Porous materials occur everywhere in nature and with porous polymers we try to imitate them and try to use their numerous special properties. Some porous materials are very fragile, while others exhibit exceptional mechanical properties, which are greatly influenced by the microstructure of the material (distribution, shape and the proportion of the pores in the material). Porous materials offer a wide range of useful applications such as tissue engineering, targeted drug delivery, separation processes, insulation etc. It is because of the many possibilities of use that it is necessary to know the mechanical and hydrodynamic properties of materials and to understand the dependence of the properties they exhibit on the microstructure and porosity.
As part of my master's thesis, I investigated the influence of porosity and microstructure of porous methacrylate polymers on their mechanical and hydrodynamic properties. Using free radical polymerization, monolithic porous polymers of two different microstructures were prepared (partial microstructure, which is obtained by bulk polymerization in the presence of porogenic solvents and polyHIPE microstructure, which is obtained by polymerization of HIPE emulsions), chemical composition was the same in both cases. By performing a compression test, the compression modulus of both microstructures was determined, and for the polyHIPE monoliths a test of hydrodynamic properties was also performed. The results were explained with porosity and microstructure. The characteristics of the microstructure were explained based on SEM images. From the experimental data, the equations of the dependence of the compression modulus on the porosity for both types of material were derived. The results indicate that polyHIPE materials have a higher compression modulus and thus a more solid microstructure than partial monoliths and are therefore useful even at higher porosity values, as they better withstand pressure loads.
The optimal porosity for polyHIPE materials, at which the material has sufficient permeability, and at the same time the pressure drop across the monolith is low enough to not damage its internal microstructure was mathematically determined in the end. According to the results, the prepared polymer material in polyHIPE form is mechanically stable in wide range of porosity for tested experimental parameters.
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