LECTURE 5: THE POLYMER THAT IS SOURCED FROM AIR AND WATER

Transcription

1 LECTURE 5: THE POLYMER THAT IS SOURCED FROM AIR AND WATER

2 CELLULOSE IN THE BIOSPHERE Main component of higher plant cell walls Also formed by some algae, fungi, bacteria, and marine animals (Whistler, 1997, Kirk- Othmer, 1993) Wood cell wall image: A.J. Panshin, Carl de Zeeuw; Textbook of Wood Technology, 4 th edition

3 various other plant fibers, commercial sources other than wood pulp and cotton linters. (Hanna, 2001; Ang, 2001; Franz, 1990) oat hulls wheat straw soybean hulls jute sugar beet pulp corn cobs or stalks rice hulls bamboo ramie bagasse (sugar cane stalks) flax

4 BILLIONS OF TONNES OF MATERIAL (THAT S A LOT OF STORED CO2) Eichhorn et al. J. Mater. Sci. 2001

5 TWO GLUCOSE UNITS TOGETHER = CELLOBIOSE OH HO HO O OH OH OH OH HO HO OH O OH OH HO O OH HO O O O HO HO OH O OH OH OH

6 Cellulose is the scaffolding of the plant cell wall Courtesy, Forest Products Lab Pulping and bleaching 1 µm Forest Products Laboratory A cube of wood Wood fiber ~3 mm length ~50 µm dia. 200 nm Nanoscale cellulose 6

7 CELLULOSE IS ALWAYS FOUND AS A BUNDLE MICROFIBRIL IN NATURE Existence (cell wall, secondary cell wall for wood 40~50%) Functionality (main structural component) [Microfibril portion of this figure adapted from J. K. C. Rose and A. B. Bennett, Cooperative Disassembly of the Cellulose-Xyloglucan Network of Plant Cell Walls: Parallels Between Cell Expansion and Fruit Ripening, Trends Plant Sci. 4, (1999).]

8 INTRA- AND INTER H-BONDS STICK CHAINS TOGETHER K.H. Gardner, J. Blackwell, ACS symposium series, in: J.C. Arthur Jr. (Ed.), Am. Chem. Soc., Washington D.C., 1974, Vol. 48, pp.42-55

9 CELLULOSE CHAINS ARE PACKED TOGETHER IN A SEMICRYSTALLINE FORM

10 NATIVE CELLULOSE COMES IN AN ORDERED ARRANGEMENT 2.0x10 1 Plane x10 1 WP 1.0x x10 0 FWHM Neutron crystallography, molecular dynamics, and quantum mechanics studies of the nature of hydrogen bonding in cellulose I, Nishiyama et al. Biomacromolecules, (2008) 9: Theta

11 SOME ORDER DISRUPTED ALONG FIBRIL Potential kinks in fibrils Habibi et al. 2010

12 CELLULOSE BUNDLES ARE EXCELLENT REINFORCEMENT FOR THE WOOD CELL WALL Difficult to penetrate the surface layers of cellulose to crystalline core Not just glycosidic bonds at C1-C4 holding together chains self reinforcement through hydrogen bonds Limited free space within the microfibril bundle

13 SO WHY CAN T CELLULOSE FLOW LIKE OTHER POLYMERS WHEN HEATED? Thermoplastics flow when heated and can be dissolved in some solvent* Thermosets are cured and do not flow when heated because each chain is linked with another forming a network. *Starch can be made into thermoplastic starch which can soften because the crystalline structure is disrupted and the starch is heavily plasticized. as a linear or branched polymer is not crosslinked, it can usually be manipulated to behave as a thermoplastic.

14 CELLULOSE MICROFIBRILS ARE DIFFICULT TO ISOLATE FROM STARTING SOURCE Wood pulp Cotton linters Requires separation of noncellulosic components Image sources:

15 DELIGNIFICATION OF WOOD PROVIDES A WONDERFUL MATERIAL FOR INDUSTRY Cellulose pulp is used for numerous materials Paper, tissue, gun cotton, thickners, coatings, tool handles, medical membranes, filters, textiles Delignification in the chemical pulping process removes the bulk of lignin Use of pulp in chemical industry is impacted by purity and average degree of polymerization of cellulose Pulping processes, level of extraction, and species impact solubility and reactions Highest purity pulps require significant bleaching with oxidative chemicals Large environmental impact

16 MICROFIBRILS FROM WOOD PULP ARE WOUND UP LIKE THREADS ON A ROPE Uetani and Yano 2011 Biomacromolecules Typical paper making fibers ~3-5mm in length Total diameter of fiber is on the order of µm Cell wall thickness is 1-5 µm

17 AFTER REMOVING THE OTHER COMPONENTS FROM WOOD THE FIBERS RETAIN SHAPE Strong intermolecular forces hold cellulose bundles together Cellulose can be dissolved in novel/exotic highly polar solvents Dimethylacetamide with LiCl M-methylmorpholine oxide (lyocell process) Ionic liquids To dissolve in typical organic solvents must modify into derivatives Cellulose acetate Cellulose ethers can dissolve in water Carboxymethyl cellulose Hydroxyethylcellulose Very difficult to disrupt bundles and utilize New technologies creating nanocellulose

18 Three approaches to isolate microfibrils and fibril fragments Enzymatic or chemical modification Atom economy? Paakko et al.

19 Method 1 creates cellulose nanocrystals Battista In Cellulose Technology Research. ACS Symposium Series 10 pg Renneckar et al In Cellulose Nanocomposites. ACS Symposium Series 938 pg Cellulose + mineral acid + water + heat

20 Method 2 & 3 creates a network of fibril bundles 15 to 50nm in diameter. (top) wet grinder and (bottom) pressure shear homogenizer from Masuko and Microfluidics, respectively. Iwamoto et al. Abe et al.

21 Fibrillation of modified pulp using blender Uetani and Yano 2011 Biomacromolecules

22 Oxidation followed by sonication unwinds the fiber Sonicated oxidized wood pulp

23 How stiff are these cellulose materials? Measurement of elastic modulus of single cellulose microfibrils using atomic scope microscopy By Iwamoto, Shinichiro; Isogai, Akira; Iwata, Tadahisa From Cellulose Communications (2010), 17(3), The elastic moduli of single microfibrils prepd. by TEMPO-oxidn. and acid hydrolysis were ± 31.3 and ± 28.8 GPa, resp. The result showed that the exptl. detd. modulus of the highly cryst. tunicate microfibrils was in agreement with the elastic modulus of native cellulose crystals. Note, the crystal modulus is only reported to be ~138 GPa from theoretical studies

24 Strength There is little data out there in terms of measuring the strength of individualized nanoparticles. An interesting modeling approach was used to estimate strength. Published in: Tsuguyuki Saito; Ryota Kuramae; Jakob Wohlert; Lars A. Berglund; Akira Isogai; Biomacromolecules Article ASAP DOI: /bm301674e Copyright 2012 American Chemical Society

25 (a) TEM image of negatively stained NCC dropcast from a dilute suspension (scale bar = 200 nm). (b) Schematic illustration of the chiral nematic organization of NCC embedded within an organosilica matrix. (c) Solid-state 13C CP/MAS NMR spectra of composite sample C3 (green) and mesoporous organosilica CMO3 (blue). (d) N2 isotherm and BJH pore-size distribution (inset) for CMO3. Published in: Kevin E. Shopsowitz; Wadood Y. Hamad; Mark J. MacLachlan; J. Am. Chem. Soc. 2012, 134, DOI: /ja210355v Copyright 2011 American Chemical Society

26 Published in: Kevin E. Shopsowitz; Wadood Y. Hamad; Mark J. MacLachlan; J. Am. Chem. Soc. 2012, 134, DOI: /ja210355v Copyright 2011 American Chemical Society

27 SUMMARY Cellulose is derived from photosynthesis Starch differs from cellulose because of the glycosidic linkage (this impact is significant!!!) Cellulose is a semicrystalline polymer where there is significant organization of chains in a bundle Hydrogen bonding and dispersion forces hold cellulose chains together After delignification, wood cellulose can be utilized for a variety of purposes Modifying cellulose dramatically changes its properties.