Browsing by Author "Forsythe, JS"

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    Molecular level and microstructural characterisation of thermally sensitive chitosan hydrogels
    (Royal Society of Chemistry, 2009-09-15) Crompton, KE; Forsythe, JS; Horne, MK; Finkelstein, DI; Knott, RB
    Chitosan-glycerophosphate (GP) is a physiological pH solution at room temperature which forms a physical hydrogel upon heating to 37 degrees C. The hydrogel is suitable for biomedical applications and in particular as a biodegradable scaffold for tissue engineering. Since the structure of the hydrogel is critical to cell-material interactions, small angle neutron scattering (SANS) and ultra SANS (USANS) were used to examine the molecular conformation of chitosan chains and the larger scale microstructure. On the nanoscale, the hydrogel is described in terms of a static component (characteristic length, Xi) which accounts for the physical cross-links, and a dynamic component (correlation length, xi) which accounts for solution-like properties. Over the range 0.25-1.5 w/v% chitosan concentration the molecular structure is dependent on concentration with the characteristic length decreasing from similar to 450 angstrom to similar to 300 angstrom, and the correlation length increasing from similar to 110 angstrom to similar to 130 angstrom. The chitosan chains were arranged at a larger scale into polymer-rich aggregates of 1-2 mu m diameter which decreased in size as the chitosan concentration increased. Such structural information is important for tailoring the hydrogel for specific applications. © 2009, Royal Society of Chemistry
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    An x-ray and neutron reflectometry study of 'PEG-like' plasma polymer films
    (The Royal Society, 2012-05-07) Menzies, DJ; Nelson, A; Shen, HH; McLean, KM; Forsythe, JS; Gengenbach, TR; Fong, C; Muir, BW
    Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles. A proportion of the plasma polymer hydrogen atoms were shown to be exchangeable, while QCM-D measurements were inaccurate in detecting associated water in lower power films that contained loosely bound material. The higher protein resistance of the films deposited at a low load power was attributed to its greater chemical and structural similarity to that of poly(ethylene glycol) graft surfaces. These studies demonstrate the utility of using X-ray and NR analysis techniques in furthering the understanding of the chemistry of these films and their interaction with water and proteins. Copyright © The Royal Society 2012.