Influence of water on localized and delocalized molecular mobility of cellulose

Abstract

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.

Influence of hydrogen bonds on glass transition and dielectric relaxations of cellulose

“…The activation parameters are reported in Figures 9 and 10. These results are coherent with published data from mechanical and dielectric studies [28][29][30][31]49]. The activation energy of the γ mode increases with the hydration level whereas it decreases for the β mode.…”

“…We have already shown that the fruitful synergy of DDS/TSC combination allows us to investigate the changes within the molecular dynamics of cellulose caused by water influences [28,29]. These results stimulate us to study the issue of cellulose glass transition with different water contents using the classical techniques of DSC.…”

“…Dielectric dynamic spectroscopy (DDS) has been already used on polysaccharides like cellulose and its derivatives [22][23][24][25][26][27][28][29]. Four dielectric relaxations modes are usually observed γ, β, β wet and α, in the order of increasing temperatures [22][23][24][25][26][27][28][29].…”

“…Four dielectric relaxations modes are usually observed γ, β, β wet and α, in the order of increasing temperatures [22][23][24][25][26][27][28][29]. The dielectric properties of cellulose have been also investigated by combined DDS/TSC [28].…”

Dielectric and mechanical properties of various species of Madagascan woods

“…These two relaxation modes have been resolved experimentally in a series of elementary thermograms revealing the existence of a discrete distribution of relaxation times. According to the literature, the c relaxation mode of cellulose has been attributed to molecular mobility of Roig et al 2011a) and the b relaxation mode of cellulose to molecular mobility of glycosidic rings thanks to b 1-4 glycosidic bonds (Saad et al 1996;Saad and Furuhata 1997;Einfeldt et al 2000aEinfeldt et al , b, 2001Einfeldt et al , 2003Einfeldt et al , 2004Einfeldt and Kwasniewski 2002;Meissner et al 2000;Jafarpour et al 2007Jafarpour et al , 2009). Lignin has also been studied by TSC in the low temperature range.…”