2018

Jump to: 2017, 2016, 2015

Open AccessArticle Effect of Counterion Valence on Conformational Behavior of Spherical Polyelectrolyte Brushes Confined between Two Parallel Walls

by Lujuan Li, Qianqian Cao and Chuncheng Zuo

Polymers 2018, 10(4), 363; doi:10.3390/polym10040363

Received: 22 February 2018 / Revised: 21 March 2018 / Accepted: 22 March 2018 / Published: 24 March 2018

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Abstract

We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains.

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We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. For the monovalent case, the increase of the charge fraction leads to extended brush conformation for different slit width (distance between two walls) but collapsed brush in the presence of trivalent counterions is observed. The confinement does not affect electrostatic correlation between trivalent counterions and charged monomers. However, it was found that narrow slit width contributes to stronger electrostatic correlation for the monovalent case. This is because more monovalent counterions are inside the brush at strong confinement, but almost all trivalent counterions are trapped into the brush independently of the slit width. The diffusion of counterions under the confinement is related to the electrostatic correlation. Our simulations also reveal that the brush thickness depends on the slit width nonlinearly. Full article

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2017

Jump to: 2018, 2016, 2015

Open AccessArticle Hydrophilic Polyelectrolyte Multilayers Improve the ELISA System: Antibody Enrichment and Blocking Free

by Xing Lai, Gan Gao, Junji Watanabe, Huiyu Liu and Heyun Shen

Polymers 2017, 9(2), 51; doi:10.3390/polym9020051

Received: 19 December 2016 / Revised: 17 January 2017 / Accepted: 24 January 2017 / Published: 12 February 2017

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Abstract

In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as

[...] Read more.

In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as cationic and anionic polyelectrolytes. On the negatively-charged (PDDA/PAA)₃ polyelectrolyte multilayers the hydrophilic PAA surface could efficiently decrease the magnitude of the noise signal, by inhibiting nonspecific adsorption even without blocking reagent adsorption. Moreover, the (PDDA/PAA)₃ substrate covalently immobilized the primary antibody, greatly increasing the amount of primary antibody adsorption and enhancing the specific detection signal compared with a conventional PS plate. The calibration curve of the (PDDA/PAA)₃ substrate showed a wide linear range, for concentrations from 0.033 to 33 nM, a large specific signal change, and a detection limit of 33 pM, even though the conventional blocking reagent adsorption step was omitted. The (PDDA/PAA)₃ substrate provided a high-performance ELISA system with a simple fabrication process and high sensitivity; the system presented here shows potential for a variety of immunosensor applications. Full article

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Open AccessArticle The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes

by Feriel Meriem Lounis, Joseph Chamieh, Laurent Leclercq, Philippe Gonzalez and Hervé Cottet

Polymers 2017, 9(2), 50; doi:10.3390/polym9020050

Received: 19 November 2016 / Revised: 11 January 2017 / Accepted: 19 January 2017 / Published: 4 February 2017

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Abstract

The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL)

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The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) molar mass on the interaction with statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been systematically investigated for different PAMAMPS chemical charge densities (15% and 100%) and different ionic strengths. The study of the ionic strength dependence of the binding constant allowed the determination of the total number of released counter-ions during the formation of the PEC, which can be compared to the total number of counter-ions initially condensed on the individual polyelectrolyte partners before the association. Interestingly, this fraction of released counter-ions, which was strongly dependent on the PLL molar mass, was almost independent of the PAMAMPS charge density. These findings are useful to predict the binding constant according to the molar mass and charge density of the polyelectrolyte partners. Full article

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Open AccessArticle Polyion Complex Vesicles with Solvated Phosphobetaine Shells Formed from Oppositely Charged Diblock Copolymers

by Keita Nakai, Kazuhiko Ishihara, Michael Kappl, Syuji Fujii, Yoshinobu Nakamura and Shin-ichi Yusa

Polymers 2017, 9(2), 49; doi:10.3390/polym9020049

Received: 31 December 2016 / Revised: 24 January 2017 / Accepted: 30 January 2017 / Published: 4 February 2017

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Abstract

Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer

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Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer agent. The degree of polymerization for PMPC, cationic PMAPTAC, and anionic PAMPS blocks was 20, 190, and 196, respectively. Combining two solutions of oppositely charged diblock copolymers, PMPC-b-PMAPTAC and PMPC-b-PAMPS, led to the spontaneous formation of polyion complex vesicles (PICsomes). The PICsomes were characterized using ¹H NMR, static abd dynamic light scattering, transmittance electron microscopy (TEM), and atomic force microscopy. Maximum hydrodynamic radius (R_h) for the PICsome was observed at a neutral charge balance of the cationic and anionic diblock copolymers. The R_h value and aggregation number (N_agg) of PICsomes in 0.1 M NaCl was 78.0 nm and 7770, respectively. A spherical hollow vesicle structure was observed in TEM images. The hydrodynamic size of the PICsomes increased with concentration of the diblock copolymer solutions before mixing. Thus, the size of the PICsomes can be controlled by selecting an appropriate preparation method. Full article

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Open AccessReview Engineering Cell Surfaces with Polyelectrolyte Materials for Translational Applications

by Peipei Zhang, Michelle L. Bookstaver and Christopher M. Jewell

Polymers 2017, 9(2), 40; doi:10.3390/polym9020040

Received: 11 December 2016 / Revised: 18 January 2017 / Accepted: 19 January 2017 / Published: 28 January 2017

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Abstract

Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field.

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Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field. Over the past decade, modification of cell surfaces with natural or synthetic materials has been studied to exploit this complexity for both fundamental and translational goals. In this review we present the existing biomedical technologies for engineering cell surfaces with one important class of materials, polyelectrolytes. We begin by introducing the challenges facing the cell surface engineering field. We then discuss the features of polyelectrolytes and how these properties can be harnessed to solve challenges in cell therapy, tissue engineering, cell-based drug delivery, sensing and tracking, and immune modulation. Throughout the review, we highlight opportunities to drive the field forward by bridging new knowledge of polyelectrolytes with existing translational challenges. Full article

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Open AccessArticle Polymer Conformations in Ionic Microgels in the Presence of Salt: Theoretical and Mesoscale Simulation Results

by Hideki Kobayashi, Rene Halver, Godehard Sutmann and Roland G. Winkler

Polymers 2017, 9(1), 15; doi:10.3390/polym9010015

Received: 21 November 2016 / Revised: 22 December 2016 / Accepted: 29 December 2016 / Published: 5 January 2017

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Abstract

We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account

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We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account explicitly, and charge-charge interactions are described by the Coulomb potential. By varying the charge interaction strength and salt concentration, we characterize the swelling of the polyelectrolytes and the charge distribution. In particular, we determine the amount of trapped mobile charges inside the microgel and the Debye screening length. Moreover, we analyze the polymer extension theoretically in terms of the tension blob model taking into account counterions and salt ions implicitly by the Debye–Hückel model. Our studies reveal a strong dependence of the amount of ions absorbed in the interior of the microgel on the electrostatic interaction strength, which is related to the degree of the gel swelling. This implies a dependence of the inverse Debye screening length κ on the ion concentration; we find a power-law increase of κ with the Coulomb interaction strength with the exponent

3 / 5

for a salt-free microgel and an exponent

1 / 2

for moderate salt concentrations. Additionally, the radial dependence of polymer conformations and ion distributions is addressed. Full article

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2016

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Open AccessArticle Influence of Polyelectrolyte Multilayer Properties on Bacterial Adhesion Capacity

by Davor Kovačević, Rok Pratnekar, Karmen Godič Torkar, Jasmina Salopek, Goran Dražić, Anže Abram and Klemen Bohinc

Polymers 2016, 8(10), 345; doi:10.3390/polym8100345

Received: 16 August 2016 / Revised: 11 September 2016 / Accepted: 14 September 2016 / Published: 26 September 2016

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Abstract

Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were

[...] Read more.

Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were determined by atomic force microscopy and tensiometry. The surface charge was examined by the zeta potential measurements of silica particles covered with polyelectrolyte multilayers, whereby ionic strength and polyelectrolyte concentrations significantly influenced the build-up process. For adhesion experiments, we used the bacterium Pseudomonas aeruginosa. The extent of adhered bacteria on the surface was determined by scanning electron microscopy. The results showed that the extent of adhered bacteria mostly depends on the type of terminating polyelectrolyte layer, since relatively low differences in surface roughness and hydrophobicity were obtained. In the case of polyelectrolyte multilayers terminating with a positively charged layer, bacterial adhesion was more pronounced than in the case when the polyelectrolyte layer was negatively charged. Full article

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Open AccessCommunication Rheological Properties of DNA Molecules in Solution: Molecular Weight and Entanglement Influences

by Lourdes Mónica Bravo-Anaya, Frédéric Pignon, Félix Armando Soltero Martínez and Marguerite Rinaudo

Polymers 2016, 8(8), 279; doi:10.3390/polym8080279

Received: 17 June 2016 / Revised: 25 July 2016 / Accepted: 29 July 2016 / Published: 3 August 2016

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Abstract

Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA

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Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA from salmon sperm was purified and then studied in solutions in a wide concentration range (between 0.5 and 1600 mg/mL). The intrinsic viscosity of this low molecular weight DNA sample was firstly determined and the evidence of the overlap concentration was detected around the concentration of 125 mg/mL. The chain characteristics of these short molecules were studied in terms of the influence of their molecular weight on the solution viscosities and on the overlap parameter C_DNA[η]. Furthermore, to complete previously reported experimental data, solutions of a large molecular weight DNA from calf-thymus were studied in a high concentration range (up to 40 mg/mL). The rheological behavior is discussed in terms of the generalized master curve obtained from the variation of the specific viscosity at zero shear rate (η_sp,0) as a function of C_DNA[η]. Full article

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Open AccessArticle Physicochemical Properties of Biopolymer Hydrogels Treated by Direct Electric Current

by Żaneta Król, Magdalena Malik, Krzysztof Marycz and Andrzej Jarmoluk

Polymers 2016, 8(7), 248; doi:10.3390/polym8070248

Received: 22 April 2016 / Revised: 17 June 2016 / Accepted: 27 June 2016 / Published: 12 July 2016

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Abstract

The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC)

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The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC) of 400 mA for a duration of five minutes. There were three types of gels prepared for the purpose of the study: C, control; H, gels on the basis of hydrosols that were treated with DC; and G, gels treated with DC. In the course of the study, the authors carried out the following analyses: Texture Profile Analysis (TPA), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Swelling Ratio (SR). Furthermore, the color and pH of hydrogels were measured. The FTIR spectra showed that the structures of gelatine, carrageenan and sodium alginate do not significantly change upon applying DC. The results of TPA, SR, color and pH measurement indicate that hydrogels’ properties are significantly dependent on the type of polymer, its concentration and the type of the gel. By changing those parameters, the characteristics of such gels can be additionally tuned, which extends their applicability, e.g., in the food industry. Moreover, the analysis revealed that SR of H gel gelatine after 72 h of storage was 1.84-times higher than SR of the control sample, which indicated that this gel may be considered as a possible component for wound dressing materials. Full article

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Open AccessArticle Effect of Very High Charge Density and Monomer Constitution on the Synthesis and Properties of Cationic Polyelectrolytes

by Hamideh Ahmadloo, Ricardo Losada and Christine Wandrey

Polymers 2016, 8(6), 234; doi:10.3390/polym8060234

Received: 8 March 2016 / Revised: 16 May 2016 / Accepted: 30 May 2016 / Published: 16 June 2016

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Abstract

The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The

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The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The high level of counterion condensation reduces the ionic strength in the polymerizing batch when the monomer molecules connect to PEL chains. This has the consequence that the hydrodynamic and excluded volume of the PEL molecules will change. Studies of the free radical polymerization revealed non-ideal polymerization kinetics already at low conversion and additionally autoacceleration above a certain monomer concentration and conversion. Similar autoacceleration was not observed for monomers yielding PEL with charge spacing of 0.25 or 0.5 nm. Coulomb interactions, monomer association, steric effects, and specific features of the monomer constitution have been evaluated concerning their contributions to the concentration dependence and conversion dependence of kinetic parameters. The different backbone constitutions of di-M and di-A not only influence the polymerization kinetics but also equip poly(di-M) with higher hydrolytic stability. The experimental results confirm the impact of electrochemical parameters and the necessity to reconsider their inclusion in kinetic models. Full article

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Open AccessArticle SANS from Salt-Free Aqueous Solutions of Hydrophilic and Highly Charged Star-Branched Polyelectrolytes

by François Boué, Jérôme Combet, Bruno Demé, Martine Heinrich, Jean-Georges Zilliox and Michel Rawiso

Polymers 2016, 8(6), 228; doi:10.3390/polym8060228

Received: 29 February 2016 / Revised: 14 May 2016 / Accepted: 23 May 2016 / Published: 8 June 2016

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Abstract

Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q₁

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Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q₁*, is related to a position order between star cores and scales as q₁* ∝ c^1/3. The second, of abscissa q₂*, is also observed in the scattering function of a semi-dilute solution of NaPSS linear polyelectrolytes. In the dilute regime (c < c*, non-overlapping stars), peak abscissa does not depend on concentration c and is just an intramolecular characteristic associated with the electrostatic repulsion between arms of the same star. In the semi-dilute regime, due to the star interpenetration, the scattering function – through the peak position, reflects repulsion between arms of the same star or of different stars. The c threshold between these distinct c-dependencies of q₂* in the dilute and semi-dilute regimes is estimated as c*. Just as simple is the measurement of the geometrical radius R of the star obtained from the q₁* value at c* through the relation 2R = 2π/q₁*. By considering NaPSS stars of the same functionality with different degrees of polymerization per arm N_a, we find R scaling linearly with N_a, suggesting an elongated average conformation of the arms. This is in agreement with theoretical predictions and simulations. Meanwhile the value of q₂* measured in the dilute regime does not allow any inhomogeneous counterion distribution inside the stars to be revealed. Full article

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Open AccessArticle Influence of Polyplex Formation on the Performance of Star-Shaped Polycationic Transfection Agents for Mammalian Cells

by Alexander Raup, Ullrich Stahlschmidt, Valérie Jérôme, Christopher V. Synatschke, Axel H. E. Müller and Ruth Freitag

Polymers 2016, 8(6), 224; doi:10.3390/polym8060224

Received: 12 April 2016 / Revised: 30 May 2016 / Accepted: 1 June 2016 / Published: 6 June 2016

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Abstract

Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have

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Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have never before been compared side-by-side, e.g., in view of structural effects. Herein four star-shaped polycationic structures, all based on (2-dimethylamino) ethyl methacrylate (DMAEMA) building blocks, were investigated for their potential to deliver DNA to adherent (CHO, L929, HEK-293) and non-adherent (Jurkat, primary human T lymphocytes) mammalian cells. The investigated vectors included three structures where the PDMAEMA arms (different arm length and grafting densities) had been grown from a center silsesquioxane or silica-coated γ-Fe₂O₃-core and one micellar structure self-assembled from poly(1,2-butadiene)-block PDMAEMA polymers. All nano-stars combined high transfection potential with excellent biocompatibility. The micelles slightly outperformed the covalently linked agents. For method development and optimization, the absolute amount of polycation added to the cells was more important than the N/P-ratio (ratio between polycation nitrogen and DNA phosphate), provided a lower limit was passed and enough polycation was present to overcompensate the negative charge of the plasmid DNA. Finally, the matrix (NaCl vs. HEPES-buffered glucose solution), but also the concentrations adjusted during polyplex formation, affected the results. Full article

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Open AccessArticle Polypeptide-Nanoparticle Interactions and Corona Formation Investigated by Monte Carlo Simulations

by Fabrice Carnal, Arnaud Clavier and Serge Stoll

Polymers 2016, 8(6), 203; doi:10.3390/polym8060203

Received: 19 February 2016 / Revised: 11 May 2016 / Accepted: 12 May 2016 / Published: 25 May 2016

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Abstract

Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and

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Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and denaturation. In this paper, the impact of neutral and charged nanoparticles (NPs) is investigated by Monte Carlo simulations on polypeptide (PP) chains with primary structure based on bovine serum albumin. The influence of pH, salt valency, and NP surface charge density is systematically studied. It is found that the PP is extended at extreme pH, when no complex formation is observed, and folded at physiological pH. PP adsorption around oppositely-charged NPs strongly limits chain structural changes and modifies its acid/base properties. At physiological pH, the complex formation occurs only with positively-charged NPs. The presence of salts, in particular those with trivalent cations, introduces additional electrostatic interactions, resulting in a mitigation of the impact of negative NPs. Thus, the corona structure is less dense with locally-desorbed segments. On the contrary, very limited impact of salt cation valency is observed when NPs are positive, due to the absence of competitive effects between multivalent cations and NP. Full article

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Open AccessFeature PaperArticle Porphyrin Diacid-Polyelectrolyte Assemblies: Effective Photocatalysts in Solution

by Sabine Frühbeißer, Giacomo Mariani and Franziska Gröhn

Polymers 2016, 8(5), 180; doi:10.3390/polym8050180

Received: 19 March 2016 / Revised: 18 April 2016 / Accepted: 25 April 2016 / Published: 4 May 2016

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Abstract

Developing effective and versatile photocatalytic systems is of great potential in solar energy conversion. Here we investigate the formation of supramolecular catalysts by electrostatic self-assembly in aqueous solution: Combining positively charged porphyrins with negatively charged polyelectrolytes leads to nanoscale assemblies where, next to

[...] Read more.

Developing effective and versatile photocatalytic systems is of great potential in solar energy conversion. Here we investigate the formation of supramolecular catalysts by electrostatic self-assembly in aqueous solution: Combining positively charged porphyrins with negatively charged polyelectrolytes leads to nanoscale assemblies where, next to electrostatic interactions, π–π interactions also play an important role. Porphyrin diacid-polyelectrolyte assemblies exhibit a substantially enhanced catalytic activity for the light-driven oxidation of iodide. Aggregates with the hexavalent cationic porphyrin diacids show up to 22 times higher catalytic activity than the corresponding aggregates under neutral conditions. The catalytic activity can be increased by increasing the valency of the porphyrin and by choice of the loading ratio. The structural investigation of the supramolecular catalysts took place via atomic force microscopy and small angle neutron scattering. Hence, a new facile concept for the design of efficient and tunable self-assembled photocatalysts is presented. Full article

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Open AccessArticle Evaluation of the Performance of Dual Polyelectrolyte Systems on the Re-Flocculation Ability of Calcium Carbonate Aggregates in Turbulent Environment

by Maria G. Rasteiro, Fernando A. Garcia, David Hunkeler and Ineide Pinheiro

Polymers 2016, 8(5), 174; doi:10.3390/polym8050174

Received: 17 January 2016 / Revised: 28 March 2016 / Accepted: 18 April 2016 / Published: 29 April 2016

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Abstract

Flocculation can be used in turbulent environments resulting in floc breakage due to shearing. The degree of re-flocculation relates directly to product quality and process efficiency. This study aimed at looking for alternatives to improve the re-flocculation ability of aggregates when polyelectrolytes (PEL)

[...] Read more.

Flocculation can be used in turbulent environments resulting in floc breakage due to shearing. The degree of re-flocculation relates directly to product quality and process efficiency. This study aimed at looking for alternatives to improve the re-flocculation ability of aggregates when polyelectrolytes (PEL) are used as flocculation agents. Moreover, because branched PEL have proved previously to lead to high flocculation efficiencies, the work presented focus on the improvement of the re-flocculation ability of branched PEL. Thus, a selection of branched polymers were used primarily as flocculation aid and after flocs break up a linear polymer was added to the system in order to improve re-flocculation. Different mixtures were tested with the objective to try to induce, during re-flocculation, complementary flocculation mechanisms, favoring the patching mechanism. Re-flocculation improved significantly with this strategy. Laser Diffraction Spectroscopy was used to monitor the flocculation and re-flocculation processes supplying information about the floc size and structure. Since inorganic materials, namely bentonite, have been widely used to improve the re-flocculation capacity of polyelectrolytes, the results of using dual polyelectrolyte systems were compared with the effect of adding bentonite to the system. Full article

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Open AccessArticle Thermodynamic Analysis of the Conformational Transition in Aqueous Solutions of Isotactic and Atactic Poly(Methacrylic Acid) and the Hydrophobic Effect

by Ksenija Kogej

Polymers 2016, 8(5), 168; doi:10.3390/polym8050168

Received: 25 January 2016 / Revised: 15 April 2016 / Accepted: 20 April 2016 / Published: 28 April 2016

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Abstract

The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid)

[...] Read more.

The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) (PMA), isotactic (iPMA) and atactic (aPMA), in water. These isomers are chemically equivalent and differ only in the arrangement of functional groups along the chain. A complete thermodynamic analysis of the transition of the PMA chains from the compact to the extended form (comprising the conformational transition) in water in the presence of three alkali chlorides is conducted by determining the free energy, enthalpy, and entropy changes of the process as a function of temperature, and therefrom also the heat capacity change. The heat capacity change of the transition is positive (+20 J/K mol) for aPMA and negative (−50 J/K mol) for iPMA. This result suggests a different affinity of PMA isomers for water. The conformational transition of iPMA is parallel to the transfer of polar solutes into water, whereas that of aPMA agrees with the transfer of nonpolar solutes into water. Full article

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Open AccessArticle Mesogenic Polyelectrolyte Gels Absorb Organic Solvents and Liquid Crystalline Molecules

by Yusuke Nishikori, Kazuya Iseda, Kenta Kokado and Kazuki Sada

Polymers 2016, 8(4), 148; doi:10.3390/polym8040148

Received: 28 January 2016 / Revised: 12 April 2016 / Accepted: 13 April 2016 / Published: 19 April 2016

Cited by 4 | PDF Full-text (1564 KB) | HTML Full-text | XML Full-text | Supplementary Files

Abstract

In this paper, mesogenic polyelectrolyte gels (MPEgels) tethering mesogenic groups on the side chains were synthesized from a mesogenic monomer and ionic monomer via a conventional radical polymerization process. The obtained MPEgels absorbed various organic solvents in a wide range of dielectric constants

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In this paper, mesogenic polyelectrolyte gels (MPEgels) tethering mesogenic groups on the side chains were synthesized from a mesogenic monomer and ionic monomer via a conventional radical polymerization process. The obtained MPEgels absorbed various organic solvents in a wide range of dielectric constants from chloroform (ε = 7.6) to DMSO (ε = 46.5). The electrostatic repulsion among the polymer chains and the osmotic pressure between the interior and exterior of the MPEgel is responsible for the high swelling ability, revealed by the common ion effect using tetra(n-hexyl)ammonium tetra(3,5-bis(trifluoromethyl)phenylborate (THATFPB). The obtained MPEgels could also absorb liquid crystalline molecules such as 4-cyano-4’-pentylbiphenyl (5CB), analogously caused by the above-mentioned polyelectrolyte characteristic. The MPEgels exhibited liquid crystal transition temperature (T_NI) on differential scanning calorimetry (DSC) measurement, and the increase of the ionic group content lowered T_NI. The MPEgels absorbing liquid crystalline molecules exhibited differing T_NI, dependent on the compatibility of the mesogenic group on the side chain to the liquid crystalline molecule. Full article

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Open AccessArticle Modification of Spherical Polyelectrolyte Brushes by Layer-by-Layer Self-Assembly as Observed by Small Angle X-ray Scattering

by Yuchuan Tian, Li Li, Haoya Han, Weihua Wang, Yunwei Wang, Zhishuang Ye and Xuhong Guo

Polymers 2016, 8(4), 145; doi:10.3390/polym8040145

Received: 31 January 2016 / Revised: 14 March 2016 / Accepted: 8 April 2016 / Published: 15 April 2016

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Abstract

Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the

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Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the zeta potential indicated the success of layer-by-layer (LBL) deposition. The change of the structure during the construction of multilayer modified SPBs was observed by small-angle X-ray scattering (SAXS). SAXS results indicated that some PAH chains were able to penetrate into the PAA brush for the PAA-PAH double-layer modified SPBs whereas part of the PAH moved towards the outer layer when the PAsp layer was loaded to form a PAA-PAH-PAsp triple-layer system. The multilayer modified SPBs were stable upon changing the pH (5 to 9) and ionic strength (1 to 100 mM). The triple-layer modified SPBs were more tolerated to high pH (even at 11) compared to the double-layer ones. SAXS is proved to be a powerful tool for studying the inner structure of multilayer modified SPBs, which can establish guidelines for the a range of potential applications of multilayer modified SPBs. Full article

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Open AccessReview Activated Charge-Reversal Polymeric Nano-System: The Promising Strategy in Drug Delivery for Cancer Therapy

by Yichen Hu, Xiao Gong, Jinming Zhang, Fengqian Chen, Chaomei Fu, Peng Li, Liang Zou and Gang Zhao

Polymers 2016, 8(4), 99; doi:10.3390/polym8040099

Received: 29 January 2016 / Revised: 10 March 2016 / Accepted: 14 March 2016 / Published: 5 April 2016

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Abstract

Various polymeric nanoparticles (NPs) with optimal size, tumor-targeting functionalization, or microenvironment sensitive characteristics have been designed to solve several limitations of conventional chemotherapy. Nano-sized polymeric drug carrier systems have remarkably great advantages in drug delivery and cancer therapy, which are still plagued with

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Various polymeric nanoparticles (NPs) with optimal size, tumor-targeting functionalization, or microenvironment sensitive characteristics have been designed to solve several limitations of conventional chemotherapy. Nano-sized polymeric drug carrier systems have remarkably great advantages in drug delivery and cancer therapy, which are still plagued with severe deficiencies, especially insufficient cellular uptake. Recently, surface charge of medical NPs has been demonstrated to play an important role in cellular uptake. NPs with positive charge show higher affinity to anionic cell membranes such that with more efficient cellular internalization, but otherwise cause severe aggregation and fast clearance in circulation. Thus, surface charge-reversal NPs, specifically activated at the tumor site, have shown to elegantly resolve the enhanced cellular uptake in cancer cells vs. non-specific protein adsorption dilemma. Herein, this review mainly focuses on the effect of tumor-site activated surface charge reversal NPs on tumor treatment, including the activated mechanisms and various applications in suppressing cancer cells, killing cancer stem cell and overcoming multidrug resistance, with the emphasis on recent research in these fields. With the comprehensive and in-depth understanding of the activated surface charge reversal NPs, this approach might arouse great interest of scientific research on enhanced efficient polymeric nano-carriers in cancer therapy. Full article

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Open AccessArticle The Effect of Temperature Treatment on the Structure of Polyelectrolyte Multilayers

by Maximilian Zerball, André Laschewsky, Ralf Köhler and Regine von Klitzing

Polymers 2016, 8(4), 120; doi:10.3390/polym8040120

Received: 29 January 2016 / Revised: 14 March 2016 / Accepted: 24 March 2016 / Published: 2 April 2016

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Abstract

The study addresses the effect of thermal treatment on the internal structure of polyelectrolyte multilayers (PEMs). In order to get insight into the internal structure of PEMs, Neutron Reflectometry (NR) was used. PEMs with a deuterated inner block towards the substrate and a

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The study addresses the effect of thermal treatment on the internal structure of polyelectrolyte multilayers (PEMs). In order to get insight into the internal structure of PEMs, Neutron Reflectometry (NR) was used. PEMs with a deuterated inner block towards the substrate and a non-deuterated outer block were prepared and measured in 1% RH and in D₂O before and after a thermal treatment. Complementarily, PEMs with the same number of layers but completely non-deuterated were investigated by ellipsometry. The analysis for the overall thickness (d), the average scattering length density (SLD) and the refractive index (n) indicate a degradation of the PEM. The loss in material is independent of the number of layers, i.e., only a constant part of the PEM is affected by degradation. The analysis of the internal structure revealed a more complex influence of thermal treatment on PEM structure. Only the outermost part of the PEM degenerates, while the inner part becomes denser during the thermal treatment. In addition, the swelling behavior of PEMs is influenced by the thermal treatment. The untreated PEM shows a well pronounced odd—even effect, i.e., PDADMAC-terminated PEMs take up more water than PSS-terminated PEMs. After the thermal treatment, the odd-even effect becomes much weaker. Full article

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Open AccessArticle Systematic Limitations in Concentration Analysis via Anomalous Small-Angle X-ray Scattering in the Small Structure Limit

by Guenter Goerigk, Sebastian Lages and Klaus Huber

Polymers 2016, 8(3), 85; doi:10.3390/polym8030085

Received: 10 February 2016 / Revised: 7 March 2016 / Accepted: 8 March 2016 / Published: 16 March 2016

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Abstract

Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb²⁺ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering

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Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb²⁺ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering contribution of the Pb²⁺ cations, and from subsequent analysis of the resonant-invariant, the amount of Pb²⁺ cations condensed onto the polyanions with respect to the total amount of Pb²⁺ cations in the solvent was estimated. In order to scrutinize systematic limitations in the determination of the chemical concentrations of resonant scattering counterions in the collapsed phase, Monte Carlo simulations have been performed. The simulations are based on structural confinements at variable size in the range of few nanometers, which represent the collapsed subdomains in the polyanions. These confinements were gradually filled to a high degree of the volume fraction with resonant scattering counterions giving access to a resonant-invariant at a variable degree of filling. The simulations revealed in the limit of small structures a significant underestimation of the true degree of filling of the collapsed subdomains when determining chemical concentrations of Pb²⁺ cations from the resonant invariant. Full article

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Open AccessArticle Polyelectrolyte Threading through a Nanopore

by Pai-Yi Hsiao

Polymers 2016, 8(3), 73; doi:10.3390/polym8030073

Received: 23 January 2016 / Revised: 23 February 2016 / Accepted: 24 February 2016 / Published: 3 March 2016

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Abstract

Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time ⟨ τ ⟩ is shown to follow a scaling law N^α, and the exponent α increases monotonically from

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Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time 〈 τ 〉 is shown to follow a scaling law N^α, and the exponent α increases monotonically from 1.16 (4) to 1.40 (3) with E. The result is double-checked by the calculation of mean square displacement of translocation coordinate, which asserts a scaling behavior t^β (for t near τ) with β complying with the relation αβ = 2. At a fixed chain length N, 〈τ〉 displayed a reciprocal scaling behavior E⁻¹ in the weak and also in the strong fields, connected by a transition E^−1.64(5) in the intermediate fields. The variations of the radius of gyration of chain and the positions of chain end are monitored during a translocation process; far-from-equilibrium behaviors are observed when the driving field is strong. A strong field can strip off the condensed ions on the chain when it passes the pore. The total charges of condensed ions are hence decreased. The studies for the probability and density distributions reveal that the monomers in the trans-region are gathered near the wall and form a pancake-like density profile with a hump cloud over it in the strong fields, due to fast translocation. Full article

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Open AccessFeature PaperArticle pH-Responsive Intra- and Inter-Molecularly Micelle Formation of Anionic Diblock Copolymer in Water

by Masanobu Mizusaki, Yoshihiko Shimada, Yotaro Morishima and Shin-ichi Yusa

Polymers 2016, 8(2), 56; doi:10.3390/polym8020056

Received: 25 January 2016 / Revised: 14 February 2016 / Accepted: 16 February 2016 / Published: 19 February 2016

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Abstract

Poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-block-poly(sodium11-(acrylamido)undecanoate) (PAMPS–PAaU) was synthesized via reversible addition-fragmentation chain transfer (RAFT)-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (M_w/M_n = 1.23). The pH-induced association behavior

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Poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-block-poly(sodium11-(acrylamido)undecanoate) (PAMPS–PAaU) was synthesized via reversible addition-fragmentation chain transfer (RAFT)-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (M_w/M_n = 1.23). The pH-induced association behavior of PAMPS–PAaU in 0.1 M NaCl aqueous solutions as a function of solution pH was investigated by ¹H NMR spin-spin relaxation time, dynamic light scattering (DLS), static light scattering (SLS), and fluorescence probe techniques. These results indicated that PAMPS–PAaU formed polymer micelles in 0.1 M NaCl aqueous solutions at pH < 9. At pH = 8–9, the polymer formed the micelles intramolecularly due to hydrophobic self-association of the PAaU block within the single polymer chain. On the other hand, at pH < 8, micellization occurred intermolecularly to form polymer micelles comprising hydrophobic PAaU cores and hydrophilic PAMPS shells. Full article

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Open AccessArticle Conformation and Rheological Properties of Calf-Thymus DNA in Solution

by Lourdes Mónica Bravo-Anaya, Marguerite Rinaudo and Félix Armando Soltero Martínez

Polymers 2016, 8(2), 51; doi:10.3390/polym8020051

Received: 7 January 2016 / Revised: 3 February 2016 / Accepted: 5 February 2016 / Published: 11 February 2016

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Abstract

Studies of DNA molecule behavior in aqueous solutions performed through different approaches allow assessment of the solute-solvent interactions and examination of the strong influence of conformation on its physicochemical properties, in the presence of different ionic species and ionic concentrations. Firstly, the conformational

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Studies of DNA molecule behavior in aqueous solutions performed through different approaches allow assessment of the solute-solvent interactions and examination of the strong influence of conformation on its physicochemical properties, in the presence of different ionic species and ionic concentrations. Firstly, the conformational behavior of calf-thymus DNA molecules in TE buffer solution is presented as a function of temperature. Secondly, their rheological behavior is discussed, as well as the evidence of the critical concentrations, i.e., the overlap and the entanglement concentrations (C* and C_e, respectively) from steady state flow and oscillatory dynamic shear experiments. The determination of the viscosity in the Newtonian plateau obtained from flow curves η ( ) allows estimation of the intrinsic viscosity and the specific viscosities at zero shear when C[η] < 40. At end, a generalized master curve is obtained from the variation of the specific viscosity as a function of the overlap parameter C[η]. The variation of the exponent s obtained from the power law η~ ^−s for both flow and dynamic results is discussed in terms of Graessley’s analysis. In the semi-dilute regime with entanglements, a dynamic master curve is obtained as a function of DNA concentration (C_DNA > 2.0 mg/mL) and temperature (10 °C < T < 40 °C). Full article

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2015

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Open AccessReview Recent Progress and Perspectives in the Electrokinetic Characterization of Polyelectrolyte Films

by Ralf Zimmermann, Carsten Werner and Jérôme F. L. Duval

Polymers 2016, 8(1), 7; doi:10.3390/polym8010007

Received: 2 December 2015 / Revised: 22 December 2015 / Accepted: 23 December 2015 / Published: 31 December 2015

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Abstract

The analysis of the charge, structure and molecular interactions of/within polymeric substrates defines an important analytical challenge in materials science. Accordingly, advanced electrokinetic methods and theories have been developed to investigate the charging mechanisms and structure of soft material coatings. In particular, there

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The analysis of the charge, structure and molecular interactions of/within polymeric substrates defines an important analytical challenge in materials science. Accordingly, advanced electrokinetic methods and theories have been developed to investigate the charging mechanisms and structure of soft material coatings. In particular, there has been significant progress in the quantitative interpretation of streaming current and surface conductivity data of polymeric films from the application of recent theories developed for the electrohydrodynamics of diffuse soft planar interfaces. Here, we review the theory and experimental strategies to analyze the interrelations of the charge and structure of polyelectrolyte layers supported by planar carriers under electrokinetic conditions. To illustrate the options arising from these developments, we discuss experimental and simulation data for plasma-immobilized poly(acrylic acid) films and for a polyelectrolyte bilayer consisting of poly(ethylene imine) and poly(acrylic acid). Finally, we briefly outline potential future developments in the field of the electrokinetics of polyelectrolyte layers. Full article

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Collection Editor Dr. Christine Wandrey Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC-GE, CH C1 392, station 6, CH-1015 Lausanne, Switzerland Website \| E-Mail Fax: +41 21 693 96 85 Interests: water-soluble polymers; polyelectrolytes; polyelectrolyte complexes; hydrogels; biomaterials; radical polymerization/copolymerization; characterization of charged macromolecule; analytical ultracentrifugation
Collection Editor Prof. Dr. Ruth Freitag Chair for Process Biotechnology, Faculty of Engineering Sciences, University of Bayreuth, 95440 Bayreuth, Germany Website \| E-Mail Fax: +49 921 55 7375 Interests: stimuli-responsive; materials; bioconjugates; synthetic biodelivery systems; bioseparation engineering; scaffolds for tissue engineering; encapsulation; monolithic stationary phases for chromatography and electrochromatography
Collection Editor Dr. Ulrich Scheler Leibniz-Institut für Polymerforschung Dresden e.V. Hohe Strasse 6, D-01069 Dresden, Germany Website \| E-Mail Fax: +49 351 4658 231 Interests: polyelectrolytes, polyelectrolyte complexes and polyelectrolyte multilayers, counterion condensation, complex polymer systems, NMR.