Swelling of cellulose. Puu Cellulose Chemistry Michael Hummel

Transcription

1 Swelling of cellulose Puu Cellulose Chemistry Michael Hummel

2 Content Swelling basics Fiber structure Swelling through different solvents Ballooning Nature s functional swelling 2

3 to swell become larger or rounder in size, typically as a result of an accumulation of fluid 3

4 Understanding of swelling Important initial step in several processes: obtaining regenerated fibers (e.g., viscose and Lyocell) Mercerization functionalization of cellulose under heterogeneous and homogeneous reaction conditions El Seoud et al. Cellulose 2008, 15, Klemm D, Philipp B, Heinze T, Heinze U, Wagenknecht W (1998) Comprehensive cellulose chemistry. Wiley-VCH, Weinheim 4

5 Types of swelling in cellulose Intercrystalline swelling swelling agent penetrates the intercrystalline "amorphous regions and enters the interstices between the fibrillary structure units (elementary fibrils and their random assemblies) Crystallites amorphous region voids H. Krässig, Cellulose Structure, Accessibility and Reactivity Chemistry of the Textiles Industry (Ed. C.Carr) M.A. Wilding, The structure of fibres 5

6 Types of swelling in cellulose Intracrystalline swelling swelling agent enters the fibrillar interstices and penetrates via the interlinking regions from both ends into the elementary crystallites, in most cases causing drastic changes in the crystal lattice structure Crystallites amorphous region voids H. Krässig, Cellulose Structure, Accessibility and Reactivity Chemistry of the Textiles Industry (Ed. C.Carr) M.A. Wilding, The structure of fibres 6

7 Structure recap (A) cotton fibers according (B) softwood tracheids and hardwood libriform fibers C, surface of cuticle L, lumen ML, middle lamella (mainly lignin) P, primary wall (approx. 1 µ.m thick) R, reversal of the fibril spiral S1, transition lamella or "winding layer" of secondary wall (approx. 1 µ.m thick) S2, main body of secondary wall (approx. 4 µm thick) T, tertiary wall W, wart layer. H. Krässig, Cellulose Structure, Accessibility and Reactivity K. Gotze (Ed.), Chemiefasern nach dem Viskoseverfahren, Chapter 5, p. X, Springer Verlag, Berlin, 1967); D. Fengel and G. Wegener, Wood: Chemistry, Ultrastructure, Reactions, Chapter 2, p. 15, Walter de Gruyter, Berlin, 1984). 7

8 Swelling through different solvents Swelling of cellulose: decreases with increasing crystallinity decreases with increasing DP depends on number and structure of micro pores depends on the solvent properties 8

9 Swelling through different solvents Extent of solvent uptake and swelling strongly depends on solvent characteristics such as molar volume or various solvent descriptors used to quantify the polarity native 1-butanol water Fidale et al. Macomol. Chem. Phys. 2008, 209,

10 Swelling through different solvents Extent of solvent uptake and swelling strongly depends on solvent characteristics such as molar volume or various solvent descriptors used to quantify the polarity native acetonitrile DMSO Fidale et al. Macomol. Chem. Phys. 2008, 209,

11 Swelling through different solvents Solvent needs to interact with cellulosic hydroxyl groups for efficient swelling El Seoud et al. Cellulose 2008, 15,

12 Swelling through different solvents Solvent needs to interact with cellulosic hydroxyl groups for efficient swelling Fidale et al. Macomol. Chem. Phys. 2008, 209,

13 Swelling through different solvents Solvents are described by a multitude of discriptors Hildebrand s solubility parameter, d Hildebrand, which can be split into three components, namely d D (van der Waals dispersion forces), d H (hydrogenbonding), and d P (Keesom s dipole interactions) molar volume V S Gutmann s acceptor (AN) and donor (DN) number Kamlet-Taft: solvent acidity a s, basicity b s, and dipolarity/polarizabilty p s 13

14 Swelling through different solvents V S applicable for homologous series of solvents 14

15 Swelling through different solvents V s solvent molar volume; d Hildebrand Hildebrand solubility parameter and d P polar component; b s Kamlet-Taft basicity; p s dipolarity/polarizability; DN donor number El Seoud et al. Cellulose 2008, 15,

16 Swelling through different solvents V s solvent molar volume; d Hildebrand Hildebrand solubility parameter and d P polar component; b s Kamlet-Taft basicity; p s dipolarity/polarizability; DN donor number Fidale et al. Macomol. Chem. Phys. 2008, 209,

17 Swelling through different solvents Several descriptors needed to establish correlation with swelling = El Seoud et al. Cellulose 2008, 15,

18 Swelling through different solvents Calculated nsw based on the descriptors V s solvent molar volume; b s Kamlet-Taft basicity; p s dipolarity/polarizability nsw=a+bv s +cb s +dp s Cotton Eucalyptus pulp Fidale et al. Macomol. Chem. Phys. 2008, 209,

19 Cellulose swelling: gross structure of cellulose as a moiety of particles, fibers, or a film (i.e., solid cellulosic phase) maintained, despite significant changes of physical properties and an increase in sample volume due to uptake of the swelling agent Cellulose dissolution: transition from a two-phase system to a onephase system (clear solution), in which the original supramolecular structure of cellulose is destroyed However, there is often no clear-cut borderline between a swelling process and a dissolution process 19

20 Ballooning Cotton DP 1400 (8 wt% NaOH, -8 ºC) 20

21 Ballooning Spruce pulp DP 800 (8 wt% NaOH, -8 ºC) 21

22 Ballooning Cotton linter DP 620 (8 wt% NaOH, -8 ºC) 22

23 Swelling and dissolution Solvent quality Mode 1: Fast dissolution by disintegration into rod-like fragments Mode 2: Large swelling by ballooning and then dissolution of the whole fiber Mode 3: Large swelling by ballooning and partial dissolution of the fiber, still keeping its fiber shape Mode 4: Homogeneous swelling and no dissolution of any part of the fiber Mode 5: No swelling and no dissolution (non-solvent) 23

24 Mode 2: Balloning 24

25 Mode 2: Balloning A: unswollen fiber B: dissolution and ballooning C: undissolved P and S1 cell wall encapsulating dissolved cellulose Navard, Cuissinat. 7th International Symposium "Alternative Cellulose : Manufacturing, Forming, Properties", Sep 2006, Rudolstadt, Germany. 7 p., <hal > 25

26 Mode 2: Balloning Phase 1: balloon formation Phase 2: balloon bursting Phase 3: dissolution of the unswollen sections Phase 4: dissolution of the balloon membrane scraps 26

27 Mode 2: Balloning Budtova, Navard Cellulose 2016, 23,

28 Dissolution of enzymatically treated fibers Phase 1: homogeneous swelling of the treated fibers Phase 2: unwinding of the treated cotton and wood fibers. Once the treated cotton and wood fibers are swollen, a unwinding of its structure occurs. Phase 3: dissolution of the cellulose fibers; unwinding of treated cotton and wood fibers Navard, Cuissinat. 7th International Symposium "Alternative Cellulose : Manufacturing, Forming, Properties", Sep 2006, Rudolstadt, Germany. 7 p., <hal > 28

29 Dissolution of enzymatically treated fibers t = 325 sec t = 346 sec t = 360 sec untwisting due to the release of internal stresses built during the biosynthesis of fibers; as the treated cellulose fibers release their internal stresses, the pitch of the helical structure increases Navard, Cuissinat. 7th International Symposium "Alternative Cellulose : Manufacturing, Forming, Properties", Sep 2006, Rudolstadt, Germany. 7 p., <hal > 29

30 Nature s functional swelling Plants use the orientation of cellulose microfibrils to create cell walls with anisotropic properties and hygromorphism related to specific functions Microfibril angle (MFA) varies in different layers S2: 0-60º Burgert, Fratzl Integr. Comparat. Biol. 2009, 49, Fratzl et al. Faraday Discuss., 2008, 139,

31 MFA variations The lower the microfibril angle (MFA), the higher the modulus of elasticity of the wood, Burgert, Fratzl Integr. Comparat. Biol. 2009, 49, Fratzl, Barth Nature 2009, 462,

32 Nature s functional swelling Swelling of the cell can generate either tensile or compressive stresses depending mainly on different patterns of deposition of cellulose fibrils Burgert, Fratzl Integr. Comparat. Biol. 2009, 49,

33 Nature s functional swelling Internal stress upon swelling cause upward bend of conifer branches. Horizontal growth and uprighting of a conifer branch as a consequence of the combined action of upper and lower tissue parts, which enables the living tree to direct the organs towards a predetermined position. Fratzl, Barth Nature 2009, 462,

34 Functional swelling Hygromorphism due to composite structure of differently structures tissue layers: release of ripe seeds from conifer cones; upon drying in ambient air, pine cones open due to a bending movement wet dry Burgert, Fratzl Phil. Trans. R. Soc. A 2009, 367,

35 Functional swelling Architecture of wheat awns allows them to perform swimming movements and to propel the seed along and into the ground Burgert, Fratzl Phil. Trans. R. Soc. A 2009, 367,

36 Summary questions What is swelling? Which domains of cellulose are prone to water uptake? Which solvents are causing most swelling in cellulose? What is ballooning? What is the reason for ballooning? Examples for Nature using cellulose swelling? How is the microfibril angle connected to this? 36