Diffusivity of small molecules in polymers: Carboxylic acids in polystyrene

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Bernardo, G (Author) Other; Choudhury, RP (Author) Other; Beckham, HW (Author) Other

Journal

Title: Polymer

Vol. 53

Pages: 976-983

ISSN: 0032-3861

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 4 Citations

Other information

Authenticus ID: P-002-CZP

DOI: 10.1016/j.polymer.2012.01.009

Abstract (EN): Gravimetry was used to study the diffusion of a homologous series of linear carboxylic acids (C-n, with n = 2, 6-16) in amorphous polystyrene at temperatures from 35 degrees C to 165 degrees C, that is, both below and above the polymer glass transition temperature of 100 degrees C. All the mass uptake results are well described by a simple Fickian model (for t < t(1/2)) 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(n(2)D) versus n suggest that higher-n carboxylic acids diffuse through a reptation-like mechanism at higher temperatures.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8