Εξειδίκευση τύπου :	Άρθρο σε περιοδικό τύπο
Τίτλος:	Hydration effects on thermal transitions and molecular mobility in Xanthan gum polysaccharides
Δημιουργός/Συγγραφέας:	Tegopoulos, Sokratis N [EL] Παπαγιαννόπουλος, Αριστείδης[EN] Papagiannopoulos, Aristeidis Kyritsis, Apostolos
Ημερομηνία:	2024-01-11
Γλώσσα:	Αγγλικά
ISBN:	14639076
DOI:	10.1039/d3cp04643e
Άλλο:	38205826
Περίληψη:	In this work, the xanthan gum (XG) polysaccharide is studied over a wide range of temperatures and water fractions 0 ≤ hw ≤ 0.70 (on a wet basis) by employing differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). The investigation reveals that the critical water fraction for ice formation is about 0.35. Glass transition temperature (Tg) was determined through calorimetry experiments for all the samples studied. Water acts as a strong plasticizer, i.e., decreasing Tg, for water fractions up to about 0.35. A secondary (local) relaxation process is recorded in both dry and hydrated samples, which is sensitive to the presence of water molecules. This fact indicates that this process originates due to the orientation of small polar groups of the side chain, or/and due to the local main chain dynamics. Two types of long-range charge transport processes were resolved. The first is related to the conductive paths being formed via bulk-like ice structures (at high hydration levels), whereas the second can be attributed to proton mobility via the hydrogen bond (HB) network of non-freezing water existing in XG. Interestingly, this process is exactly the same in all the hydrated samples with hw > 0.25. With respect to the sample with hw = 0.27, a Vogel-Tammann-Fulcher (VTF)-like polarization process has also been recorded which seems to be related to long-range charge mobility via interconnected water clusters. As far as we are aware, this is the first time that XG is studied in terms of glass transition and molecular mobility over a wide range of hydration levels combining DSC and BDS techniques.
Τίτλος πηγής δημοσίευσης:	Physical chemistry chemical physics : PCCP
Θεματική Κατηγορία:	[EL] Φυσική και θεωρητική χημεία[EN] Physical and theoretical chemistry [EL] Φασματοσκοπία[EN] Spectroscopy
Λέξεις-Κλειδιά:	Calorimeters Glass Glass transition Hydration Molecules Calorimetry experiment
Όροι και προϋποθέσεις δικαιωμάτων:	This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.
Ηλεκτρονική διεύθυνση στον εκδότη (link):	https://doi.org/10.1039/D3CP04643E
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο