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Separating solvation from molecular diffusion in polymers
Author(s) -
Elabd Yossef A.,
Barbari Timothy A.
Publication year - 2001
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690470603
Subject(s) - solvation , penetrant (biochemical) , diffusion , chemistry , fourier transform infrared spectroscopy , polymer , copolymer , methylene , polymer chemistry , implicit solvation , analytical chemistry (journal) , chemical engineering , molecule , organic chemistry , thermodynamics , physics , engineering
The diffusion of methyl ethyl ketone (MEK) in two vinyl alcohol/vinyl butyral (VA/VBu) copolymers (11‐ and 19‐wt. % VA) was studied at low vapor activities using Fourier transform infrared‐attenuated total reflectance (FTIR‐ATR) spectroscopy. MEK has the ability to interact through hydrogen bonding to sites in the polymer and was chosen to study the effect of penetrant–polymer solvation on molecular diffusion. The assumption of local equilibrium was verified by examining the time‐evolved concentrations of hydrogen‐bound and free MEK determined from the carbonyl (C = O) stretching bands. A mathematical model that accounted explicitly for solvation during the diffusion process was developed. Solvation hindered the diffusion of MEK in the VA/VBu copolymer by factors of 2.0 (11‐wt. % VA) and 2.6 (19‐wt. % VA). After separating solvation from diffusion, true diffusion coefficients of MEK were compared to those of methylene chloride (CH 2 Cl 2 ), a noninteracting penetrant of similar size to MEK. Within experimental error, true diffusion coefficients for MEK were the same as those for CH 2 C1 2 over the concentration range studied.