| الوصف: |
Porozni materiali so dandanes predmet nenehnega preiskovanja, saj njihova porozna struktura omogoča uporabo na marsikaterem področju. Tako jih najdemo v separacijskih procesih, uporabljajo se kot katalizatorji, zadnje čase pa najdemo aplikacije tudi na področju biomedicine. Pričujoča diplomska naloga se osredotoča na porozne polimerne materiale, ki jih dobimo največkrat z radikalsko verižno polimerizacijo monomernih enot. Poznamo več tehnik sinteze poroznih polimernih materialov, kot je recimo uporaba porogenih topil ali anorganskih soli v okviru diplomske naloge pa smo uporabili tehniko polimerizacije kontinuirne faze emulzije z visokim deležem notranje faze. Oljna faza je vsebovala monomerno enoto stiren in zamreževalo divinilbenzen, vodna faza pa elektrolit kalcijev klorid heksahidrat. Iniciatorski sistem je bil sestavljen iz termičnega iniciatorja, AIBN in redoks iniciatorja, TEMED. Preverjali smo hipotezo, da dobimo z naraščajočo hitrostjo mešanja manjše velikosti por, saj se tako dispergirane kapljice notranje faze razbijejo na manjše kapljice. Z dodatkom redoks iniciatorja po koncu mešanja emulzije sprožimo takojšnjo tvorbo radikalov, s čimer emulzija polimerizira preden ima možnost razpada oziroma preden se začno združevati kapljice notranje faze. Za mešanje smo uporabili dva različna mešalna nastavka, ki se razlikujeta v premeru mešalnega propelerja, ter primerjali velikosti por, ki jih dobimo z vsakim. Za ugotovitev, kateri nastavek daje pore manjših velikosti, smo vzorce karakterizirali s SEM analizo, preko katere smo preučevali morfologijo vzorcev, in porozimetrije po BET modelu adsorpcije plinov na trdnih površinah, s čimer smo dobili vrednosti specifičnih površin vzorcev. Iz grafov porazdelitve velikosti por smo potrdili hipotezo, da se velikost por manjša z višanjem hitrosti mešanja emulzije, ugotovili pa smo tudi, da dobimo v primerjavi z manjšim nastavkom z večjim nastavkom manjše pore. Porous materials are nowadays the subject of continuous research, as their porous structure allows them to be used in many areas. Thus, they are found in separation processes, can be used as catalysts, with their recent applications are also being found in the field of biomedicine. This thesis focuses on porous polymeric materials, which are most often synthesized through radical chain polymerization of monomer units. Several techniques are known for the synthesis of porous polymeric materials, as is for instance the use of porous solvents or inorganic salts nonetheless, within the framework of this thesis, the technique of continuous phase emulsion polymerization with a high proportion of internal phase was used. The oil phase contained a styrene monomer unit and a divinylbenzene as a crosslinker, whilst the aqueous phase contained calcium chloride hexahydrate as an electrolyte. The initiator system consisted of a thermal initiator, AIBN, and a redox initiator, TEMED. We tested the hypothesis to obtain a smaller pore size with increasing mixing rate, since the dispersed internal phase droplets break down into smaller droplets. Adding a redox initiator after the emulsion has been mixed, triggers the immediate formation of radicals, thereby starting the process of polymerisation before the emulsion has the potential to decay. Two different mixing attachments, differing in the diameter of the mixing propeller, were used for mixing, and the pore sizes obtained with each were compared. To determine which attachment gives pores of smaller size, samples were characterized by SEM analysis, through which we examined the morphology of the samples, and porosimetry based on the BET model of gas adsorption on solid surfaces, which yielded us the values of specific surface areas of the samples. Stemming from the graphs of the pore size distribution, we confirmed the hypothesis that the pore size decreases as the emulsion mixing rate increases, and we also found out that the use of a larger attachment results in smaller pores compared to a smaller one. |
