Georgios Bokias - Academia.edu (original) (raw)

Papers by Georgios Bokias

Research paper thumbnail of Organic hydrogels as potential sorbent materials for water purification

Research paper thumbnail of Polymeric Antimicrobial Coatings Based on Quaternary Ammonium Compounds

Coatings

Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending... more Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending and crosslinking and studied as a function of the ratio of reactive groups and the type of biocidal groups, after curing at room temperature or 120 • C. For this purpose, two series of copolymers with complementary reactive groups, 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 resulting in covalently bound (4-vinylbenzyl dimethylhexadecylammonium chloride, VBCHAM) and electrostatically attached (hexadecyltrimethylammonium 4-styrene sulfonate, SSAmC 16) units. The crosslinking reaction between the carboxylic group of acrylic acid (AA) and the epoxide group of glycidyl methacrylate (GMA) of these copolymers led to the stabilization of the coatings through reactive blending. The so developed coatings were cured at room temperature and 120 • C, and then immersed in ultra-pure water and aqueous NaCl solutions at various concentrations for a time period up to three months. Visual inspection of the integrity of the materials coated onto glass slides, gravimetry, scanning electron microscopy (SEM) characterization, as well as the determination of total organic carbon (TOC) and total nitrogen (TN) of the solutions, were used to investigate the parameters affecting the release of the materials from the coatings based on these systems. The results revealed that curing temperature, complementary reactive groups' content, and type of antimicrobial species control the release levels and the nature of releasable species of these environmentally-friendly antimicrobial coatings.

Research paper thumbnail of Multifunctional Polymeric Platform of Magnetic Ferrite Colloidal Superparticles for Luminescence, Imaging, and Hyperthermia Applications

ACS applied materials & interfaces, Jan 28, 2016

Adequately designed multiresponsive water-soluble graft copolymers were used to serve as a multif... more Adequately designed multiresponsive water-soluble graft copolymers were used to serve as a multifunctional polymeric platform for the encapsulation and transfer in aqueous media of hydrophobic magnetic nanoparticles (MNPs). The backbone of the graft copolymers was composed of hydrophilic sodium methacrylate units, hydrophobic dodecyl methacrylate units, and luminescent quinoline-based units, while either the homopolymer poly(N-isopropylacrylamide) or a poly(N,N-dimethylacrylamide-co-N-isopropylacrylamide) copolymer was used as thermosensitive pendent side chains. The polymeric platform forms micellar-type assemblies in aqueous solution, and exhibits pH-responsive luminescent properties and a lower critical solution temperature behavior in water. Depending on the design of the side chains, the cloud point temperatures were determined at 38 and 42 °C, close or slightly above body temperature (37 °C). Above the critical micelle concentration (CMC), both graft copolymers can effectively...

Research paper thumbnail of Investigation of the association in water of sodium dodecyl sulfate with a positively charged copolymer based on N -isopropylacrylamide

Research paper thumbnail of Association of hydrophobically modified positively charged N-isopropylacrylamide copolymers with the nonionic surfactant Triton X-100

Polymer, Apr 30, 2001

The association in dilute aqueous solution of the nonionic surfactant t-octylphenoxy polyoxyethan... more The association in dilute aqueous solution of the nonionic surfactant t-octylphenoxy polyoxyethanol (Triton X-100) with hydrophobically modi®ed copolymers based on an N-isopropylacrylamide (NIPAM) backbone is presented. The NIPAM-based copolymers contain also N,N-[(dimethylamino)propyl] methacrylamide (MADAP), the content x of MADAP varying from 0 up to 25 mol%, completely alkylated with dodecylbromide or octadecylbromide. The highly hydrophobic copolymers are characterised by a compact conformation in aqueous solution, due to the formation of intrachain hydrophobic aggregates. Association with Triton X-100 leads to the destruction of these intrachain aggregates and to their replacement by mixed alkyl/surfactant ones, revealed macroscopically by a gradual viscosity increase upon addition of surfactant. Fluorescence probing studies and dialysis equilibrium experiments con®rmed that polymer/surfactant association starts in the vicinity of the critical micelle concentration (CMC) of Triton X-100.

Research paper thumbnail of Poly(sodium styrene sulfonate)-b-poly(methyl methacrylate) dibloclc copolymers through direct atom transfer radical polymerization: Influence of hydrophilic―hydrophobic balance on self-organization in aqueous solution

European Polymer Journal, 2011

A series of poly(sodium styrene sulfonate)-b-poly(methyl methacrylate), PSSNa-b-PMMA, amphiphilic... more A series of poly(sodium styrene sulfonate)-b-poly(methyl methacrylate), PSSNa-b-PMMA, amphiphilic diblock copolymers have been synthesized through atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in N,N-dimethylformamide/water mixtures, starting from a PSSNa macroinitiator. The kinetics of the polymerization was followed by 1 H NMR, while the chemical composition of the copolymers was verified by a variety of techniques, such as 1 H NMR, FTIR and TGA. The MMA content of the copolymers ranges from 0 up to 60 mol%, while the number-average molecular weight of the PSSNa macroinitiator was 9000 g/mol. The self-association of the diblock copolymers in aqueous solution was compared to the respective behavior of similar random P(SSNa-coMMA) copolymers through optical density measurements, pyrene fluorescence probing, dynamic light scattering and surface tension measurements. It is shown that the diblock copolymers form micellar structures in water, characterized by an increasing hydrophobic character and a decreasing size as the length of the PMMA block increases. These micellelike structures turn from surface inactive to surface active as the length of the PMMA block increases. Moreover, contrary to the MMA-rich random copolymers, the respective diblock copolymers form water insoluble polymer/surfactant complexes with cationic surfactants such as hexadecyltrimethyl ammonium bromide (HTAB), leading to materials with antimicrobial activity.

Research paper thumbnail of Soluble Hydrogen-Bonding Interpolymer Complexes and pH-controlled Thickening Phenomena in Water

Macromolecules, Jan 29, 2003

ABSTRACT The hydrogen-bonding interpolymer association between poly(acrylic acid) (PAA) and the p... more ABSTRACT The hydrogen-bonding interpolymer association between poly(acrylic acid) (PAA) and the poly(N,N-dimethylacrylamide) (PDMAM) side chains of a negatively charged graft copolymer was studied in aqueous solutions. The graft copolymers, P(AA-co-AMPSA)-g-PDMAM, contain 50 wt % PDMAM, while their backbone comprises acrylic acid (AA) and mostly 2-acrylamido-2-methylpropane sulfonic acid (AMPSA) units. The formation, at low pH, of compact and soluble hydrogen-bonding interpolymer complexes between PAA and the side PDMAM chains, is suggested by combining turbidimetry and dilute solution viscosity measurements. Moreover, in semidilute solutions, the pH-controlled association−dissociation of these water-soluble hydrogen-bonding interpolymer complexes results in a spectacular pH-controlled thickening behavior.

Research paper thumbnail of Temperature- and solvent-sensitive hydrogels based on N -isopropylacrylamide and N , N -dimethylacrylamide

Polymer Bulletin, 2007

ABSTRACT The swelling behaviour in water-dioxane mixtures of hydrogels containing N-isopropylacry... more ABSTRACT The swelling behaviour in water-dioxane mixtures of hydrogels containing N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) is investigated as a function of dioxane content and temperature. The composition of the hydrogels, reported as the mol percentage of DMAM units, x, varies from 0 up to 100. It is found that the hydrogel containing only NIPAM units, GPNIPAM, deswells significantly in the water-rich region, while the hydrogel containing only DMAM units, GPDMAM, presents a pronounced deswelling in the dioxane-rich region. This deswelling becomes less significant with decreasing the DMAM content x, when using the hydrogels of the copolymers GP(NIPAM-co-DMAMx). This swelling behaviour of the hydrogels results from a combination of the lower critical solution temperature-type cononsolvency behaviour of poly(N-isopropylacrylamide) with the upper critical solution temperature-type cononsolvency behaviour of poly(N,N-dimethylacrylamide) in water-dioxane mixtures.

Research paper thumbnail of Physicochemical study of the complexation of poly(acrylic acid) with Cu2+ ions in water

Journal of Applied Polymer Science, Apr 15, 2008

Research paper thumbnail of Interpolymer association between poly(acrylic acid) and vinyl alcohol‐vinyl acetate copolymers in dilute aqueous solutions

Macromolecular Chemistry and Physics, Nov 1, 1991

Research paper thumbnail of Release of Polymeric Biocides from Synthetic Matrices for Marine Biofouling Applications

Agriculture and Agricultural Science Procedia, 2015

ABSTRACT Marine biofouling is a natural phenomenon representing one of the greatest problems in m... more ABSTRACT 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 2 M 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.

Research paper thumbnail of Quinoline-functionalized cross-linked poly (vinyl acetate) and poly (vinyl alcohol) nanoparticles as potential pH-responsive luminescent sensors

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.

Research paper thumbnail of Ionic Hydrogels as Potential Sorbent Materials of Organic and Inorganic Charged Pollutants

Journal of Surfaces and Interfaces of Materials, 2014

ABSTRACT

Research paper thumbnail of Control of the lower critical solution temperature - Type cononsolvency properties of poly(N-isopropylacrylamide) in water - Dioxane mixtures through copolymerisation with acrylamide

ABSTRACT The behaviour of the homopolymers poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide (... more ABSTRACT The behaviour of the homopolymers poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide (PAM) and random copolymers of N-isopropylacrylamide (NIPAM) with acrylamide (AM) was studied by turbidimetry and viscometry in mixtures of water with dioxane. It was found that the well-known lower critical solution temperature-type cononsolvency properties of PNIPAM in water–dioxane mixtures, observed in the water-rich region, can be effectively controlled by copolymerisation of NIPAM with AM. Thus, the cononsolvency properties of the copolymers in water–dioxane mixtures are shifted to higher temperatures and restricted within a narrower solvent composition region as the acrylamide content of the copolymers increases. A significant decrease of the reduced viscosity of the systems exhibiting phase separation properties was observed upon heating, indicative of the collapse of the (co)polymer chains as temperature approaches the corresponding cloud point temperature. Furthermore, when temperature is fixed close to

Research paper thumbnail of Potentiometric Investigation of Hydrogen-Bonded Interpolymer Complexation

Formation, Structure and Applications, 2009

Research paper thumbnail of Doubly-grafted copolymers with hydrophilic and thermosensitive side chains: Thermosensitivity and complexation with surfactants

Journal of Colloid and Interface Science, 2014

The behavior in aqueous solution of the doubly-grafted anionic polyelectrolyte poly(sodium 2-acry... more The behavior in aqueous solution of the doubly-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate-)-g-poly(N-isopropylacry-lamide)-g-poly(N,N-dimethylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM, was compared to that of the single-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate)-g-poly(N-isopropylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM. The investigation through turbidimetry, pyrene fluorescence probing, viscometry and dynamic light scattering revealed that the existence of the hydrophilic poly(N,N-dimethylacrylamide), PDMAM, side chains in the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM did not perturb the thermoresponsiveness of the poly(N-isopropylacrylamide), PNIPAM, side chains, but favoured the stabilization in water of the core-corona nanoparticles, formed upon heating the aqueous solution above the Lower Critical Solution Temperature (LCST) of PNIPAM chains. In a similar manner, the complexes formed between the cationic surfactant N,N,N,N-dodecyltrimethylammonium chloride, DTAC, and the oppositely charged backbone of the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM were stabilized in water by the PDMAM side chains. Thus, phase separation was prevented upon heating the aqueous solution above LCST. Moreover, the (1)H NMR study revealed that the fraction of PNIPAM chains forming solid-like aggregates at high temperature increased substantially in the presence of DTAC, as a consequence of the net charge decrease of the backbone due to the polymer/DTAC complexation.

Research paper thumbnail of Development of Cu2+- and/or phosphonium-based polymeric biocidal materials and their potential application in antifouling paints

Progress in Organic Coatings, 2012

ABSTRACT

Research paper thumbnail of Interpolymer Complexes of Poly(acrylamide) and Poly(N-isopropylacrylamide) with Poly(acrylic acid): a Comparative Study

Polymer International, 1996

Research paper thumbnail of Simultaneous lower and upper critical solution temperature-type co-nonsolvency behaviour exhibited in water–dioxane mixtures by linear copolymers and hydrogels containingN-isopropylacrylamide andN,N-dimethylacrylamide

Polymer International, 2006

The co-nonsolvency behaviour in water-dioxane mixtures of linear copolymers and hydrogels consist... more The co-nonsolvency behaviour in water-dioxane mixtures of linear copolymers and hydrogels consisting of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) was studied as a function of solvent composition and temperature. The composition of the copolymers, P(NIPAM-co-DMAMx), in DMAM units, x, varies from x = 0 up to x = 100%. It is shown that the copolymers combine the lower critical solution temperature (LCST)-type co-nonsolvency behaviour of poly-NIPAM with the upper critical solution temperature (UCST)-type co-nonsolvency behaviour of poly-DMAM. Depending on x, both the LCST-and UCST-type co-nonsolvency behaviour may be simultaneously observed in water-rich and dioxane-rich solvent mixtures, respectively. Due to this complex phase separation behaviour, the variation of the reduced viscosity of the linear copolymers, as well as the swelling-deswelling behaviour of the respective hydrogels, are shown to be temperature-and solvent-sensitive.

Research paper thumbnail of The intrinsic viscosity of poly(acrylic acid) and partially neutralized poly(acrylic acid) by isoionic dilution

Polymer International, 1993

The isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acr... more The isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acrylic acid) (PAA) sample as a function of neutralization degree, i, at low ionic strength, I= 1.0×10 -3 M. The results obtained for the counterion activity are in close agreement with Manning's theory for counterion condensation. The influence of the ionic strength, I, on [η] and on the Huggins coefficient, k', was also examined and the exponents of the scaling laws relating these two parameters with I were found

Research paper thumbnail of Organic hydrogels as potential sorbent materials for water purification

Research paper thumbnail of Polymeric Antimicrobial Coatings Based on Quaternary Ammonium Compounds

Coatings

Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending... more Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending and crosslinking and studied as a function of the ratio of reactive groups and the type of biocidal groups, after curing at room temperature or 120 • C. For this purpose, two series of copolymers with complementary reactive groups, 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 resulting in covalently bound (4-vinylbenzyl dimethylhexadecylammonium chloride, VBCHAM) and electrostatically attached (hexadecyltrimethylammonium 4-styrene sulfonate, SSAmC 16) units. The crosslinking reaction between the carboxylic group of acrylic acid (AA) and the epoxide group of glycidyl methacrylate (GMA) of these copolymers led to the stabilization of the coatings through reactive blending. The so developed coatings were cured at room temperature and 120 • C, and then immersed in ultra-pure water and aqueous NaCl solutions at various concentrations for a time period up to three months. Visual inspection of the integrity of the materials coated onto glass slides, gravimetry, scanning electron microscopy (SEM) characterization, as well as the determination of total organic carbon (TOC) and total nitrogen (TN) of the solutions, were used to investigate the parameters affecting the release of the materials from the coatings based on these systems. The results revealed that curing temperature, complementary reactive groups' content, and type of antimicrobial species control the release levels and the nature of releasable species of these environmentally-friendly antimicrobial coatings.

Research paper thumbnail of Multifunctional Polymeric Platform of Magnetic Ferrite Colloidal Superparticles for Luminescence, Imaging, and Hyperthermia Applications

ACS applied materials & interfaces, Jan 28, 2016

Adequately designed multiresponsive water-soluble graft copolymers were used to serve as a multif... more Adequately designed multiresponsive water-soluble graft copolymers were used to serve as a multifunctional polymeric platform for the encapsulation and transfer in aqueous media of hydrophobic magnetic nanoparticles (MNPs). The backbone of the graft copolymers was composed of hydrophilic sodium methacrylate units, hydrophobic dodecyl methacrylate units, and luminescent quinoline-based units, while either the homopolymer poly(N-isopropylacrylamide) or a poly(N,N-dimethylacrylamide-co-N-isopropylacrylamide) copolymer was used as thermosensitive pendent side chains. The polymeric platform forms micellar-type assemblies in aqueous solution, and exhibits pH-responsive luminescent properties and a lower critical solution temperature behavior in water. Depending on the design of the side chains, the cloud point temperatures were determined at 38 and 42 °C, close or slightly above body temperature (37 °C). Above the critical micelle concentration (CMC), both graft copolymers can effectively...

Research paper thumbnail of Investigation of the association in water of sodium dodecyl sulfate with a positively charged copolymer based on N -isopropylacrylamide

Research paper thumbnail of Association of hydrophobically modified positively charged N-isopropylacrylamide copolymers with the nonionic surfactant Triton X-100

Polymer, Apr 30, 2001

The association in dilute aqueous solution of the nonionic surfactant t-octylphenoxy polyoxyethan... more The association in dilute aqueous solution of the nonionic surfactant t-octylphenoxy polyoxyethanol (Triton X-100) with hydrophobically modi®ed copolymers based on an N-isopropylacrylamide (NIPAM) backbone is presented. The NIPAM-based copolymers contain also N,N-[(dimethylamino)propyl] methacrylamide (MADAP), the content x of MADAP varying from 0 up to 25 mol%, completely alkylated with dodecylbromide or octadecylbromide. The highly hydrophobic copolymers are characterised by a compact conformation in aqueous solution, due to the formation of intrachain hydrophobic aggregates. Association with Triton X-100 leads to the destruction of these intrachain aggregates and to their replacement by mixed alkyl/surfactant ones, revealed macroscopically by a gradual viscosity increase upon addition of surfactant. Fluorescence probing studies and dialysis equilibrium experiments con®rmed that polymer/surfactant association starts in the vicinity of the critical micelle concentration (CMC) of Triton X-100.

Research paper thumbnail of Poly(sodium styrene sulfonate)-b-poly(methyl methacrylate) dibloclc copolymers through direct atom transfer radical polymerization: Influence of hydrophilic―hydrophobic balance on self-organization in aqueous solution

European Polymer Journal, 2011

A series of poly(sodium styrene sulfonate)-b-poly(methyl methacrylate), PSSNa-b-PMMA, amphiphilic... more A series of poly(sodium styrene sulfonate)-b-poly(methyl methacrylate), PSSNa-b-PMMA, amphiphilic diblock copolymers have been synthesized through atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in N,N-dimethylformamide/water mixtures, starting from a PSSNa macroinitiator. The kinetics of the polymerization was followed by 1 H NMR, while the chemical composition of the copolymers was verified by a variety of techniques, such as 1 H NMR, FTIR and TGA. The MMA content of the copolymers ranges from 0 up to 60 mol%, while the number-average molecular weight of the PSSNa macroinitiator was 9000 g/mol. The self-association of the diblock copolymers in aqueous solution was compared to the respective behavior of similar random P(SSNa-coMMA) copolymers through optical density measurements, pyrene fluorescence probing, dynamic light scattering and surface tension measurements. It is shown that the diblock copolymers form micellar structures in water, characterized by an increasing hydrophobic character and a decreasing size as the length of the PMMA block increases. These micellelike structures turn from surface inactive to surface active as the length of the PMMA block increases. Moreover, contrary to the MMA-rich random copolymers, the respective diblock copolymers form water insoluble polymer/surfactant complexes with cationic surfactants such as hexadecyltrimethyl ammonium bromide (HTAB), leading to materials with antimicrobial activity.

Research paper thumbnail of Soluble Hydrogen-Bonding Interpolymer Complexes and pH-controlled Thickening Phenomena in Water

Macromolecules, Jan 29, 2003

ABSTRACT The hydrogen-bonding interpolymer association between poly(acrylic acid) (PAA) and the p... more ABSTRACT The hydrogen-bonding interpolymer association between poly(acrylic acid) (PAA) and the poly(N,N-dimethylacrylamide) (PDMAM) side chains of a negatively charged graft copolymer was studied in aqueous solutions. The graft copolymers, P(AA-co-AMPSA)-g-PDMAM, contain 50 wt % PDMAM, while their backbone comprises acrylic acid (AA) and mostly 2-acrylamido-2-methylpropane sulfonic acid (AMPSA) units. The formation, at low pH, of compact and soluble hydrogen-bonding interpolymer complexes between PAA and the side PDMAM chains, is suggested by combining turbidimetry and dilute solution viscosity measurements. Moreover, in semidilute solutions, the pH-controlled association−dissociation of these water-soluble hydrogen-bonding interpolymer complexes results in a spectacular pH-controlled thickening behavior.

Research paper thumbnail of Temperature- and solvent-sensitive hydrogels based on N -isopropylacrylamide and N , N -dimethylacrylamide

Polymer Bulletin, 2007

ABSTRACT The swelling behaviour in water-dioxane mixtures of hydrogels containing N-isopropylacry... more ABSTRACT The swelling behaviour in water-dioxane mixtures of hydrogels containing N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) is investigated as a function of dioxane content and temperature. The composition of the hydrogels, reported as the mol percentage of DMAM units, x, varies from 0 up to 100. It is found that the hydrogel containing only NIPAM units, GPNIPAM, deswells significantly in the water-rich region, while the hydrogel containing only DMAM units, GPDMAM, presents a pronounced deswelling in the dioxane-rich region. This deswelling becomes less significant with decreasing the DMAM content x, when using the hydrogels of the copolymers GP(NIPAM-co-DMAMx). This swelling behaviour of the hydrogels results from a combination of the lower critical solution temperature-type cononsolvency behaviour of poly(N-isopropylacrylamide) with the upper critical solution temperature-type cononsolvency behaviour of poly(N,N-dimethylacrylamide) in water-dioxane mixtures.

Research paper thumbnail of Physicochemical study of the complexation of poly(acrylic acid) with Cu2+ ions in water

Journal of Applied Polymer Science, Apr 15, 2008

Research paper thumbnail of Interpolymer association between poly(acrylic acid) and vinyl alcohol‐vinyl acetate copolymers in dilute aqueous solutions

Macromolecular Chemistry and Physics, Nov 1, 1991

Research paper thumbnail of Release of Polymeric Biocides from Synthetic Matrices for Marine Biofouling Applications

Agriculture and Agricultural Science Procedia, 2015

ABSTRACT Marine biofouling is a natural phenomenon representing one of the greatest problems in m... more ABSTRACT 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 2 M 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.

Research paper thumbnail of Quinoline-functionalized cross-linked poly (vinyl acetate) and poly (vinyl alcohol) nanoparticles as potential pH-responsive luminescent sensors

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.

Research paper thumbnail of Ionic Hydrogels as Potential Sorbent Materials of Organic and Inorganic Charged Pollutants

Journal of Surfaces and Interfaces of Materials, 2014

ABSTRACT

Research paper thumbnail of Control of the lower critical solution temperature - Type cononsolvency properties of poly(N-isopropylacrylamide) in water - Dioxane mixtures through copolymerisation with acrylamide

ABSTRACT The behaviour of the homopolymers poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide (... more ABSTRACT The behaviour of the homopolymers poly(N-isopropylacrylamide) (PNIPAM), polyacrylamide (PAM) and random copolymers of N-isopropylacrylamide (NIPAM) with acrylamide (AM) was studied by turbidimetry and viscometry in mixtures of water with dioxane. It was found that the well-known lower critical solution temperature-type cononsolvency properties of PNIPAM in water–dioxane mixtures, observed in the water-rich region, can be effectively controlled by copolymerisation of NIPAM with AM. Thus, the cononsolvency properties of the copolymers in water–dioxane mixtures are shifted to higher temperatures and restricted within a narrower solvent composition region as the acrylamide content of the copolymers increases. A significant decrease of the reduced viscosity of the systems exhibiting phase separation properties was observed upon heating, indicative of the collapse of the (co)polymer chains as temperature approaches the corresponding cloud point temperature. Furthermore, when temperature is fixed close to

Research paper thumbnail of Potentiometric Investigation of Hydrogen-Bonded Interpolymer Complexation

Formation, Structure and Applications, 2009

Research paper thumbnail of Doubly-grafted copolymers with hydrophilic and thermosensitive side chains: Thermosensitivity and complexation with surfactants

Journal of Colloid and Interface Science, 2014

The behavior in aqueous solution of the doubly-grafted anionic polyelectrolyte poly(sodium 2-acry... more The behavior in aqueous solution of the doubly-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate-)-g-poly(N-isopropylacry-lamide)-g-poly(N,N-dimethylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM, was compared to that of the single-grafted anionic polyelectrolyte poly(sodium 2-acrylamido-2-methylpropanesulfonate-co-sodium acrylate)-g-poly(N-isopropylacrylamide), P(AMPSNa-co-ANa)-g-PNIPAM. The investigation through turbidimetry, pyrene fluorescence probing, viscometry and dynamic light scattering revealed that the existence of the hydrophilic poly(N,N-dimethylacrylamide), PDMAM, side chains in the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM did not perturb the thermoresponsiveness of the poly(N-isopropylacrylamide), PNIPAM, side chains, but favoured the stabilization in water of the core-corona nanoparticles, formed upon heating the aqueous solution above the Lower Critical Solution Temperature (LCST) of PNIPAM chains. In a similar manner, the complexes formed between the cationic surfactant N,N,N,N-dodecyltrimethylammonium chloride, DTAC, and the oppositely charged backbone of the doubly-grafted copolymer P(AMPSNa-co-ANa)-g-PNIPAM-g-PDMAM were stabilized in water by the PDMAM side chains. Thus, phase separation was prevented upon heating the aqueous solution above LCST. Moreover, the (1)H NMR study revealed that the fraction of PNIPAM chains forming solid-like aggregates at high temperature increased substantially in the presence of DTAC, as a consequence of the net charge decrease of the backbone due to the polymer/DTAC complexation.

Research paper thumbnail of Development of Cu2+- and/or phosphonium-based polymeric biocidal materials and their potential application in antifouling paints

Progress in Organic Coatings, 2012

ABSTRACT

Research paper thumbnail of Interpolymer Complexes of Poly(acrylamide) and Poly(N-isopropylacrylamide) with Poly(acrylic acid): a Comparative Study

Polymer International, 1996

Research paper thumbnail of Simultaneous lower and upper critical solution temperature-type co-nonsolvency behaviour exhibited in water–dioxane mixtures by linear copolymers and hydrogels containingN-isopropylacrylamide andN,N-dimethylacrylamide

Polymer International, 2006

The co-nonsolvency behaviour in water-dioxane mixtures of linear copolymers and hydrogels consist... more The co-nonsolvency behaviour in water-dioxane mixtures of linear copolymers and hydrogels consisting of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) was studied as a function of solvent composition and temperature. The composition of the copolymers, P(NIPAM-co-DMAMx), in DMAM units, x, varies from x = 0 up to x = 100%. It is shown that the copolymers combine the lower critical solution temperature (LCST)-type co-nonsolvency behaviour of poly-NIPAM with the upper critical solution temperature (UCST)-type co-nonsolvency behaviour of poly-DMAM. Depending on x, both the LCST-and UCST-type co-nonsolvency behaviour may be simultaneously observed in water-rich and dioxane-rich solvent mixtures, respectively. Due to this complex phase separation behaviour, the variation of the reduced viscosity of the linear copolymers, as well as the swelling-deswelling behaviour of the respective hydrogels, are shown to be temperature-and solvent-sensitive.

Research paper thumbnail of The intrinsic viscosity of poly(acrylic acid) and partially neutralized poly(acrylic acid) by isoionic dilution

Polymer International, 1993

The isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acr... more The isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acrylic acid) (PAA) sample as a function of neutralization degree, i, at low ionic strength, I= 1.0×10 -3 M. The results obtained for the counterion activity are in close agreement with Manning's theory for counterion condensation. The influence of the ionic strength, I, on [η] and on the Huggins coefficient, k', was also examined and the exponents of the scaling laws relating these two parameters with I were found