Functional aligned porous materials via directional freezing and frozen UV initiated polymerization

摘要

The work in this thesis is split into three experimental chapters: The first section involves the development of the directional freezing and frozen polymerization method to prepare crosslinked aligned porous polymers with improved mechanical stability. Monomer solutions were directionally frozen in liquid nitrogen to orientate the growth of solvent crystals and the frozen samples are polymerized by UV irradiation. The solvent is removed under vacuum at room temperature to produce aligned porous structure. The mechanical stability is improved by two orders of magnitude compared to the usually freeze-dried porous materials. The materials are modified with graphene and a conducting polymer to make conducting monoliths, whilst maintaining the aligned porous structure. The aligned porous monolith is also assessed by high performance liquid chromatography (HPLC), showing fast separation of hydrocarbon compounds with low back-pressure. The second section uses directional freezing and frozen UV initiated polymerization to prepare aligned porous stimuli-responsive hydrogels. Oligo-ethylene glycol methacrylates and dimethylamino ethyl methacrylate monomers were used to produce temperature and pH-responsive hydrogels respectively. Aligned porous morphologies are observed in both dry and hydrated states. The hydrogels exhibit stimuli-responsive behaviour in aqueous conditions and anisotropic compressive strength and diffusion behaviour with respect to freezing direction. Section three uses directional freezing and frozen UV polymerization method to prepare aligned porous monoliths containing silica. The surface of the materials was post-functionalized to make two different types of aligned porous composites. Hydrothermal synthesis using Teflon lined autoclaves was used to functionalize monoliths separately with silver and metal organic frameworks (MOFs). The MOF composite materials were used as a stationary phase to try and separate a mixture of organic compounds.