Pa. Drake et Pw. Bohn, INTERFACIAL EVENTS ASSOCIATED WITH CASE-II DIFFUSION IN THE POLY(METHYLMETHACRYLATE) CH3OH SYSTEM/, Applied spectroscopy, 50(8), 1996, pp. 1023-1029
Surface plasmon (SP) resonance measurements were used to monitor Case
II swelling events in the poly (methylmethacrylate) (PMMA)/CH3OH syste
m on the nanometer-length scale. A simple one-dimensional swelling mod
el effectively correlates measured shifts in SP angular resonance posi
tions to instantaneous film thickness, z, and permeant volume fraction
, phi. Swelling motions in continuous polymer films less than 10 nm in
thicknesses are easily resolved. Permeant molecules are incorporated
at the PMMA interface by a mechanism consistent with a modified Thomas
-Windle (TW) model. Temperature differences in sorption kinetics are i
nterpreted in terms of differences in how the elongational viscosity o
f PMMA depends on temperature. Efflux profiles show evidence of a two-
part sample reconstruction process from the rubbery to the glassy stat
e, in which CH3OH leaves the sample rapidly, followed by a slower retu
rn of the PMMA chains to their original density. While interfacial swe
lling motions appear in general form to mirror those of the macroscopi
c sample surface, measured interfacial penetrant volume fraction value
s differ from those measured on the macroscopic-length scale in that t
hey exhibit a substantial dependence on sample temperature.