Characterization of cellulose with NMR

Transcription

1 Characterization of cellulose with NMR Lars Nordstierna & Åsa Östlund Applied Surface Chemistry

2 NMR SPECTROSCOPY EXPERIMENTAL NMR Direct information chemical analysis quantitative analysis

3 NMR SPECTROSCOPY EXPERIMENTAL NMR 1) Liquid NMR 2) Liquid NMR, Chemical Shift Imaging 3) Solid State NMR 13 C 4) NMR Cryoporometry

4 Liquid NMR I Dissolution and Gelation of Cellulose in TBAF/DMSO Solutions: The Roles of Fluoride Ions and Water Situation: To chemically modify cellulose to reach high yield dissolved cellulose Cellulose is insoluble in water but soluble in salt containing solvents e.g.: LiCl/DMAc (McCormick, Lichatowich,J. Polym. Sci. 1979, 17) TBAF/DMSO (Heinze et al., Macromol. Chem. Phys. 2000, 201) Ionic liquids, 1 butyl 3 methylimidazolium cation with Cl, Br, SCN (Swatloski et al., JACS 2002, 124) Cellulose solutions hygroscopic and transforms into gels in the presence of water Aim in Paper I: To increase understanding of interactions between cellulose and the solvent ions, and the impact of water Method: NMR Spectroscopy

5 Liquid NMR I 19 FNMR a) Shift change TBAF/DMSO F - SiF -2 6 HF Change in the chemical surrounding TBAF/DMSO + 1% cellulose b) Peak broadening F [ppm] Association to a larger molecule OR A distribution of molecular surroundings

6 Liquid NMR I Dissolution and gelation of cellulose in TBAF/DMSO Elimination of water will increase the effect of F electrostatic separation of the cellulose chains Dissociated salt: small ion will associate to OH cellulose Bulky counter ion to reduce the attraction between the ions

7 Liquid NMR II Chemical Shift Imaging NMR to track gel formation Courtesy of A. Viridén Situation: In many applications hydrogels and transport of molecules in hydrogels are of interest e.g.: Drugs diffusing through a water swollen tablet Urine uptake of diapers The mass transport of the components in the system is dependent on their interaction with the material, the osmotic pressure, and concentration gradients Diffusion coefficient Aim in Paper II: To monitor multi component mass transport Method: 19 F and 1 H Chemical Shift Imaging

8 Liquid NMR II Gel GelGel Gel Gel Gel H2OGel Gel

9 Liquid NMR II Extract diffusion from the images H 2 O Gel D = σ 2 /2t Östlund et al, J. Coll. Interface Sci 344 (2010)

10 Solid State NMR I Chalmers University Lars of Nordstierna Technology PAPER PULP 13 C SPECTRUM

11 Solid State NMR PAPER PULP 13 C SPECTRUM

12 Solid State NMR PROJECT Purpose the effect of regeneration conditions on structural properties Objective to study regenerated cellulose with regard to coagulation medium and drying conditions - pore size distribution (nm-scale) - morphology

13 Solid State NMR METHODS Drying 5 conditions (never-dried ->..humidity ->..oven) Solid characterization regenerated material - solid-state NMR spectroscopy - NMR cryoporometry

14 Solid State NMR Chalmers University Lars of Nordstierna Technology PAPER PULP 13 C SPECTRUM

15 Solid State NMR I Chalmers University Lars of Nordstierna Technology RESULTS Morphology cellulose I (native) cellulose II (H 2 O) amorphous (alcohols)

16 Solid State NMR I Chalmers University Lars of Nordstierna Technology RESULTS

17 RESULTS Solid State NMR Chalmers University Lars of Nordstierna Technology Crystallinity Coagulation media: Water increased crystallinity upon drying

18 NMR cryoporometry RESULTS Porosity pore collapse upon drying -> increased amount of nm-pores similar behavior for films coagulated in all solvents (both crystalline and amorphous films)

19 NMR SPECTROSCOPY EXPERIMENTAL NMR 1) Liquid NMR 2) Liquid NMR, Chemical Shift Imaging 3) Solid State NMR 13 C 4) NMR Cryoporometry

20 ACKNOWLEDGMENT Funding Södra Skogsägarna Foundation for Research SP Technical Research Institute of Sweden The Swedish Research Council Formas Equipment and Facilities Forest Products and Chemical Engineering, Chalmers Swedish NMR Centre