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Partitioning and phase equilibria of PEGylated excipients in fluorinated liquids

Paul, Alison, Talbot, Gemma Louise, Bowles, James William, James, Jennifer, Griffiths, Peter Charles and Rogueda, Philippe G. 2010. Partitioning and phase equilibria of PEGylated excipients in fluorinated liquids. International Journal of Pharmaceutics 387 (1-2) , pp. 230-235. 10.1016/j.ijpharm.2009.12.004

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Abstract

Mixtures of common polymeric excipients and hydrofluoroalkane (HFA) liquids show rich and complex phase behaviour. Phase diagrams and phase compositions are reported for poly(ethylene glycol)s with varying levels of end-group methylation in mixed solvent systems consisting of the model propellant 2H,3H-perfluoropentane (HPFP) and the fully fluorinated analogue perfluoropentane (PFP). Studies have been performed as a function of molecular weight as well as end group chemistry (monomethyl, MM; dimethyl, DM; and dihydroxyl, DH), and for binary polymer mixtures in HPFP/PFP solvent systems. The solvent composition required to induce phase separation by addition of the non-hydrogen bonding PFP is strongly dependent on end-group concentrations. It shows a linear increase with increasing methylation, whilst remaining insensitive to OH group concentration in dihydroxylated PEG systems. For single polymer systems it is observed that strong partitioning of the polymer is observed, and changes in polymer concentration occurring across the phase diagram are a result of changing solvent partitioning between upper and lower phases. These solvent effects are dependent on the composition (wt% PFP) in the solvent mixture. The linear dependence of solvent composition required to induce phase separation at fixed polymer concentration on end group concentrations can be used to predict the phase behaviour for mixtures of monomethylated PEG with either dimethyl or dihydroxyl PEGs, whereas mixtures of dihydroxyl with dimethyl end-capped PEGs show a deviation from linear behaviour with dominance of the dihydroxyl end groups, which is reflected in the obtained phase diagrams. This study hence progresses understanding of factors that influence solubility of PEG-type polymers in HFAs and will facilitate the identification of predictive methodologies for formulation.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Uncontrolled Keywords: Ethylene glycol ; Ethylene oxide oligomers ; Fluorinated solvents ; Solubility ; Phase equilibria ; Lower consolute solution temperature ; End-group contribution ; Partitioning NMR
Publisher: Elsevier
ISSN: 0378-5173
Last Modified: 04 Jun 2017 02:08
URI: http://orca-mwe.cf.ac.uk/id/eprint/9742

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