Online seminars and conferences arranged by WWSC
As the covid-19 pandemic cancelled all scientific conferences and physicals gathering in 2020, and so far in 2021, WWSC went digital with open online seminars. In cooperation with Treesearch all presentations are live-streamed over YouTube, and in most cases also available to watch afterwards. The online presentations have attracted a lot of interest with both national as international viewers.
Below you can find the presentations and abstracts of the online presentations so far. The lignin series is ongoing at the present moment, and thus more videos will be added.
Lignin online series (Spring 2021)
Lignin is in the spotlight in this online series, covering research from the biosynthesis to the application of novel materials. The webinars are ongoing and the full program is found at treesearch.se. More talks will be added to the list below. In the series leading researchers from both outside and within the center are invited, giving the audience an up-to-date overview over the lignin area.
Contact for the lignin webinars is professor Martin Lawoko.
Edouard Pesquet, Associate Professor, Stockholm University
Genetic and cellular regulations of lignin composition in herbaceous and woody plants
Lignins are phenolic heteropolymers which accumulate in cell walls to confer specialized functions to specific cell types such as mechanical resistance, sap conduction or apoplast impermeabilisation. Specific lignins are thus deposited in these different cell types and vary in amounts, composition and localization in the different layers of their cell walls, but also dynamically change to adapt to developmental and environmental constrains [1]. This cellular complexity has represented an important unknown, which hindered the complete understanding of plant lignification and the optimal use of plant biomass for biorefinery processes. To investigate the cellular regulation of lignification in both herbaceous and woody plants, efforts were focused on the optimisation of in situ quantification techniques on whole plant biopsies to directly monitor lignin properties (amount and composition) at the sub-cellular and cellular levels. Two wide-field microspectroscopy methods were optimized, using ”RGB-absorbance” and Raman spectroscopy, and validated on sets of synthetic monomers and polymers as well as many genetically engineered plants with modified lignins [2-4]. These optimized methods revealed that the lignification of each cell types resulted from a combination of specific genetic processes, different levels of cellular cooperation and cell wall specific lignin accumulation capacities, which varied during plant development not only to control lignin amount and composition but also residue position in the lignin polymers [2-4]. In the present seminar, these different methods will be presented as well as novel unpublished data on the use of these methods to elucidate the regulation processes controlling the lignification of each specific cell types.
[1] Pesquet et al. (2019) Current Opinion in Plant Biotechnology – https://doi.org/10.1016/j.copbio.2019.02.001
[2] Blaschek et al., (2020a) Frontiers in Plant Sciences – https://doi.org/10.3389/fpls.2020.00109
[3] Blaschek et al., (2020b) ACS Sustainable Chemistry and Engineering – https://doi.org/10.1021/acssuschemeng.0c00194
[4] Yamamoto et al., (2020) ChemSusChem – https://doi.org/10.1002/cssc.202001242
Mika Sipponen, Associate Professor, Stockholm University
Lignin Nanoparticles as Interfacial Stabilizers: Pickering Emulsions, Enzymatic Catalysis, and Polymeric Composites
Lignin is a fascinating natural polymer with many essential functions in plant biomass. However, most of the lignin available from industrial processes is still burned due to the lack of commercially feasible routes to value-added materials. Lignin-based polymers1 and especially lignin nanoparticles (LNPs)2 simplify material synthesis by overcoming instability and heterogeneity of crude lignins. LNPs possess a high surface area to mass ratio owing to their anionic surface charge that render these spherical particles colloidally stable. In addition, the amphiphilic nature of LNPs present many opportunities for their use as emulsifiers and surface modification by adsorption. Here, I present our recent work on LNPs as interfacial stabilizers, including Pickering emulsions,3,4 enzymatic catalysis,5 and enzyme-assisted Pickering emulsion polymerization and composite synthesis.6,7 Challenges and future prospects for LNPs as enablers of sustainable materials chemistry will be discussed as well.
- Moreno, A. & Sipponen, M. H. Lignin-based smart materials: a roadmap to processing and synthesis for current and future applications. Mater. Horizons 7, 2237–2257 (2020). https://doi.org/10.1039/d0mh00798f
- Österberg, M., Sipponen, M. H., Mattos, B. D. & Rojas, O. J. Spherical lignin particles: A review on their sustainability and applications. Green Chem. 22, 2712–2733 (2020). https://doi.org/10.1039/C2GC36073J
- Sipponen, M. H., Smyth, M., Leskinen, T., Johansson, L.-S. & Österberg, M. All-lignin approach to prepare cationic colloidal lignin particles: Stabilization of durable Pickering emulsions. Green Chem. 19, 5831–5840 (2017). https://doi.org/10.1039/C7GC02900D
- Zou, T., Sipponen, M. H. & Österberg, M. Natural shape-retaining microcapsules with shells made of chitosan- coated colloidal lignin particles. Front. Chem. 7, 370 (2019). https://doi.org/10.3389/fchem.2019.00370
- Sipponen, M. H. et al. Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media. Nat. Commun. 9, 1–7 (2018). https://doi.org/10.1038/s41467-018-04715-6
- Moreno, A. & Sipponen, M. H. Biocatalytic nanoparticles for the stabilization of degassed single electron transfer-living radical pickering emulsion polymerizations. Nat. Commun. 11, 5599 (2020). https://doi.org/10.1038/s41467-020-19407-3
- Moreno, A., Morsali, M., Liu, J. & Sipponen, M. H. Access to Tough and Transparent Nanocomposites via Pickering Emulsion Polymerization using Biocatalytic Hybrid Lignin Nanoparticles as Functional Surfactants. Green Chem.(2021). https://doi.org/10.1039/D1GC00103E
Sipponen lab webpage: www.sipponenlab.com
Follow on Twitter: Sipponen lab
Anna Kärkönen, Senior scientist, Natural Resources Institute Finland (Luke)
Lignin biosynthesis in Norway spruce
Lignin constitutes 20–32% of woody plant cell walls, being the second most abundant biopolymer after cellulose. In a growing tree, wood formation with the final phase of lignin deposition occurs in a thin cell layer inside the cambium. The spatial isolation of the developing wood tissue makes the studies related to wood development difficult in muro. In my group, both native trees and a cell culture of Picea abies (Norway spruce) are used to study lignin biosynthesis. The cell culture is a unique system where some cells differentiate into tracheids (ca. 3% of total cells), whereas most of the cells remain undifferentiated. Lignin polymer with a structural similarity to native lignin is constitutively formed in the culture medium (Simola et al. 1992, Warinowski et al. 2016; Giummarella et al. 2019).
The spruce tissue culture line has been an object for several studies focusing on biosynthesis and structure of the extracellular lignin (e.g. Kärkönen et al. 2002; Koutaniemi et al. 2007; Laitinen et al. 2017). The emphasis has been on the enzymes involved in activation of lignin precursors (peroxidases and / or laccases), as well as in the characterisation of the genes for enzymes responsible for monolignol biosynthesis and their polymerisation.
My research interests originated from the observation that H2O2 removal from the culture medium strongly reduces the amounts of extracellular lignin. As H2O2 is needed by peroxidases this data suggest that peroxidases have the main role in activation of monolignols for lignin biosynthesis in the spruce cell culture. This led to the question of the origin of H2O2 in the cell wall during lignin formation. The role of redox active enzymes in plasma membranes, like respiratory burst oxidase homolog, Rboh, have been studied (Kärkönen and Kuchitsu 2015). To study regulation of lignin biosynthesis, a large scale phenolic and transciptomic profiling was conducted using the extracellular lignin-forming cell culture with lignin formation and when lignin formation was inhibited by scavenging of H2O2. This inhibited the action of peroxidases (Laitinen et al. 2017). The results show that apoplastic redox state regulates not only phenolic metabolism, but the whole cellular metabolism. The work also identified several novel proteins (e.g. carbohydrate oxidoreductases) for further evaluation.
In addition to the tissue culture, developing xylem of spruce is used as a research material. The origin of monolignols used in developing tracheids for cell wall lignification has been investigated by RNA-Seq and single cell metabolomics. For RNA-Seq, developing ray parenchymal cells and tracheids were separately collected by laser capture microdissection. In addition, single cell metabolome analysis was conducted in living plantlets, and both monolignols and monolignol glucosides were detected in both cell types (Blokhina et al. 2019). The results show that similarly to that in dicotyledonous species, in Norway spruce ray parenchymal cells contribute in monolignol production in addition to developing tracheids. Currently, the mechanism of transport of monolignols, the precursors for lignin into the apoplast is being studied (Väisänen et al. 2020).
- Blokhina O, Laitinen T, Hatakeyama Y, Delhomme N, Paasela T, Zhao L, Street NR, Wada H, Kärkönen A, Fagerstedt KV (2019) Ray cells contribute to monolignol biosynthesis in developing xylem of Norway spruce. Plant Physiol 181: 1552-1572
- Giummarella N, Koutaniemi S, Balakshin M, Kärkönen A, Lawoko M (2019) Nativity of lignin carbohydrate bonds substantiated by novel biomimetic synthesis. J Exp Bot 70: 5591-5601
- Kärkönen A, Koutaniemi S, Mustonen M, Syrjänen K, Brunow G, Kilpeläinen I, Teeri TH, Simola LK (2002) Lignification related enzymes in Picea abies suspension cultures. Physiol Plant 114: 343-353
- Kärkönen A, Kuchitsu K (2015) Reactive oxygen species in cell wall metabolism and development in plants. Phytochemistry, 112: 22–32
- Koutaniemi S, Warinowski T, Kärkönen A, Alatalo E, Fossdal CG, Saranpää P, Laakso T, Fagerstedt KV, Simola LK, Paulin L, Rudd S, Teeri TH (2007) Expression profiling of the lignin biosynthetic pathway in Norway spruce using EST sequencing and real-time RT-PCR. Plant Mol Biol 65: 311-328
- Laitinen T, Morreel K, Delhomme N, Gauthier A, Schiffthaler B, Nickolov K, Brader G, Lim KJ, Teeri TH, Street NR, Boerjan W, Kärkönen A (2017) A key role for apoplastic H2O2 in Norway spruce phenolic metabolism. Plant Physiol 174: 1449–1475
- Simola, LK, Lemmetyinen J, Santanen A (1992) Lignin release and photomixotrophism in suspension cultures of Picea abies. Physiol Plant 84: 374-379
- Väisänen E#, Takahashi J, Obudulu O, Bygdell J, Karhunen P, Blokhina O, Laitinen T, Teeri TH, Wingsle G, Fagerstedt KV, Kärkönen A (2020) Hunting monolignol transporters: membrane proteomics and biochemical transport assays with membrane vesicles of Norway spruce. J Exp Bot 71: 6379–6395
- Warinowski T, Koutaniemi S, Kärkönen A, Sundberg I, Toikka M, Simola LK, Kilpeläinen I, Teeri TH (2016) Peroxidases bound to the growing lignin polymer produce natural-like extracellular lignin in a cell culture of Norway spruce. Front Plant Sci 7: 1523. doi: 10.3389/fpls.2016.01523.
Charlotta Turner, Professor, Department of Chemistry, Centre for Analysis and Synthesis, Lund University
Analysis of lignin by supercritical fluid technology and high-resolution mass spectrometry
Chemical analysis of lignin is a multifaceted challenge due to
A. technical lignin samples are often quite complex, containing a “soup” of different compounds and matrix effects can be severe; and
B. chemical standards are usually lacking for many lignin monomers and most lignin oligomers.
This lecture will discuss these challenges and demonstrate solutions for how to accomplish extraction, chromatographic separation and qualitative and quantitative analysis of lignin monomers and oligomers in different types of technical lignin samples. Especially, the use of sub- and supercritical fluid extraction, ultrahigh performance supercritical fluid chromatography and high-resolution mass spectrometry will be discussed. Finally, some preliminary results on uncertainties in molecular weight determination when using size exclusion chromatography, and universal detection by charged aerosol detection, will be presented.
- J. Prothmann, et al., Non‐targeted analysis strategy for the identification of phenolic compounds in complex technical lignin samples, ChemSusChem, 2020, 13, 4605-4612. https://doi.org/10.1002/cssc.202000951
- J. Prothmann, et al., Identification of lignin oligomers in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn), Anal. Bioanal. Chem., 2018, 410, 7803-7814, https://doi.org/10.1007/s00216-018-1400-4
- M. Sun, et al., Comprehensive on-line two-dimensional liquid chromatography×supercritical fluid chromatography with trapping column-assisted modulation for depolymerised lignin analysis, J. Chromatogr. A, 2018, 1541, 21-30. https://doi.org/10.1016/j.chroma.2018.02.008.
- J. Prothmann, et al., Ultrahigh performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC/QTOF-MS) for analysis of lignin-derived monomeric compounds in processed lignin samples, Anal. Bioanal. Chem., 2017, 409, 7049-7061, https://doi.org/10.1007/s00216-017-0663-5
Peter Olsén, Researcher KTH/WWSC
Lignin from a Polymer Synthetic Perspective
Lignin is the most abundant aromatic biopolymer found in nature; however, its uses in refined material applications are still scarce. This talk focuses on transforming lignin into functional precursors suitable for material applications by combining fractionation and selective polymerization techniques. Addition polymerization via ring-opening polymerization from the active lignin core has the advantage of retaining the solubility of the copolymer and provides insights into the structural changes that occur to the lignin backbone during synthesis. Understanding how the lignin backbone change during synthesis is vital for transforming lignin into new bio-based materials with predictable and reproducible properties. The vision is to understand the polymer-synthetic boundaries for lignin, what factors we need to consider, and how we can design systems that make full use of this fantastic biopolymer.
Mats Johansson, Professor, KTH/WWSC
Lignin-based thermosets
Lignin is an abundant source for aromatic building blocks in thermoset polymers. This presentation will first give a brief background into thermoset polymers in general and how the structure of a thermoset polymer can be designed to obtain suitable properties for various applications. Examples on how this design options can be used to tailor physical and mechanical properties of thermosets built from lignin fractions will then be given. The examples will mainly use functionalized lignin fractions with subsequent crosslinking using thiol-ene chemistry.
WWSC and Treesearch virtual conference series (Spring 2020)
During Spring 2020 Wallenberg Wood Science Center and Treesearch arranged a virtual conference series, as a way of keeping the scientific discussion ongoing during the covid-19 pandemic. In the series, WWSC members and researchers closely linked to the center was invited to present their field of research in live-streamed webinars, held two times per week.
Merima Hasani, Chalmers
Putting together the puzzle of cellulose interactions in aqueous alkaline solutions: from cations to CO2
Our understanding of fundamental interactions governing properties of cellulose aqueous alkaline solutions is still surprisingly limited. The role of the cation, the action of additives and interactions with CO2(g) are some of the aspects that require more attention and that will be discussed in this talk.
Peter Olsén, KTH
Synthetic Strategies for Decorating Biopolymers with Rings
The presentation is about the synthetic combination of ring-opening reactions and and biopolymers. How should we think, what is the challenge and is it beneficial for the final material properties.
Anette Larsson, Chalmers
Cellulose derivatives controlling the drug release rate from oral formulations
Controlled drug release is a demand for many pharmaceutics to become useful. This can be achieved in different ways, for example by having the drug embedded in a matrix of polymer or a polymeric coating that surrounds a unit containing the drug. This presentation will show the ability to use cellulose derivatives to control the drug release rate, and particular focusing on coated drug release systems. The transport of the drug through a coating can be controlled by creating pores in the coating via addition of pore forming agents, and the ability for polymers to phase separate is one way to create pores.
We used a mixture of the cellulose derivatives hydroxypropyl cellulose (a water-soluble polymer) and ethylcellulose (water- insoluble polymer), and dissolved these polymers in an organic solvent (ethanol). During the coating process, the dry content increases, which leads to that the two polymers undergo spinodal decomposition. Upon exposure to aqueous medium the water-soluble polymer dissolves and is transport out from the coating, where the remaining coating contains a porous structure. The pore structure depends on the phase separation, which is sensitive to the ratio between water-soluble and water-insoluble polymers, the molecular weights of the polymers, the process conditions during the coating etc. It was concluded that the drug release rate correlated to the pore structure, and we have been together with co-workers been able to simulate the permeability and drug release rate.
Per Larsson, KTH
Chemically modified fibres with new possibilities
Wood-sourced fibres are indeed a natural part of our daily life and are predicted to be a key material in the sustainable society of tomorrow. However, there are material properties of cellulosic materials that limit an even broader use, for example cellulose’s low ductility and lack of (thermo)plasticity, which typically limit the primary processing and design possibilities to two-dimensional sheets and therefrom formed geometries.
This presentation demonstrates how cellulose fibres can be chemically modified to exhibit increased ductility as well as thermoplasticity by converting some the cellulose in the fibres to dialcohol cellulose. Owing to these desirable material properties, complex-shaped structures could be demonstrated through hydroforming and extrusion.
Martin Lawoko, KTH
Consolidated “Lignin First” Biorefining: Processing Strategies for quality Lignin
Lignin has attracted attention as bio-based polymer precursor for material synthesis. The progress in realizing this potential has however been slow, mainly due to the notorious heterogeneity in the structure of the available technical lignins. Such heterogeneity present analytical challenges which are manifested in the lack of detailed knowledge of the molecular structure. New processing strategies are therefore required for extraction of quality lignin and constitute the so-called “Lignin-First biorefining” concepts. Secondly, integration of biorefineries is necessary for circularity, but is often compromised by the quality differences of the obtained fractions. With these challenges and concerns, we present herein, a green “lignin first” biorefining process that is consolidated with the production of polymeric hemicellulose and cellulose-rich fractions. Focus will be on the lignin component, specifically, developing fundamental understanding on the prerequisites for such a process concept to produce lignin with a high level of preserved native structural elements, high purity, good yields and size homogeneity. Structural changes are studied by advanced 1D and 2D NMR techniques and used to probe reaction mechanisms that inform processing strategies.
Torbjörn Pettersson, KTH
AFM beyond imaging – towards molecular understanding of cellulose interactions
Today there is a push towards replacing petroleum-based material with materials from bio-based resources. Components from wood are highly attractive in this ongoing transformation. This drive leads to incorporation of cellulose in new types of materials and in new types of applications. While working on new materials and new applications, understanding of the interactions between the different components is of great interest. To be able to gain understanding the ability to measure and evaluate the interactions between the used components is important. We are using high resolution measurements such as atomic force microscopy (AFM) to measure this type of interaction on a micrometre and nanometre length scale for multiple different cellulose applications.
This presentation will be an overview on the topic “AFM beyond imaging” where force measurements have been performed to evaluate interactions between cellulose and other materials. The applications are ranging from compatibility issues in composites, measuring flexibility, elasticity of never dried pulp fibres, cellulose model beads, and evaluate chemical reactions induced when components are forced in close contact. With these AFM measurements we have gained information that increased our molecular understanding in the different systems.
Tomas Rosén, KTH
Alignment and nanoscale dynamics of flowing nanocellulose
New advances to make nanostructured materials from nanocellulose have resulted in impressive properties and fascinating applications demonstrated for 1D-materials (e.g. filaments), 2D-materials (e.g. membranes) and 3D-materials (e.g. 3D-printing). In most applications, the material properties rely on the process-conditions, which most often include shear or extensional deformations to align cellulose nanofibrils (CNF) and nanocrystals (CNC) with hydrodynamic forces. However, the alignment mechanism is very different in these two types of flows, and the collective motion in semi-dilute systems of CNF/CNC is far from trivial. To obtain a greater understanding of the nanoscale dynamics, there is a need for proper comparisons between experiments and numerical/theoretical models with as little reduction of dimensionality as possible. However, a key issue is the fact that experimental characterization usually only provides a projected representation of the three-dimensional system and alignment in planar deformations, such as the shear flow, will depend on the viewing direction. In this talk, it will be demonstrated how projected orientation distributions of CNF/CNC can be obtained with small angle X-ray scattering (SAXS) and how to properly compare these with numerical models. This demonstration will rely on our recent work both in extensional flow [1] and in shear flow [2].
[1] Rosén et al. (2018), J. Chem. Phys. C 122(12).
[2] Rosén et al. (2020), Phys. Rev. E 101(3).
Lars Berglund, KTH
Transparent wood and other materials from delignified wood scaffolds
Existing forest products tend to be based on either wood pulp fibers or various forms of native wood, from sawmill waste, via strands and veneer to wooden boards and laminated structures. The commercial success of bleached chemical Kraft pulp is exceptional, and a large part of Swedish economy relies on this specific delignified fiber. For this reason it is of both technical and scientific interest to investigate the potential of delignified veneer, and material concepts based on delignified veneer. The delignification process itself is briefly described, and the characteristics of delignified veneer are presented. Polymer composites based on this wood scaffold are discussed, in particular optical transmittance, optical properties in general, and the potential for functionalization in the context of photonic materials. There are also possibilities to apply concepts previously used for nanocellulose materials; and some examples are presented. This includes methods to increase the specific surface area and control nanostructure of the material. Delignified veneer offers many challenges, eg avoiding veneer disintegration into fibers. It also provides interesting opportunities, since protocols for nanocellulose modification and polymer matrix nanocomposites can be used for new types of nanomaterials.
Further reading
Berglund, L. A.; Burgert, I., Bioinspired Wood Nanotechnology for Functional Materials. Advanced Materials 2018, 30 (19).
Li, Y. Y.; Vasileva, E.; Sychugov, I.; Popov, S.; Berglund, L., Optically Transparent Wood: Recent Progress, Opportunities, and Challenges. Advanced Optical Materials 2018, 6 (14).
Gunnar Westman, Chalmers
Surface modification of nanocrystalline cellulose
Nanocellulose has had an enormous interest for more than ten years. Some argue that derivatives of nanocellulose will never reach large-scale production and become a part of commercial products whereas others see its potential as the material of the future. The seminar will be on nanocrystalline cellulose, CNC, with focus on chemical modification and the importance of having a molecular perspective on it. It will be a general introduction that will be narrowed down to water-based systems for chemical modification of CNC. As an illustrative example on the importance of having a molecular perspective when performing modification of CNC a project on hydrofobization of the sulphate groups on the CNC surface will be presented, showing how the surface topology can be tuned and how this affect the aggregation and alignment of the derivatives.
Stephan Roth, KTH/DESY
Large-area cellulose nanofiber thin films – observing their fabrication and functionality in situ
Our understanding of fundamental interactions governing properties of cellulose aqueous alkaline solutions is still surprisingly limited. The role of the cation, the action of additives and interactions with CO2(g) are some of the aspects that require more attention and that will be discussed in this talk.Cellulose nanofibrils (CNF) exhibit exceptional mechanical properties due to their defect free molecular structure. Thus, they constitute excellent building blocks for advanced template materials for functional thin film applications. To tackle the challenge of large-area coating of functional thin films, spray coating is one method of choice. It is compatible to industrial style roll-to-roll coating and easily scalable. Especially layer-by-layer is readily applicable. At the same time, many functional polymers for organic photovoltaics and electronics are water-based, making them ideal candidates for functionalizing CNF thin film templates. Often, this implies layer-by-layer fabrication of functional stacks. It is therefore of prime importance understand in the interaction of complex fluids with the (nano)porous bio-based material. Crucial parameters are the type of functional polymer and solvent components, the drying conditions, process parameters, and substrate/media properties. The aim of this contribution is to present the potential of in situ observations of fluid-CNF interaction on the nanoscale for tailoring such functional stacks, starting from the coating process itself.
Lennart Bergström, Stockholm University
Tailoring wet strength and heat transfer of nanocellulose-based films and foams
Eva Malmström, KTH
Polymers are enabling molecular engineering of the interface in cellulose-containing bionanocomposites
By 2050, the plastic waste accumulated in nature or landfills is estimated to be around 12 billion tons, assuming that the current production and waste management trends continue. The rapidly growing environmental awareness has increased the interest for cellulose-containing materials to a completely new level. Especially the nanocelluloses have attracted significant interest due to their low specific weight and their promising mechanical properties. However, to utilize their full potential in material applications, it is often necessary to control the surface properties to prevent aggregation, enhance thermal and water resistance as well as to impart processability for example.
The surface properties of cellulose can be modified by polymers, either by covalent or non-covalent approaches. The covalent approach can either be performed by ring-opening polymerization of lactones for instance, from the hydroxyl groups available on the cellulose surface, or by controlled radical polymerization from an immobilized initiator. The non-covalent approach is based on adsorption of a polymer to the cellulose surface. Nanocelluloses are often charged from the manufacturing process to impart colloidal stability and the charges can be utilized to electrostatically adsorb charged polymers while maintaining the colloidal stability.
Hitherto, the majority of all described routes for polymer modification of nanocelluloses involves the use of organic solvents. We have recently increased our efforts to develop more water-based procedures for efficient engineering of the interface of cellulose. So far, our work has mainly made use of tailor-made latex nanoparticles synthesized through RAFT-mediated surfactant free emulsion polymerization with subsequent polymerization induced self-assembly (PISA), and more recently also by a combination of grafting-to and grafting-from. This strategy involves the design of an oligomeric macroinitiator, containing both cationically charged groups that allow for adsorption to cellulose and initiating moieties that can be used for grafting-from once the macroinitiator is physiosorbed to nanocellulose.
The aim of this contribution is to discuss some of our most recent findings when using polymer chemistry as a tool to engineer the surface of nanocelluloses, and to present some characteristics of the corresponding materials.
Daniel Söderberg, KTH
Challenges for spinning fibres from nanocellulose
Spinning of cellulosic filaments is far from a novelty, viscose filaments could be spun already in the late 19th century. Today there is a wide variety of filament materials originating from cellulose that are spun under industrial conditions using well-understood spinning processes. Furthermore, significant efforts have been made aimed at the fabrication of filaments from cellulose nanofibrils (CNF) during the last decade, and they typically apply conventional spinning processes and aim at achieving favorable properties by developing spinnable liquids that allow the use of these processes. However, given the nature of CNF, being very slender particles, the application of existing knowledge on macroscopic fiber suspension flows provides insights that offer new routes process routes that give improved mechanical performance, which also have been applied to proteins. The ideal process would align CNF in the direction of the formed thread and by some means preserve this controlled structure during drying.
