Lars Nordstierna

 
Dr Hanna de la Motte
Dr Åsa Östlund 
PhD student Alexander Idström
PhD student Jonatan Borg
 
My research profile is characterization and development of soft matter where my three main materials are cellulose, coatings, and surfactants and surface-active particles. My central method in characterization of soft matter is NMR spectroscopy. In all my research projects there is an environmental vision to develop sustainable materials. In all projects, collaborations play an important role in that development and most often include the participation of external industrial partners.
 
Renewable and Modifiable CELLULOSE
Paper pulp is a cellulose-based biomaterial from plant sources. In the development to improve or functionalize this material it is important to be able to tune the physicochemical properties. These properties, such as flexibility, strength, solubility, and hygroscopicity are highly directed by the interactions between constituents on a molecular level. The large group of both natural and chemically treated cellulose materials is characterized by complexity, both with regard to composition and structure. The microscopic structure is distinguished by a large heterogeneity. This heterogeneity, of various length scales, is determined by the strength and distribution of intermolecular interactions between incorporated cellulose molecules.
 
Successful characterization is decisive and, in my opinion, NMR spectroscopy has an important and unique role in this work. I am working in several extensive interdisciplinary research collaborations with focus on cellulose: SuMo Biomaterials, the Avancell Centre for Fibre Engineering, Mistra Future Fashion, CelluNova, and ForTex. One ongoing project focuses on the effect of co-crystallization in paper pulp and nanocrystalline cellulose. Another project regards functionalization of nanocrystalline cellulose and the phase-related effects of water interaction. A third research question concerns dissolution and regeneration of cellulose where the focus is to understand the molecular mechanisms between cellulose and solvent constituents. The purpose of my research in this area is to link microscopic characterization with macroscopic properties in native and modified cellulose.
 
Sustainable and Protective COATINGS
To protect a painted house facade from surface growth of mold or algae, anti-growth agents are mixed in the paint. Most of the applications, used in the past and based on heavy metals, have today been banned due to their negative impact on the environment. Current protective coating applications that use biocides lose the protection quite rapidly as the small molecules render a fast diffusional biocide leakage. Alternative and more environmentally friendly treatments are therefore required to improve decay resistance. My research has shown a promising improvement of anti-growth protection by the use of encapsulated biocides that slows down the surface flux from the coating. The biocide is placed into microcapsules, from where it is slowly distributed into the surrounding coating matrix. The reduced mobility renders a sustained surface flux and anti-growth protection.
 
Formulation of microcapsules relies on molecular self-association in order to create the higher hierarchies up to above micron size. In addition to formulation methodology, my research focuses on biocide transport within the microcapsules and in complete coating systems. One example of a scientific problem is the intrinsic correlation between soft matter microstructure and biocide migration in the coating material. Other instrumentation than NMR is frequently preferable in these studies and complementary surface-related studies include various (confocal, electron, atomic force) microscopy methods. In this research area I work closely to both paint and biocide manufactures as Caparol and Lanxess. In a long-term perspective, the ambition is to develop surface protection systems that are both economically and ecologically sustainable.
 
Biodegradable and Functionalized: SURFACTANTS AND SURFACE-ACTIVE PARTICLES
Several classes of surfactants in the industry will most probably be legislatively prohibited in the near future due to environmental reasons and there is a strong need to find applicable and environmentally friendly alternatives. I believe that novel biodegradable surfactants and also surface-modified particles have a large potential as these materials have gained a lot of interest in recent years, mainly due to the large number of potential applications within the areas of e.g. personal care, food, medicine and coating applications. One of my current research projects focuses on the development of new biodegradable surfactants of gemini type. These surfactants have shown remarkable properties regarding surface activity and self-association. Another ongoing project concerns functionalization of silica particles to induce surface activity. Properly designed, such particles can render emulsions and foams with exceptional lifetime.
 
In these projects, a variety NMR of methods is used – from solid-state NMR to NMR diffusometry – to characterize the structure-dependent associative behavior of both surfactants and silica particles. Knowledge about the associative formation is necessary in the development of improved and new substances and materials. NMR provides the possibility to study molecular dynamics and structure over a broad window of time and length scales and can, for example, provide access to intermolecular dynamics, motional restrictions, association phenomena, phase transitions, and structural changes. My main industrial partner in this research area is AkzoNobel and the purpose of the research projects is to find environmentally benign solutions to various technical problems within the field of applied surface-and colloid chemistry. 

Published: Fri 08 Mar 2013. Modified: Thu 19 Feb 2015