John Webster

Science and Technology Facilities Council | STFC · Rutherford Appleton Laboratory

Interfacial adsorption is a molecular process occurring during the production, purification, transport, and storage of antibodies, with a direct impact on their structural stability and subsequent implications on their bioactivities. While the average conformational orientation of an adsorbed protein can be readily determined, its associated struct...

Hypothesis: Saponins are a class of plant derived surfactants which are widely used in food related foams and emulsions, aerated drinks, and in pharmaceuticals and cosmetics. As a potential biosourced and renewable ingredient in a wider range of surfactant based formulations their potential is intimately associated with their mixing with synthetic...

Saponins are surface active glycosides which can be extracted from a range of different plant species. This class of biosurfactants is of much current interest because of their biocompatibility and biosustainability, and a range of other interesting properties. The Quillaja saponin, the focus of this paper, is extensively used in foods, beverages a...

Although surfactants have been widely used in skin care and other related applications, our knowledge about how surfactants interact with stratum corneum (SC) lipids remains limited. This work reports how surfactants interact with a lipid SC model by neutron diffraction and molecular dynamics (MD) simulations, focusing on examining the impact of su...

Saponins are plant based biosurfactants that are obtained from a wide variety of plant species. They are surface active glycosides with a hydrophobic group, which is commonly a triterpenoid or steroidal group, and saccharide hydrophilic units. Their structures are markedly different from conventional synthetic surfactants, and present interesting c...

Saponins are a class of bio-surfactants obtained from a wide variety of plant species. They are surface active glycosides which are used in the stabilisation of foams and emulsions in many food, drink and cosmetic applications. Their wider utilisation and application will involve their mixture with different synthetic and bio-derived surfactants, p...

There is an increased interest in the use of natural surfactant as replacements for synthetic surfactants due to their biosustainable and biocompatible properties. A category of natural surfactants which are attracting much current interest is the triterpenoid saponins; surface active components found extensively in a wide range of plant species. A...

Antimicrobial peptides are promising alternatives to traditional antibiotics. A group of self-assembling lipopeptides was formed by attaching an acyl chain to the N-terminus of α-helix-forming peptides with the sequence C x -G(IIKK) y I-NH2 (C x G y , x = 4-12 and y = 2). C x G y self-assemble into nanofibers above their critical aggregation concen...

Hypothesis The α-sulfo alkyl ester, AES, surfactants are a class of anionic surfactants which have potential for improved sustainable performance in a range of applications, and an important feature is their enhanced tolerance to precipitation in the presence of multivalent counterions. It is proposed that their adsorption properties can be adjuste...

Hypothesis Surfactants are widely used in agri-sprays to improve pesticide efficiency, but the mechanism underlying their interactions with the surface wax film on plants remains poorly understood. To facilitate physical characterisations, we have reconstituted wheat cuticular wax films onto an optically flat silicon substrate with and without octa...

Saponins are naturally occurring biosurfactants present in a wide range of plant species. They are highly surface active glycosides, and are used to stabilise foams and emulsions in foods, beverages and cosmetics. They have great potential for an even wider range of applications, especially when mixed with different synthetic surfactants. Understan...

The formation of surface multilayer structures, with the addition of multivalent electrolytes, has been observed in a range of different anionic surfactants; and notably the sodium oxyethylene glycol alkyl sulfate, SAES, and alkyl ester sulfonate, AES, surfactants. The addition of increasing amounts of AlCl3 results in increasing surface layering,...

As part of the ISIS TS1 project, work has been carried out on the cryogenic hydrogen moderator system, the main focus being understanding and improving the ratio of spin isomers in the liquid hydrogen moderator.

The interaction of nonionic surfactant hexaethylene glycol monododecyl ether (C12E6) with a reconstituted cuticular wheat wax film has been investigated by spectroscopic ellipsometry (SE) and neutron reflection (NR) to help understand the role of the leaf wax barrier during pesticide uptake, focusing on the mimicry of the actions adjuvants impose o...

Chemical vapor deposition (CVD) is now a well-established method to create monolayer graphene films. Poly(methyl methacrylate) (PMMA) film is often coated onto graphene film during production to make it mechanically robust for transfer and further handling. However, it is hard to remove the coated PMMA, and any residual polymers remaining can affec...

Spectroscopic ellipsometry (SE) and neutron reflection (NR) data for the adsorption of a monoclonal antibody (mAb, termed COE-3, pI 8.44) at the bare SiO2/water interface are here compared to simulations based on DLVO theory. COE-3 adsorption was characterized by an initial rapid increase in the surface adsorbed amount (Γ) followed by a plateau. On...

The composition of an adsorbed layer at the air--water interface of a quinary mixture consisting of three conventional surfactants, octa-ethylene glycol monododecyl ether (C12E8), dodecane-6-p-sodium benzene sulfonate (LAS6), and diethylene glycol monododecyl ether sodium sulfate (SLE2S) mixed with two biosurfactants, the rhamnolipids L-rhamnosyl-L...

The composition of the air-water adsorbed layer of the ternary surfactant mixture, octaethylene monododecyl ether, C12E8, sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene glycol monododecyl sulphate, SLES, and of each of the binary mixtures, with varying amounts of electrolyte, has been studied by neutron reflectivity. The measurem...

The composition of the adsorbed layer of a ternary surfactant mixture at the air-water interface has been studied by neutron reflectivity. The adsorption of the ternary mixture of octaethylene monododecyl ether, C12E8, sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene glycol monododecyl sulphate, SLES, and of each of the binary mixt...

Surface and interfacial adsorption of antibody molecules could cause structural unfolding and desorbed molecules could trigger solution aggregation, resulting in the compromise of physical stability.Although antibody adsorption is important and its relevance to many mechanistic processes has been proposed, few techniques can offer direct structural...

The rate of release or evaporation of perfume molecules from surfaces is a key factor in determining the impact of the perfume in a range of applications relating to home and personal care products. For mixtures of the anionic surfactant sodium dodecylsulfate and the model perfume linalool the rate of change of adsorption with time due to forced ai...

Neutron and X-ray reflectivity of model membranes is increasingly used as a tool for the study of membrane structures and dynamics. As the systems under study become more complex, and as long, all-atom molecular-dynamics (MD) simulations of membranes become more available, there is increasing interest in the use of MD simulations in the analysis of...

Gram-negative bacteria are an increasingly serious source of antibiotic-resistant infections, partly owing to their characteristic protective envelope. This complex, 20 nm thick barrier includes a highly impermeable, asymmetric bilayer outer membrane (OM), which plays a pivotal role in resisting antibacterial chemotherapy. Nevertheless, the OM mole...

Gram-negative bacteria are an increasingly serious source of antibiotic-resistant infections, partly owing to their characteristic protective envelope. This complex, 20 nm thick barrier includes a highly impermeable, asymmetric bilayer outer membrane (OM), which plays a pivotal role in resisting antibacterial chemotherapy. Nevertheless, the OM mole...

miscellaneous_information

Langmuir surface pressure, small angle neutron scattering (SANS), and neutron reflectivity (NR) studies have been performed to determine how formulation of the antifungal drug, amphotericin B (AmB), with sodium cholesteryl sulfate (SCS) - as in Amphotec® - affects its interactions with ergosterol-containing (model fungal cell) and cholesterol-conta...

The structure of the adsorbed protein layer at the oil/water interface is essential to the understanding of the role of proteins in emulsion stabilization, and the lack of suitable techniques has, to this date, limited our ability to glean the mechanistic events of protein adsorption at such buried interfaces. This paper reports on a novel experime...

The Tween nonionic surfactants are ethoxylated sorbitan esters, which have twenty ethylene oxide groups attached to the sorbitan headgroup and a single alkyl chain, Lauric, Palmitic, Stearic or Oleic. They are an important class of surfactants which are extensively used in emulsion and foam stabilization; in applications associated with foods, cosm...

The conformation of charged surfactants at the oil-water interface was recently reported. With the aim to assess the role of the head group size on the conformation of the adsorbed layer, we have extended these studies to a series of non-ionic dodecanol ethoxylate surfactants (C12En, ethylene oxide units n from 6 to 12). The study was performed usi...

Neutron reflectivity measurements have been used to study the surface adsorption of the polyethylene sorbitan monostearate surfactant, with degrees of ethoxylation varying from three to twenty ethylene oxide groups, with the globular protein hydrophobin. The surface interaction between the ethoxylated polysorbate nonionic surfactants and the hydrop...

The effect of different trivalent counterions, Al(3+), Cr(3+), Sc(3+), Gd(3+), and La(3+), on the surface adsorption and Al(3+), Cr(3+), and Sc(3+) for solution self-assembly of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate has been studied by neutron reflectivity and small angle neutron scattering. The strong binding...

The synergistic interactions between certain ethoxylated polysorbate nonionic surfactants and the protein hydrophobin result in spontaneous self-assembly at the air-water interface to form layered surface structures. The surface structures are characterised using neutron reflectivity. The formation of the layered surface structures is promoted by t...

The calcium-mediated interaction of DNA with monolayers of the non-toxic, zwitterionic phospholipid, 1,2-distearoyl-sn-glycero-3-phosphocholine when mixed with 50 mol% of a second lipid, either the zwitteronic 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine or neutral cholesterol was investigated using a combination of surface pressure-area isotherms...

The influence of the alkyl chain length on surface multilayer formation at the air–water interface for the anionic surfactant sodium diethylene glycol monoalkyl ether sulfate, SAE2S, in the presence of Al3+ multivalent counterions, in the form of AlCl3, is described. In the absence of electrolyte, the saturated monolayer adsorption is determined by...

The adsorption of a series of cationic lipopeptide surfactants, C14Kn (where C14 denotes the myristic acyl chain and Kn represents n number of lysine residues) at the hydrophobic solid/water interface has been studied using spectroscopic ellipsometry (SE) and neutron reflection (NR). The hydrophobic C8 surface was prepared by grafting a monolayer o...

Neutron reflectivity, NR, and surface tension, ST, have been used to study the surface adsorption properties at the air-water interface of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate (sodium lauryl ether sulfate, SLES) in the presence of Al3+ multivalent counterions, by the addition of AlCl3. In the absence of AlCl3...

X-ray and neutron reflection studies, the latter in conjunction with contrast variation, have been combined to study the interaction of calf thymus DNA (ctDNA) with monolayers of distearoylphosphatidylcholine (DSPC) in the presence of 20 mM Ca 2+ ions, at the air–liquid interface as a function of surface pressure (10, 20, 30 and 40 mN m À1). Analys...

Neutron reflectivity and surface tension have been used to investigate the solution pH and oligoamine molecular weight dependence of the adsorption of sodium dodecyl sulfate (SDS)/oligoamine mixtures at the air-water interface. For diethylenetriamine, triamine, or triethylenetetramine, tetramine mixed with SDS, there is monolayer adsorption at pH 7...

The development and testing of the SuPerior Rate for INTER (SPRINTER) detector is described. Based on a microstrip gas chamber (MSGC), the aim of the project was to produce a matched pair of high-counting-rate detectors capable of replacing the existing ³He tubes currently used on the INTER reflectometer of the ISIS spallation neutron so...

We report the structural study of mixed monolayers of partially deuterated N,N'-di-hexadecyl-(d33)-4,13-diaza-18-crown-6 ether (d-ACE16) and palmitic acid (PA) at the oil-water interface, in order to understand the mechanism of metal ion transport through Permeation Liquid Membrane (PLM) devices. The composition of the mixed monolayers remains cons...

The kinetics of re-equilibration of the anionic surfactant sodium dodecylbenzene sulfonate at the air-solution interface have been studied using neutron reflectivity (NR). The experimental arrangement incorporates a novel flow cell in which the subphase can be exchanged (diluted) using a laminar flow whilst the surface region remains unaltered. The...

The development and testing of the SuPerior Rate for INTER (SPRINTER) detector is described. Based on a Microstrip Gas Chamber (MSGC) the aim of the project was to produce a matched pair of high counting rate detectors capable of replacing the existing 3He tubes currently used on the INTER reflectometer of the ISIS spallation neutron source. The de...

The effect of polymer molecular weight and solution pH on the surface properties of the anionic surfactant sodium dodecylsulfate, SDS, and a range of small linear poly(ethyleneimine), PEI, polyelectrolytes of different molecular weights has been studied by surface tension, ST, and neutron reflectivity, NR, at the air-solution interface. The strong...

A neutron reflectivity study of the phospholipid 1,2-distearoyl-sn-glycero-3-phosphocholine at the hexadecane–water interface is reported as a function of spread amount. Two isotopic contrasts have been used to determine the structure of the phospholipid molecule in the buried interfacial region. The results indicate a roughened or diffuse monolaye...

The impact of ethyleneimine architecture on the adsorption behavior of mixtures of small poly(ethyleneimines) and oligoethyleneimines (OEIs) with the anionic surfactant sodium dodecylsulfate (SDS) at the air-solution interface has been studied by surface tension (ST) and neutron reflectivity (NR). The strong surface interaction between OEI and SDS...

We have prepared and characterized a series of multifluorocarbon end-functional polyethylene additives, which when blended with polyethylene matrices increase surface hydrophobicity and lipophobicity. Water contact angles of >112° were observed on spin-cast blended film surfaces containing less than 1% fluorocarbon in the bulk, compared to ~98° in...

Proteins that translocate across cell membranes need to overcome a significant hydrophobic barrier. This is usually accomplished via specialized protein complexes, which provide a polar transmembrane pore. Exceptions to this include bacterial toxins, which insert into and cross the lipid bilayer itself. We are studying the mechanism by which large...

Three reflectometers have been built on the Second Target Station at the ISIS neutron facility. These instruments: INTER, POLREF and OFFSPEC take advantage of the high flux and broad bandwidth available on the Second Target Station to provide experimental opportunities in the study of soft matter and thin film magnetism.

We have investigated a novel method of remotely switching the conformation of a weak polybase brush using an applied voltage. Surface-grafted polyelectrolyte brushes exhibit rich responsive behavior and show great promise as "smart surfaces", but existing switching methods involve physically or chemically changing the solution in contact with the b...

Lipopeptides are an important group of biosurfactants expressed by microorganisms. Because they are well-known for being biocompatible, biodegradable, and highly surface active, they are attractive for a wide range of applications. Natural lipopeptide surfactants are however impure; it is hence difficult to use them for exploring the structure-func...

The structure of the adsorbed palmitic acid at the iron oxide/oil interface has been investigated using polarized neutron reflectometry. The palmitic acid was found to be strongly adsorbed at the oxide/oil interface resulting in a monolayer of thickness 16 ± 4 Å for 150 and 500 ppm palmitic acid concentrations (16 ± 5 Å for the 1000 ppm solution)....

Neutron reflectometry is a well established technique for the study of nanometre scale layered systems which are of direct relevance to a broad range of disciplines cutting across the physical and life sciences [11. Whitten , D.G. and Rowell , R.L. 2009 . Langmuir , 25 : 3917 – 4242 . [CrossRef], [PubMed], [Web of Science ®]View all references,22....

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes grown by surface-initiated polymerization from a polyanionic macroinitiator adsorbed at the sapphire-water interface have been used as a substrate to study the interaction between the weak polyelectrolyte PDMAEMA and the oppositely charged surfactant sodium dodecyl sulfate (SDS) with neutr...

Lipopeptidesurfactants are composed of amino acids and fatty acids and carry the inherent benefits of biocompatibility, degradability, functionality and easiness for structural design. In this work, the interfacial adsorption of a novel lipopeptidesurfactantC14K1 has been examined by combining the measurements of spectroscopic ellipsometry (SE) and...

The adsorbed amount of partially deuterated dihexadecyl-diaza-18-crown-6 ether (d-ACE16) in the presence of different chain length fatty acids as a function of surface pressure was determined by neutron reflectometry technique. The highest adsorbed amount of the azacrown ether was observed for the mixture of ACE16 with hexadecanoic (palmitic) acid,...

Neutron reflectometry has been used to determine the interface structure and swelling of thin polymer films, when annealed in contact with a series of 1-alkyl-3-methylimidazolium ionic liquids (ILs). By choosing immiscible polymer/IL combinations, we have established that thin polymer films can be annealed for several hours in contact with ILs at t...

A Langmuir-Blodgett film of aliphatic substituted phthalocyanines on a C18 silane supporting layer coupled onto a silicon substrate has been investigated using neutron reflectometry. This multilayer structure is seen as a possible candidate for phthalocyanine-lipid biosensor devices. The results show the suitability of the C18 ligands as an anchori...

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes have been grown by surface-initiated atom transfer radical polymerization (SI-ATRP) from a polyanionic macroinitiator adsorbed at the sapphire-water interface, and neutron reflectivity has been used to characterize the structures and pH response of the brushes. The polymer brushes are well...

Short peptide surfactants have recently emerged as a new class of amphiphiles, with tremendous potential in improving surface biocompatibility and mediating interfacial DNA immobilization. To establish their basic interfacial adsorption properties, cationic peptide surfactants V(m)K(n) have been studied by combining the measurements of spectroscopi...

We report the neutron reflectometry study of partially deuterated di-hexadecyl-diaza-18-crown-6 ether (d-ACE-16) at the air-water and the oil-water interfaces. At the air-water interface, the thickness of the monolayer is smaller than that for a fully stretched d-ACE-16 molecule, suggesting a tilt of the alkyl chains with respect to the normal. At...

We report information regarding the structure at the interface between hexadecane and an aqueous solution of trimethyl tetradecyl ammonium bromide (C14TAB) with appropriate deuterium labeling. We also report the role of the headgroup size and the charge on structures at the oil-water interface by comparing the data for C14TAB to that for a deuterat...

Time-resolved specular neutron reflectivity measurements are presented and interpreted for electroactive polyvinylferrocene (PVF) films subject to potentiodynamic electrochemical control. New data acquisition methodology allows an effective measurement time scale on the order of seconds, which is an improvement over conventional methodology by 2 to...

We determined the density profile of a high-molecular-weight globular protein (bovine serum albumin, BSA) solution at the methoxy tri(ethylene glycol)-terminated undecanethiol SAM/protein solution interface by neutron reflectivity measurements. Information about the interactions between oligo(ethylene glycol) (OEG)-terminated self-assembled monolay...

The structure of the monolayer formed at an air/water interface by the phospholipid distearoylphosphatidylcholine (DSPC) has been determined as a function of the monolayer surface pressure (pi) using Brewster angle microscopy and neutron reflectivity. The microscopy studies demonstrate that the DSPC molecules form an extremely homogeneous monolayer...

Short surfactant-like peptides bearing the molecular architecture of hydrophilic and hydrophobic moieties are attractive for a wide range of biological and technological applications. However, to realize the benefits offered by them we need to understand the basic physiochemical properties arising from their interfacial self-assembly and solution a...

The development, installation and commissioning of a compact neutron focussing device has recently been completed on the SXD single crystal diffractometer at ISIS. Such devices provide a relatively inexpensive method of significantly increasing the long wavelength neutron flux available for small samples, such as those often used on SXD, without si...

The monolayer formed at an air/water interface by the synthetic non-ionic surfactant, 1,2-di-O-octadecyl-rac-glyceryl-3-(omega-methoxydodecakis (ethylene glycol)) (2C18E12) has been characterized using Langmuir trough measurements, Brewster angle microscopy (BAM), and neutron reflectometry. The BAM and reflectometry studies were performed at four d...

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C8F17 fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted FxdPSy, where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blended with unfun...

Surface pressure measurements, external reflection-Fourier transform infrared spectroscopy, and neutron reflectivity have been used to investigate the lipid-binding behavior of three antimicrobial peptides: melittin, magainin II, and cecropin P1. As expected, all three cationic peptides were shown to interact more strongly with the anionic lipid, 1...

The surface, phase and aggregation behaviour of mixtures of 1-alkyl-3-methylimidazolium halide, [C(n)mim]X, where n is the alkyl chain length, with water has been explored using a variety of methods. Critical micelle concentrations (cmc) and micelle structures have been determined for aqueous [C(n)mim]Br solutions for n=2, 4, 6, 8, and 10. Small-an...

Despite advances in the development of new drugs, a drug may never reach the target organ, or it may be difficult to achieve the necessary level of drug in the body. Large doses can result in serious side effects and can harm normal, as well as diseased, cells and organs, and for this reason it is vital that controlled release and the targeting of...

We have used neutron reflectometry to characterize the swelling behaviour of brushes of poly[2-(diethyl amino)ethyl methacrylate], a polybase, as a function of pH. The brushes, synthesized by the “grafting from” method of atom transfer radical polymerization, were observed to approximately double their thickness in low pH solutions, although the pK...

INTER is a high resolution, high-flux neutron reflectometer for the study of chemical interfaces with particular emphasis on adsorption at the air–water interface. One of the particular strengths of neutron reflection is that it can be applied to ‘wet’ interfaces to obtain information at better than molecular resolution. This, allied with H/D subst...

A series of side-chain liquid crystal polymers have been screened for successhl deposition using the Langmuir Blodgett method. It was found that the best materials had glass transitions below room temperature. The behaviour of the spread film of one material was studied in detail using surface isotherms, surface potential, X-ray and neutron reflect...

The structure of a zwitterionic phosphocholine (PC) surfactant monolayer adsorbed on the surface of water has been determined using neutron reflectivity in combination with H/D isotopic substitution. The most significant results of this study are the level of hydration of the PC headgroup and the lack of dehydration with increasing temperature and...

Fluorosurfactants with several structural modifications have been synthesized, and the air/water interface and bulk aggregation properties investigated. The compounds were fluorinated ethylene oxide (EO) nonionics where the number and position of the hydrophilic group(s) has been radically altered to generate linear, bolaform, and Y-shaped analogue...

An existing discrepancy in the determined values of the width of the hexadecane-water interface as determined from X-ray reflection (XR) and recent neutron reflection (NR) measurements has been resolved. The NR-determined width reported here is 6.0 +/- 1.0 Angstroms, which compares extremely well with the XR-determined value of 6.0 +/- 0.2 Angstrom...

Adsorption of water-soluble, zwitterionic n-hexadecylphosphorylcholine (C(16)PC) amphiphiles has been examined at the hexadecane-aqueous solution interface using neutron reflectivity (NR) and interfacial tension measurements. The results of both methods indicate that the limiting area per surfactant molecule at the interface at the critical micelle...

Neutron reflectometry has been employed to examine the nature of the critical adsorption surface scaling function for a near-critical mixture of hexane-d14+perfluorohexane adsorbing to a solid substrate from the liquid one-phase region. The analysis method of Dietrich and Schack has been applied to examine the nature of the power-law part of the cr...

The adsorption of a range of single chain zwitterionic phosphocholine surfactants (C(n)P(m)C) at the air/liquid interface has been studied by a combination of surface tension and neutron reflectivity. The critical micellar concentration (CMC) for C(n)PC (or C(n)P(2)C), where n varied from 12, 14 to 16, was found to be 0.91, 0.14, and 1.2 x 10(-2) m...

We describe in situ neutron reflectivity (NR) and RAIRS studies of the chemical modification of films of a polypyrrole-based conducting polymer derived from the pentafluorophenyl ester of poly(pyrrole-N-propanoic acid) (PFP) electrodeposited on electrode surfaces. We explore the role of the solvent in controlling the rate of reaction with solution-...

The results of X-ray and neutron scattering, and Fourier transform infrared (FTIR) studies presented here to understand the effect of hydrophilicity or hydrophobicity of substrate in determining molecular orientation of three-tailed amphiphilic salt ferric stearate in Langmuir–Blodgett films. Molecules in the first monolayer deposited on hydrophili...

The surface behavior of a range of surfactant [Ru(bipy)(2)(p,p'-dialkyl-2,2'-bipy)]Cl(2) complexes, which we express as Ru(q)(p)C(n) where n is the alkyl chain length, p refers to the substitution position on the bipyridine ligand (=4 or 5), and q (=1 or 2) is the number of substituted alkyl chains, has been examined using neutron reflectometry. Th...

We report the application and refinement of a recently developed method for structural studies at a liquid–liquid interface using neutron reflectometry. The technique involves the entrapment of a thin oil layer between a silicon substrate and an aqueous subphase. The thin oil film is prepared by spin-coating an oil film on to an oleophilically trea...

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, "grafted from" brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/ sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 <...

The in-situ conformations of peptide layers formed from the adsorption of two different synthetic 15-mer peptides at the hydrophilic silicon oxide/aqueous solution interface have been determined using neutron reflectivity (NR). The first peptide is based on the native sequence of a protein-binding domain within a heteromeric transcriptional activat...

The composition and structure of interfaces between single crystal Al2O3 (sapphire) samples and liquid Sn–V alloys, containing 1% and 3% V, have been characterized in situ at high temperature using neutron reflection spectroscopy. Measurements made at 900°C are shown to be consistent with a thin (10–25 nm) AlV2O4 layer forming at the solid/liquid i...

Neutron reflectometry measurements suggest that the interfacial structure normal to the free surface of two short-chain amphiphilic 1-alkyl-3-methylimidazolium-based ionic liquids is inhomogeneous, with the inhomogeneity extending 40 Å. For the two liquids studied (1-butyl-3-methylimidazolium tetrafluoroborate and 1-octyl-3-methylimidazolium hexafl...

Hydrogenous and deuterated isomers of poly(ethylene oxide) have been capped at one end by a C6F13 fluorocarbon group. For the three molecular weights investigated (ca. 2000, 5000, and 10 000 g mol(-1)), the surface tensions of the aqueous solutions decrease over the concentration range 10(-1) to 10(-2) g mL(-1), the lowest surface tension observed...

A graft copolymer with a polynorbornene backbone and deuteriopoly(ethylene oxide) grafts has been spread on aqueous subphases with dissolved hydrogenous poly(ethylene oxide) at different concentrations. The surface pressure isotherms of the spread film are very different from that obtained on water alone. A negative surface pressure is initially ob...

In situ neutron reflectivity measurements have been made on spin cast polyvinylferrocene (PVF) films maintained under electrochemical potential control. The data show that the interiors of both oxidized and reduced films are close to homogeneous. The results show that neutron reflectivity measurements, including isotopic substitution, can provide n...