Defence of doctoral thesis: Arne Stamm – Exploring the Use of Terpenes as Renewable Polymer Feedstock
Rising environmental awareness and responsibility has increased the demand for novel, bio-based sustainable materials. Therefore, there is an extensive need to research and develop closed-loop materials from novel feedstocks that can be generated using benign, environmentally friendly synthetic routes. The work presented in this thesis was focused on the development of polymeric materials from biomass waste-feedstocks. Especially the use of turpentine, a classical underutilized side-stream of the forest industry, and its main component α-pinene was the key objective of this work. To showcase the inherent potential of terpenes as a source material for novel biopolymers, α-pinene was transformed into different monomers and subsequently polymerized. The synthesis and polymerization of the pinene derived sobreryl methacrylate (SobMA) was studied using different radical polymerization techniques, including free radical polymerizations and controlled procedures. Post-modifications were further demonstrated by synthesizing crosslinked thin films, utilizing the tertiary alcohol and the unsaturation present in each monomer unit. The same methacrylic monomer was further utilized for the polymerization of amphiphilic block copolymers to form cationic polymer latexes. Pinene derived polyesters were further developed via two different pathways. In the first pathway, α-pinene was oxidized into the bicyclic verbanone based lactone (VaL) and subsequently polymerized resulting in a biobased semicrystalline polyester. In the second pathway, polyesters were synthesized via polycondensation, utilizing the diol (1-(1′-hydroxyethyl)-3-(2′-hydroxyethyl)-2,2-dimethylcyclobutane (HHDC)) obtained from the oxidative cleavage of the double bond of α-pinene together with unsaturated biobased diacids. The resulting terpene based unsaturated polyester resins were afterwards crosslinked via UV-irradiation to yield polyester networks with adjustable properties. The use of enzymatic catalysis in key synthetic steps was elaborated to showcase the potential of replacing harsh chemical conditions with mild reaction conditions in aqueous environment.