Layer-by-Layer Nanocoating on Lignocellulose Fibers: Conductive Polymers and Nanoparticles

Transcription

1 Layer-by-Layer Nanocoating on Lignocellulose Fibers: Conductive Polymers and Nanoparticles 2006 International Conference on Nanotechnology, April 26-28, 2006 Atlanta, GA Presented by: Yuri Lvov, and George Grozdits, Zonghuan Lu, M. Agarwal Title: Doctor Company: Louisiana Tech University, and Nano Pulp and Paper Co Nano Pulp & Paper

2 Layer-by-Layer Nanocoating on Lignocellulose Fibers 1) Nanoassembly on pulp microfibers, to systematically modify their surface charge and roughness; development of a repair process for broken fibers for better recycling. Biomimetic approach for synthesis in fiber lumen. Conductive fibers; ink-jet printing on fibers. 2) Smart paper with embedded sensors and polymeric microdevices, - fluorescent nanolayers and polymeric microchips to convert paper passive matrix to active matrix. Incorporation of cheap of micro- and nanosystems for home security purposes

3 Layer-by-Layer Nanocoating on Lignocellulose Fibers LbL assembly on pulp fibers was optimized using the following parameters: a) number of layers, b) salt concentrations, ph, temperature, solvents; c) polyelectrolyte molecular weights, d) time of deposition, and e) multilayer composition. We analyze colloidal stability of LbL-coated fibers and how homogeneous is the coating. Modification of mill broke. Conductive pulp fibers were made based on nanocoating with polythiophene (conductivity S/cm); frequency dependant capacity Fiber coating with nanoparticles (SiO2, clay) both on fiber surface and in lumen Integration of Nanocomposite Fibers into Paper: Nanocoated fibers were integrated in paper-making process. We optimize inter-fiber interactions by mixing LbL-treated positive and negative pulp in different ratio. Better recycling through LbL coating of mill broke was developed. Integration of conductive fibers gave paper with controlled conductivity (+ electrical microdevices) Nanotubule clay coated fibers will give paper loading / sustained release properties

4 Layer-by-layer Nanoassembly Poly(styrene sulfunate) (PSS, MW ~70 000) Poly(dimethyl diallylamide) (PDDA, MW ~100, ,000) Poly(ethylene imine) (PEI, MW ~70, 000) Poly(3,4-oxyethyleneoxythiophene)/poly(styrene sulfonate) LbL technology is based on the sequential deposition of oppositely charged polyelectrolytes, nanoparticles, or enzymes on surfaces of variable shape allowing the formation of multilayer shells from a wide range of components with nanometer precision.

5 Layer-by-layer Nanoassembly Polycations (PAH, PEI, PDDA) Polyanion PSS-PEDOT, PAA, CMC, PSS Filtering System Filtering System Setup for coating polyelectrolytes on pulp wood microfibers

6 Layer-by-Layer Nanocoating on Lignocellulose Fibers Detection of nano assemblies on and in cellulose fibers & fiber walls Confocal images ξ potential

7 Enhanced Paper Stability in Basic Media? 150 Zeta Potential (mv) Pulp (PDDA\PSS)3 (PDDA\PSS)3+PDDA (PAH\PSS)3 (PAH\PSS)3+PAH (PEI\PSS) ph (PEI\PSS)3+PEI Surface potential of pulp fibers treated with polycation/polyanion multilayers. All layers were deposited at ph 6.5 and then tested at different ph. For a PSS outermost coating, an electrical potential between -30 to -70 mv with ph values between 3 and 9 which indicates a much stronger charge than for virgin uncoated pulp. Pulp fibers coated with PEI has an outermost surface potential +65 to +35 mv in the same ph region. Therefore, LbL treated pulp have better colloidal stability which prevents undesirable preliminary wet formation of the fiber aggregates.

8 Mixture of Oppositely Charged LbL-Pulp 60 positive+negative pulp 50 Tensile Index N m/g orginal pulp orginal+positive pulp orginal+negative pulp 0 Confocal images of a mixture of positive (green) and negative (red) fibers coated with a composition of (PAH/RIBTC-PSS)2, (FITS-PAH/PSS/FITC-PAH); upper images - only FITC fluorescence (left), only RIBTC fluorescence (right), lower images - transmission image (left), and superposition of both RIBTC and FITC fluorescence (right). b: Tensile strength test results of handsheets made from LbL-coated fibers of (PAH/PSS)3-3.5 compositions and their mixtures with untreated pulp fibers.

9 Broken Pulp Fibers 70 Tensile Index (N.m/g) control (0%) 10% 20% 30% 40% Broken Fiber ratio (%) Broken softwood pulp fibers were prepared by chopping and passing through a 20 mesh giving average fiber length of 0.3 mm which is approximately 20 % of normal virgin pulp length. Broken pulp was coated with (PAH/PSS)2 + PAH multilayer to make it positive. Then, paper was made with addition of these broke. Tensile tests have shown ca 50 % increase of paper strength for LbL modified pulp (a). Of particular promise is the ability to mix virgin pulp and broken pulp of opposite surface charges, this produced paper of even higher strength and allowed up to 40 % broken pulp admixed in paper making

10 Wood Microfiber Device Top View Side View PEDOT-PSS Coated Microfiber Silver Epoxy Coated Fiber Copper Polyimide Sheet Silver Epoxy Uncoated Fiber

11 Conductivity of a Single Fiber PEI - PEDOT/PSS Measurement Length=0.2 mm Current (A) 4-bilayers 3-bilayers 2-bilayers 1-bilayer Voltage (V) Current is proportional to the number of layers in the coating. Conductivity is S/cm for 4 bilayer polythiophene (PEDOT-PSS/PEI) coating of 16 nm thickness both on inner and outer surfaces for unbeaten fibers. For beaten one conductivity is higher: 5 S/cm

12 Conductive Wood Microfibers; Electrical Characteristics Conductivity (S/cm) Wood fiber coated with different polycations & PEDOT/PSS PEI 10 8 PEI+salt PAH+salt Number of Bilayers PAH The above figure shows the conductivity versus number of bilayers when PEDOT-PSS is coated in alternate with different polycations such as PAH, PAH (0.5 M NaCl), PEI, PEI (0.5 M NaCl). It was observed that the wood microfibers coated PEDOT-PSS in alternate with PEI shows highest conductivity among the samples prepared. This can be inferred to that denser coating is formed when PEDOT-PSS is coated in alternate with PEI.

13 Conductive Paper SEM micrograph of the hand sheet prepared using wood microfibers coated with PEDOT-PSS in alternate with PEI Photographic image of the full hand sheet

14 Conductive Paper - Tensile strength and Porosity Tensile index (N. m/g) Control 100% conducting Porosity (sec.) Control 100% conducting 0 0 Type of Paper Type of Paper 1. It can observed that the conducting handsheet coated with PEDOT-PSS have higher tensile index value than control handsheet. The burst and tear test gave similar results indicating higher paper strength. 2. Porosities for all the above handsheets increased drastically compared to the control sample composed of virgin microfibers without coating. For the control sample, it took 37.7 seconds for 100 cubic centimeter air to pass through it. For the handsheets coated with PEDOT-PSS conductive polymer, the time reduced to seconds; it is about a % time reduction.

15 Silica Coating on Wood Microfibers Nanoparticle Coating on pulp fibers Original fibers Fiber-(PAH/silica)2 Coating pulp fiber with SiO 2 nanoparticle of different size (45 and 73 nm) and different bilayers were carried out: With LBL coating, nanoparticles can be fixed to the fiber surface which allows optimization of the surface property, such as surface roughness and permeability, to meet specific paper making s demand. Fiber-(PAH/silica)5

16 Polycation/Silica Multilayer Coating on Fibers Two bilayers of PAH/PSS+PAH/75-nm SiO2 Confocal fluorescent image of the LbL coating in water 100-nm latex nanoparticle are loosely attached.

17 Clay Coating on Pulp Clay coating on single fiber ca 5 wt % clay loading Single Montmorillonite flake has ca 500 nm diameter 0.5%pulp with 4mg/ml 70K PAH and 5mg/ml Montmorillonite clay Composition: Pulp fiber/(pah/mont)3, ph 6

18 Ceramic Nanotubes Halloysite clay of 50 nm diameter with 15 nm lumen, and of nm length (IMERYS halloysite) A: Halloysite tubules and their cross-section in the insertion (TEM), B: Halloysite loaded with CaCo3 Nanocoating: 2 bilayers of PDDA/Halloysite clay The thickness of nanoparticle and nanotube layers can be estimated as 29 ± 2 nm, and 57.4 ± 3 nm for SiO2/PDDA, and halloysite/pdda bilayers, respectively. Paper hand sheets porosity increased 2-time; tensile strength-slightly lower

19 Conclusions 1. LbL-nanocoating of pulp fibers was demonstrated. Both the external and internal surface of the fibers were coated with polymer or nanoparticle multilayers of nm. Polyelectrolytes with medium and high molecular weight do not enter into the delignified fiber cell walls and form a continuous coating with increased deposition over fiber wall openings. 2. Paper tensile strength increase: mixing positively and negatively charge LbL-treated pulp we increased the paper tensile strength on 50%. Recycling of broken short fibers with LbL coating was demonstrated. 3. LbL coating of fibers with conductive multilayer of (PEDOT-PSS/PAH) demonstrated a linear increase in conductivity with the number of layers, with bulk value of 1-5 S/cm. Conductive paper was produced from these fibers. Electric signature. 4. Controlled multilayer nanoparticle coating on fibers was demonstrated for SiO2, Montmorillonite (plate-like), and Halloysite (tubule) clay nanoparticles. Possible biomedical applications.

20 Layer-by-Layer Nanocoating on Lignocellulose Fibers PRESENTED BY Yuri Lvov Name Title Professor Company Louisiana Tech University, and Nano Pulp and Paper LLC // address Acknowledgements Daniel Coughlin, SAPPI Fine Paper; Phil Jones and David Gittins, IMERYS; Stephen Cox, International Paper, Bastrup Mill, LA - for useful discussions and samples The work was supported by NSF-NIRT grant # , NIH grant # 1RO1 EB , and Louisiana Governor Bio/nanotechnology Initiative grant