Voorbereiding van poreuze materialen met behulp van fase-inversiebenadering

This doctoral research explores the fabrication of porous polymeric materials using thermally induced phase separation (TIPS), aiming to enhance the sustainability of the method through the use of novel, low-toxicity solvents and better understanding of the process parameters. A systematic investigation was conducted across multiple polymer/solvent systems, integrating experimental, theoretical, and computational methods to evaluate material behavior, thermodynamic interactions, and morphological outcomes. The first part of the dissertation focused on understanding the influence of solvent removal strategies, specifically lyophilization and solvent extraction, on the resulting morphology and properties of porous materials prepared via TIPS. Using a well-established polystyrene (PS)/cyclohexane (CH) system, it was shown that the solvent removal method significantly affects the pore size distribution, porosity, and overall material morphology. Lyophilization generally resulted in higher porosity and larger pore sizes compared to solvent extraction. These findings emphasize that the final step of the TIPS process is not merely a technical detail but a critical design parameter. Furthermore, insulation properties of prepared PS foams were assessed indicating application potential as both sound and thermal insulation in one layer of material. To offer sustainable alternative to commonly used polymer/solvent systems, a systematic solvent screening was conducted using Hansen solubility theory. Out of 846 compounds, several novel low-toxicity, low-cost, and high melting point solvents were identified for the processing of two widely used biopolymers: poly(ε-caprolactone) (PCL) and polylactic acid (PLA). The newly identified PCL/(methyl p-toluate) (MPTOL) system emerged as particularly promising. It exhibited suitable properties for low-energy processing due to a disparity between freezing points of the system and melting temperature of the MPTOL (~34°C) allowing solvent removal at room temperature. Additionally, acetic acid (AA) is presented and studied as a promising alternative to commonly used PLA solvents. Extensive experimental and computational characterization of the novel PCL/MPTOL and PLA/AA systems was performed, including phase diagram construction using cloud and freezing point measurements supplemented by computational modelling of binodal and spinodal curves via Flory-Huggins theory and PC-SAFT equation of state. These diagrams provided valuable insight into phase behavior enabling control of the process conditions to prepare tailored material for specific applications. In the case of the PCL/MPTOL system, highly porous materials with average pore sizes below 100 nm and porosities exceeding 70% were successfully prepared. The system allowed for significant morphological tunability based on polymer concentration entailing application potential in a variety of industry fields. Different PLA types were screened, and the most suitable candidate (PLA6) was selected for subsequent material preparation. The influence of PLA concentration and solvent removal was systematically studied showing strong influence of the solvent removal method on the final porous morphology. The utilization of water as an extraction agent allowed preparation of porous structures with average pore sizes near 20 nm with "vinegar" as a waste stream. Furthermore, the biocompatibility of the prepared materials was validated via cell cultivation on the surface of the prepared materials, showcasing application potential in tissue engineering application assuming TIPS cooling regimen alteration to allow for formation of bigger pores required for cell infiltration into the porous structure. In summary, this doctoral research delivers substantial advancements in both the fundamental understanding and practical implementation of more sustainable TIPS processing. The dissertation highlights the solvent removal step as a key morphological factor, introduces several low-toxicity solvent systems with experimentally verified suitability, and demonstrates the fabrication of porous materials with broad application potential. The outcomes contribute valuable tools for greener polymer processing and open new avenues for the design of functional materials in the biomedical, separation and insulation sectors.