Ya. Elabd et al., Effect of penetrant-polymer interactions on molecular diffusion in conformational isomers of a heterogeneous polymer, MACROMOLEC, 34(18), 2001, pp. 6268-6273
The diffusion of deuterated hexane in conformational isomers of a heterogen
eous polymer, H12MDI (4,4'-dicyclohexylmethane diisocyanate)BD (1,4-butaned
iol)/PTMO (poly(tetramethylene oxide)), was investigated at a fixed hard se
gment content of 30 wt % and compared to the diffusion of acetonitrile. The
effective diffusion coefficient of acetonitrile decreases with increasing
trans-trans isomer content while that for deuterated hexane remains constan
t. These results suggest that the trend observed from acetonitrile diffusio
n is a function of penetrant-polymer interactions and not tortuosity effect
s. A model with penetrant-polymer binding to the surface of the dispersed h
ard segment domains of the heterogeneous polymer was developed to elucidate
the main factors contributing to the interaction or hindrance effect, whic
h were determined to be the "available" surface binding sites and the surfa
ce-to-volume ratio of the hard segment domains. FTIR-ATR spectroscopy was u
sed to quantify this interaction effect, and SAXS was used to confirm the f
indings.