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PhD Defence Piet Driest | Poly(urethane-isocyanurate) networks - synthesis, properties and applications

Poly(urethane-isocyanurate) networks - synthesis, properties and applications

Piet Driest is a PhD student in the research group Biomaterials Science and Technology (BST). His supervisors are prof.dr. D.W. Grijpma and prof.dr. D. Stamatialis from the Faculty of Science and Technology.

This thesis describes our research on aliphatic poly(urethane-isocyanurate) (PUI) networks. Currently, these materials are widely applied in the coatings and adhesives industry. However, owing to their generally high toughness, excellent optical properties and good biocompatibility, aliphatic PUI networks are attractive materials for biomedical applications as well. In this work, we investigate the synthesis and material properties of aliphatic PUI networks as well as their potential application in a biomedical context.

In the first part of this thesis (chapters 3 and 4), the viscosity of liquid aliphatic isocyanurates is investigated. These compounds are important industrial precursors in the conventional 2-component production of PUI materials. Viscosity is a key parameter for their industrial processing. Despite that, surprisingly little is known about the chemical interactions that dictate the viscosity of isocyanurate liquids. Using series of model compounds and a combined experimental and computational approach, relevant (inter)molecular interactions present in isocyanurate liquids are identified. Thereby, we provide a first framework for describing the previously poorly-understood viscosity characteristics of these liquids.

In the second part of this thesis (chapter 5), focus is gradually shifted from liquid precursors towards polymer materials. The process of PUI network formation and the microscopic network structure of PUI materials are investigated. We present a newly-developed synthesis method for producing PUI networks with a well-defined microscopic network structure. Thereby, we aim to address some of the drawbacks that are typically associated with the conventional 2-component synthesis of these materials.

In the third part of this thesis (chapters 6, 7 and 8), we explore the possibilities and limits of our newly-developed synthesis method in terms of resulting material properties and potential applications. Several new PUI networks and hydrogels are presented, demonstrating useful (combinations of) material properties for biomedical application. Relevant properties include water uptake, elastic modulus, ultimate tensile strength, toughness and crystallinity. Finally, we show that certain PUI type hydrogels are suitable for application as contact lens materials owing to their beneficial combination of high toughness in the water-swollen state, excellent optical properties and good biocompatibility.