Niklas Warlin's thesis contributes with important knowledge on molecular design, synthesis and characterization of biobased polymers
Niklas Warlin defended his thesis during 2022. The main focus of his research is molecular design, synthesis and characterization of bio-based polyesters and polyurethanes - aiming to achieve sustainable materials with enhanced thermal stability, chemical recyclability, and low carbon footprint. In his research, he gets motivated both by greater things, like trying to solve existential crises like global warming or the plastic pollution problem, but also by the smaller things, like day-to-day successes in the laboratory.
Niklas Warlin defended his thesis within STEPS work package two during 2022. Photo: Kennet Ruona.
He completed his PhD within STEPS work package two: biobased polymers and upscaling. He was based at the Centre for Analysis and Synthesis, Department of Chemistry, Lund University.
What are the main findings?
Since my thesis is divided into five chapters, depending on my five papers, I will try to summarise the findings in five parts: Paper 1: I developed a synthesis procedure for a new rigid bio-based monomer and demonstrated that it can be used for polyester and polyurethane synthesis. Interestingly, this monomer is more suitable for polyurethane synthesis due to thermal stability issues at the high temperatures required for polyesters. Paper 2: I synthesized another bio-based monomer and used it for polyurethane synthesis. These polyurethanes could be spun into fibers, and chemically recycled in the presence of acid. Paper 3: A new efficient method for synthesising 5-hydroxymethylfurfural was developed. Interestingly, a biphasic system of water and the green solvent dimethylcarbonate resulted in very high conversion and yields. Paper 4: Several new monomers were synthesised using lignin-based phenols and sugar-based furans. The monomers were suitable for polyurethane synthesis, and could be reversibly crosslinked by the Diels-Alder reaction to improve their mechanical and thermal properties. Paper 5: A new type of acetal monomer was synthesized from lignin-based phenols and used to synthesize polyesters. These polyesters could also be chemically recycled but required harsher conditions (as compared to paper 2) due to the different type of acetal bond.
Did anything surprise you during your work?
Many things! One thing that stands out is the thermal stability of furans. In the early stages of my PhD studies, I was surprised by how sensitive many furans tend to be towards high temperatures. Especially considering that furandicarboxylic acid can be used for synthesizing PEF, which requires a reaction temperature of at least 220 °C. Later, I learned that the electron density on the furan ring is extremely crucial for the thermal stability, and that the reason furandicarboxylic acid can be used to synthesize PEF at 250 °C is due to the two electrons withdrawing carboxylic acid groups; thus deactivating the furan.
How does your work relate to other research on plastics?
My research focus on design of bio-based monomers and polymers with low carbon footprint, enhanced mechanical and thermal properties, that can be recycled by different methods. Carbohydrates and lignin have been identified as important sources of renewable starting materials which is why I have tried to valorize these sources in particular. The reason I try to make the polymers polyesters and polyurethanes are that they constitute a significant portion of industrial plastics (~6-8 % each of the total global production of polymers) and we have many partners who are interested in these polymers. Our partners also have a lot of expertise in these fields of course. There are other types of polymers which could be made from my monomers (e.g. polycarbonates, polyamides, epoxies) and these polymers would certainly be interesting to study, for other researchers.
How can your research be used by stakeholders - i.e, who could it benefit?
I believe one of the major findings was how different furans are affected by high temperatures. This may be used by stakeholders to identify what groups of polymers should be targeted depending on what starting material/molecules they are selling. An example from my thesis is the monomer in my first paper. I struggled for two years to make polyesters from it but never really achieved good results. After less than six months of working with polyurethanes, I made polymers with far better properties than the polyesters. I therefore believe polyurethanes are more likely to reach quick commercial success than polyesters if you sell furans. Aside from this, I have also made many interesting monomers (one was used in the demo-product, StepOn) which might be scaled up to further, to reach pilot scale production of polymers.
In terms of societal impact and reach out activities: I have personally supervised six project and master students, been a lab/exercise teacher for hundreds of engineering students, held several popular scientific lectures for students ranging from 10-18 years, attended and presented at three conferences, and been interviewed by a podcast.
What are your views on the plastic system?
Plastics are an essential group of materials for society, which is demonstrated by the fact that there are polymers in virtually all things that can be bought. The environmental problems with plastics stems from how they are used, and especially how they aredisposed of. With an educated population (who collect used plastic products instead of throwing them away) and efficient recycling practices, most of the environmental issues caused by plastic consumption could be resolved.
What drives you as a researcher?
I am motivated both by greater things like trying to solve existential crises like global warming or the plastic pollution problem, but also by smaller things, like day-to-day successes in the laboratory. For example by successfully synthesizing a new molecule, publishing a paper, or helping a student understand a chemical reaction. I believe both parts are equally necessary for me to function as a scientist. Without a grand goal my work would feel excruciatingly pointless, and without small day-to-day victories my work would be painfully boring.
Read about STEPS Work Package Two: Biobased Polymers and Upscaling