Georgia Lainioti | University of Patras (original) (raw)

Papers by Georgia Lainioti

Coatings

Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combini... more Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combining inorganic mineral huntite (H5) and polymeric additives synthesized in the present work into a polymeric formulation. In order to improve the dispersion of the Mg- (and Ca)-based H5 particles, additives containing phosphonium and acidic groups were employed to homogenize the inorganic fillers into the polymer matrix. Specific blend combinations of the commercial matrix Ecrovin® LV 340 eco with huntite and the additives poly(benzyltriphenylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSBTPB60) and poly(hexadecyltributylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSTBHDPB80), combining acidic and phosphonium groups, led to LOI values of 34.5% and 33.5%, respectively. The novel flame-retardant polymeric coatings inhibited the combustion of the coated wood substrates, which is attributed to the combination of acidic groups that promote the dispersion of inorganic filler in the pol...

International Journal of Molecular Sciences

The synthesis of environmentally friendly antimicrobial polymeric coatings, especially in the cas... more The synthesis of environmentally friendly antimicrobial polymeric coatings, especially in the case of aquaculture, that inhibit the growth of bio-deposits is a very important issue that will contribute to the cost reduction of nets’ cleaning process as well as the protection of the submarine wealth from the biostatic substances used so far. In the present work, the antimicrobial polymers P(SSAmC16-co-VBCHAMx) and the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) were synthesized, bearing quaternary ammonium compounds, electrostatically bound and covalently attached at the same polymer chain. The combination of the two types is of particular importance, as it can provide effective antimicrobial polymeric materials with self-polishing capabilities as a result of the released nature of the antimicrobial, in combination with the permanent local action of the immobilized species. The cross-linking reaction of the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) with the homopolymer polyacrylic acid...

Polymers

Wood and wood-based products are extensively used in the building sector due to their interesting... more Wood and wood-based products are extensively used in the building sector due to their interesting combination of properties. Fire safety and fire spread, however, are of utmost concern for the protection of buildings. Therefore, in timber structures, wood must be treated with fire-retardant materials in order to improve its reaction to fire. This article highlights the flame retardancy of novel hybrid organic–inorganic halogen-free coatings applied on plywood substrates. For this purpose, either a huntite-rich mineral (H5) or its modified nano-Mg (OH)2 type form (H5-m), acting as an inorganic (nano) filler, was functionalized with reactive oligomers (ROs) and incorporated into a waterborne polymeric matrix. A water-soluble polymer (P (SSNa-co-GMAx)), combining its hydrophilic nature with functional epoxide groups, was used as the reactive oligomer in order to enhance the compatibility between the filler and the matrix. Among various coating compositions, the system composed of 13% p...

International Journal of Molecular Sciences, 2021

One of the concerns today’s societies face is the development of resistant pathogenic microorgani... more One of the concerns today’s societies face is the development of resistant pathogenic microorganisms. The need to tackle this problem has driven the development of innovative antimicrobial materials capable of killing or inhibiting the growth of microorganisms. The present study investigates the dependence of the antimicrobial activity and solubility properties on the hydrophilicity/hydrophobicity ratio of antimicrobial coatings based on quaternary ammonium compounds. In this line, suitable hydrophilic and hydrophobic structural units were selected for synthesizing the antimicrobial copolymers poly(4-vinylbenzyl dimethyldodecylammonium chloride-co-acrylic acid), P(VBCDDA-co-AA20) and poly(dodecyltrimethylammonium 4-styrene sulfonate-co-glycidyl methacrylate), P(SSAmC12-co-GMA20), bearing an alkyl chain of 12 carbons either through covalent bonding or through electrostatic interaction. The cross-linking reaction of the carboxylic group of acrylic acid (AA) with the epoxide group of g...

Materials, 2019

Novel cross-linked hydrogels were synthesized as potential materials for the development of smart... more Novel cross-linked hydrogels were synthesized as potential materials for the development of smart biofertilizers. For this purpose, hydrogels were prepared using collagen hydrolysate recovered from tannery waste. The water-soluble polymer poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMAx)) was among others used for the cross-linking reaction that combined hydrophilic nature with epoxide groups. The synthetic procedure was thoroughly investigated in order to ensure high percentage of epoxide groups in combination with water-soluble behavior. The copolymer did not show cytotoxicity against normal lung, skin fibroblasts, or nasal polyps fibroblasts. Through the present work, we also present the ability to control the properties of cross-linked hydrogels by altering copolymer’s composition and cross-linking parameters (curing temperature and time). Hydrogels were then studied in terms of water-uptake capacity for a period up to six days. The techniques Proton Nucl...

ACS applied materials & interfaces, Jan 28, 2016

In the present work, reactive blending of copolymers with complementary functional groups was app... more In the present work, reactive blending of copolymers with complementary functional groups was applied to control their antimicrobial activity and antifouling action in real conditions. For this purpose, two series of copolymers, poly(4-vinylbenzyl chloride-co-acrylic acid), P(VBC-co-AAx), and poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate), P(SSNa-co-GMAx), were synthesized via free radical copolymerization and further modified by the incorporation of biocidal units either covalently (4-vinyl benzyl dimethylhexadecylammonium chloride, VBCHAM) or electrostatically bound (cetyltrimethylammonium 4-styrenesulfonate, SSAmC16). The cross-linking reaction of the carboxylic group of acrylic acid (AA) with the epoxide group of glycidyl methacrylate (GMA) of these two series of reactive antimicrobial copolymers was explored in blends obtained through solution casting after curing at various temperatures. The combined results from the ATR-FTIR characterization of the membranes, solubi...

Molecules, 2015

In the present work a detailed study of new bacteriostatic copolymers with quaternized ammonium g... more In the present work a detailed study of new bacteriostatic copolymers with quaternized ammonium groups introduced in the polymer chain through covalent attachment or electrostatic interaction, was performed. Different copolymers have been considered since beside the active species, the hydrophobic/hydrophilic nature of the co-monomer was also evaluated in the case of covalently attached bacteriostatic groups, aiming at achieving permanent antibacterial activity. Homopolymers with quaternized ammonium/phosphonium groups were also tested for comparison reasons. The antimicrobial activity of the synthesized polymers after 3 and 24 h of exposure at 4 and 22˝C was investigated on cultures of Gram-negative (P. aeruginosa, E. coli) and Gram-positive (S. aureus, E. faecalis) bacteria. It was found that the combination of the hydrophilic monomer acrylic acid (AA), at low contents, with the covalently attached bacteriostatic group vinyl benzyl dimethylhexadecylammonium chloride (VBCHAM) in the copolymer P(AA-co-VBCHAM88), resulted in a high bacteriostatic activity against P. aeruginosa and E. faecalis (6 log reduction in certain cases). Moreover, the combination of covalently attached VBCHAM units with electrostatically bound cetyltrimethylammonium 4-styrene sulfonate (SSAmC 16) units in the P(SSAmC 16-co-VBCHAMx) copolymers led to efficient antimicrobial materials, especially against Gram-positive bacteria, where a log reduction between 4.9 and 6.2 was verified. These materials remain remarkably efficient even when they are incorporated in polysulfone membranes.

Agriculture and Agricultural Science Procedia, 2015

Marine biofouling is a natural phenomenon representing one of the greatest problems in marine tec... more Marine biofouling is a natural phenomenon representing one of the greatest problems in marine technology (navigation, aquaculture nets, etc). To circumvent these problems, antifouling paints or coatings, i.e. matrices containing biocidal species, are used to protect the submerged surfaces and objects. Polymers containing quaternary phosphonium or quaternary ammonium groups are promising biocidal materials. Such a biocidal polymeric material is the polymeric salt PSSAmC16 formed between the polystyrene sulfonate anion and the cetyltrimethylammonium cation. When embedded into a paint or a polymeric matrix, the cation of PSSAmC16 is gradually dissolved in the surrounding water through an ion exchange mechanism, offering the biocidal protection of the surface. In the present work, the release of PSSAmC16 from the synthetic polymeric matrix poly(methyl methacrylate), PMMA, was evaluated, as a function of the contact time with the surrounding aqueous environment. The PSSAmC16 content in the matrix varied from 0 up to 40 % (wt/wt), while aqueous NaCl solutions with a salt concentration up to 2M were investigated. The release of the polymeric biocidal was quantified through Total Organic Carbon (TOC) and Total Nitrogen (TN) measurements. Both methods reveal that the major part of the polymeric biocidal is released within a few days, while release increases with the PSSAmC16 content and it is enhanced by the salinity.

Procedia Engineering, 2012

Polymers, 2016

A novel concept for the use of an immiscible and non-meltable polymer, such as sodium polystyrene... more A novel concept for the use of an immiscible and non-meltable polymer, such as sodium polystyrene sulfonate (PSSNa), in order to prepare polyethylene non-woven breathable membranes is described. Membranes were fabricated by melt compounding of properly functionalized PE (P(E-co-AA)) and PSSNa (P(SSNa-co-GMA)) copolymers in the presence of water soluble polyethylene glycol (PEG). The inability of PSSNa derivatives to be melted was overcome by using PEG, which was easily meltable thus inducing PSSNa processability improvement. PEG was removed after membrane fabrication and therefore also acted as a porogen. Carbon nanotubes, functionalized with PSSNa moieties or alkyl groups, were also incorporated in the membranes with the aim of improving the porous connectivity and increasing the water vapor transmission rate. The morphology of the membranes was investigated through Scanning Electron Microscopy (SEM). Water vapor transmission rate (permeation) (WVTR) measurements for the porous membranes showed increased values in comparison with the neat PE ones. A further increase of WVTR was observed with the addition of CNTs to the polymer membranes.

European Polymer Journal, 2014

Linear copolymers, P(MMA-co-VBC) and P(SSNa-co-VBC), of 4-vinylbenzyl chloride (VBC) with hydroph... more Linear copolymers, P(MMA-co-VBC) and P(SSNa-co-VBC), of 4-vinylbenzyl chloride (VBC) with hydrophobic (methyl methacrylate, MMA) or hydrophilic anionic (sodium styrene sulfonate, SSNa) monomers were prepared through free radical polymerization. The molar content of MMA or SSNa units ranges from 0% up to 90% (mol/mol). After polymerization, VBC was quaternized using short chain (triethylamine, TEAM) or long chain (N,N-dimethylhexadecylamine, HAM) amines. FTIR and 1 H NMR verified that the P(MMA-co-VBC) series were fully quaternized, leading to hydrophobic polycations P(MMA-co-VBCTEAM) or hydrophobic/hydrophobically modified polycations P(MMA-co-VBCHAM), while the P(SSNa-co-VBC) series were partially quaternized, leading to polyampholytes P(SSNa-co-VBCTEAM-co-VBC) and hydrophobically modified polyampholytes P(SSNa-co-VBCHAM-co-VBC). To overcome partial quaternization problems, hydrophobically modified polyampholytes P(SSNaco-VBCHAM) were synthesized through direct polymerization of SSNa and vinylbenzyl dimethylhexadecylammonium chloride (VBCHAM). The solubility and self-association behavior of these copolymers in water were investigated through turbidimetry, Nile Red fluorescence probing, dynamic light scattering and f-potential measurements. It is found that phase separation and self-association are mostly affected by the copolymer's net charge and not the nature of the hydrophobic or charged unit. Moreover, the introduction of cationic amphiphilic units (VBCHAM) not only favors the self-association of the final hydrophobically modified polymers, forming aggregates in aqueous solution, but may also lead to polymers with antimicrobial activity.

Journal of Applied Polymer Science, 2016

This work describes the development of porous membranes based on blends of an aromatic polyether ... more This work describes the development of porous membranes based on blends of an aromatic polyether bearing main and side chain pyridine units (AP) with hydrophilic ionic polymers, like poly(sodium 4-styrenesulfonate) (PSSNa) and its acid form (PSSH), or non-ionic like polyvinylpyrrolidone and polyethylene glycol. Porous membranes were obtained after the removal of the water soluble polymers from the respective blend. The effect of various parameters such as water soluble polymer used (pore former), blend composition, casting solvent, and solvent evaporation level on porous structure formation was studied thoroughly. Specifically, SEM examination for the aforementioned systems indicated various porous morphologies depending on experimental conditions as well as thermodynamic and kinetic parameters occurring during their formation. The thermal properties of the membranes were influenced by the kind of the pore former, as revealed by thermogravimetric analysis. Special attention was paid to the systems AP/ PSSNa and AP/PSSH to evaluate their miscibility via dynamic mechanical analysis and ATR-FTIR spectroscopy. AP/PSSNa membranes have been preliminary used to test the water permeability for water purification. The tests revealed high water flux values at increased PSSNa concentrations.

Sensors and Actuators B: Chemical, 2015

ABSTRACT A series of cross-linked organic nanoparticles (NPs) have been prepared through emulsion... more ABSTRACT A series of cross-linked organic nanoparticles (NPs) have been prepared through emulsion copolymerization of vinyl acetate (VAc) and of luminescent quinoline based monomers in the presence of divinylbenzene. Furthermore, hydrolysis of VAc led to the respective cross-linked poly(vinyl alcohol) nanoparticles. The two luminescent vinylic quinoline derivatives employed, namely 2,4-diphenyl-6-(4-vinylphenyl)quinoline (SDPQ) or 2-(pyridin-2-ylo)-6-styrene-4-phenylquinoline (QPy), were used at feed compositions of 1 mol% and 2 mol%. The chemical composition and the success of hydrolysis have been assessed through infrared spectroscopy, while scanning electron microscopy verified that the spherical shape and the size (∼50–100 nm) of the NPs are practically unaffected by the hydrolysis process. The pH-sensitive luminescence behavior of the NPs, arising from the protonation/deprotonation equilibrium of the quinoline groups, was investigated in aqueous dispersions or in solid state after incorporation of the NPs in a poly(lactic acid) (PLA) matrix. Depending on the system, either two distinct bands at ∼420 nm and ∼480 nm, corresponding to the unprotonated and the protonated form of the quinoline derivative, or a gradual shift from ∼420 nm to ∼480 nm were observed upon decreasing pH. The photoluminescence inspection of the surrounding aqueous environment confirmed that the leaching of the NPs from the PLA matrix is very limited or negligible. Moreover, our initial studies suggest that the photoluminescence response of the solid systems is quite fast (a few minutes), indicating that they are promising for the design of adequate solid pH-responsive luminescent sensors.

PLoS ONE, 2014

Novel Carbon Nanotube-Polymer Hybrids were synthesized as potential materials for the development... more Novel Carbon Nanotube-Polymer Hybrids were synthesized as potential materials for the development of membranes for water treatment applications in the field of Membrane Bioreactors (MBRs). Due to the toxicological concerns regarding the use of nanomaterials in water treatment as well as the rising demand for safe drinking water to protect public health, we studied the functionalization of MWCNTs and Thin-MWCNTs as to control their properties and increase their ability of embedment into porous anisotropic polymeric membranes. Following the growth of the hydrophilic monomer on the surface of the properly functionalized CNTs, that act as initiator for the controlled radical polymerization (ATRP) of sodium styrene sulfonate (SSNa), the antimicrobial quaternized phosphonium and ammonium salts were attached on CNTs-g-PSSNa through non-covalent bonding. In another approach the covalent attachment of quaternized ammonium polymeric moieties of acrylic acid-vinyl benzyl chloride copolymers with N,N-dimethylhexadecylamine (P(AA12-co-VBCHAM)) on functionalized CNTs has also been attempted. Finally, the toxicological assessment in terms of cell viability and cell morphological changes revealed that surface characteristics play a major role in the biological response of functionalized CNTs.

Separation Science and Technology, 2011

ABSTRACT Gravitational field-flow fractionation (GrFFF) was applied for the study of the growth o... more ABSTRACT Gravitational field-flow fractionation (GrFFF) was applied for the study of the growth of Saccharomyces cerevisiae yeast strain, in the presence or the absence of corn and wheat starch granules as immobilization carriers. Fermentations were conducted at different values of pH (3.0, 4.0, 5.0, and 6.0) and initial glucose concentration (177 g/L, 205 g/L, 247 g/L and 300 g/L) in order to find the most favorable situation for the growth and proliferation of Saccharomyces cerevisiae cells. The distinction of the phases of the yeast cell cycle was also succeeded by the same technique. The results indicate that the growth of yeast cells was enhanced at pH 5.0 and glucose concentrations of 177 g/L and 205 g/L. Higher glucose concentrations (247 g/L and 300 g/L) acted as an inhibitor to cell proliferation. Immobilization on wheat starch provided wider peak profiles, suggesting a broad size of cells and lower concentrations of haploid cells comparing to cells immobilized on corn starch granules. The determination of Michaelis-Menten constants for free and immobilized cells proved the higher affinity of immobilized cells towards the substrate. The values found were in good agreement with those reported in literature.

Preparative Biochemistry and Biotechnology, 2012

The technique of reversed-flow gas chromatography (RFGC) was employed for the determination of th... more The technique of reversed-flow gas chromatography (RFGC) was employed for the determination of the alcoholic fermentation phases and of kinetic parameters for free and immobilized cell systems, at different initial glucose concentrations and temperature values. In addition to this, due to its considerable advantages over other techniques, RFGC was used for the characterization of a new biocatalyst, yeast cells immobilized on starch gel, and especially wheat starch gel. Immobilization of wine yeast Saccharomyces cerevisiae AXAZ-1 was accomplished on wheat and corn starch gels in order to prepare new biocatalysts with great interest for the fermentation industry. The RFGC led with great accuracy, resulting from a literature review, to the determination of reaction rate constants and activation energies at each phase of the fermentation processes. A maximum value of rate constants was observed at initial glucose concentration of 205 g/L, where a higher number of yeast cells was observed. The increase of glucose concentrations had a negative influence on the growth of AXAZ-1 cells and rate constants were decreased. The decrease of fermentation temperature caused a substantial reduction in the viability of immobilized cells as well as in rate constant values. Activation energies of corn starch gel presented lower values than those of wheat starch gel. However, the two supports showed higher catalytic efficiency than free cell systems, proving that starch gels may act as a promoter of the catalytic activity of the yeast cells involved in the fermentation process.

Journal of Liquid Chromatography & Related Technologies, 2011

The Gravitational field-flow fractionation (GFFF) in combination with the conventional gas chroma... more The Gravitational field-flow fractionation (GFFF) in combination with the conventional gas chromatography and high-performance liquid chromatography were applied in order to study the effect of temperature (15°, 20°, 25°, and 30°C) on the fermentation kinetics and the proliferation of the alcohol-resistant and psychrophilic Saccharomyces cerevisiae (AXAZ-1) yeast strain, in the presence or absence of wheat starch granules as immobilization carrier. The results indicated that both systems (free and immobilized cells) performed better at 30°C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. The duration and the rate of the fermentation process were shorter in the case of immobilized cells as compared with free cells, which is in accordance with literature. Moreover, wheat starch granules proved to be capable and efficient for the immobilization process as it is a cheap material, of food grate purity, available in large amounts. The activation energy for the fermentation process (Ea) was reduced in the case of immobilized cells as compared with free cells.

Journal of Chromatography A, 2010

In the present work two separation techniques, namely the gravitational field-flow fractionation ... more In the present work two separation techniques, namely the gravitational field-flow fractionation (GrFFF) and the reversed-flow gas chromatography (RFGC), are proposed for the distinction of the growth phases of Saccharomyces cerevisiae (AXAZ-1) yeast cycle at different temperatures (30 degrees C, 25 degrees C, 20 degrees C, and 15 degrees C) and pH (2.0, 3.0, 4.0 and 5.0) values. During the fermentation processes, differences observed in the peak profiles, obtained by GrFFF, can be related with the unlike cell growth. The distinction of the phases of AXAZ-1 cell cycle with the GrFFF, was also confirmed with the RFGC technique, which presented similar fermentation time periods for the alcoholic fermentation phases. Simultaneously, the reaction rate constant for each phase of the fermentation process and the activation energies were determined with the aid of the RFGC technique. Finally, the application of both the GrFFF and the RFGC techniques, in combination with high-performance liquid chromatography, allowed us to find the ideal experimental conditions (temperature and pH) for the alcoholic fermentation by AXAZ-1. The results indicate that S. cerevisiae cells performed better at 30 degrees C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. Moreover, the pH of the medium (pH 5.0) resulted in higher fermentation rates and ethanol productivities.

Journal of Chromatographic Science, 2013

The kinetics of the fermentation process has gained increasing interest, not only in the scientif... more The kinetics of the fermentation process has gained increasing interest, not only in the scientific community, but in the industrial world as well. Information concerning the improvement of batch fermentation performance may potentially be valuable for the designing of scale-up processes. Intensive studies have been conducted with the use of various chromatographic techniques, such as conventional gas chromatography, reversed-flow gas chromatography (RFGC), high-performance liquid chromatography, field-flow fractionation and others. In the present study, specific focus is placed on the employment of RFGC, a method that can successfully be applied for the determination of physicochemical quantities, such as reaction rate constants and activation energies, at each phase of the alcoholic fermentation. In contrast to conventional chromatographic techniques, RFGC can lead to substantial information referring to the evaluation of fermentation kinetics at any time of the process. Moreover, gravitational field-flow fractionation, a sub-technique of field-flow fractionation, presents the ability to monitor the proliferation of Saccharomyces cerevisiae cells through their elution profiles that can be related to the different cell growth stages. The combination of the two techniques can provide important information for kinetic study and the distinction of the growth phases of yeast cell proliferation during alcoholic fermentations conducted under different environmental conditions.