Differential scanning calorimetry of aqueous polymer solutions and gels

摘要

AbstractThe melting phenomena of aqueous polymer solutions and gels have been investigated by differential scanning calorimetry (DSC). The polymers used were synthetic polyacrylamide and poly(vinyl alcohol) samples as well as guar and xanthan gums. By using an empirical relation, the energy measured from the area under the melting peak yielded heats of mixing and sorption, when fitted by an association factor computed from the data. This factor (independent of the concentration) is a measure of the water fraction associated with the polymer and has a definite and characteristic value for a given polymer in water. When a crosslinking agent (potassium pyroantimoniate or chromic nitrate) was added to the water–polymer system, the association factor varied with the polymer concentration; the macromolecular chains thus become less accessible to penetrating water. If a branched gel was obtained owing to the formation of chemical crosslinks, a hump appeared on the melting pea