1. Poly(vinyl pyridine) and Its quaternized derivatives: understanding their solvation and solid state propertiesKaterina Mavronasou, Alexandra Zamboulis, Panagiotis A. Klonos, Apostolos Kyritsis, Dimitrios Bikiaris, Raffaello Papadakis, Ioanna Deligkiozi, 2022, original scientific article Abstract: A series of N-methyl quaternized derivatives of poly(4-vinylpyridine) (PVP) were synthesized in high yields with different degrees of quaternization, obtained by varying the methyl iodide
molar ratio and affording products with unexplored optical and solvation properties. The impact
of quaternization on the physicochemical properties of the copolymers, and notably the solvation
properties, was further studied. The structure of the synthesized polymers and the quaternization
degrees were determined by infrared and nuclear magnetic spectroscopies, while their thermal
characteristics were studied by differential scanning calorimetry and their thermal stability and
degradation by thermogravimetric analysis (TG-DTA). Attention was given to their optical properties,
where UV-Vis and diffuse reflectance spectroscopy (DRS) measurements were carried out. The optical
band gap of the polymers was calculated and correlated with the degree of quaternization. The study
was further orientated towards the solvation properties of the polymers in binary solvent mixtures
that strongly depend on the degree of quaternization, enabling a better understanding of the key
polymer (solute)-solvent interactions. The assessment of the underlying solvation phenomena was
performed in a system of different ratios of DMSO/H2O and the solvatochromic indicator used was
Reichardt’s dye. Solvent polarity parameters have a significant effect on the visible spectra of the
nitrogen quaternization of PVP studied in this work and a detailed path towards this assessment
is presented.
Keywords: poly(4-vinylpyridine), poly(N-methyl-4-vinylpyridinium iodide), quaternization, solvatochromism, preferential solvation, optical energy gap
Published in DKUM: 26.03.2025; Views: 0; Downloads: 6
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2. Effect of monomer type on the synthesis and properties of poly(ethylene furanoate)Johan Stanley, Zoi Terzopoulou, Panagiotis A. Klonos, Alexandra Zamboulis, Eleftheria Xanthopoulou, Savvas Koltsakidis, Dimitrios Tzetzis, Lidija Fras Zemljič, Dimitra A. Lambropoulou, Apostolos Kyritsis, George Z. Papageorgiou, Dimitrios Bikiaris, 2023, original scientific article Abstract: This work aimed to produce bio-based poly(ethylene furanoate) (PEF) with a high molecular weight using 2,5-furan dicarboxylic acid (FDCA) or its derivative dimethyl 2,5-furan dicarboxylate (DMFD), targeting food packaging applications. The effect of monomer type, molar ratios, catalyst, polycondensation time, and temperature on synthesized samples’ intrinsic viscosities and color intensity was evaluated. It was found that FDCA is more effective than DMFD in producing PEF with higher molecular weight. A sum of complementary techniques was employed to study the structure– properties relationships of the prepared PEF samples, both in amorphous and semicrystalline states. The amorphous samples exhibited an increase in glass transition temperature of 82–87 ◦C, and annealed samples displayed a decrease in crystallinity with increasing intrinsic viscosity, as analyzed by differential scanning calorimetry and X-ray diffraction. Dielectric spectroscopy showed moderate local and segmental dynamics and high ionic conductivity for the 2,5-FDCA-based samples. The spherulite size and nuclei density of samples improved with increased melt crystallization and viscosity, respectively. The hydrophilicity and oxygen permeability of the samples were reduced with increased rigidity and molecular weight. The nanoindentation test showed that the hardness and elastic modulus of amorphous and annealed samples is higher at low viscosities due to high intermolecular interactions and degree of crystallinity.
Keywords: bio-based polymers, poly(ethylene furanoate), polycondensation, thermal properties, mechanical properties, oxygen transmission rates
Published in DKUM: 13.02.2025; Views: 0; Downloads: 3
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3. Kraft lignin/tannin as a potential accelerator of antioxidant and antibacterial properties in an active thermoplastic polyester-based multifunctional materialKlementina Pušnik Črešnar, Alexandra Zamboulis, Dimitrios Bikiaris, Alexandra Aulova, Lidija Fras Zemljič, 2022, original scientific article Abstract: This research focuses on key priorities in the field of sustainable plastic composites that will lead to a reduction in CO2 pollution and support the EU’s goal of becoming carbon neutral by 2050. The main challenge is to develop high-performance polyphenol-reinforced thermoplastic composites, where the use of natural fillers replaces the usual chemical additives with non-toxic ones, not only to improve the final performance but also to increase the desired multifunctionalities (structural, antioxidant, and antibacterial). Therefore, poly (lactic acid) (PLA) composites based on Kraft lignin (KL) and tannin (TANN) were investigated. Two series of PLA composites, PLA-KL and PLA-TANN, which contained natural fillers (0.5%, 1.0%, and 2.5% (w/w)) were prepared by hot melt extrusion. The effects of KL and TANN on the PLA matrices were investigated, especially the surface physicochemical properties, mechanical properties, and antioxidant/antimicrobial activity. The surface physicochemical properties were evaluated by measuring the contact angle (CA), roughness, zeta potential, and nanoindentation. The results of the water contact angle showed that neither KL nor TANN caused a significant change in the wettability, but only a slight increase in the hydrophilicity of the PLA composites. The filler loading, the size of the particles with their available functional groups on the surfaces of the PLA composites, and the interaction between the filler and the PLA polymer depend on the roughness and zeta potential behavior of the PLA-KL and PLA-TANN composites and ultimately improve the surface mechanical properties. The antioxidant properties of the PLA-KL and PLA-TANN composites were determined using the DPPH (2,2′-diphenyl-1-picrylhydrazyl) test. The results show an efficient antioxidant behavior of all PLA-KL and PLA-TANN composites, which increases with the filler content. Finally, the KL- and PLA-based TANN have shown resistance to the Gram-negative bacteria, E. coli, but without a correlation trend between polyphenol filler content and structure.
Keywords: poly (lactic acid), Kraft lignin, tannin, multifunctionality of PLA composites, surface mechanical properties, antioxidant/antibacterial activity
Published in DKUM: 18.09.2023; Views: 495; Downloads: 209
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