Title Priprava celuloznih hidrogelova sa srebrovim nanočesticama Title (english) Preparation of cellulose hydrogels with silver nanoparticles Author Katarina Lenac Mentor Elvira Vidović (mentor)Committee member Elvira Vidović (predsjednik povjerenstva)Committee member Marijana Kraljić Roković (član povjerenstva)Committee member Mirela Leskovac (član povjerenstva)Granter University of Zagreb Defense date and country 2019-09-16, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Celuloza je najrasprostranjeniji polisaharid na Zemlji koji se sve više istražuje za pripravu novih vrsta materijala. Naročito su značajna svojstva biokompatibilnosti i biorazgradivosti celuloze. Tri hidroksilne skupine sadržane na svakoj glukoznoj jedinici omogućuju provedbu različitih modifikacija i umrežavanje lanaca te pripravu hidrogelova. Hidrogelovi celuloze i nanočestica srebra već su istraživani u svrhu dobivanja antibakterijskih kompozitnih materijala koji imaju biokompatibilna svojstva, lako se razgrađuju i nisu štetni za okoliš. Uvođenjem novih funkcijskih skupina na osnovni polisaharidni lanac mijenjanju se svojstava hidrogela. Cilj ovog rada bio je prirediti hidrogelove na bazi celuloze graftirane sa dimetilaminoetil-metakrilatom (DMAEMA) te ih naknadno modificirati uvođenjem srebrovih nanočestica. U pripravi hidrogelova korišten je funkcijski monomer DMAEMA koji u svojoj strukturi ima amino skupinu osjetljivu na promjenu pH. Srebro je poznato po antibakterijskom djelovanju, a također ima i katalitičku primjenu, pa bi ovakav hidrogel mogao poslužiti na primjer kao nosač katalizatora. Ovakvim kombiniranjem tvari različitih karakteristika pruža se mogućnost stvaranja novih materijala prestižnih svojstava za vrlo različite primjene, od senzora do različitih nosača i prevlaka, od farmacije, medicine, industrije obrade voda i slično. Polimerizacija DMAEMA na celulozu provedena je u otapalu N,N-dimetil acetamid/LiCl uz peroksidni inicijator Trigonox 21 pri temperaturi od 90 °C. N,N-metilen-bis-akrilamid (MBA) korišten je kao umreživač. Prilikom sinteze hidrogelova mijenjani su količinski omjeri celuloze i DMAEMA (1:1 i 1:3) te celuloze i MBA (5:1 i 2,5:1). Nanočestice srebra sintetizirane su iz otopine srebrova nitrata uz ekstrakt ružmarina pri sobnoj temperaturi i 80 °C. Čestice srebra unutar hidrogelova zarobljene su na dva načina: a) bubrenjem hidrogelova u pripravljenoj suspenziji nanočestica srebra, b) bubrenjem hidrogelova u otopini srebrova nitrata. Pripremljeni hidrogelovi karakterizirani su infracrvenom spektroskopijom kako bi se odredio udio metakrilatnog polimera u hidrogelu. Također, pripremljenim hidrogelovima određen je stupanj bubrenja u deioniziranoj vodi, dok je morfologija uzorka i prisutnost srebra određena pretražnom elektronskom mikroskopijom. Termogravimetrijskom analizom određena je toplinska stabilnost hidrogelova. Na temelju omjera vrpci pri 1724 i 897 cm^-1 utvrđeno je da najveći udio PDMAEMA imaju hidrogelovi čija je reakcija polimerizacije trajala 5 h s omjerom celuloze i DMAEMA 1:1. Određivanjem stupnja bubrenja utvrđeno je da hidrogel s manjom količinom MBA bubri najviše (oko 500 %), hidrogel s većom količinom MBA bubri oko 250 %, dok sfera celuloze bubri oko 80 %. Termogravimetrijskom analizom određeno je da sfera celuloze ima veću toplinsku stabilnost od hidrogelova, a razlika iznosi oko 60 °C.
Abstract (english) Cellulose is the most abudant polysaccharide on Earth and is being increasingly researched for design of new materials. Biocompatibility and biodegradability are particularly important properties of cellulose. Three hydroxyl groups on each glucose unit enable various modifications, crosslinking of the chains and preparations of hydrogels. Cellulose based hydrogels and silver nanoparticles have already been studied as the antibacterial composite materials that are biocompatible, easily degradable and environmentaly friendly. Properties of hydrogels can be changed by introducing new functional groups on the basic polysaccharide chain. The aim of this study was to prepare cellulose based hydrogels grafted with dimethylaminoethyl methacrylate (DMAEMA) and modify them later on by introducing silver nanoparticles. DMAEMA was used as functional monomer in preparations of hydrogels, which has a pH sensitive amino group in its structure. Silver is known for its antibacterial activity and also has a catalytic use, so this hydrogel could serve as a catalyst carrier. Such a combination of substances of different intrinisic characteristics gives the opportunity to create new materials of prestigious properties for very different applications, from sensors to versatile carriers and coatings with a good prospective use regarding e.g. pharmacy, medicine, water treatment industry, etc. DMAEMA polymerization on cellulose was carried out in N,N-dimethyl acetamide/LiCl solvent system with a peroxide initiator Trigonox 21 at 90 °C. N,N-methylene-bis-acrylamide (MBA) was used as the crosslinker. Quantitative ratios were altered during synthesis of hydrogels: cellulose and DMAEMA (1:1 and 1:3) and cellulose and MBA (5:1 and 2.5:1). Silver nanoparticles were synthesized from silver nitrate solution with rosemary extract at room temperature and at 80 °C. Silver particles were captured in hydrogels by: a) swelling of hydrogels in the prepared suspension of silver nanoparticles, b) swelling of hydrogels in silver nitrate solution. Prepared hydrogels were characterized by infrared spectroscopy to determine the fraction of methacrylate polymer in the hydrogel. Also, the degree of swelling is determined for prepared hydrogels swollen in deionized water, while the morphology of the sample and the presence of silver were determined by scanning electron microscopy. Thermogravimetric analysis was used to determine the thermal stability of hydrogels. Based on the band ratios at 1724 and
897 cm^-1, it was found that the highest fraction of PDMAEMA had hydrogels with a ratio of cellulose and DMAEMA 1:1, polymerized for 5 hours. By determining the degree of swelling, it was found that the hydrogel with a smaller amount of MBA swelled the most (about 500%), the hydrogel with a higher amount of MBA swelled about 250%, and the cellulose sphere swelled about 80%. Thermogravimetric analysis determined that the cellulose sphere had a higher thermal stability than hydrogels whereat the registered difference was about 60 °C.
Keywords
graftiranje
hidrogel
bubrenje
srebrove nanočestice
Keywords (english)
grafting
hydrogel
swelling
silver nanoparticles
Language croatian URN:NBN urn:nbn:hr:149:349181 Study programme Title: Applied Chemistry - Undergraduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry Type of resource Text File origin Born digital Access conditions Access restricted to students and staff of home institution Terms of use Created on 2023-05-24 13:40:50
