Abstract
Dynamic vapor sorption (DVS) coupled with deuterium exchange was applied in determining the amount of hydroxyl (OH) groups accessible for deuteration in pulps and pure cellulose quantitatively. The samples studied with the method were different types of chemical pulps as well as microcrystalline and amorphous cellulose powders. The measurement sequence consisted of drying the samples first until the change in sample mass was less than 0.0005% min−1 followed by rewetting the sample with deuterium oxide (D2O) vapor at set relative humidity (RH) of 95% for 600 min and then drying the sample again the same way as the initial drying was done. The method allows determination of the absolute amount of OH groups accessible to deuterium exchange in the samples fully automatically within 1 day. In addition, the equilibrium moisture contents (EMC) of the samples were measured at RH 95% without prior drying enabling the assessment of the EMC of the samples in as-received state without the need to assess the effect of drying. The accessibilities of chemical pulps were found to vary between 54 and 61% of the theoretical maximum, whereas the accessibilities of microcrystalline cellulose and amorphous cellulose were 51 and 63%, respectively. Interestingly, it was found that the accessible OH group content and the EMC of the samples in mol kg−1 correlated with each other and that, in fact, their ratio was close to one.Graphical abstract
Highlights
Cellulose plays a significant role in the on-going shift from fossil-based economies to renewable resourcebased bioeconomies
For determining the accessibility of the pulps and cellulose powders, only one drying-rewetting-drying cycle was applied in this work to minimize hornification, i.e. cellulose microfibril aggregation, associated with drying of the samples
The amount of accessible OH groups in several different types of chemical pulps and pure cellulose samples was quantified based on Dynamic vapor sorption (DVS) with deuterium exchange
Summary
Cellulose plays a significant role in the on-going shift from fossil-based economies to renewable resourcebased bioeconomies. As an abundant and renewable biopolymer, cellulose is in the key position when choosing sustainable raw materials. Manufacturing novel cellulosic products, such as cellulosic nanomaterials (Brinchi et al 2013; Habibi et al 2010), biofuels (Lienqueo et al 2016; Sun and Cheng 2002) and regenerated cellulose materials (Stepan et al 2016; Wang et al 2016), requires in most cases chemical modification of cellulose or even its dissolution. The availability of the OH groups has been related with the water uptake of cellulose fibers in aqueous environment. The means to assess the accessibility of the OH groups in cellulose for water has been a topical question for decades and remains to be so, perhaps more than ever, today
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