The seminar starts at 13.15

Abstract:

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.

About Eva: Eva Malmström is Professor at  KTH and Head of the Division of Coating Technology. She is a PI in WWSC, the newly started competence centre FibRe and Treesearch. From the 1st of April 2020 she is director of WWSC.

The seminar starts at 13.15

Abstract:

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.

About Stephan: Stephan is Adjunct professor at KTH and Beamline Manager at DESY, Hamburg

The seminar starts at 10.15

Abstract:

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.

About Gunnar: Gunnar Westman is Professor in organic chemistry at Chalmers. He is a PI in WWSC and is deputy director in Treesearch.

Note that this lecture is available through a separate link via KTH and that the docent lecture starts at 10.00

Title: The untapped potential of the soil microbiota for energy and materials

Link to Zoom meeting: kth-se.zoom.us>>

Link to KTH calendar >>

This Tuesday there is no seminar in the Treesearch and WWSC virtual conference series, instead you can take part of a docent lecture by Lauren McKee at KTH.

This lecture is only available through live-streaming.

The seminar starts at 13.15

Note that the full presentation will only be available live

Abstract: 

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).

.

The seminar starts at 10.15

Abstract:

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).

About Tomas: Tomas is researcher at KTH and working in Treesearch with the ForMAX project.

The seminar starts at 10.15

Abstract: 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.

About Torbjörn: Torbjörn is Associate Professor at KTH.

The seminar starts at 10.15

Abstract:

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.

About Martin: Martin is Associate Professor at KTH.

On this Thursday Treesearch is holding an online conference on the recently initiated Industrial Postdoc program. 

Read more and register here >>

The seminar starts at 10.15

Abstract:

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.

About Per: Per is a researcher at KTH Fibre and Polymer Technology.

The seminar starts at 13.15

Abstract:

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.

About Anette: Anette is Professor Professor in pharmaceutical technology at Chalmers and Co-director for Area of Advance Production. She is also the director of the recently started competence centre FibRe.

The seminar starts at 13.15

Abstract:

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.

About Peter: Peter is a postdoc at WWSC, KTH, with a special interest in organic chemistry

The seminar starts at 10.15

Abstract:

About Monica: Monica is professor at KTH and head of the Division of Wood Chemistry and Pulp Technology.

The seminar starts at 13.15

Abstract: 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.

About Merima: Merima Hasani is associate professor at Chemistry and Chemical Engineering, Chalmers.