Effect of ratio of comonomers on the morphology of poly(divinylbenzene-co- ethylhexyl acrylate-co-acrylic acid)

Porozni polimerni monoliti so bili pripravljeni s polimerizacijo obeh faz emulzije z visokim deležem notranje faze. V vodni fazi smo uporabili: kalijev peroksodisulfat, akrilno kislino in metilenbisakrilamid. Masni delež akrilne kisline je bil 2 % ali 5 %. V organski fazi so bili prisotni: span 80, 2-etilheksil akrilat, divinilbenzen in v nekaterih primerih še stiren. Monomer divinilbenzen je služil kot zamreževalo v organski fazi, monomer metilenbisakrilamid pa kot zamreževalo v vodni fazi. Monoliti so bili 2 %, 3 %, 5 % ali 10 % zamreženi z metilenbisakrilamidom. Kalijev peroksodisulfat je služil kot iniciator oziroma kot sredstvo, ki pospeši polimerizacijo. Elastičnost materiala smo povečali z 2-etilheksil akrilatom, ki je služil kot komonomer. Ugotovili smo, kako poliakrilna kislina glede na različen pH medij spreminja prostornino znotraj praznin monolita. Spreminjali smo delež 2-etilheksil akrilata in divinilbenzena ter preučevali mehanske lastnosti vzorcev ter njihovo morfologijo. Emulzijo z visokim deležem notranje faze smo prelili v plastičen kalup in jo izpostavili vplivom toplote (približno 60 oC), da smo sprožili polimerizacijo. Dobimo visoko porozen, zamrežen monoliten material. Zaradi razpada materiala pri čiščenju in sušenju smo začeli dodajati še stiren. Dodani stiren je izboljšal mehanske lastnosti polimerov. Z vrstično elektronsko mikroskopijo smo določili morfologijo monolitnega materiala in s tem potrdili njihovo poroznost ter ugotovili, kakšen je povprečen premer praznin monolita. Z infrardečo spektroskopijo smo preverili kemijsko strukturo monolitov. Monolitom smo izmerili povratni tlak s pomočjo visoke ločljivostne tekočinske kromatografije.Porous polymeric monoliths were prepared by the polymerisation of both phases of high internal phase emulsions. Potassium persulfate, acrylic acid and methylenebisacrylamide were used in the aqueous phase. Concentration of acrylic acid was 2 % or 5 % (mass), respectively. Span 80, 2-ethylhexyl acrylate, divinylbenzene and in some cases styrene were present in the organic phase. Monomer divinylbenzene was used as a crosslinker in the organic phase and methylenebisacrylamide was the crosslinker in the aqueous phase. Monoliths were 2 %, 3 %, 5 % or 10 % crosslinked with methylenebisacrylamide. Potassium persulfate was used as the initiator. Elasticity of the material was increased by using 2-ethylhexyl acrylate as a comonomer. Added acrylic acid induced alternation of back pressure of the monolith. We presumed that polyacrylic acid is changing its volume inside the voids of the material with the alternation of the pH media. Content of 2-ethylhexyl acrylate and divinylbenzene was varied in order to determine mechanical characteristics and morphology of the samples. High internal phase emulsions were cast in plastic moulds and exposed to high temperatures (approximately 60 oC) in order to start the polymerisation. Highly porous, crosslinked monolithic material was obtained. We started adding styrene because the resulting material was brittle after cleaning and drying. Addition of styrene improved the visual mechanical properties of the polymers. The morphology of monolithic material was determined using scanning electron microscopy. Their porosity was confirmed and average diameter of voids was determined by image analysis. IR spectroscopy was used to confirm the chemistry of the monoliths. The back pressure of monoliths was measured with high performance liquid chromatography pump