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Molecular mobility of hydroxyethyl cellulose (HEC) films characterised by thermally stimulated currents (TSC) spectroscopy

Molecular mobility of hydroxyethyl cellulose (HEC) films characterised by thermally stimulated currents (TSC) spectroscopy

Owusu-Ware, Samuel K., Boateng, Joshua ORCID: 0000-0002-6310-729X, Jordan, Daniel, Portefaix, Sara, Tasseto, Renata, Ramano, Carmen D. and Antonijević, Milan D. (2016) Molecular mobility of hydroxyethyl cellulose (HEC) films characterised by thermally stimulated currents (TSC) spectroscopy. International Journal of Pharmaceutics, 497 (1-2). pp. 222-227. ISSN 0378-5173 (Print), 1873-3476 (Online) (doi:10.1016/j.ijpharm.2015.11.052)

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Abstract

Molecular mobility has long been established to relate to textural properties and stability of polymer films and is therefore an important property to characterise to better understand pharmaceutical film formulations. The molecular mobility of solvent cast hydroxyethyl cellulose (HEC) films has been investigated by means of thermally stimulated current (TSC) below the temperature at which the film was formed. Preliminary physical characterisation of the films was performed using XRPD, TGA, DSC and texture analysis (tensile properties). XRPD results showed the films to be completely amorphous with Tg determined by DSC to be 127 ± 1 °C. TGA analysis showed the films to contain 8 ± 1% water and film was dried to only 0.06 ± 0.01% water content when heated to 160 °C. Application of TSC detected molecular mobility in HEC films at sub-zero temperatures. Two motional transitions with average relaxation time of 50 ± 3 s were identified; a β-relaxation at −57 ± 2 °C, attributed to localised non-cooperative orientation of HEC polymer chain ends and the hydroxyethyl side groups and an α-relaxation, originating from cooperative segmental mobility, at −20 ± 2 °C. The tensile properties i.e., elongation, tensile strength and elastic modulus of the HEC film have been related to the molecular relaxation processes detected by TSC.

Item Type: Article
Uncontrolled Keywords: Molecular mobility, Hydroxyethyl cellulose (HEC), Polymeric films, Thermally stimulated current (TSC), Tensile properties
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Department of Pharmaceutical, Chemical & Environmental Sciences
Last Modified: 13 Jul 2017 14:21
Selected for GREAT 2016: GREAT a
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/14226

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