In this work, thermally stimulated currents (TSC) analyses combined with dynamic dielectric spectroscopy (DDS) have been applied to the investigation of molecular mobility of cellulose. The correlation between results obtained by both methods allows us to attribute the low temperature DDS relaxation mode to the c-mode resolved in TSC. The values of its activation parameters point out that the chain mobility remains localized. At high temperature, the various dielectric relaxation phenomena are separated by applying a recent analytical protocol. The comparison between the activation enthalpy values obtained by DDS and TSC leads to the assignment of the socalled a-mode to cooperative movements of polymeric sequences. The Arrhenius behavior of a-relaxation time is explained using the strong/fragile pattern. The influence of water content on secondary and primary relaxation modes was examined as well.
a b s t r a c tThe influence of hydration on cellulose molecular mobility is investigated by two dielectric methods at different molecular scale. The mobility of side groups, assigned to c mode, for dried cellulose increases. The water molecules have an anti-plasticizer effect on c mode due to the water-polymer hydrogen bonding. For the b relaxation mode, only observed by the Thermo Stimulated Current technique, the hydration plays a role of plasticizer. The a relaxation mode assigned to the delocalized cooperative mobility of long chain segments of cellulose is plasticized by water. The study of activated parameters deduced from fractional polarization procedure, shows an increase of the activation enthalpy range with dehydration. It permits to conclude that reduction of hydrogen bonds density leading to a more extended cooperative mobility.
In this work, thermally stimulated currents (TSC) analyzes combined with dynamic dielectric spectroscopy (DDS) have been applied to the investigation of polymers' molecular mobility involves in poplar cell wall. The molecular origin of the various dielectric relaxations has been determined. Cellulose and lignin effects in wood dielectric response were distinguished. The correlation between results obtained by both dielectric methods allows us to follow molecular mobility involved in delocalized movement as primary relaxation mode. For these two major components of wood, the evolution of relaxation times involve in a-relaxation mode is explained using the strong/fragile pattern. We compared the cellulose and lignin in situ and ex situ responses to interpret wood compound behavior. The importance of structural wood interactions which modified the molecular mobility of polymer components will be underlined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.