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Thermodynamics of water–biopolymer interactions: Irreversible sorption by two uniform sorbent phases
Author(s) -
Bryan William P.
Publication year - 1987
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360260307
Subject(s) - sorption , biopolymer , thermodynamics , chemistry , sorbent , hysteresis , adsorption , organic chemistry , polymer , physics , quantum mechanics
Abstract In order to understand the mutual interactions between water and a biopolymer, thermodynamic analysis of sorption isotherms of water vapor by the biopolymer is necessary. These isotherms are irreversible and show sorption hysteresis. The reasons for such behavior are not established. As a continuation of previous work, general relationships for thermodynamic quantities of sorption are derived for the general case when the sorbent consists of two uniform phases. As in the case of a single sorbent phase, the Clausius–Clapeyron equation can be used to obtain differential entropies of sorption. Two special cases for the two‐phase situation—equilibrium hysteresis and partial equilibrium hysteresis—are plausible models for the irreversibility seen in water–biopolymer interactions. When differential entropy of sorption is plotted as a function of amount of water sorbed per mole of biopolymer, irregularities are generally seen. It is suggested that these irregularities reflect changes in conformation and/or dynamics of the biopolymer molecule.