Isoplethal phase study methods, during which temperature is varied at const
ant composition, have seen little change during the last few years. However
, isothermal methods (in which composition is varied at constant temperatur
e) have undergone significant development. The deuterium-NMR variant of the
classic isothermal analytic method has grown in importance. Also, more and
better use has been made of qualitative isothermal swelling methods ('pene
tration experiments') to supplement other data. The quantitative Diffusive
Interfacial Transport (DIT) method, first reported in 1987, has been much i
mproved by replacing interferometry, as the basis for analysis, with the de
termination of water by NIR microspectroscopy. The resulting DIT-NIR method
appears to be very general, and should see broad application in the future
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