Prepletene polimerne mreže (ang. »interpenetrating polymer networks«, IPN) predstavljajo posebno vrsto vsestransko uporabnih večkomponentnih polimernih sistemov. Gre za preplet dveh polimernih mrež, ki med seboj nista kovalentno povezani. Tak material vsebuje mikro domene obeh polimernih komponent in tako deloma ohrani lastnosti obeh polimerov.
Sinteza IPN običajno poteka v dveh zaporednih reakcijah, z ustreznim izborom monomerov pa je možna tudi sinteza v enem koraku. Pri tem je potrebno zagotoviti, da polimerizaciji posameznih monomerov potekata po ortogonalnih mehanizmih in se med seboj ne motita. Preverili smo, ali to velja za prosto radikalsko polimerizacijo stirena in polimerizacijo z odpiranjem obroča ε-kaprolaktona. Preučili smo kinetiko izbranih polimerizacij in določili pogoje, pri katerih oba izbrana monomera polimerizirata z enako hitrostjo, saj pričakujemo, da se s sočasno polimerizacijo verige temeljiteje prepletajo in s tem velikosti domen posameznih komponent manjšata.
Nadalje smo IPN uporabili kot prekurzorje za pripravo poroznih polistirenskih ogrodij. Domene poli(ε-kaprolaktona) (PCL) smo selektivno odstranili s hidrolitsko razgradnjo, kar je vodilo do nastanka por v polistirenskem ogrodju. Preučili smo, kako na poroznost polistirenskega skeleta vplivajo način priprave, zamreženost, sočasnost obeh vrst polimerizacij in molska masa PCL. Porozno morfologijo skeleta smo preučevali z elektronsko vrstično mikroskopijo (SEM), iz adsorpcijskih izoterm pa smo določili specifične površine skeletov po Brunauer-Emmett-Teller metodi (BET). S sočasno sintezo IPN smo po nadaljnji obdelavi dobili mezo- in mikroporozne polimere s specifičnimi površinami do 89 m2/g, medtem ko smo po zaporedni pripravi dobili makroporozne polimere z zanemarljivo majhnimi specifičnimi površinami.Interpenetrating polymer networks (IPN) represent unique and versatile materials in the field of multicomponent polymer systems, composed of non-covalently linked chains. Such materials exhibit micro-sized domains of polymeric components and thus partly preserve characteristics of both polymers.
A common procedure for the synthesis of IPN usually takes place in two sequential steps. Appropriate selection of monomers allows a one-step synthesis where the orthogonality of polymerization mechanisms is of cruical importance. Orthogonality of free radical polymerization of styrene and ring-opening polymerization of ε-caprolactone was investigated and confirmed. Under assumption that simultaneous conversions of monomers lead to smaller domains in IPN, the kinetics of such polymerizing system was also investigated.
Further on, IPNs were used as the precursors for the preparation of porous polystyrene framework. For this purpose the domains of poly(ε-caprolactone) (PCL) were selectively hydrolized to produce the pores in the polystyrene framework. The effects of synthetic procedure used, cross-linking, simultaneity of orthogonal reactions and molar mass of PCL on the porosity of polystyrene framework were investigated. The porous morphology of polystyrene framework was studied using scanning electrone microscopy (SEM), whereas from the adsorption isotherms the specific surface areas were calculated using the Brunauer-Emmett-Teller method (BET). We have demonstrated that the simultaneously prepared IPNs offer an advantage over the sequentially prepared IPNs since the pore size decreased down to micropores and, subsequentely, the surface area increased from negligable values up to 89 m2/g
