Functional and responsive polyglycidol based microgels as activating support for (bio)catalysts in aqueous medium
- Funktionelle und responsive Mikrogele basierend auf Polyglycidol als aktivierendes Trägermaterial für (Bio)Katalysatoren in wässrigem Medium
Engel, Stefan; Möller, Martin (Thesis advisor); Pich, Andrij (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2019
With the end of the 1980s the demand of a paradigm change from reaction efficiency towards sustainable processes in chemical industry arised. During this time, the term “green chemistry” was established and up to now did not lose its importance when talking about sustainable chemistry. In 1998 Anastas and Warner published the “12 principles of green chemistry” which include among others waste and pollution prevention and the design of energy efficient processes, less toxic and more degradable chemicals. Biocatalysts and their immobilization play an important role in the implementation of green chemistry in industrial processes. The scope of this thesis is to investigate if microgels with their open and penetrable structure can be used as supporting material to modify and tailor the local environment of an immobilized (bio)catalyst (i) to protect it against external influences like solvents and (ii) to activate it by physical interaction with the gel. Therefore, the enzymatic ring-opening polymerization of ε-caprolactone (ε-CL) with the enzyme Candida antarctica lipase B (CaLB) is used as a model reaction, with the aim to increase the polymerization activity in aqueous medium. Different immobilization techniques, tailored microgel design based on polyglycidoles, enzyme engineering and surfactant coating are presented as methods to control the water content in the environment of CaLB and their effect on the catalytic activity is evaluated and compared to Novozym 435, the commercially available CaLB immobilized on acrylic resin beads. By immobilization of a deglycosylated CaLB variant a catalytic system with strongly reduced hydrolytic and enhanced polymerization activity was obtained, being even higher than the polymerization activity of Novozym 435.Further, it is the purpose of this thesis to investigate how microgels can be functionalized after crosslinking to provide binding sites for bio- and organocatalysts to further improve their efficiency. Two approaches are described: (i) partly hydrolysis of an ester containing crosslinker to obtain carboxy functional microgels and (ii) synthesis of coumarin functional prepolymers, which allows reversible photocrosslinking towards microgels. By these methods temperature and pH responsive microgels were obtained and the binding of bis(pyrazolyl)ethane, an inorganic catalyst for C-C coupling reactions, to the coumarin dimers was presented as a new route for microgel functionalization.