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State-of-the-Art Polymer Science and Technology in Greece II

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Innovation of Polymer Science and Technology".

Deadline for manuscript submissions: 31 December 2024 | Viewed by 20084

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Special Issue Editors

Prof. Dr. George Z. Papageorgiou

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1. Department of Chemistry, University of Ioannina, P.O. Box 1186, GR-45110 Ioannina, Greece
2. Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 45110 Ioannina, Greece
Interests: sustainable and green industrial chemistry; polymer nanocomposites; materials characterization
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Prof. Dr. Nektaria-Marianthi Barkoula

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Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece
Interests: structure-property relationships in materials; durability of polymers/polymer composites and cement-based composites; tribological behavior of polymers; metals and composites; biodegradable/biobased polymers; recyclability; eco-composites, nanocomposites/multi-functional materials/hierarchical composites
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Prof. Dr. Marinos Pitsikalis

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Laboratory of Industrial Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771 Zografou, Greece
Interests: polymer synthesis; polymer characterization; self-assembly of copolymers in selective solvents
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Prof. Dr. Kostas Karatasos

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Physical Chemistry Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece
Interests: molecular simulations; structure/property relationship; physical chemistry of soft matter systems; polymer-based composites; biomedical applications of polymers

Prof. Dr. Dimitrios Bikiaris

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Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR 54124 Thessaloniki, Greece
Interests: synthesis and characterization of polyesters; development of biobased polymers; biodegradable polymers; polymer composites and nanocomposites; synthesis and characterization of copolymers; polymer blends; recycling of polymers with various techniques; enzymatic hydrolysis studies; modification of natural polymers; polymer for wastewater treatment pollutant removal; polymers for tissue engineering and drug delivery applications; drug–polymer solid dispersions; drug targeting; drug nanoencapsulation and microencapsulation
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Prof. Dr. Georgios Bokias

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Department of Chemistry, University of Patras, 26504 Patras, Greece
Interests: polymer synthesis and characterization; stimuli-responsive and functional polymeric materials; synthetic and reversible hydrogels; optically-labelled polymers; hybrid inorganic/organic soft materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The use of polymeric materials has contributed to the improvement of everyday life. Polymer production has shown an exponential increase over the last decades, reaching 400 million tons in 2018, and it is expected to exceed 1,200 million tons in 2050, with 750 million tons of plastics being recycled. Polymer science is a continuously growing field, and it is expected to play a key role in the bioeconomy and circular economy. In Greece, the field of polymer science and technology is served by numerous researchers from various groups, working on polymer synthesis, polymer characterization, polymer physics, polymer theory, polymer physical chemistry, polymer engineering/technology, and polymer composites/nanocomposites, as well as in the design/development of added-value functional polymeric materials for emerging applications in all technological fields. After the success of the first Special Issue, "State-of-the-Art Polymer Science and Technology in Greece", this second Special Issue aspires to collect high-quality papers by Greek Scientists, covering all the subfields of polymer science and technology.

Prof. Dr. George Z. Papageorgiou
Prof. Dr. Nektaria-Marianthi Barkoula
Prof. Dr. Marinos Pitsikalis
Prof. Dr. Kostas Karatasos
Prof. Dr. Dimitrios Bikiaris
Prof. Dr. Georgios Bokias
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

polymer synthesis
polymer characterization
polymer physics
polymer physical chemistry
polymer rheology
polymer technology
polymer theory
self-assembly of polymers in selective solvents
self-assembly of polymers in bulk
polymer properties
applications of polymers
polymer composites
biopolymers
functional/responsive polymers
recycling of polymers
polymers in industry

Published Papers (14 papers)

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Research

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16 pages, 3206 KiB

Open AccessArticle

A Remarkable Impact of pH on the Thermo-Responsive Properties of Alginate-Based Composite Hydrogels Incorporating P2VP-PEO Micellar Nanoparticles

by Amalia Iliopoulou, Zacharoula Iatridi and Constantinos Tsitsilianis

Polymers 2024, 16(7), 886; https://doi.org/10.3390/polym16070886 - 24 Mar 2024

Viewed by 576

Abstract

A heterograft copolymer with an alginate backbone, hetero-grafted by polymer pendant chains displaying different lower critical solution temperatures (LCSTs), combined with a pH-responsive poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer forming micellar nanoparticles, was investigated in aqueous media at various pHs. Due to its thermo-responsive side chains, the copolymer forms hydrogels with a thermo-induced sol–gel transition, above a critical temperature, T_gel (thermo-thickening). However, by lowering the pH of the medium in an acidic regime, a remarkable increase in the elasticity of the formulation was observed. This effect was more pronounced in low temperatures (below T_gel), suggesting secondary physical crosslinking, which induces significant changes in the hydrogel thermo-responsiveness, transforming the sol–gel transition to soft gel–strong gel. Moreover, the onset of thermo-thickening shifted to lower temperatures followed by the broadening of the transition zone, implying intermolecular interactions between the uncharged alginate backbone with the PNIPAM side chains, likely through H-bonding. The shear-thinning behavior of the soft gel in low temperatures provides injectability, which allows potential applications for 3D printing. Furthermore, the heterograft copolymer/nanoparticles composite hydrogel, encapsulating a model hydrophobic drug in the hydrophobic cores of the nanoparticles, was evaluated as a pH-responsive drug delivery system. The presented tunable drug delivery system might be useful for biomedical potential applications. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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17 pages, 5205 KiB

Open AccessArticle

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds

by Efterpi Avdeliodi, Anastasia Tsioli, Georgios Bokias and Joannis K. Kallitsis

Polymers 2024, 16(2), 270; https://doi.org/10.3390/polym16020270 - 18 Jan 2024

Viewed by 786

Abstract

The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance—Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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21 pages, 2151 KiB

Open AccessArticle

Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance

by Sara Gjoshi, Paraskevi Loukopoulou, Michaela Plevova, Jaromir Hnat, Karel Bouzek and Valadoula Deimede

Polymers 2024, 16(1), 99; https://doi.org/10.3390/polym16010099 - 28 Dec 2023

Viewed by 903

Abstract

Mechanically robust anion-exchange membranes (AEMs) with high conductivity and long-term alkali resistance are needed for water electrolysis application. In this work, aryl-ether free polyaromatics containing isatin moieties were prepared via super acid-catalyzed copolymerization, followed by functionalization with alkaline stable cyclic quaternary ammonium (QA) cationic groups, to afford high performance AEMs for application in water electrolysis. The incorporation of side functional cationic groups (pyrrolidinium and piperidinium) onto a polymer backbone via a flexible alkyl spacer aimed at conductivity and alkaline stability improvement. The effect of cation structure on the properties of prepared AEMs was thoroughly studied. Pyrrolidinium- and piperidinium-based AEMs showed similar electrolyte uptakes and no obvious phase separation, as revealed by SAXS and further supported by AFM and TEM data. In addition, these AEMs displayed high conductivity values (81. 5 and 120 mS cm⁻¹ for pyrrolidinium- and piperidinium-based AEM, respectively, at 80 °C) and excellent alkaline stability after 1 month aging in 2M KOH at 80 °C. Especially, a pyrrolidinium-based AEM membrane preserved 87% of its initial conductivity value, while at the same time retaining its flexibility and mechanical robustness after storage in alkaline media (2M KOH) for 1 month at 80 °C. Based on ¹H NMR data, the conductivity loss observed after the aging test is mainly related to the piperidinium degradation that took place, probably via ring-opening Hofmann elimination, alkyl spacer scission and nucleophilic substitution reactions as well. The synthesized AEMs were also tested in an alkaline water electrolysis cell. Piperidinium-based AEM showed superior performance compared to its pyrrolidinium analogue, owing to its higher conductivity as revealed by EIS data, further confirming the ex situ conductivity measurements. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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20 pages, 2765 KiB

Open AccessArticle

Synthesis and Modeling of Poly(L-lactic acid) via Polycondensation of L-Lactic Acid

by Alexis Theodorou, Vasilios Raptis, Chrissie Isabella Maria Baltzaki, Thrassyvoulos Manios, Vagelis Harmandaris and Kelly Velonia

Polymers 2023, 15(23), 4569; https://doi.org/10.3390/polym15234569 - 29 Nov 2023

Cited by 1 | Viewed by 1554

Abstract

We present synthetic experiments of lactic acid (LA) polycondensation to produce poly(lactic acid) (PLA) as well as kinetic modeling calculations that capture the polymer molecular weight increase with time, given the initial concentrations. Tin-octoate-catalyzed polycondensation of (D,L)- or L-lactic acid was carried out in pre-dried toluene after azeotropic dehydration for 48–120 h at 130–137 °C. The polymerization was optimized by varying lactic acid and catalyst concentrations as well as the temperature. Gel permeation chromatography was used to experimentally follow the evolution of molecular weights and the products were characterized by NMR, TGA, DSC and IR. Under optimal conditions, PLLA with weight-average molecular weight (M_w) of 161 kDa could be obtained. The rate equations that describe polycondensation kinetics were recast in a condensed form that allowed very fast numerical solution and calculation of the number-average molecular weight with time. Deviations with respect to the experiment were minimized in a least-squares fashion to determine rate constants. The optimized kinetics parameters are shown to reproduce the experimental data accurately. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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22 pages, 4559 KiB

Open AccessArticle

Synthesis of Poly(ethylene furanoate) Based Nanocomposites by In Situ Polymerization with Enhanced Antibacterial Properties for Food Packaging Applications

by Johan Stanley, Eleftheria Xanthopoulou, Matjaž Finšgar, Lidija Fras Zemljič, Panagiotis A. Klonos, Apostolos Kyritsis, Savvas Koltsakidis, Dimitrios Tzetzis, Dimitra A. Lambropoulou, Diana Baciu, Theodore A. Steriotis, Georgia Charalambopoulou and Dimitrios N. Bikiaris

Polymers 2023, 15(23), 4502; https://doi.org/10.3390/polym15234502 - 23 Nov 2023

Cited by 2 | Viewed by 1018

Abstract

Poly(ethylene 2,5-furandicarboxylate) (PEF)-based nanocomposites containing Ce–bioglass, ZnO, and ZrO₂ nanoparticles were synthesized via in situ polymerization, targeting food packaging applications. The nanocomposites were thoroughly characterized, combining a range of techniques. The successful polymerization was confirmed using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, and the molecular weight values were determined indirectly by applying intrinsic viscosity measurements. The nanocomposites’ structure was investigated by depth profiling using time-of-flight secondary ion mass spectrometry (ToF-SIMS), while color measurements showed a low-to-moderate increase in the color concentration of all the nanocomposites compared to neat PEF. The thermal properties and crystallinity behavior of the synthesized materials were also examined. The neat PEF and PEF-based nanocomposites show a crystalline fraction of 0–5%, and annealed samples of both PEF and PEF-based nanocomposites exhibit a crystallinity above 20%. Furthermore, scanning electron microscopy (SEM) micrographs revealed that active agent nanoparticles are well dispersed in the PEF matrix. Contact angle measurements showed that incorporating nanoparticles into the PEF matrix significantly reduces the wetting angle due to increased roughness and introduction of the polar -OH groups. Antimicrobial studies indicated a significant increase in inhibition of bacterial strains of about 9–22% for Gram-positive bacterial strains and 5–16% for Gram-negative bacterial strains in PEF nanocomposite films, respectively. Finally, nanoindentation tests showed that the ZnO-based nanocomposite exhibits improved hardness and elastic modulus values compared to neat PEF. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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18 pages, 3911 KiB

Open AccessArticle

Improvement of Water Vapor Permeability in Polypropylene Composite Films by the Synergy of Carbon Nanotubes and β-Nucleating Agents

by Glykeria A. Visvini, Georgios N. Mathioudakis, Amaia Soto Beobide, Zoi Piperigkou, Aris E. Giannakas, Stavros Messaritakis, Giannis Sotiriou and George A. Voyiatzis

Polymers 2023, 15(22), 4432; https://doi.org/10.3390/polym15224432 - 16 Nov 2023

Viewed by 944

Abstract

A notable application of polymeric nanocomposites is the design of water vapor permeable (WVP) membranes. “Breathable” membranes can be created by the incorporation of micro/nanofillers, such as CaCO₃, that interrupt the continuity of the polymeric phase and when subjected to additional uniaxial or biaxial stretching this process leads to the formation of micro/nanoporous structures. Among the candidate nanofillers, carbon nanotubes (CNTs) have demonstrated excellent intrinsic WVP properties. In this study, chemically modified MWCNTs with oligo olefin-type groups (MWCNT-g-PP) are incorporated by melt processes into a PP matrix; a β-nucleating agent (β-ΝA) is also added. The crystallization behavior of the nanocomposite films is evaluated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The WVP performance of the films is assessed via the “wet” cup method. The nanohybrid systems, incorporating both MWCNT-g-PP and β-NA, exhibit enhanced WVP compared to films containing only MWCNT-g-PP or β-NA. This improvement can be attributed to the significant increase in the growth of α-type crystals taking place at the edges of the CNTs. This increased crystal growth exerts a form of stress on the metastable β-phase, thereby expanding the initial microporosity. In parallel, the coexistence of the inherently water vapor-permeable CNTs, further enhances the water vapor permeability reaching a specific water vapor transmission rate (Sp.WVTR) of 5500 μm.g/m².day in the hybrid composite compared to 1000 μm.g/m².day in neat PP. Notably, the functionalized MWCNT-g-PP used as nanofiller in the preparation of the “breathable” PP films demonstrated no noteworthy cytotoxicity levels within the low concentration range used, an important factor in terms of sustainability. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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13 pages, 2657 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Structural Insight into poly(dimethylsiloxane)-b-poly(2-vinylpyridine) Copolymers

by Gkreti-Maria Manesi, Ioannis Moutsios, Dimitrios Moschovas, Georgios Papadopoulos, Christos Ntaras, Martin Rosenthal, Loic Vidal, Georgiy G. Ageev, Dimitri A. Ivanov and Apostolos Avgeropoulos

Polymers 2023, 15(21), 4227; https://doi.org/10.3390/polym15214227 - 25 Oct 2023

Viewed by 1172

Abstract

In this study, the use of anionic polymerization for the synthesis of living poly(dimethylsiloxane) or PDMS-Li⁺, as well as poly(2-vinylpyridine) or P2VP-Li⁺ homopolymers, and the subsequent use of chlorosilane chemistry in order for the two blocks to be covalently joined leading to PDMS-b-P2VP copolymers is proposed. High vacuum manipulations enabled the synthesis of well-defined materials with different molecular weights (

{\bar{Μ}}_{n}

, from 9.8 to 36.0 kg/mol) and volume fraction ratios (φ, from 0.15 to 0.67). The

{\bar{Μ}}_{n}

values, dispersity indices, and composition were determined through membrane/vapor pressure osmometry (MO/VPO), size exclusion chromatography (SEC), and proton nuclear magnetic resonance spectroscopy (¹H NMR), respectively, while the thermal transitions were determined via differential scanning calorimetry (DSC). The morphological characterization results suggested that for common composition ratios, lamellar, cylindrical, and spherical phases with domain periodicities ranging from approximately 15 to 39 nm are formed. A post-polymerization chemical modification reaction to quaternize the nitrogen atom in some of the P2VP monomeric units in the copolymer with the highest P2VP content, and the additional characterizations through ¹H NMR, infrared spectroscopy, DSC, and contact angle are reported. The synthesis, characterization, and quaternization of the copolymer structure are important findings toward the preparation of functional materials with enhanced properties suitable for various nanotechnology applications. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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15 pages, 7104 KiB

Open AccessArticle

End-Of-Use Fly Ash as an Effective Reinforcing Filler in Green Polymer Composites

by Anastasios C. Patsidis and Manolis Souliotis

Polymers 2023, 15(16), 3418; https://doi.org/10.3390/polym15163418 - 16 Aug 2023

Cited by 3 | Viewed by 825

Abstract

The aim of this study is to use fly ash powder in an environmentally friendly matrix, in a novel way, addressing environmental and disposal problems. Fly ash/epoxy composites were prepared and studied varying the filler content. An investigation of structural and morphological characteristics was conducted using of X-ray diffraction patterns and scanning electron microscopy images, which revealed the successful fabrication of composites. Thermomechanical properties were studied via dynamic mechanical analysis and static mechanical tests. The composites exhibited an improved mechanical response. Broadband dielectric spectroscopy was used to investigate the dielectric response of the composite systems over the frequency range from 10⁻¹ to 10⁷ Hz and the temperature range from 30 to 160 °C. The analysis revealed the presence of three relaxation processes in the spectra of the tested systems. Interfacial polarization, the glass-to-rubber transition of the polymer matrix, and the rearrangement of polar side groups along the polymer chain are the processes that occur under a descending relaxation time. It was found that dielectric permittivity increases with filler content. Finally, the influence of filler content and the applied voltage under dc conditions was analyzed to determine the ability of the composites to store and retrieve electric energy. Fly ash improved the efficiency of the storing/retrieving energy of the composites. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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16 pages, 3437 KiB

Open AccessEditor’s ChoiceArticle

Nucleophilic Aromatic Substitution of Pentafluorophenyl-Substituted Quinoline with a Functional Perylene: A Route to the Modification of Semiconducting Polymers

by Stefania Aivali, Konstantinos C. Andrikopoulos and Aikaterini K. Andreopoulou

Polymers 2023, 15(12), 2721; https://doi.org/10.3390/polym15122721 - 18 Jun 2023

Cited by 1 | Viewed by 1079

Abstract

A systematic study of the influence of the chemical substitution pattern of semiconducting polymers carrying side chain perylene diimide (PDI) groups is presented. Semiconducting polymers based on perflurophenyl quinoline (5FQ) were modified via a readily accessible nucleophilic substitution reaction. The perfluorophenyl group was studied as an electron-withdrawing reactive functionality on semiconducting polymers that can undergo fast nucleophilic aromatic substitution. A PDI molecule, functionalized with one phenol group on the bay area, was used for the substitution of the fluorine atom at the para position in 6-vinylphenyl-(2-perfluorophenyl)-4-phenyl quinoline. The final product was polymerized under free radical polymerization providing polymers of 5FQ incorporated with PDI side groups. Alternatively, the post-polymerization modification of the fluorine atoms at the para position of the 5FQ homopolymer with the PhOH-di-EH-PDI was also successfully tested. In this case, the PDI units were partially introduced to the perflurophenyl quinoline moieties of the homopolymer. The para-fluoro aromatic nucleophilic substitution reaction was confirmed and estimated via ¹H and ¹⁹F NMR spectroscopies. The two different polymer architectures, namely, fully or partially modified with PDI units, were studied in terms of their optical and electrochemical properties, while their morphology was evaluated using TEM analysis, revealing polymers of tailor-made optoelectronic and morphological properties. This work provides a novel molecule-designing method for semiconducting materials of controlled properties. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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16 pages, 3255 KiB

Open AccessArticle

Triple Hydrophilic Statistical Terpolymers via RAFT Polymerization: Synthesis and Properties in Aqueous Solutions

by Dimitrios Vagenas and Stergios Pispas

Polymers 2023, 15(11), 2492; https://doi.org/10.3390/polym15112492 - 29 May 2023

Viewed by 1628

Abstract

In this work, we report the synthesis of novel triple hydrophilic statistical terpolymers consisting of three different methacrylate monomers with varying degrees of responsivity to solution conditions. Terpolymers of the type poly(di(ethylene glycol) methyl ether methacrylate-co-2-(dimethylamino)ethylmethacrylate-co-oligoethylene glycol methyl ether methacrylate), P(DEGMA-co-DMAEMA-co-OEGMA), and of different compositions, were prepared by using the RAFT methodology. Their molecular characterization was carried out using size exclusion chromatography (SEC) and spectroscopic techniques, including ¹H-NMR and ATR-FTIR. Studies in dilute aqueous media by dynamic and electrophoretic light scattering (DLS and ELS) show their potential responsiveness regarding changes in temperature, pH, and kosmotropic salt concentration. Finally, the change in hydrophilic/hydrophobic balance of the formed terpolymer nanoparticles during heating and cooling was studied using fluorescence spectroscopy (FS) in conjunction with pyrene giving additional information on the responsiveness and internal structure of the self-assembled nanoaggregates. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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20 pages, 3994 KiB

Open AccessEditor’s ChoiceArticle

Statistical Copolymers of N–Vinylpyrrolidone and 2–Chloroethyl Vinyl Ether via Radical RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition of the Statistical Copolymers

by Nikolaos V. Plachouras and Marinos Pitsikalis

Polymers 2023, 15(8), 1970; https://doi.org/10.3390/polym15081970 - 21 Apr 2023

Viewed by 2613

Abstract

The radical statistical copolymerization of N–vinyl pyrrolidone (NVP) and 2–chloroethyl vinyl ether (CEVE) was conducted using the Reversible Addition–Fragmentation chain Transfer (RAFT) polymerization technique, employing [(O–ethylxanthyl)methyl]benzene (CTA-1) and O–ethyl S–(phthalimidylmethyl) xanthate (CTA-2) as the Chain Transfer Agents (CTAs), leading to P(NVP–stat–CEVE) products. After optimizing copolymerization conditions, monomer reactivity ratios were estimated using various linear graphical methods, as well as the COPOINT program, which was applied in the framework of the terminal model. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the monomers’ mean sequence lengths. Thermal properties of the copolymers were studied by Differential Scanning Calorimetry (DSC) and kinetics of their thermal degradation by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), applying the isoconversional methodologies of Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS). Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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25 pages, 10184 KiB

Open AccessArticle

Effect of Micro- and Nano-Lignin on the Thermal, Mechanical, and Antioxidant Properties of Biobased PLA–Lignin Composite Films

by Sofia P. Makri, Eleftheria Xanthopoulou, Panagiotis A. Klonos, Alexios Grigoropoulos, Apostolos Kyritsis, Konstantinos Tsachouridis, Antonios Anastasiou, Ioanna Deligkiozi, Nikolaos Nikolaidis and Dimitrios N. Bikiaris

Polymers 2022, 14(23), 5274; https://doi.org/10.3390/polym14235274 - 02 Dec 2022

Cited by 17 | Viewed by 2920

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. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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Review

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59 pages, 4818 KiB

Open AccessReview

Use of Electrospinning for Sustainable Production of Nanofibers: A Comparative Assessment of Smart Textiles-Related Applications

by Marina Stramarkou, Ioannis Tzegiannakis, Erifyli Christoforidi and Magdalini Krokida

Polymers 2024, 16(4), 514; https://doi.org/10.3390/polym16040514 - 14 Feb 2024

Viewed by 1372

Abstract

Textile production is a major component of the global industry, with sales of over USD 450 billion and estimations of an 84% increase in their demand in the next 20 years. In recent decades, protective and smart textiles have played important roles in the social economy and attracted widespread popularity thanks to their wide spectrum of applications with properties, such as antimicrobial, water-repellent, UV, chemical, and thermal protection. Towards the sustainable manufacturing of smart textiles, biodegradable, recycled, and bio-based plastics are used as alternative raw materials for fabric and yarn production using a wide variety of techniques. While conventional techniques present several drawbacks, nanofibers produced through electrospinning have superior structural properties. Electrospinning is an innovative method for fiber production based on the use of electrostatic force to create charged threads of polymer solutions. Electrospinning shows great potential since it provides control of the size, porosity, and mechanical resistance of the fibers. This review summarizes the advances in the rapidly evolving field of the production of nanofibers for application in smart and protective textiles using electrospinning and environmentally friendly polymers as raw materials, and provides research directions for optimized smart fibers in the future. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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21 pages, 5724 KiB

Open AccessEditor’s ChoiceReview

Thermodynamics of the Glassy Polymer State: Equilibrium and Non-Equilibrium Aspects

by Costas Panayiotou

Polymers 2024, 16(2), 298; https://doi.org/10.3390/polym16020298 - 22 Jan 2024

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Abstract

This work examines, first, the non-equilibrium character of the glassy state of polymer systems and its significance in the development of novel materials for important technological applications. Subsequently, it summarizes the essentials of the generalized lattice fluid approach for the description of this highly complex non-equilibrium behavior with an approximate and simple, yet analytically powerful formalism. The working equations are derived in a straightforward and consistent manner by clearly defining the universal and specific variables needed to describe the discussed properties. The role of the non-random distribution of molecular species and free volume in the glassy system is also examined, as is the role of strong specific interactions, such as hydrogen-bonding networks. This work also reports examples of applications in a variety of representative systems, including glass densification, retrograde vitrification, increase in glass-transition temperature in hydrogen-bonded polymer mixtures, and hysteresis phenomena in sorption–desorption from glassy polymer matrices. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece II)

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