engleski

ANTIMICROBIAL FUNCTIONALIZATION OF POLYLACTIDE POLYMERS THROUGH BULK AND PLASMA MODIFICATION

The aim of this thesis was to develop innovative renewable products of biodegradable characteristics with broad application possibilities. Silver (Ag) is an efficacious and an useful antibacterial agent and thus was incorporated into the PLA polymer either in bulk or by surface modifications. Surface modification of PLA with silver was performed by two different plasma treatments using pure Ag layer and Ag nanoparticles embedded in a matrix. Antimicrobial activity of PLA films was measured against two Gram-positive bacteria Listeria monocytogenes (DMSZ15675) and Staphylococcus aureus ( ATCC 6538) and two Gram-negative bacteria Salmonella typhimurium (TA100) and Escherichia coli (DSMZ 30083). Further characterisation of polylactide films was performed by contact angle measurment in order to determine their hydrophilicity. Obtained results of modified PLA - revealed that presence of only small amounts of silver can show antibacterial properties when used in bulk or surface modifications. Further low molecular chitosan, which is a biopolymer was also used for antimicrobial finishing and it was used for bulk modifications of PLA polymer and showed improvement of the antimicrobial properties of materials. Glycerol (GA) and polyethylene glycol (PEG) improved hydrophilic characteristics of PLA surfaces and facilitates contact with bacteria and improve the antimicrobial efficacy of the PLA. Surface active agent polyethylene glycol tert-octylphenyl ether (T2) and tetraethylene glycol dodecyl ether (T1), improved hydrophilic characteristics of PLA surfaces and facilitates even better contact with bacteria and improve the antimicrobial efficacy of the PLA. The plasma conditions and parameters showed a strong influence on plasma-deposited thin films, which resulted with the improvement of hydrophilicity and antimicrobial properties. Silver release of different coatings on the films was investigated by using Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). PLA bulk sample exhibited the biggest Ag release after 21 day in water. PLA bulk and surfaces modified sample exhibited the higher percentage of silver released from surfaces obtained from nano silver composites than from the surfaces obtained from silver sputtered process. Surface characterisation of PLA films was performed with XPS analysis (X-ray Photoelectron Microscopy). Obtained results showed that PLA bulk modified samples do not contains silver on the surface of the films, and that nanocomposites films contain less silver than films obatined with plasma sputtered process.

Polylactide polimer (PLA); Biogradibility issues; Antimicrobial finishing; Bacteria; Silver; Chitosan; low molecular weight; Plasma Sputtering; Nano-composite; Antimicrobial effectiveness; Surface characterisation; Thermal characterisation; Silver release

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