Saccharides as renewable resources for novel functional materials
by Stefanie Rühlicke
Date of Examination:2020-11-11
Date of issue:2021-01-21
Advisor:Prof. Dr. Kai Zhang
Referee:Prof. Dr. Kai Zhang
Referee:Prof. Dr. Bodo Saake
Files in this item
Format:PDFDescription:Dissertation, Stefanie Rühlicke, "Saccharides as renewable resources for novel functional materials"
EnglishSaccharides, also known as carbohydrates, are ubiquitous and have been used by men for millennia. The high variability of the saccharides ensures a wide field of applications. In general, saccharides could be subdivided into three groups. Firstly, the group of mono- or disaccharides, which are the so-called simple sugars, mostly hexoses or pentoses, such as glucose, or a combination of two components as it is the case with lactose. They form the basic building blocks for the biosynthesis of natural compounds. Furthermore, they are the basic building block for the oligosaccharides, which contain three to ten sugar units and the polysaccharides which have more than ten sugar units. The high variation and combination possibilities of saccharides leads to a broad field of applications. The field contains simple uses as for nourishment, as energy supplier, source for clothes and paper. Besides this, the field also contains more complex uses such as resources for hydrogels, for the production of transparent biologic degradable packaging for food, for the generating of flexible electronical films or for the production of novel vaccines or new drugs for the treatment of neurodegenerative illnesses like Alzheimer disease or the Parkinson disease. Furthermore, the naturally occurring saccharides serve as inspiration for novel modifications of saccharides or mimetic oligo- and polysaccharides. The focus of the research lies on different aspects. One of those is the production of glycosidic linked monosaccharides for the synthetic production of oligo- and polysaccharides. Another one is the construction of new sugar-based oligomers or polymers with non-glycosidic linkages, for example by click linking like the copper-catalysed azide alkyne coupling, a thiol ene coupling or via a UGI reaction. In this presented paper, cellulose, as an example for a natural renewable polysaccharide, was used as resource for a two-step containing heterogeneous esterification with a long chain alky acid chloride (stearoylchloride or lauroylchlroride) in the first step and cinnamoylchloride in the second step. Over this two step-synthesis two novel cellulose mix esters SCC (stearoylated cinnamoylated cellulose ester) and LCC (lauroylated cinnamoylated cellulose ester) were successfully generated and have been completely chemically characterised via FTIR, NMR spectroscopy and DSC. Afterwards, the products were tested on outstanding material properties. It turned out, that both products were able to form transparent flexible films, which showed solvent and temperature driven properties. Moreover, the films revealed the ability of self-healing. Alongside the use of cellulose as a biopolymer, galactose as a natural and biological interesting monosaccharide was used for further modifications as a basic material. Galactose was provided in a six-step synthesis on the one hand with an end standing alkene and a thiol group and on the other hand with an end standing alkyne and a thiol group. Due to the high reactivity of the unprotected thiol groups, the precursor molecules were completely chemically analysed via FTIR and NMR spectroscopy. Afterwards, a basic investigation of the necessary reaction conditions for a successful thiol-yne respectively thiol-ene coupling, that lead to click linked linear respectively branched oligosaccharide chains, was examined. Besides the modifications described, galactose was further used as resource in another six-step reaction with the goal of introducing an alkene and an azide functionalisation. The molecule was synthesised with an overall yield of 32 % and the product was completely examined via FTIR and NMR spectroscopy. Afterwards, the obtained product was converted via a symmetrical copper catalysed azide alkyne coupling with 1,7-octadiyne to a symmetrical di triazole. The triazole was tested on antifungal properties with the two different fungi stains Coniophora puteana and Trametes versicolor. Furthermore, alternative modification possibilities were shown, like a reaction leading to novel oligo- or polysaccharides. The presented study is a monography, containing one publication. After a general introduction, followed by the objectives, the three main topic blocks, each containing a literature overview of the respective topic area, as well as a detailed presentation of the results with the corresponding discussion and a summary, are presented before moving on to a final general summary. The main topic blocks can be found in the chapters 3 through 5.
Keywords: Saccharides; Cellulose; Materials