We report on how the local structure and the diffusional motion change upon increasing the alkyl chain length in 1-alkyl-3-methylimidazolium cation ionic liquids. This study has been performed by combining pulse field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy and small angle X-ray scattering (SAXS) experiments. The cationic side chain length varies from ethyl (n = 2) to hexadodecyl (n = 16), while the anion is always bis(trifluoromethanesulfonyl)imide (TFSI). We find that the self-diffusivity of the individual ionic species is correlated to the local structure in the corresponding ionic liquid, namely the nano-segregation into polar and non-polar domains. In agreement with previous results, we observe that for relatively short alkyl chains the cations diffuse faster than the anions; however we also note that this difference becomes less evident for longer alkyl chains and a cross-over is identified at n ≈ 8 with the anions diffusing faster than the cations. Our results indicate that this controversial behavior can be rationalized in terms of different types of cation-cation and anion-anion orderings, as revealed by a detailed analysis of the correlation lengths and their dispersion curves obtained from SAXS data. We also discuss the validity of the Stokes-Einstein relation for these ionic liquids and the evolution of the extrapolated cationic radius that was found to depend non-strictly linearly on n, in agreement with the cation-cation correlation lengths.

This study presents results that show that the fine structure of arabinoxylan affects its interaction with cellulosic surfaces, an important understanding when designing and evaluating properties of xylan-cellulose-based materials. Arabinoxylan samples, with well-defined structures, were prepared from a wheat flour arabinoxylan with targeted enzymatic hydrolysis. Turbidity measurements and analyses using NMR diffusometry showed that the solubility and the hydrodynamic properties of arabinoxylan are determined not only by the degree of substitution but also by the substitution pattern. On the basis of results obtained from adsorption experiments on microcrystalline cellulose particles and on cellulosic model surfaces investigated with quartz crystal microbalance with dissipation monitoring, it was also found that arabinoxylan adsorbs irreversibly on cellulosic surfaces and that the adsorption characteristics, as well as the properties of the adsorbed layer, are controlled by the fine structure of the xylan molecule.

Solutions of cellulose in a mixture of tetrabutylammonium fluoride and dimethyl sulfoxide (TBAF/DMSO) containing small and varying amounts of water were studied by nuclear magnetic resonance (NMR). By measuring the composition dependences of 19 F NMR and 1 H NMR chemical shifts and line widths, details on the dissolution and gelation mechanisms for cellulose in TBAF/DMSO were elucidated. Our results suggest that the strongly electronegative fluoride ions act as hydrogen bond acceptors to cellulose hydroxyl groups, thus dissolving the polymer by breaking the cellulose-cellulose hydrogen bonds and by rendering the chains an effective negative charge. It was found that the fluoride ions also interact strongly with water. Small amounts of water remove the fluoride ions from the cellulose chains and allow reformation of the cellulose-cellulose hydrogen bonds, which leads to formation of highly viscous solutions or gels even at low cellulose concentrations.

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Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.

Cyclodextrins (CDs) can form inclusion complexes with a wide variety of molecules making them very attractive in different areas, such as pharmaceutics, biochemistry, food chemistry and textile. In this communication we will report on the physico-chemical characterization of cellulose modified with CDs by means of infra-red spectroscopy (FTIR), cross polarization magic angle spinning solid state nuclear magnetic resonance (CP-MAS NMR), polarized optical microscopy (POM) and thermal gravimetric analysis (TGA). Both CP-MAS NMR and FTIR indicate that CDs are chemically attached to cellulose backbone through the formation of ester bonds. Furthermore, the CD-grafted cellulose was dissolved in a "superphosphoric" acid solution but, despite the increase of hydrophilicity due to the modification, POM revealed that grafted cellulose was less soluble when compared to the unmodified polymer. The formation of a complex CD-cellulose network is suggested.

To investigate the duration of breastfeeding and the impact of maternal factors for cessation of breastfeeding in twin infants, the authors undertook a population-based cohort study. Breastfeeding data obtained from Child Health Centres were matched with data on infant and maternal demographics from Swedish national registers. A total of 1.657 twins were included, of whom 695 were born preterm. Breastfeeding frequencies in preterm twins were 79% at 2 months, 58% at 4 months, 39% at 6 months, 14% at 9 months, and 6% at 12 months. In term twins, the corresponding frequencies were 84%, 63%, 45%, 18%, and 6%, respectively. In both preterm and term mothers, mothers who had a lower educational level or smoked at first antenatal care visit were subject to earlier cessation of breastfeeding by 6 months of age. In addition, in mothers of term infants, mothers who were < 23 years old or primiparous had a higher risk for cessation of breastfeeding before 6 months. Thus, mothers of twins have a good potential to breastfeed, but additional support is needed for those more susceptible to early cessation of breastfeeding.

Herein, we explore the intrinsic ability of cellulose dissolved in NaOH(aq) to reversibly capture CO 2 . The stability of cellulose solutions differed significantly when adding CO 2 prior to or after the dissolution of cellulose. ATR-IR spectroscopy on cellulose regenerated from the solutions, using ethanol, revealed the formation of a new carbonate species likely to be cellulose carbonate. To elucidate the interaction of cellulose with CO 2 at the molecular level, a 13 C NMR spectrum was recorded on methyl α-D-glucopyranoside (MeO-Glcp), a model compound, dissolved in NaOH(aq), which showed a difference in chemical shift when CO 2 was added prior to or after the dissolution of MeO-Glcp, without a change in pH. The uptake of CO 2 was found to be more than twice as high when CO 2 was added to a solution after the dissolution of MeO-Glcp. Altogether, a mechanism for the observed CO 2 capture is proposed, involving the for-