Water in glassy carbohydrates: Opening it up at the nanolevel

Duncan Kilburn, Johanna Claude, Raffaele Mezzenga, Gunter Dlubek, Ashraf Alam, Job Ubbink

Research output: Contribution to journalArticlepeer-review

84 Scopus citations

Abstract

Sorption of water by glassy biopolymers and the effects of absorbed water on molecular mobility including plasticization, matrix rearrangements, and diffusion are poorly understood mainly because molecular and structural analyses are scarce. Here, we report the first investigation of the nanostructure of amorphous carbohydrates and the plasticizing effects of water by combining positron annihilation lifetime spectroscopy (PALS) and thermodynamic analysis. Surprisingly, we find that the average volume of the voids between the polymer chains increases with the water content of the matrix while the density of the matrix increases. Consequently, the free volume of the carbohydrate matrix decreases continuously up to the glass transition, primarily by the filling or elimination of the smallest intermolecular voids. We conclude that a so far unknown length scale, the typical size of intermolecular voids, is of fundamental importance in understanding the interaction of water with amorphous carbohydrates and their ensuing plasticization.

Original languageEnglish (US)
Pages (from-to)12436-12441
Number of pages6
JournalJournal of Physical Chemistry B
Volume108
Issue number33
DOIs
StatePublished - Aug 19 2004
Externally publishedYes

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