Reflectance in AFM-IR: Implications for Interpretation and Remote Analysis of the Buried Interface.

AFM-IR combines the chemical sensitivity of infrared spectroscopy with the lateral resolution of scanning probe microscopy, allowing nanoscale chemical analysis of almost any organic material under ambient conditions. As a result, this versatile technique is rapidly gaining popularity among materials scientists. Here, we report a previously overlooked source of data and artifacts in AFM-IR analysis; reflection from the buried interface.

Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution.

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. It is proposed that a characteristic blob size associated with the grafted (brush) layer defines the region through which the r-PEG diffusion occurs.

3D printed fluidics with embedded analytic functionality for automated reaction optimisation.

Additive manufacturing or '3D printing' is being developed as a novel manufacturing process for the production of bespoke micro- and milliscale fluidic devices. When coupled with online monitoring and optimisation software, this offers an advanced, customised method for performing automated chemical synthesis. This paper reports the use of two additive manufacturing processes, stereolithography and selective laser melting, to create multifunctional fluidic devices with embedded reaction monitoring capability.

Submicron Patterning of Polymer Brushes: An Unexpected Discovery from Inkjet Printing of Polyelectrolyte Macroinitiators.

Using an electrostatic-based super inkjet printer we report the high-resolution deposition of polyelectrolyte macroinitiators and subsequent polymer brush growth using SI-ARGET-ATRP. We go on to demonstrate for the first time a submicron patterning phenomenon through the addition of either a like charged polyelectrolyte homopolymer or through careful control of ionic strength. As a result patterning of polymer brushes down to ca.

Correction: Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states.

Correction for 'Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states' by Martin Wåhlander, et al., Nanoscale, 2016, DOI: 10.1039/c6nr01502f.

Surface chemistry of Ti6Al4V components fabricated using selective laser melting for biomedical applications.

Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM-AF surface was observed to be porous with an average surface roughness (Ra) of 17.

Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states.

We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1-440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI.

Photoactive composite films prepared from mixtures of polystyrene microgel dispersions and poly(3-hexylthiophene) solutions.

Whilst polystyrene microgels belong to the oldest family of microgel particles, their behaviours when deposited onto substrates or prepared as composites have received little attention. Because polystyrene microgels are solvent-swellable, and inherently colloidally stable, they are well suited to form composites with conjugated polymers. Here, we investigate the morphology and light absorption properties of spin coated composite films prepared from mixed dispersions of polystyrene microgels and poly(3-hexylthiophene) (P3HT) for the first time.

Thiol-ene immobilisation of carbohydrates onto glass slides as a simple alternative to gold-thiol monolayers, amines or lipid binding.

Carbohydrate arrays are a vital tool in studying infection, probing the mechanisms of bacterial, viral and toxin adhesion and the development of new treatments, by mimicking the structure of the glycocalyx. Current methods rely on the formation of monolayers of carbohydrates that have been chemically modified with a linker to enable interaction with a functionalised surface. This includes amines, biotin, lipids or thiols.

Anion-specific effects on the behavior of pH-sensitive polybasic brushes.

The anion-specific solvation and conformational behavior of weakly basic poly(2-dimethylamino)ethyl methacrylate (poly(DMA)), poly(2-diethylamino)ethyl methacrylate (poly(DEA)), and poly(2-diisopropylamino)ethyl methacrylate (poly(DPA)) brushes, with correspondingly increasing inherent hydrophobicity, have been investigated using in situ ellipsometric and quartz crystal microbalance with dissipation (QCM-D) measurements. In the osmotic brush regime, as the initial low concentration of salt is increased, the brushes osmotically swell by the uptake of solvent as they become charged and the attractive hydrophobic inter- and intrachain interactions are overcome. With increased ionic strength, the brushes move into the salted brush regime where they desolvate and collapse as their electrostatic charge is screened.

Hydrophobic effects within the dynamic pH-response of polybasic tertiary amine methacrylate brushes.

The solvation and swelling behaviour of three dialkylaminoethyl methacrylate polymer brushes, of varying hydrophobicity, have been investigated using a combination of in situ ellipsometry and a quartz crystal microbalance with dissipation (QCM-D). At low pH the tertiary amine groups of the three polymers are protonated and all three brushes are significantly solvated and swell by adopting an extended conformation. As the pH is increased the weak polybasic brushes become increasingly deprotonated and collapse via solvent expulsion.

Functionalisation of Ti6Al4V components fabricated using selective laser melting with a bioactive compound.

Surface modification of an implant with a biomolecule is used to improve its biocompatibility and to reduce post-implant complications. In this study, a novel approach has been used to functionalise phosphonic acid monolayers with a drug. Ti6Al4V components fabricated using selective laser melting (SLM) were functionalised with Paracetamol (a pharmaceutically relevant biomolecule) using phosphonic acid based self-assembled monolayers (SAMs).

Critical salt effects in the swelling behavior of a weak polybasic brush.

The swelling behavior of poly(2-(diethylamino)ethyl methacrylate) (PDEA) brushes in response to changes in solution pH and ionic strength has been investigated. The brushes were synthesized by ARGET ATRP methodology at the silica-aqueous solution interface via two different surface-bound initiator approaches: electrostatically adsorbed cationic macroinitiator and covalently anchored silane-based ATRP initiator moieties. The pH-response of these brushes is studied as a function of the solvated brush thickness in a constant flow regime that elucidates the intrinsic behavior of polymer brushes.

Design and additive manufacture for flow chemistry.

We review the use of additive manufacturing (AM) as a novel manufacturing technique for the production of milli-scale reactor systems. Five well-developed additive manufacturing techniques: stereolithography (SL), multi-jet modelling (MJM), selective laser melting (SLM), laser sintering (LS) and fused deposition modelling (FDM) were used to manufacture a number of miniaturised reactors which were tested using a range of organic and inorganic reactions.

Polyelectrolyte brush pH-response at the silica-aqueous solution interface: a kinetic and equilibrium investigation.

Polymer brushes are commonly used to modify the properties of solid surfaces. Here a family of polybasic poly(2-(diethylamino)ethyl methacrylate) brushes have been grown using ARGET ATRP from a cationic macroinitiator adsorbed on two types of silica surfaces: QCM crystals and oxidised silicon wafers. The pH-response of these brushes is investigated as a function of brush thickness in a constant flow environment in order to focus on the intrinsic dynamics of the polymer brushes.

Effect of colloidal substrate curvature on pH-responsive polyelectrolyte brush growth.

Coatings consisting of polymer brushes are an effective way to modify solid interfaces. Polymer brush-modified hybrid particles have been prepared by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) of 2-(diethylamino)ethyl methacrylate (DEA) on silica particles. We have optimized the synthesis with respect to changing the reducing agent, temperature, and reaction solvent from an aqueous ethanol mixture to an aqueous methanol mixture.

pH-Responsive Brush-Modified Silica Hybrids Synthesized by Surface-Initiated ARGET ATRP.

Brush-modified silica hybrids have been synthesized by growing poly(2-(diethylamino)ethyl methacrylate) (poly(DEA)) brushes on 120 nm diameter silica particles by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP). This is the first report of using SI-ARGET ATRP to synthesize poly(DEA) brushes. The kinetics of poly(DEA) brush growth in 4:1 v/v ethanol/water was monitored.

Structure and collapse of a surface-grown strong polyelectrolyte brush on sapphire.

We have used neutron reflectometry to investigate the behavior of a strong polyelectrolyte brush on a sapphire substrate, grown by atom-transfer radical polymerization (ATRP) from a silane-anchored initiator layer. The initiator layer was deposited from vapor, following treatment of the substrate with an Ar/H(2)O plasma to improve surface reactivity. The deposition process was characterized using X-ray reflectometry, indicating the formation of a complete, cross-linked layer.

A neutron reflectivity study of surfactant self-assembly in weak polyelectrolyte brushes at the sapphire-water interface.

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 neutron reflectivity. At pH 3, multilayered structures are formed in which the interlayer separation (∼40 Å) is comparable to the dimensions of a SDS bilayer or micelle. The number of repeating layers that form depends on brush thickness, ranging from three layers in a relatively thin brush (5 nm dry thickness) to 15 layers in a relatively thick brush (17 nm dry thickness).

Neutron reflectivity study of the structure of pH-responsive polymer brushes grown from a macroinitiator at the sapphire-water interface.

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-described by Gaussian density profiles with an additional thin, dense layer close to the solid-liquid interface for the thicker brushes at pH 7 and 9, which produces a spike in the density profile. The spike in the distribution accounts for less than 5% of the polymer and disappears as the brushes swell at pH 3.

Co-nonsolvency effects for surface-initiated poly(2-(methacryloyloxy)ethyl phosphorylcholine) brushes in alcohol/water mixtures.

Surface-initiated atom transfer radical polymerization (SI-ATRP) has been used to grow brushes of poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) from silicon wafers using a polyelectrolytic macroinitiator on planar silicon wafers. Film thicknesses of up to 450 nm were possible within 21 h, and the effect of adding activator and deactivator species on the brush growth rate was studied. The solvation of PMPC brushes in mixed alcohol/water solvents was investigated using in situ ellipsometry.

Direct measurement of normal and shear forces between surface-grown polyelectrolyte layers.

This paper presents measurements, using the surface force balance (SFB), of the normal and shear forces in aqueous solutions between polyelectrolyte layers grown directly on mica substrates (grafted-from). The grafting-from was via surface-initiated atom transfer radical polymerization (surface-initiated ATRP) using a positively charged methacrylate monomer. X-ray reflectometry measurements confirm the successful formation of polyelectrolyte layers by this method.

Layer-by-layer deposition of polyelectrolyte macroinitiators for enhanced initiator density in surface-initiated ATRP.

The layer-by-layer (L-b-L) deposition of oppositely charged polyelectrolytic macroinitiators has been demonstrated on planar silica substrates. The build-up of the macroinitiator multilayers was monitored by ellipsometry (up to 21 layers) and dual polarization interferometry (up to 17 layers) and good agreement was found between these techniques. The increase in L-b-L thickness was approximately linear, with an average thickness of 2.

Countywide survey of the current practice of chlamydia detection in primary care.

Background: The Chief Medical Officer's (CMO's) Advisory Group on Chlamydia trachomatis (chlamydia) published its report in 1998 and a national screening programme is anticipated. Meanwhile the Public Health Laboratory Service (PHLS) reports that the number of positive diagnoses of genital chlamydia continued to rise throughout the last decade.

Objectives: To consider the current practice of Gloucestershire general practitioners (GPs) for detecting genital chlamydia infections, and based on the findings to help the development of local guidelines and sexual health service provision.

Polymer brushes via surface-initiated polymerizations.

Polymer brushes produced by controlled surface-initiated polymerization provide a route to surfaces coated with well-defined thin polymer films that are covalently bound to the substrate. All of the major controlled polymerization techniques have been applied to the synthesis of polymer brushes and examples of each are presented here. Many examples of brush synthesis in the literature have used the living atom transfer radical polymerization (ATRP) system, and in this tutorial review a particular focus is given to examples of this technique.