Microcellular open porous polyester membranes from thiol-ene polymerisations of high internal phase emulsions

A high internal phase emulsion templating procedure is applied for the preparation of membranes which exhibit an open porous morphology with interconnected macro pores and open porous surfaces. A doctor blading procedure is used to cast the high internal phase emulsion onto glass substrates. Continuous phase of the emulsions contain divinyladipate and pentaerythritol tetrakis(3-mercaptopropionate) which are photopolymerised using the thiol-ene click chemistry to yield polyester type polymer network. The resulting polymer morphology features primary pores as a result of emulsion's droplet phase, with diameters between 7 and 14 mu m and interconnecting pores as a result of polymerisation shrinkage, with diameters between 1.6 and 2.2 mu m. The highly porous and interconnected morphology mirrors the precursor emulsion structure with a dense packing of internal (aqueous) phase droplets. Doctor blades with different slit dimensions are used for casting thus producing membranes with different thicknesses while in all cases typical polyHIPE morphology is observed. Mechanical tests show a dependence of tensile modulus and tensile strength on the membrane thickness and also on pore size distribution.