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Publications - 2011

Previous year | Overview

Flurbiprofen encapsulation using pluronic triblock copolymers.

Shirin Alexander, Terence Cosgrove, Stuart W. Prescott, and Thomas C. Castle

Langmuir (2011) 27, 8054-8060
DOI: 10.1021/la201124c


Pulsed-field gradient stimulated-echo nuclear magnetic resonance (NMR) and surface tension measurements have been used to study the effect of drug addition on the micellization behavior of pluronic triblock copolymers (P103, P123, and L43). The addition of 0.6 wt % flurbiprofen to Pluronic P123 and P103 solutions reduced their cmc and promoted micellization. Also, a substantial increase in the hydrodynamic radius of Pluronic P103 from 5 to 10 nm was observed, along with an increased fraction of polymer micellized, demonstrating that the polymers solubilize this nonsteroidal anti-inflammatory drug.

A small-angle neutron scattering study of poly(ethylene oxide) microstructure in aqueous poly(styrenesulfonate sodium) solutions.

Zewei Bai, Yue Xie, Chunhai Chen, Terence Cosgrove, and Dong Qiu

Journal of Colloid and Interface Science(2011) 358, 226-229
DOI: 10.1016/j.jcis.2011.03.015


Dilute aqueous solutions of d-PEO and PSSNa mixtures were studied by 2H NMR spectroscopy and small-angle neutron scattering (SANS). The interactions between d-PEO and PSSNa were found to be negligible both in the presence and absence of NaCl. At very dilute concentration (0.7 mg mL?1), d-PEO chains were still found to be slightly collapsed at ambient temperature in water. Upon the addition of PSSNa, aggregates of d-PEO were observed with d-PEO coils loosely associated with each other. The average centre to centre distance between d-PEO coils, which was calculated from the maxima in SANS spectra, was similar to the size of the individual coils. The effect of a simple salt, NaCl, on d-PEO-PSSNa interaction was investigated. Salt addition induced a breakdown of the dilute d-PEO aggregates.

Structure of colloidal sphere-plate mixtures.

N. Doshi, G. Cinacchi, J. S. van Duijneveldt, T. Cosgrove, S. W. Prescott, I. Grillo, J. Phipps, and D. I. Gittins

Journal of Physics: Condensed Matter (2011) 23, 194109
DOI: 10.1088/0953-8984/23/19/194109


In addition to containing spherical pigment particles, coatings usually contain plate-like clay particles. It is thought that these improve the opacity of the paint film by providing an efficient spacing of the pigment particles. This observation is counterintuitive, as suspensions of particles of different shapes and sizes tend to phase separate on increase of concentration. In order to clarify this matter a model colloidal system is studied here, with a sphere-plate diameter ratio similar to that found in paints. For dilute suspensions, small angle neutron scattering revealed that the addition of plates leads to enhanced density fluctuations of the spheres, in agreement with new theoretical predictions. On increasing the total colloid concentration the plates and spheres phase separate due to the disparity in their shape. This is in agreement with previous theoretical and experimental work on colloidal sphere-plate mixtures, where one particle acts as a depleting agent. The fact that no large scale phase separation is observed in coatings is ascribed to dynamic arrest in intimately mixed, or possibly micro-phase separated structures, at elevated concentration.

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