Towards sugar- and lignin-based polyesters and polyurethanes with enhanced properties

The enormous production and consumption of fossil-based plastics has caused severe environmental challenges such as pollution of the ocean, increased CO2-emissions, and various health problems. Many of these concerns are intimately connected to the use of fossil fuels in the production of polymers. For this reason, there is a considerable interest to develop bio-based monomers to mitigate some of the issues connected to fossil-based plastics. However, new bio-based monomers are often expensive and need some material
advantages to facilitate their market entry. In this context, we have designed several new monomers by converting bio-based molecules such as 5-chloromethylfurfural (CMF), 5-hydroxymethylfurfural (HMF) and
vanillin into rigid diols for polyester and polyurethane synthesis. This thesis has been divided into 5 chapters describing the most important findings from each underlying project.
In Chapter 1 and 2, HMF was reacted with pentaerythritol and di(trimethylolpropane) to make two rigid diols with cyclic acetal structures. The monomer made from HMF and pentaerythritol was predicted to have an
exceptionally low carbon footprint according to our LCA calculations. These diols were further used to synthesize a series of polyesters and polyurethanes with increased glass transition temperatures. Polyurethane
synthesis was deemed more suitable for this type of monomers, since degradation occurred at the high temperatures required for polyester synthesis. The obtained polyurethanes were used to prepare coatings and
textile fibers. Furthermore, the cyclic acetal structure of the monomers enabled chemical recycling under acidic conditions. In Chapter 3, HMF was produced in a continuous process from fructose, using water and dimethylcarbonate (DMC) in a biphasic system. Both yield and conversion were excellent, demonstrating the
utility of DMC for HMF synthesis. The HMF synthesized by this method was sufficiently pure for preparation of the monomers in Chapters 1 and 2 in comparable yields to commercial HMF. In Chapter 4, three rigid diols
were prepared from CMF and various lignin-based monomeric aldehydes including 4-hydroxybenzaldehyde, vanillin and syringaldehyde. The diol made from vanillin and CMF was used to prepare a series of thermoplastic
polyurethanes with increased glass transition temperatures. The polymers were then cross-linked with DielsAlder chemistry, which could be reversed at higher temperature. This may facilitate its reprocessing and recycling. In Chapter 5, two rigid monomers were produced from potentially lignin-derived phenols, and used to prepare a series of polyesters with tunable thermal properties. The polymers could potentially be chemically recycled by acid hydrolysis.