Focus Areas 2/3 Forest Nanomaterials/Control of Water Lignocellulosic Interactions for Modification of Properties

Focus Area 2: Forest Nanomaterials Technical Challenges Nano-fractionalization and nano-catalysis for separations; Non covalent disassembly/re-assembly Entropic effects in the assembly and disassembly of nanomaterials in forest materials Focus Area 2: Forest Nanomaterials Target: Liberation and use of nanocellulose building blocks

Cellulose Morphology (William T Cellulose Morphology (William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY) Left – SEM of exploded http://www.chem.vt.edu/chem-dept/helm/3434WOOD/notes1/ultra1.html Right – schematic of a tracheid - Cote- Fiber (cell) White pine tracheids ESF archives Wood Cell Schematic Cote -ESF Microfibril Hanna, ESF

Cellulose Nanowhiskers Field-emission electron micrograph of freeze-dried cellulose whiskers of nanoscale cross-sectional dimensions prepared at Paprican’s Vancouver laboratory from H2SO4 hydrolyzed bleached Kraft softwood pulp W. Hamad. Can. Jour. Chem. Eng. 84. Oct. 2006. pp513 – 519

Nanocrystalline Cellulose 200 nm William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210 25% - 30% strength of Carbon Nanotubes

Surface Area vs. Aspect Ratio Montmorillonite Clay: Length: 1 nm Diameter: 200 – 400 nm Aspect Ratio: 0.005 – 0.0025 (200 – 400) Cellulose Nanocrystals: Length: 100 nm – several mm Diameter: 3 – 20 nm Aspect Ratio: 10 – 10,000 William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210

Crystal and Microfibril Preparation (William T Crystal and Microfibril Preparation (William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY) Extraction, Bleaching: Dewax- Soxhlet Mill Alkali solution Sodium chlorite homogenize Hydrolysis (for nanocrystals): acid (HCl, H2SO4) concentrations ( 65%) temperature (40°C) hydrolysis time (1 – 2 h) acid-to-substrate ratio (0.1 – 0.5 mol/g) Microfibrils Nanocrystals + Acid 20g in 400mkl toluene/200ml ethanol 6h @115-118c

Liberation and Use of Nanocellulose Need Identify/develop more commercially attractive methods to liberate nanocellulose, in either the whisker or crystalline forms Once liberated, nanomaterials must be: Characterized Stabilized Incorporated into existing and new applications

Focus Area 3 : Understand the control of water-lignocellulose interaction for modification of properties Target Understand water forest materials interactions Control effects of water on wood and paper properties Shed water more efficiently Technical Challenges Interfacial properties at nanoscale Production of hydrophilic/hydrophobic switchable surfaces Biological activity control

Background The response of lignocellulosics to moisture (liquid and vapor) is due almost entirely to the supermolecular structure of the biopolymers and nanoscale structures of the composites that comprise the wood fiber Primary microfibrils – 4 –10 nm in cross-section Microfibril angle Degree of crystallinity Species, growing conditions, processing conditions – all affect interactions between water and lignocellulosics

Background Control/modification of surfaces of lignocellulosic materials using nano coatings or impregnation of nano particles can be used to provide physical/chemical barriers to modify the effect of moisture by changing wetting (hydrophilicity/hydrophobicity) and adhesion forces. Durability and other end use properties of wood and paper products closely tied to the response to moisture Interfiber bond strength - paper Dimensional stability – wood and paper Decay, fungi, rot, UV stability - wood Very large volumes of water are handled in the manufacture of forest products. Nano materials which can modify drainage rates and drying could result in significant reductions in energy requirements.

WATER VAPOR AS A PROBE TO CHARACTERIZE SURFACES AND NANOSTRUCTURES

Softwood Bleached Kraft WATER VAPOR ACCESSIBLE SURFACE AREA AND SURFACE ENERGY OF ADSORPTION FOR SELECTED MODEL COMPOUNDS AND PULPS PULP SAMPLE AVERAGE S. A. (m2/g) AVERAGE S.E.A. (ergs/cm2) Microgranular Cell. (model) 103.71 189.85 CarboxyMethyl Cell. 215.89 197.12 Xylan Powder - Larch 349.20 198.14 Softwood Bleached Kraft 173.57 171.87 TMP 226.32 137.14 Radiata Pine Pulp 148.7 175.2 Pine (Russian) 144.4 174.1 Eucalyptus 132.7 187.7

Summary Lignocellulosic fiber is a nanocomposite Water accessible surface area determined by nanostructure which is dependent on species and pulping processes Surface energy of adsorption Model compounds show impact of different functional groups and the concentration of those groups on the surface Pulps show differences due to both pulping process and species Eucalyptus has a lower accessible surface area, but a significantly higher surface energy of adsorption indicating a higher concentration of hydrophilic groups on the accessible surface

Examples

Relate to Macroscopic Properties 1 cm Growth rings 50 mm Cell wall layers

News, 45 g/m² Moisturized sheet Dry sheet ESEM - Environmental Scanning Electron Microscope G. A. Baum 2003

Water Droplets on “Nanoseal” Treated Wood Nanoparticles adhere directly to the substrate molecules (molecular bonding) and assemble into an invisible ultra-thin nanoscopic mesh providing a long lasting, self-cleaning, hydrophobic surface. The wood is protected against decay, fungi and rot. It is dimensionally and UV stable. It will not wear off and cannot be removed by water, normal cleaning agents or high pressure equipment.

Wood Surface Repels Water Droplets Water droplets rest on a wood surface impregnated with BASF’s “Lotus Spray” The surface is superhydrophobic . Thus contact area between the surface of the wood and the water is reduced to a minimum, and the adhesive forces are greatly decreased making the water drops assume a globular form.