Mechanical properties of porous methacrylate polymers

Porozni materiali se pojavljajo povsod v naravi, s poroznimi polimeri pa jih poskušamo posnemati in izkoristiti številne posebne lastnosti, ki jih imajo. Nekateri porozni materiali so zelo krhki, drugi pa izkazujejo izjemne mehanske lastnosti, na kar ima velik vpliv prav mikrostruktura materiala (razporeditev, oblika in delež por v materialu). Porozni polimerni materiali ponujajo široko paleto uporabnih aplikacij: tkivno inženirstvo, tarčna dostava zdravil, separacijski procesi, izolacija itd. Prav zaradi številnih možnosti uporabe pa je nujno poznavanje mehanskih in pretočnih lastnosti materialov ter razumevanje odvisnosti lastnosti, ki jih izkazujejo, od mikrostrukture in poroznosti. V okviru magistrske naloge sem raziskovala vpliv poroznosti in mikrostrukture poroznih metakrilatnih polimerov na njihove mehanske in pretočne lastnosti. Z verižno radikalsko polimerizacijo sem pripravila monolitne porozne polimere dveh različnih mikrostruktur (delčna mikrostruktura, ki jo dobimo s polimerizacijo v masi v prisotnosti porogenih topil in poliHIPE mikrostruktura, ki jo dobimo s polimerizacijo HIPE emulzij), kemijska sestava pa je bila v obeh primerih enaka. Materialom obeh mikrostruktur sem preko kompresijskega testa določila kompresijski modul, za poliHIPE monolite pa sem izvedla tudi test pretočnih lastnosti in rezultate razložila s poroznostjo in mikrostrukturo. Značilnosti mikrostrukture sem opisala s pomočjo SEM posnetkov. Iz eksperimentalnih podatkov sem izpeljala enačbe odvisnosti kompresijskega modula od poroznosti za oba tipa materiala. Ugotovila sem, da imajo poliHIPE materiali višji kompresijski modul in s tem bolj trdno mikrostrukturo od delčnih monolitov in so zato uporabni tudi pri višjih poroznostih, saj bolje kljubujejo tlačnim obremenitvam. Na koncu sem za poliHIPE materiale še matematično poskusila določiti optimalno poroznost, pri kateri je material dobro pretočen, hkrati pa je padec tlaka čez monolit dovolj nizek, da ne poškoduje njegove notranje mikrostrukture. Prišla sem do zaključka, da je pripravljen material v poliHIPE obliki stabilen v širokem območju poroznosti glede na eksperimentalne parametre, ki sem jih testirala.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\u27s 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