Provider: - Institution: - Data provided by Europeana Collections- In the theoretical part of this thesis, the most relevant literature data on chemical composition, structure and reactivity of ...cellulose are reviewed. Basic characteristic of natural (cotton and hemp) and man-made (lyocell) cellulose fibers are shown. An overview of the achieved results and published papers related to field of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, with special attention to the TEMPO-mediated oxidation of cellulose material is given. This review is the basis for the experimental part. In the experimental part of the thesis, the influence of the TEMPO-mediated oxidation on chemical composition, structure and properties of natural and man-made cellulose fibers was studied. As natural fibers cotton and hemp fibers, and from man-made liocel fibers have been modified. Unmodified and modified fibers were characterized in terms of weight loss values, carbonyl (Ca-acetate, Cu-number and GPC/CCOA method) and carboxyl contents (Ca-acetate, potentiometric titration and GPC/FDAM method), molecular weight distribution (GPC technique), crystallinity index (iodine sorption value), and changes on the surface of fibers (SEM technique). Also, oxidised fibers were characterized in terms of the geometric (fineness), physico-mechanical (tensile strength and elongation) and sorption properties (moisture sorption, water retention power, iodine sorption), as well as the capacity of sorption of different ions. The TEMPO-mediated oxidation has influence on weight loss and changes in fineness of the modified fibers. Oxidized cotton and lyocell fibers show minimal increase of fineness, while oxidized hemp fibers get a significant increase in fineness. In the case of hemp fibers, which contain noncellulosic materials beside the cellulose, TEMPO-oxidation leads to a significant removal of hemicelluloses and lignin. For all oxidized fibers, depending on the conditions of modification, a higher crystallinity index is obtained, while the tensile strength of fiber decreases. By the TEMPO-mediated oxidation of cellulose fibers, significant amount of carboxyl groups can be introduced into cellulose fibers, and the amount of these functional groups is controllable by selecting the oxidation conditions. Due to introduced hidrophylic carboxyl groups, the hemisorption properties od oxidized fibers increase. Good sorption properties and changes in the structure of modified fibers, allow the use of these fibers for sorption of different ions and molecules from their aqueous solution. Increasing of the sorption properties was confirmed by sorption of silver ions, which are selected to achieve the antimicrobial properties of oxidized fibers, which makes them very suitable for bioactive and medical fibers obtaining. The antimicrobial activity of silver-loaded cellulose fibers against different pathogens: Staphylococcus aureus, Escherichia coli, and Candida albicans was evaluated in vitro. This study demonstrates the potential of the selective TEMPO-mediated oxidization towards natural and man-made cellulose fibers, with the aim to obtain oxicellulose fibers with specific properties.- U teorijskom delu doktorske disertacije sistematizovani su najznačajniji literaturni podaci o hemijskom sastavu, strukturi i reaktivnosti celuloze. Prikazane su osnovne karakteristike prirodnih (pamuk i konoplja) i hemijskih (liocel) celuloznih vlakana. Kao posebna celina u okviru teorijskog dela teze dat je pregled dosadašnjih dostignuća i objavljenih radova iz oblasti oksidacije pomoću 2,2,6,6-tetrametilpiperidin-1-oksil (TEMPO) radikala, sa posebnim osvrtom na oksidaciju celuloznog supstrata, što predstavlja osnovu za eksperimentalni deo ovog rada. U eksperimentalnom delu doktorske disertacije proučavan je uzajamni odnos i uticaj TEMPO-oksidacije na hemijski sastav, strukturu i svojstva različitih celuloznih vlakana. Od prirodnih vlakana modifikovana su vlakna pamuka i konoplje, a od hemijskih liocel vlakna. Nemodifikovana i modifikovana vlakna okarakterisana su sa aspekta gubitka mase, sadržaja karbonilnih (Ca-acetatna, Cu-broj i GPC/CCOA metoda) i karboksilnih grupa (Ca-acetatna, potenciometrijska i GPC/FDAM metoda), raspodele molekulskih masa (GPC tehnika), stepena kristalnosti (jodni broj) i promene površine vlakana (SEM tehnika). Takođe, određena su geometrijska (finoća), fizičko-mehanička (prekidna jačina i izduženje) i sorpciona (sorpcija vlage, vode, joda) svojstava, kao i sposobnost sorpcije različitih jona. TEMPO-oksidacija celuloznih vlakana uticala je na smanjenje mase i promenu finoće modifikovanih vlakana. Za oksidisana vlakna pamuka i liocela uočava se minimalno povećanje finoće, dok su u slučaju oksidisanih vlakana konoplje dobijena znatno finija vlakna. Kod vlakana konoplje, koja pored celuloze sadrže i prateće materije, usled oksidacije dolazi do značajnog uklanjanja hemiceluloza i lignina. U zavisnosti od uslova modifikovanja, kod svih oksidisanih vlakana, dolazi do povećanja indeksa kristalnosti, dok se prekidna jačina vlakana smanjuje. Oksidacijom pomoću TEMPO radikala dolazi do povećanja hemisorpcionih svojstava vlakana usled povećanja sadržaja karboksilnih grupa. Dobijena oksiceluloza sa povećanim sorpcionim svojstava omogućava vezivanje značajnih količina različitih jona ili molekula. Povećanje sorpcionih svojstava potvrđeno je sorpcijom jona srebra, koje je odabrano u cilju postizanja antimikrobnih svojstava oksidisanih vlakana, što ih čini veoma pogodnim za dobijanje bioaktivnih i medicinskih vlakana. Antimikrobna aktivnost je ispitana in vitro i dokazana prema mikroorganizmima: Staphylococcus aureus, Escherichia coli i Candida albicans. Dobijeni rezultati ukazuju na efikasnu mogućnost primene selektivne TEMPO-oksidacije u cilju dobijanja oksiceluloze, koja predstavlja polaznu osnovu za dobijanje širokog spektra vlakana specijalne namene.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
