Please use this identifier to cite or link to this item: http://hdl.handle.net/1822/17534

TitleDiffusivity of small molecules in polymers : carboxylic acids in polystyrene
Author(s)Bernardo, Gabriel
Choudhury, Rudra Prosad
Beckham, Haskell W.
KeywordsDiffusion
Small molecules
Polystyrene
Issue date13-Jan-2012
PublisherElsevier
JournalPolymer
Abstract(s)Gravimetry was used to study the diffusion of a homologous series of linear carboxylic acids (Cn, with n=2, 6-16) in amorphous polystyrene at temperatures from 35 ºC to 165 ºC, that is, both below and above the polymer glass transition temperature of 100 ºC. All the mass uptake results are well described by a simple Fickian model (for t < t1/2) and were used to calculate the corresponding diffusion coefficients using the thin-film approximation. Acetic acid exhibits a peculiar diffusion rate: its diffusion coefficients in polystyrene do not follow the same trend of all the remaining acids, being smaller than those of hexanoic acid at the same temperatures. Polystyrene swells at a higher rate in hexanoic and octanoic acids than in acetic acid, at the same temperature. This peculiarity is confirmed using NMR spectroscopy for acetic and hexanoic acids. For all the carboxylic acids considered, the temperature dependence of the diffusion coefficients is non-Arrhenius in character. For each liquid penetrant, its log(D) increases linearly with the decrease in liquid viscosity associated with an increase in temperature. Plots of log(n2D) versus n suggest that higher-n carboxylic acids diffuse through a reptation-like mechanism at higher temperatures.
TypeArticle
URIhttp://hdl.handle.net/1822/17534
DOI10.1016/j.polymer.2012.01.009
ISSN0032-3861
Publisher versionhttp://www.sciencedirect.com/
Peer-Reviewedyes
AccessRestricted access (UMinho)
Appears in Collections:IPC - Artigos em revistas científicas internacionais com arbitragem

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