| Abstract | U ovom radu sintetizirani su hidrogelovi na bazi celuloze kojoj je dodan još jedan vodotopivi polimer sklon formiranju hidrogelova. Pripravljene su reakcijske smjese koje sadrže 30, 50 i 70 mas% prethodno sintetiziranih polimera poli(vinil-pirolidona) (PVP), poli(N-vinilkaprolaktama) (PVCLA) i poli(dimetilaminoetil-metakrilata) (PDMAMEA). Neotapalo za pojedini sustav birano je na temelju preliminarnih pokusa u kojima je ispitana sposobnost bubrenja i sastav dobivenih hidrogelova. Za sustav PVP-celuloza odabrane su pare etanola, a za ostala dva sustava pare acetona u kojima je gelirana i otopina čiste celuloze za usporedbu. Hidrogelovi su gelirani 24 i 168 h kako bi se utvrdila razlika u svojstvima s promjenom vremena geliranja. S namjerom postizanja boljeg umrežavanja, reakcijske smjese su prije geliranja zračene γ-zrakama doze 200 kGy. Dobivenim zračenim i nezračnim hidrogelovima određeni su koeficijenti bubrenja, sastav, reološka svojstva, ciklički voltamogrami u različitim elektrolitima te morfologija. Najmanje koeficijente bubrenja pokazuju hidrogelovi PVP-celuloza, a najveće uzorci PDMAMEA-celuloza. Svi dvokomponentni hidrogelovi osim onog s 30 % PVP-a imali su veće koeficijente bubrenja od čiste celuloze. Kod svih zračenih i nezračenih uzorka koji su gelirani 24 h, koeficijenti bubrenja rastu sa smanjenjem udjela celuloze u reakcijskoj smjesi. Duže vrijeme geliranja omogućilo je bolju ugradnju dodanog polimera kod svih uzoraka sustava PVCLA-celuloza dok je za druga dva sustava povećanje uočeno samo za neke smjese. Koeficijenti bubrenja znatno su viši za hidrogelove koji su duže gelirali kod sustava PVCLA-celuloza, PDMAMEA-celuloza te za hidrogel od čiste celuloze dok je za sustav PVP-celuloza bubrenje slabije kada je hidrogel duže geliran. Određivanje reoloških svojstava na uzorcima geliranim 168 h pokazalo je da su G’ i G’’ kod svih nezračenih hidrogelova niži nego za hidrogel od čiste celuloze što ukazuje da su dobiveni hidrogelovi slabije umreženi. Iako su zračenjem za gotovo sve uzorke dobiveni hidrogelovi s nešto većim sadržajem celulozi dodanog polimera i u nekim slučajevima većim koeficijentima bubrenja, mehanička i reološka svojstva tih hidrogelova bila relativno loša. Postoji mogućnost da je korištena doza zračenja previsoka ili da je intenzitet zračenja od 23,7 kGy h^-1 prevelik pa je umjesto do boljeg umrežavanja došlo do raspadanja polimernih lanaca što čini dobivene hidrogelove vrlo krhkima. |
| Abstract (english) | In this paper, cellulose based hydrogels were synthesized to which another water-soluble polymer, prone to forming hydrogels, was added. Reaction mixtures containing 30, 50 or 70 wt% of previously synthesized polymers polyvinylpyrrolidone (PVP), poly(N-vinylcaprolactam) (PVCLA) and poly (dimethylaminoethyl methacrylate) (PDMAMEA) were prepared. The non-solvent for each system was chosen based on preliminary experiments in which the swelling ability and composition of the obtained hydrogels were tested. For the PVP-cellulose system, ethanol vapors were selected, and for the other two systems, acetone vapors were used. Pure cellulose hydrogel was also prepared for comparison. Hydrogels were gelled for 24 and 168 h in order to determine the difference in properties with the change of gelation time. In order to achieve better cross-linking, the reaction mixtures were subjected to a gamma ray source, with gamma-ray absorbed doses of 200 kGy before gelation. The swelling coefficients, composition, rheological properties, cyclic voltammograms in different electrolytes and morphology were determined for the obtained irradiated and non-irradiated hydrogels. The lowest swelling coefficients were seen in the PVP-cellulose system, and the highest in PDMAMEA-cellulose hydrogels. All two-component hydrogels except the one with 30 % PVP had higher swelling coefficients than pure cellulose. In all irradiated and non-irradiated samples that were gelled for 24 h, the swelling coefficients increase with a decrease in cellulose concentration of the reaction mixture. A longer gelation time enabled a more efficientincorporation of the added polymer in all samples of the PVCLA-cellulose system, while for the other two systems an increase was observed only for some mixtures. For PVCLA-cellulose, PDMAMEA-cellulose and pure cellulose hydrogels swelling coefficients are significantly higher for hydrogels that have gelled longer, while for the PVP-cellulose system swelling is weaker with the increase of the gelation time. Determination of rheological properties of samples gelled for 168 h showed that G’ and G’' in all non-irradiated hydrogels are lower than for pure cellulose hydrogel, which indicates that the obtained hydrogels are less cross-linked. Although the irradiation mostly produced hydrogels with a slightly higher content of polymer added to cellulose and in some cases higher swelling coefficients, the mechanical and rheological properties of these hydrogels were fairly poor. There is a possibility that the radiation dose used was too high or that the radiation intensity of 23.7 kGy h^-1 was too high, so instead of better cross-linking, polymer chains degraded, which made the obtained hydrogels very fragile. |
