Novel polyoxymethylene copolymers: chemistry and application scope of concatenated and multi-block oligomers with polyacetal segments

• Neuartige Polyoxymethylenkopolymer: Chemie und Anwendungsgebiete von verknüpften und multiblock Oligomeren mit Polyacetalsegmenten

Hoffmann, Matthias; Müller, Thomas Ernst (Thesis advisor); Leitner, Walter (Thesis advisor)

Aachen (2018)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2018

Abstract

The thesis at hand various different topics regarding the synthesis and properties of polyoxymethylene (POM) oligomers and copolymers. POM is an engineering plastics, that finds widespread applications. The general interest in POM polymers remains high, as formaldehyde can be produced from sustainable feedstocks. The present thesis is divided into 5 main chap-ters. Chapter 1 gives an overview on the history behind POM polymers, their application as materials, the cationic homopolymerisation of trioxane, the cationic copolymerisation of trioxane with other comonomers. Also the sustainability of formaldehyde and its polymers are dis-cussed. In Chapter 2, the ring-opening reaction of trioxane in the presence of acetic anhydride is discussed as a model reaction for the initial phase of the trioxane homopolymerisation. In situ IR spectroscopy was used as a tool to monitor the kinetic profile of multiple reactions per-formed with different Brønsted acidic and Lewis acidic catalysts. The role of these catalysts is discussed in the context of the mechanism of the ring-opening reaction of trioxane with acetic anhydride. Chapter 3 entails the synthesis of a series of low molecular weight oxymethylene diacetates. The crystallinity, melting- and crystallisation temperature of these com-pounds were determined. The effect of the composition of oxymethylene diacetate mixtures on their thermal properties is discussed in general. Moreover, the findings are discussed in the context of sustainable fuel applications for POM oligomers with relatively low molecular weight. In Chapter 4, the synthesis, thermal properties and the application of poly(acetalester) are discussed. Poly(acetalester) are novel and sustainable copolymers of trioxane and cyclic anhydride. The monomers are copolymerised in the presence of an open chain anhydride as chain transfer agent to achieve molecular weight control. Multiple aspects, like average length of oxymethylene segments, formation of cyclic poly(acetalester) as side products and the introduction of reactive moieties in the copolymer chain are discussed. In Chapter 5, the synthesis, the mechanism and the thermal properties of multi-block POM-PEG copolymers are dis-cussed. The control of the copolymer composition and the connection to their thermal proper-ties are explained. As outlook, the applications scope of POM in the fields of fuels, materials, lubricants and phase change materials are discussed.