1. Effect of micro- and nano-lignin on the thermal, mechanical, and antioxidant properties of biobased PLA–lignin composite filmsSofia P. Makri, Eleftheria Xanthopoulou, Panagiotis A. Klonos, Alexios Grigoropoulos, Apostolos Kyritsis, Konstantinos Tsachouridis, Antonios Anastasiou, Ioanna Deligkiozi, Nikolaos P. Nikolaidis, Dimitrios Bikiaris, 2022, original scientific article Abstract: Bio-based poly(lactic acid) (PLA) composite films were produced using unmodified soda
micro- or nano-lignin as a green filler at four different contents, between 0.5 wt% and 5 wt%. The PLA–
lignin composite polymers were synthesized by solvent casting to prepare a masterbatch, followed by
melt mixing. The composites were then converted into films, to evaluate the effect of lignin content
and size on their physicochemical and mechanical properties. Differential scanning calorimetry
(DSC), supported by polarized light microscopy (PLM), infrared spectroscopy (FTIR-ATR), X-ray
diffraction (XRD), and transmission electron microscopy (TEM) were employed to investigate the
PLA crystallization and the interactions with Lignin (L) and Nanolignin (NL). The presence of
both fillers (L and NL) had a negligible effect on the glass transition temperature (chain diffusion).
However, it resulted in suppression of the corresponding change in heat capacity. This was indicative
of a partial immobilization of the PLA chains on the lignin entities, due to interfacial interactions,
which was slightly stronger in the case of NL. Lignin was also found to facilitate crystallization, in
terms of nucleation; whereas, this was not clear in the crystalline fraction. The addition of L and
NL led to systematically larger crystallites compared with neat PLA, which, combined with the
higher melting temperature, provided indications of a denser crystal structure in the composites. The
mechanical, optical, antioxidant, and surface properties of the composite films were also investigated.
The tensile strength and Young’s modulus were improved by the addition of L and especially NL.
The UV-blocking and antioxidant properties of the composite films were also enhanced, especially
at higher filler contents. Importantly, the PLA–NL composite films constantly outperformed their
PLA–L counterparts, due to the finer dispersion of NL in the PLA matrix, as verified by the TEM
micrographs. These results suggest that bio-based and biodegradable PLA films filled with L, and
particularly NL, can be employed as competitive and green alternatives in the food packaging
industry.
Keywords: poly(lactic acid), PLA, lignin, nanolignin, composite films, nucleation, mechanical properties, antioxidant activity, food packaging
Published in DKUM: 26.03.2025; Views: 0; Downloads: 1
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2. 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: 2
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3. Thermal, molecular dynamics, and mechanical properties of poly(ethylene furanoate)/poly(ε-caprolactone) block copolymersJohan Stanley, Panagiotis A. Klonos, Aikaterini Teknetzi, Nikolaos Rekounas, Apostolos Kyritsis, Lidija Fras Zemljič, Dimitra A. Lambropoulou, Dimitrios Bikiaris, 2024, original scientific article Abstract: This study presents the synthesis and characterization of a series of multiblock copolymers, poly(ethylene 2,5-furandicarboxylate)-poly(ε-caprolactone) (PEF-PCL), created through a combination of the two-step melt polycondensation method and ring opening polymerization, as sustainable alternatives to fossil-based plastics. The structural confirmation of these block copolymers was achieved through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), ensuring the successful integration of PEF and PCL segments. X-ray Photoelectron Spectroscopy (XPS) was employed for chemical bonding and quantitative analysis, providing insights into the distribution and compatibility of the copolymer components. Differential Scanning Calorimetry (DSC) analysis revealed a single glass transition temperature (Tg), indicating the effective plasticizing effect of PCL on PEF, which enhances the flexibility of the copolymers. X-ray Diffraction (XRD) studies highlight the complex relationship between PCL content and crystallization in PEF-PCL block copolymers, emphasizing the need to balance crystallinity and mechanical properties for optimal material performance. Broadband Dielectric Spectroscopy (BDS) confirmed excellent distribution of PEF-PCL without phase separation, which is vital for maintaining consistent material properties. Mechanical properties were evaluated using Nanoindentation testing, demonstrating the potential of these copolymers as flexible packaging materials due to their enhanced mechanical strength and flexibility. The study concludes that PEF-PCL block copolymers are promising candidates for sustainable packaging solutions, combining environmental benefits with desirable material properties.
Keywords: poly(ethylene furanoate), poly(ε-caprolactone), block copolymers, thermal properties, molecular dynamics, crystallinity, mechanical properties, flexible packaging
Published in DKUM: 13.03.2025; Views: 0; Downloads: 6
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4. 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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5. Synthesis of poly(ethylene furanoate) based nanocomposites by in situ polymerization with enhanced antibacterial properties for food packaging applicationsJohan Stanley, Eleftheria Xanthopoulou, Matjaž Finšgar, Lidija Fras Zemljič, Panagiotis A. Klonos, Apostolos Kyritsis, Savvas Koltsakidis, Dimitrios Tzetzis, Dimitra A. Lambropoulou, Diana Baciu, Theodore Steriotis, Georgia Charalambopoulou, Dimitrios Bikiaris, 2023, original scientific article Keywords: biobased polymers, poly(ethylene furanoate), nanoparticles, nanocomposites, antimicrobial properties
Published in DKUM: 10.04.2024; Views: 160; Downloads: 19
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6. Synthesis and study of fully biodegradable composites based on poly(butylene succinate) and biocharKaterina Papadopoulou, Panagiotis A. Klonos, Apostolos Kyritsis, Ondřej Mašek, Christian Wurzer, Konstantinos Tsachouridis, Antonios D. Anastasiou, Dimitrios Bikiaris, 2023, original scientific article Keywords: poly(butylene succinate), biochar, biocomposites, thermal properties, thermal conductivity, molecular mobility, mechanical properties, enzymatic hydrolysis
Published in DKUM: 10.04.2024; Views: 200; Downloads: 15
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7. Fabrication of poly(ethylene furanoate)/silver and titanium dioxide nanocomposites with improved thermal and antimicrobial propertiesJohan Stanley, Eleftheria Xanthopoulou, Lidija Fras Zemljič, Panagiotis A. Klonos, Apostolos Kyritsis, Dimitra A. Lambropoulou, Dimitrios Bikiaris, 2024, original scientific article Abstract: Poly(ethylene furanoate) (PEF)-based nanocomposites were fabricated with silver (Ag) and titanium dioxide (TiO2) nanoparticles by the in-situ polymerization method. The importance of this research work is to extend the usage of PEF-based nanocomposites with improved material properties. The PEF-Ag and PEF-TiO2 nanocomposites showed a significant improvement in color concentration, as determined by the color colorimeter. Scanning electron microscopy (SEM) photographs revealed the appearance of small aggregates on the surface of nanocomposites. According to crystallinity investigations, neat PEF and nanocomposites exhibit crystalline fraction between 0–6%, whereas annealed samples showed a degree of crystallinity value above 25%. Combining the structural and molecular dynamics observations from broadband dielectric spectroscopy (BDS) measurements found strong interactions between polymer chains and nanoparticles. Contact angle results exhibited a decrease in the wetting angle of nanocomposites compared to neat PEF. Finally, antimicrobial studies have been conducted, reporting a significant rise in inhibition of over 15% for both nanocomposite films against gram-positive and gram-negative bacteria. From the overall results, the synthesized PEF-based nanocomposites with enhanced thermal and antimicrobial properties may be optimized and utilized for the secondary packaging (unintended food-contact) materials.
Keywords: active agents, antimicrobial studies, biobased polymers, crystallinity, poly(ethylene 2, 5-furandicarboxylate)
Published in DKUM: 03.04.2024; Views: 214; Downloads: 15
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