Functionalised macroporous films via emulsion templating : preparation, processing and applications

Abstract

Polymerised high internal phase emulsions, or polyHIPEs, refer to the macroporous polymers prepared via emulsion templating. PolyHIPEs are usually characterised by high porosity and interconnectivity and low density, which make them applicable in tissue engineering, construction materials and catalyst supports. However, the exploration of polyHIPE films is very limited so far. Thus this thesis will describe the works on designing flexible and tough functionalised macroporous films that are for a variety of applications. Poly(methacrylic acid) (poly(MAA)) and poly(dimethyl aminoethyl methacrylate) filled polyHIPEs were firstly prepared and characterised. The hydrogels were grafted on the surface of the pore walls in the polyHIPE scaffolds. Subsequently, poly(MAA) filled polyHIPEs were sliced into membranes and their performances were tested. The permeability and selectivity of the membranes are highly affected by the pH value of the feed solution due to the pH-sensitivity of poly(MAA). The membranes with 2% crosslinking degrees in poly(MAA) had a cut-off of 50K polyethylene glycol, suggesting applications for ultrafiltration. In the following work, mechanical properties of macroporous monoliths and films were tailored. Polyurethane diacrylate (PUDA), which is a long chain crosslinker, was copolymerised within emulsion templates to modify the mechanical properties of polyHIPEs. These macroporous polymers based on PUDA and styrene were less brittle than the conventional poly(styrene-divinylbenzene)HIPEs and possessed enhanced elastic moduli and crush strengths compared to poly(styrene-polyethylene glycol dimethacrylate)HIPEs. The tough polyHIPEs are expected to be used as scaffolds for membranes or catalysts. Subsequently, very flexible macroporous films were prepared by casting and UV polymerising emulsion templates based on PUDA and ethylhexyl acrylate. The films possessed breaking strains up to 30%. Moreover, the films showed constant mechanical behaviour under relaxation tests and cyclic tests, suggesting the capability for long term use. The films will be further designed for pressure sensor applications. A novel method to prepare macroporous films was developed in this project. Emulsion templates were printed either by rolling-pin or screen and UV polymerised subsequently, resulting in patterned macroporous films. The experiment showed that the printing process did not damage the porous structure of the films. Additionally, it is feasible to multilayer print the emulsion templates to create 3D or complex structure.