Ion-conducting polymers and membranes comprising them

An ion-conducting polymer wherein at least 80% of the repeat units comprise an ion-conducting region and a spacer region is disclosed. The ion-conducting region has an aromatic backbone of one or more aromatic groups, wherein at least one ion-conducting functional group is attached to each aromatic group. The spacer region has an aromatic backbone of at least four aromatic groups, wherein no ion-conducting functional groups are attached to the aromatic backbone. The polymer is suitable for use as a fuel cell membrane, and can be incorporated into membrane electrode assemblies.

Carbohydrate-based anti-adhesive inhibition of Vibrio cholerae toxin binding to GM1-OS immobilized into artificial planar lipid membranes

We have studied 'food grade' sialyloligosaccharides (SOS) as anti-adhesive drugs or receptor analogues, since the terminal sialic acid residue has already been shown to contribute significantly to the adhesion and pathogenesis of the Vibrio cholerae toxin (Ctx). GM1-oligosaccharide (GM1-OS) was immobilized into a supporting POPC lipid bilayer onto a surface plasmon resonance (SPR) chip, and the interaction between uninhibited Ctx and GM1-OS-POPC was measured. SOS inhibited 94.7% of the Ctx binding to GM1-OS-POPC at 10 mg/mL. The SOS EC50 value of 5.521 mg/mL is high compared with 0.2811 mu g/mL (182.5 pM or 1.825 x 10(-10) M) for GM1-OS. The commercially available sialyloligosaccharide (SOS) mixture Sunsial E (R) is impure, containing one monosialylated and two disialylated oligosaccharides in the ratio 9.6%. 6.5% and 17.5%, respectively, and 66.4% protein. However, these inexpensive food-grade molecules are derived from egg yolk and could be used to fortify conventional food additives, by way of emulsifiers, sweeteners and/or preservatives. The work further supports our hypothesis that SOS could be a promising natural anti-adhesive glycomimetic against Ctx and prevent subsequent onset of disease. (C) 2009 Elsevier Ltd. All rights reserved

Selective separation of the major whey proteins using ion exchange membranes

Synthetic microporous membranes with functional groups covalently attached were used to selectively separate beta-lactoglobulin, BSA, and alpha-lactalbumin from rennet whey. The selectivity and membrane performance of strong (quaternary ammonium) and weak (diethylamine) ion-exchange membranes were studied using breakthrough curves, measurement of binding capacity, and protein composition of the elution fraction to determine the binding behavior of each membrane. When the weak and strong anion exchange membranes were saturated with whey, they were both selective primarily for beta-lactoglobulin with less than 1% of the eluate consisting of alpha-lactalbumin or BSA. The binding capacity of a pure alpha-lactoglobulin solution was in excess of 1.5 mg/cm(2) of membrane. This binding capacity was reduced to approximately 1.2 mg/cm(2) when using a rennet whey solution (pH 6.4). This reduction in protein binding capacity can be explained by both the competitive effects of other whey proteins and the effect of ions present in whey. Using binary solution breakthrough curves and rennet whey breakthrough curves, it was shown that alpha-lactalbumin and BSA were displaced from the strong and weak anion exchange membranes by beta-lactoglobulin. Finally, the effect of ionic strength on the binding capacity of individual proteins for each membrane was determined by comparing model protein solutions in milk permeate (pH 6.4) and a 10 mM sodium phosphate buffer (pH 6.4). Binding capacities of beta-lactoglobulin, alpha-lactalbumin, and BSA in milk permeate were reduced by as much as 50%. This reduction in capacity coupled with the low binding capacity of current ion exchange membranes are 2 serious considerations for selectively separating complex and concentrated protein solutions.

Liposomes and skin: From drug delivery to model membranes

The early eighties saw the introduction of liposomes as skin drug delivery systems, initially promoted primarily for localised effects with minimal systemic delivery. Subsequently, a novel ultradeformable vesicular system (termed "Transfersomes" by the inventors) was reported for transdermal delivery with an efficiency similar to subcutaneous injection. Further research illustrated that the mechanisms of liposome action depended on the application regime and the vesicle composition and morphology. Ethical, health and supply problems with human skin have encouraged researchers to use skin models. 'IYaditional models involved polymer membranes and animal tissue, but whilst of value for release studies, such models are not always good mimics for the complex human skin barrier, particularly with respect to the stratum corneal intercellular lipid domains. These lipids have a multiply bilayered organization, a composition and organization somewhat similar to liposomes, Consequently researchers have used vesicles as skin model membranes. Early work first employed phospholipid liposomes and tested their interactions with skin penetration enhancers, typically using thermal analysis and spectroscopic analyses. Another approach probed how incorporation of compounds into liposomes led to the loss of entrapped markers, analogous to "fluidization" of stratum corneum lipids on treatment with a penetration enhancer. Subsequently scientists employed liposomes formulated with skin lipids in these types of studies. Following a brief description of the nature of the skin barrier to transdermal drug delivery and the use of liposomes in drug delivery through skin, this article critically reviews the relevance of using different types of vesicles as a model for human skin in permeation enhancement studies, concentrating primarily on liposomes after briefly surveying older models. The validity of different types of liposome is considered and traditional skin models are compared to vesicular model membranes for their precision and accuracy as skin membrane mimics. (c) 2008 Elsevier B.V. All rights reserved.

Modelling small angle neutron scattering data from electrospun fibres

Electrospinning is a technique employed to produce nanoscale to microscale sized fibres by the application of a high voltage to a spinneret containing a polymer solution. Here we examine how small angle neutron scattering data can be modelled to analyse the polymer chain conformation. We prepared 1:1 blends of deuterated and hydrogenated atactic-polystyrene fibres from solutions in N, N-Dimethylformamide and Methyl Ethyl Ketone. The fibres themselves often contain pores or voiding within the internal structure on the length scales that can interfere with scattering experiments. A model to fit the scattering data in order to obtain values for the radius of gyration of the polymer molecules within the fibres has been developed, that includes in the scattering from the voids. Using this model we find that the radius of gyration is 20% larger than in the bulk state and the chains are slightly extended parallel to the fibre axis.

Biomimetic triblock copolymer membranes: from aqueous solutions to solid supports

In the present paper, we studied the preparation of biomimetic triblock copolymer (ABA) membranes in aqueous solution and their deposition into solid supports. The self-assembly structures of the ABA in aqueous solution was investigated by using optical microscopy, dynamic light scattering, electron microscopy (EM) and SAXS. Spherical and tubular polymersomes were found at the highest concentrations investigated. The mechanism of deposition on solid supports (mica and glass) was elucidated by using atomic force microscopy (AFM). The deposition results in the formation of a uniform defect-free membrane at suitable polymer concentrations.

Chain extension in electrospun polystyrene fibres: a SANS study

Small angle neutron scattering techniques were used to quantify the size and shape of the chain conformation in electrospun fibres of atactic polystyrene prepared from solutions in methyl ethyl ketone. Aligned arrays of fibres were collected onto a rotating collector with tangential velocity varying between 0 ms-1 and approximately 15 ms-1. The measured radii of gyration of the polystyrene chains were found to be slightly higher than that expected for samples prepared from solutions in the concentrated regime. The ratio of the radius of gyration parallel and perpendicular to the chain axis was found to be approximately 1.05 in contrast to the substantial macroscopic shape transformation intrinsic to electrospinning. When the tangential velocity of the rotating collector was greater than the flight velocity of the fibres (ca. 4 ms-1), a further extension of the polymer chains was observed with a ratio of the radii of gyration increasing to 1.20 at the highest collector speeds. It is proposed that the heterogeneous processes involved, particularly solvent evaporation and the formation of a polymer skin during electrospinning play a significant role in determining the level of molecular anisotropy in the fibres.

Electrospun supramolecular polymer fibres

The electrospinning of urethane based low molecular weight polymers differing only in the nature of the hydrogen bonding end-groups has been investigated. For the end-groups with the lowest binding constants at maximum solubility only droplets, are produced at the electrode; in contrast, increasing the binding constant of the end-group results in electrospun fibres being produced. The properties of the fibres produced are subject to changes in solvent, concentration and temperature. Typical diameters for these fibres were found to be some 10 s of μm, rather than the sub-micron dimensions often produced in electrospinning systems. Such diameters are related to the high initial concentrations required; this also may influence the rate of solvent removal and preferential surface solidification which feature in these examples. A simple theoretical model is used to relate the association constant to the molecular weight required for fibre formation; significantly lower levels of association are required for higher molecular weight macromonomers compared to smaller molecular systems.

Amphoteric nano-, micro-, and macrogels, membranes, and thin films

This review describes the state-of the-art of nano-, micro- and macrogels, membranes, micro- and nanocapsules, as well as multilayered thin films exhibiting amphoteric character. The synthetic strategies and physicochemical properties of amphoteric materials are outlined in light of the stimuli-responsive behavior and their potential application in nanotechnology, biotechnology and medicine.

Breathable roofing membranes and bats: interactions, outcomes and predictions

In order to achieve sustainability it is necessary to balance the interactions between the built and natural environment. Biodiversity plays an important part towards sustainability within the built environment, especially as the construction industry comes under increasing pressure to take ecological concerns into account. Bats constitute an important component of urban biodiversity and several species are now highly dependent on buildings, making them particularly vulnerable to anthropogenic and environmental changes. As many buildings suitable for use as bat roosts age, they often require re-roofing and traditional bituminous roofing felts are frequently being replaced with breathable roofing membranes (BRMs), which are designed to reduce condensation. Whilst the current position of bats is better in many respects than 30 years ago, new building regulations and modern materials, may substantially reduce the viability of existing roosts. At the same time building regulations require that materials be fit for purpose and with anecdotal evidence that both bats and BRMs may experience problems when the two interact, it is important to know what roost characteristics are essential for house dwelling bats and how these and BRMs may be affected. This paper reviews current literature and knowledge and considers the possible ways in which bats and BRMs may interact, how this could affect existing bat roosts within buildings and the implications for BRM service life predictions and warranties. It concludes that in order for the construction and conservation sectors to work together in solving this issue, a set of clear guidelines should be developed for use on a national level.

Double jeopardy: the potential for problems when bats interact with breathable roofing membranes in the United Kingdom

In order to reduce environmental impacts and achieve sustainability, it is important to balance the interactions between the built and natural environment. The construction industry is becoming more aware of ecological concerns and the importance that biodiversity and maintenance ecosystem services has for sustainability. Bats constitute an important component of urban biodiversity and several species in the UK are highly dependent on buildings, making them particularly vulnerable to anthropogenic and environmental changes. Many buildings suitable for use as bat roosts often require re-roofing as they age and traditional bituminous roofing felts are frequently being replaced with breathable roofing membranes (BRMs). In the UK new building regulations and modern materials may substantially reduce the viability of existing roosts, yet at thesame time building regulations require that materials be fit for purpose. Reports suggest that both bats and BRMs may experience problems when the two interact. Such information makes it important to understand how house dwelling bats and BRMs may be affected. This paper considers the possible ways in which bats and BRMs may interact, how this could affect existing bat roosts within buildings and the implications for BRM service life predictions and warranties. Keywords –Breathable Roofing Membranes, Bats in Buildings, Material Deterioration, Sustainability, Conservation, Biodiversit

Electro-active nanofibres electrospun from blends of poly-vinyl cinnamate and a cholesteric liquid crystalline silicone polymer

Electrospinning was used to generate polymer nanofibres from blends of poly-vinyl cinnamate (PVCN) and a cholesteric silicone polymer. Only blends that contained at least 40 % of PVCN produced fibres. Both differential scanning calorimetry and electron dispersion spectroscopy data indicate that the samples are miscible over a wide temperature interval. The variation of fibre diameter with concentration is nonlinear with a well-defined minimum corresponding to an 80 % PVCN blend. The fibres are birefringent with Kerr constants similar to that of cholesteric liquid crystals. Although not significant, the Kerr constant increases with increasing silicone polymer concentration.

Effect of "Pollutants" on the functionality of breathable roofing membranes in a bat roost

The performance of breathable roofing membranes (BRM’s) in buildings where bats roost have been investigated using experimental measurements and numerical simulations. Measurement techniques as outlined in BS EN ISO 12572 of membranes from manufacturers in its pure state and those that have been contaminated with bat urine, faeces and natural oils transmitted via fur because they were found in bat roost have been tested for their permeability functions. The findings from this shows that there are significant differences between the functionality of the pure samples compared to the contaminated samples, with an average of about 20-30% reduction in functionality. This paper integrates modelling techniques using a heat, air and mass software with a simulink interface on a Matlab platform to investigate the moisture transfer properties of the BRMs. The simulation results demonstrate high level of condensation formation when the BRM is contaminated as compared to when it is not.

Hybrid polystyrene based electrospun fibers with spin-crossover properties

We have succeeded in the preparation of electrospun fibers of polystyrene incorporating a metallo-organic polymer of [Fe (II) (4-octadecyl-1,2,4-triazole)3(ClO4)2]n. The obtained fibers have diameters in the range 2–4 µm and show the characteristic spin-crossover transition associated with the metallo-organic polymer. The structure of both, polystyrene and the metallo-organic polymer, in the fibers was also studied.

Carbon nanotubes in electrospun polyethylene oxide nanofibres: a potential route to conducting nanofibres

Polyethylene oxide solution containing multi-walled carbon nanotubes have been electrospun onto a rotating collector to produce highly aligned arrays of electrospun nanofibers ranging in diameters from (200 – 360) nanometres. The addition of a surfactant (Triton X-100)is highly effective in dispersing carbon nanotube within an aqueous solution of polyethylene oxide and the resulting mixture can be electrospun without excessive clumping to produce nanofibers containing high loadings of nanotubes; in this case up to 5% wt thereby providing an effective route to electrically conductive nanofibres.