart W. Reynolds, Jonathan Morgan, J. Patrick A. Fairclough, Stephen M. King, Tom Swift, Mark Geoghegan, Stephen Rimmer. Highly-ordered onion micelles made from amphiphilic highly-branched copolymers. Polymer Chemistry. 2018; 9 (47):5617-5629.
Chicago/Turabian StyleSarah L. Canning; Joseph M. F. Ferner; Natalie M. Mangham; Trevor J. Wear; Stuart W. Reynolds; Jonathan Morgan; J. Patrick A. Fairclough; Stephen M. King; Tom Swift; Mark Geoghegan; Stephen Rimmer. 2018. "Highly-ordered onion micelles made from amphiphilic highly-branched copolymers." Polymer Chemistry 9, no. 47: 5617-5629.
The diffusion of rhodamine-labeled poly(ethylene glycol) (r-PEG) within surface-grafted poly(ethylene glycol) (s-PEG) layers in aqueous solution at 18 °C was measured by fluorescence correlation spectroscopy. The diffusion coefficient of r-PEG within s-PEG was controlled by the grafting density, σ, and scaled as σ–1.42±0.09. It is proposed that a characteristic blob size associated with the grafted (brush) layer defines the region through which the r-PEG diffusion occurs. The diffusion coefficients for r-PEG in semidilute solution were found to be similar to those in the brushes.
Zhenyu J. Zhang; Steve Edmondson; Matthew Mears; Jeppe Madsen; Steven P. Armes; Graham J. Leggett; Mark Geoghegan. Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution. Macromolecules 2018, 51, 6312 -6317.
AMA StyleZhenyu J. Zhang, Steve Edmondson, Matthew Mears, Jeppe Madsen, Steven P. Armes, Graham J. Leggett, Mark Geoghegan. Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution. Macromolecules. 2018; 51 (16):6312-6317.
Chicago/Turabian StyleZhenyu J. Zhang; Steve Edmondson; Matthew Mears; Jeppe Madsen; Steven P. Armes; Graham J. Leggett; Mark Geoghegan. 2018. "Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution." Macromolecules 51, no. 16: 6312-6317.
Neutron scattering has been used to investigate the solution behaviour of highly-branched poly(N-isopropylacrylamide).
Ateyyah M. Al-Baradi; Stephen Rimmer; Steven R. Carter; Johann P. De Silva; Stephen M. King; Marco Maccarini; Bela Farago; Laurence Noirez; Mark Geoghegan. Temperature-dependent structure and dynamics of highly-branched poly(N-isopropylacrylamide) in aqueous solution. Soft Matter 2018, 14, 1482 -1491.
AMA StyleAteyyah M. Al-Baradi, Stephen Rimmer, Steven R. Carter, Johann P. De Silva, Stephen M. King, Marco Maccarini, Bela Farago, Laurence Noirez, Mark Geoghegan. Temperature-dependent structure and dynamics of highly-branched poly(N-isopropylacrylamide) in aqueous solution. Soft Matter. 2018; 14 (8):1482-1491.
Chicago/Turabian StyleAteyyah M. Al-Baradi; Stephen Rimmer; Steven R. Carter; Johann P. De Silva; Stephen M. King; Marco Maccarini; Bela Farago; Laurence Noirez; Mark Geoghegan. 2018. "Temperature-dependent structure and dynamics of highly-branched poly(N-isopropylacrylamide) in aqueous solution." Soft Matter 14, no. 8: 1482-1491.
This review updates recent progress in the understanding of the behaviour of polymers at surfaces and interfaces, highlighting examples in the areas of wetting, dewetting, crystallization, and 'smart' materials. Recent developments in analysis tools have yielded a large increase in the study of biological systems, and some of these will also be discussed, focussing on areas where surfaces are important. These areas include molecular binding events and protein adsorption as well as the mapping of the surfaces of cells. Important techniques commonly used for the analysis of surfaces and interfaces are discussed separately to aid the understanding of their application.
Amy Hall; M Geoghegan. Polymers and biopolymers at interfaces. Reports on Progress in Physics 2018, 81, 036601 .
AMA StyleAmy Hall, M Geoghegan. Polymers and biopolymers at interfaces. Reports on Progress in Physics. 2018; 81 (3):036601.
Chicago/Turabian StyleAmy Hall; M Geoghegan. 2018. "Polymers and biopolymers at interfaces." Reports on Progress in Physics 81, no. 3: 036601.
The nanoscopic adhesive and frictional behaviour of end-grafted poly[2-(dimethyl amino)ethyl methacrylate] (PDMAEMA) films (brushes) in contact with gold- or PDMAEMA-coated atomic force microscope tips in potassium halide solutions with different concentrations up to 300 mM is a strong function of salt concentration. The conformation of the polymers in the brush layer is sensitive to salt concentration, which leads to large changes in adhesive forces and the contact mechanics at the tip–sample contact, with swollen brushes (which occur at low salt concentrations) yielding large areas of contact and friction–load plots that fit JKR behaviour, while collapsed brushes (which occur at high salt concentrations) yield sliding dominated by ploughing, with conformations in between fitting DMT mechanics. The relative effect of the different anions follows the Hofmeister series, with I− collapsing the brushes more than Br− and Cl− for the same salt concentration.
Maryam Raftari; Zhenyu J. Zhang; Steven R. Carter; Graham J. Leggett; Mark Geoghegan. Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution. Tribology Letters 2017, 66, 1 -9.
AMA StyleMaryam Raftari, Zhenyu J. Zhang, Steven R. Carter, Graham J. Leggett, Mark Geoghegan. Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution. Tribology Letters. 2017; 66 (1):1-9.
Chicago/Turabian StyleMaryam Raftari; Zhenyu J. Zhang; Steven R. Carter; Graham J. Leggett; Mark Geoghegan. 2017. "Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution." Tribology Letters 66, no. 1: 1-9.
The possibility of swelling of single polyelectrolyte chains in dilute aqueous solution by free ions in the presence of a small amount of salt is investigated using a mean-field approach. The swelling of chains by free ions is more likely for larger chains in solutions containing only a small amount of salt. The swollen chains are likely to retain a spherical structure.
Mark Geoghegan. The swelling of weak polyelectrolytes at low salt concentrations in dilute solution. Polymer 2017, 112, 414 -417.
AMA StyleMark Geoghegan. The swelling of weak polyelectrolytes at low salt concentrations in dilute solution. Polymer. 2017; 112 ():414-417.
Chicago/Turabian StyleMark Geoghegan. 2017. "The swelling of weak polyelectrolytes at low salt concentrations in dilute solution." Polymer 112, no. : 414-417.
Spin coating, typically used to achieve nanometre thick films, is the established method for depositing perovskite precursors at lab scale for use in solar cells. This study investigates the dynamics of spin coating perovskite. By combining experimental measurement with a semi-empirical model the evaporation rate of the dimethylformamide solvent during the spin coating of a mixed lead halide precursor is determined to be 1.2 × 10–8 m/s. When K-bar coating the same precursor the solvent does not significantly evaporate during the deposition process and when this film is crystallised on a hot plate a rough film results which gives a power conversion efficiency (PCE) of less than 2%. By increasing the airflow of the K-bar coated perovskite film during crystallisation to 2.7 × 10–4 m/s the PCE increases significantly to 8.5% through an improvement in short-circuit current and fill factor.
Jennifer A. Baker; Youmna Mouhamad; Katherine E.A. Hooper; Daniel Burkitt; Mark Geoghegan; Trystan M. Watson. From spin coating to roll‐to‐roll: investigating the challenge of upscaling lead halide perovskite solar cells. IET Renewable Power Generation 2017, 11, 546 -549.
AMA StyleJennifer A. Baker, Youmna Mouhamad, Katherine E.A. Hooper, Daniel Burkitt, Mark Geoghegan, Trystan M. Watson. From spin coating to roll‐to‐roll: investigating the challenge of upscaling lead halide perovskite solar cells. IET Renewable Power Generation. 2017; 11 (5):546-549.
Chicago/Turabian StyleJennifer A. Baker; Youmna Mouhamad; Katherine E.A. Hooper; Daniel Burkitt; Mark Geoghegan; Trystan M. Watson. 2017. "From spin coating to roll‐to‐roll: investigating the challenge of upscaling lead halide perovskite solar cells." IET Renewable Power Generation 11, no. 5: 546-549.