1
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Alziyadi MO, Denton AR. Osmotic swelling behavior of surface-charged ionic microgels. J Chem Phys 2023; 159:184901. [PMID: 37942869 DOI: 10.1063/5.0161027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 10/19/2023] [Indexed: 11/10/2023] Open
Abstract
In recent years, ionic microgels have garnered much attention due to their unique properties, especially their stimulus-sensitive swelling behavior. The tunable response of these soft, permeable, compressible, charged colloidal particles is increasingly attractive for applications in medicine and biotechnologies, such as controlled drug delivery, tissue engineering, and biosensing. The ability to model and predict variation of the osmotic pressure of a single microgel with respect to changes in particle properties and environmental conditions proves vital to such applications. In this work, we apply both nonlinear Poisson-Boltzmann theory and molecular dynamics simulation to ionic microgels (macroions) in the cell model to compute density profiles of microions (counterions, coions), single-microgel osmotic pressure, and equilibrium swelling ratios of spherical microgels whose fixed charge is confined to the macroion surface. The basis of our approach is an exact theorem that relates the electrostatic component of the osmotic pressure to the microion density profiles. Close agreement between theory and simulation serves as a consistency check to validate our approach. We predict that surface-charged microgels progressively deswell with increasing microgel concentration, starting well below close packing, and with increasing salt concentration, in qualitative agreement with experiments. Comparison with previous results for microgels with fixed charge uniformly distributed over their volume demonstrates that surface-charged microgels deswell more rapidly than volume-charged microgels. We conclude that swelling behavior of ionic microgels in solution is sensitive to the distribution of fixed charge within the polymer-network gel and strongly depends on bulk concentrations of both microgels and salt ions.
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Affiliation(s)
- Mohammed O Alziyadi
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
| | - Alan R Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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2
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Zhou B, Gasser U, Fernandez-Nieves A. Measuring the counterion cloud of soft microgels using SANS with contrast variation. Nat Commun 2023; 14:3827. [PMID: 37419879 DOI: 10.1038/s41467-023-39378-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 06/09/2023] [Indexed: 07/09/2023] Open
Abstract
The behavior of microgels and other soft, compressible colloids depends on particle concentration in ways that are absent in their hard-particulate counterparts. For instance, poly-N-isopropylacrylamide (pNIPAM) microgels can spontaneously deswell and reduce suspension polydispersity when concentrated enough. Despite the pNIPAM network in these microgels is neutral, the key to understanding this distinct behavior relies on the existence of peripheric charged groups, responsible for providing colloidal stability when deswollen, and the associated counterion cloud. When in close proximity, clouds of different particles overlap, effectively freeing the associated counterions, which are then able to exert an osmotic pressure that can potentially cause the microgels to decrease their size. Up to now, however, no direct measurement of such an ionic cloud exists, perhaps even also for hard colloids, where it is referred to as an electric double layer. Here, we use small-angle neutron scattering with contrast variation with different ions to isolate the change in the form factor directly related to the counterion cloud, and obtain its radius and width. Our results highlight that the modeling of microgel suspensions must unavoidably and explicitly consider the presence of this cloud, which exists for nearly all microgels synthesized today.
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Affiliation(s)
- Boyang Zhou
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Forschungsstrasse 111, 5232, Villigen, Switzerland
| | - Urs Gasser
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Forschungsstrasse 111, 5232, Villigen, Switzerland.
| | - Alberto Fernandez-Nieves
- Department of Condensed Matter Physics, University of Barcelona, Carrer de Martí i Franqués 1, Barcelona, 08028, Spain
- ICREA-Institucio Catalana de Recerca i Estudis Avançats, Barcelona, 08028, Spain
- Institute for Complex Systems (UBICS), University of Barcelona, Barcelona, 08028, Spain
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3
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Bergman MJ, Nöjd S, Mohanty PS, Boon N, Immink JN, Maris JJE, Stenhammar J, Schurtenberger P. On the role of softness in ionic microgel interactions. SOFT MATTER 2021; 17:10063-10072. [PMID: 34714903 PMCID: PMC8597585 DOI: 10.1039/d1sm01222c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/24/2021] [Indexed: 05/17/2023]
Abstract
Thermoresponsive microgels are a popular model system to study phase transitions in soft matter, because temperature directly controls their volume fraction. Ionic microgels are additionally pH-responsive and possess a rich phase diagram. Although effective interaction potentials between microgel particles have been proposed, these have never been fully tested, leading to a gap in our understanding of the link between single-particle and collective properties. To help resolve this gap, four sets of ionic microgels with varying crosslinker density were synthesised and characterised using light scattering techniques and confocal microscopy. The resultant structural and dynamical information was used to investigate how particle softness affects the phase behaviour of ionic microgels and to validate the proposed interaction potential. We find that the architecture of the microgel plays a marked role in its phase behaviour. Rather than the ionic charges, it is the dangling ends which drive phase transitions and interactions at low concentration. Comparison to theory underlines the need for a refined theoretical model which takes into consideration these close-contact interactions.
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Affiliation(s)
- Maxime J Bergman
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Sofi Nöjd
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Priti S Mohanty
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Niels Boon
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Jasper N Immink
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - J J Erik Maris
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Joakim Stenhammar
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Peter Schurtenberger
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
- Lund Institute for advanced Neutron and X-ray Science (LINXS), Lund University, Lund, Sweden
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4
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Aguirre-Manzo LA, González-Mozuelos P. A self-consistent Ornstein-Zernike jellium for highly charged colloids (microgels) in suspensions with added salt. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:275101. [PMID: 34047280 DOI: 10.1088/1361-648x/abfe95] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 05/06/2021] [Indexed: 06/12/2023]
Abstract
This work discusses a jellium scheme, built within the framework of the multicomponent Ornstein-Zernike (OZ) equation, which is capable of describing the collective structure of suspensions of highly charged colloids with added salt, even in the presence of finite-size multivalent microions. This approach uses a suitable approximation to decouple the microion-microion correlations from the macroion-microion profiles, which in combination with the methodology from the dressed ion theory (DIT) gives a full account of the electrostatic effective potential among the colloids. The main advantages of the present contribution reside in its ability to manage the short-range potentials and non-linear correlations among the microions, as well as its realistic characterization of the ionic clouds surrounding each macroion. The structure factors predicted by this jellium scheme are contrasted with previously reported experimental results for microgel suspensions with monovalent salts (2019Phys. Rev. E100032602), thus validating its high accuracy in these situations. The present theoretical analysis is then extended to microgel suspensions with multivalent salts, which reveals the prominent influence of the counterion valence on the makeup of the effective potentials. Although the induced differences may be difficult to identify through the mesoscopic structure, our results suggest that the microgel collapsing transition may be used to enhance these distinct effects, thus giving a feasible experimental probe for these phenomena.
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Affiliation(s)
- L A Aguirre-Manzo
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
| | - P González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
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5
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Aguirre-Manzo LA, González-Mozuelos P. Volume transition effects on the correlations and effective interactions among highly charged microgels. SOFT MATTER 2020; 16:5081-5093. [PMID: 32458939 DOI: 10.1039/d0sm00486c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Recent experimental studies have demonstrated the huge influence that the volume phase transition (VPT) has on the collective structure of highly charged thermo-responsive microgels in aqueous solution with low concentrations of added monovalent salt, thus opening a promising new route for controlling the overall properties of practical colloidal suspensions. We present here an analysis of this structure based on the effective electrostatic potential obtained with the exact methodology of the dressed ion theory (DIT). Starting with a description at the primitive model level, we determine the correlations among the components of our model system (macroions plus monovalent anions and cations) by utilizing the two-density integral equation theory, thus allowing us to consider realistic values for the microgel charges. The resulting microgel structure factors show a good agreement with the reported light scattering measurements, whereas the microscopic pair distributions reveal that in this regime the shrunken states promote an enhanced counterion absorption into the microgels. This packing of counterions inside the microgels induces strongly non-linear correlations among the microions, and in turn provokes a substantial weakening of the microgel-microgel correlations. The ensuing effective interactions are then obtained by contracting the description to the level in which only the macroions are present. We find not only that the magnitude and reach of the corresponding pair potentials are markedly inhibited in the shrunken states, but also that their general form diverges from the conventional screened Coulomb shape. This makes it necessary to rethink the concepts of effective charge and screening length.
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Affiliation(s)
- L A Aguirre-Manzo
- Departamento de Física, Cinvestav del I. P. N., Av., Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico.
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6
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Moncho-Jordá A, Quesada-Pérez M. Crossover of the effective charge in ionic thermoresponsive hydrogel particles. Phys Rev E 2019; 100:050602. [PMID: 31869873 DOI: 10.1103/physreve.100.050602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Indexed: 06/10/2023]
Abstract
We use a generalized nonlinear Poisson-Boltzmann cell model that includes excluded-volume effects to investigate whether the effective charge (Z_{eff}) of charged thermosensitive hydrogel particles increases or decreases upon the hydrogel thermal collapse. We find the existence of a crossover charge, Z^{*}, that separates two regimes. For hydrogel bare charges below Z^{*} the system shows a behavior consistent with theories based on linear approximations, i.e., Z_{eff} increases in the collapsed state. However, for bare charges above Z^{*}, the system enters an anomalous regime, in which Z_{eff} decreases in the collapsed state. We show that diluted hydrogel suspensions at low ionic strength are more likely to follow the anomalous behavior. Our theory provides a full physical justification for the controversial theoretical and experimental results reported in this regard, and describes how the interplay between electrostatic, excluded-volume and entropic effects affects this crossover.
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Affiliation(s)
- A Moncho-Jordá
- Departamento de Física Aplicada, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
- Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - M Quesada-Pérez
- Departamento de Física, Escuela Politécnica Superior de Linares, Universidad de Jaén, 23700 Linares, Jaén, Spain
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7
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Del Monte G, Ninarello A, Camerin F, Rovigatti L, Gnan N, Zaccarelli E. Numerical insights on ionic microgels: structure and swelling behaviour. SOFT MATTER 2019; 15:8113-8128. [PMID: 31589214 DOI: 10.1039/c9sm01253b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recent progress has been made in the numerical modelling of neutral microgel particles with a realistic, disordered structure. In this work we extend this approach to the case of co-polymerised microgels where a thermoresponsive polymer is mixed with acidic groups. We compare the cases where counterions directly interact with microgel charges or are modelled implicitly through a Debye-Hückel description. We do so by performing extensive numerical simulations of single microgels across the volume phase transition (VPT) varying the temperature and the fraction of charged monomers. We find that the presence of charges considerably alters the microgel structure, quantified by the monomer density profiles and by the form factors of the microgels, particularly close to the VPT. We observe significant deviations between the implicit and explicit models, with the latter comparing more favourably to available experiments. In particular, we observe a shift of the VPT temperature to larger values as the amount of charged monomers increases. We also find that below the VPT the microgel-counterion complex is almost neutral, while it develops a net charge above the VPT. Interestingly, under these conditions the collapsed microgel still retains a large amount of counterions inside its structure. Since these interesting features cannot be captured by the implicit model, our results show that it is crucial to explicitly include the counterions in order to realistically model ionic thermoresponsive microgels.
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Affiliation(s)
- Giovanni Del Monte
- Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Center for Life NanoScience, Istituto Italiano di Tecnologia, Rome, Italy
| | - Andrea Ninarello
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Fabrizio Camerin
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Department of Basic and Applied Sciences for Engineering, Sapienza University of Rome, via A. Scarpa 14, 00161 Rome, Italy
| | - Lorenzo Rovigatti
- Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Nicoletta Gnan
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
| | - Emanuela Zaccarelli
- CNR-ISC, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy. and Physics Department, Sapienza University of Rome, Piazzale A. Moro 2, 00185 Rome, Italy.
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8
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Denton AR, Alziyadi MO. Osmotic pressure of permeable ionic microgels: Poisson-Boltzmann theory and exact statistical mechanical relations in the cell model. J Chem Phys 2019; 151:074903. [DOI: 10.1063/1.5091115] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Alan R. Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
| | - Mohammed O. Alziyadi
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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9
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Moncho-Jordá A, Germán-Bellod A, Angioletti-Uberti S, Adroher-Benítez I, Dzubiella J. Nonequilibrium Uptake Kinetics of Molecular Cargo into Hollow Hydrogels Tuned by Electrosteric Interactions. ACS NANO 2019; 13:1603-1616. [PMID: 30649858 DOI: 10.1021/acsnano.8b07609] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Hollow hydrogels represent excellent nano- and microcarriers due to their ability to encapsulate and release large amounts of cargo molecules (cosolutes) such as reactants, drugs, and proteins. In this work, we use a combination of a phenomenological effective cosolute-hydrogel interaction potential and dynamic density functional theory to investigate the full nonequilibrium encapsulation kinetics of charged and dipolar cosolutes by an isolated charged hollow hydrogel immersed in a 1:1 electrolyte aqueous solution. Our analysis covers a broad spectrum of cosolute valences ( zc) and electric dipole moments (μc), as well as hydrogel swelling states and hydrogel charge densities. Our calculations show that, close to the collapsed state, the polar cosolutes are predominantly precluded and the encapsulation process is strongly hindered by the excluded-volume interaction exerted by the polymer network. Different equilibrium and kinetic sorption regimes (interface versus interior) are found depending on the value and sign of zc and the value of μc. For cosolutes of the same sign of charge as the gel, the superposition of steric and electrostatic repulsion leads to an "interaction-controlled" encapsulation process, in which the characteristic time to fill the empty core of the hydrogel grows exponentially with zc. On the other hand, for cosolutes oppositely charged to the gel, we find a "diffusion-controlled" kinetic regime, where cosolutes tend to rapidly absorb into the hydrogel membrane and the encapsulation rate depends only on the cosolute diffusion time across the membrane. Finally, we find that increasing μc promotes the appearance of metastable and stable surface adsorption states. For large enough μc, the kinetics enters an "adsorption-hindered diffusion", where the enhanced surface adsorption imposes a barrier and slows down the uptake. Our study represents the first attempt to systematically describe how the swelling state of the hydrogel and other leading physical interaction parameters determine the encapsulation kinetics and the final equilibrium distribution of polar molecular cargo.
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Affiliation(s)
- Arturo Moncho-Jordá
- Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada , Avenida Fuentenueva S/N , 18071 Granada , Spain
- Departamento de Física Aplicada, Facultad de Ciencias , Universidad de Granada , Avenida Fuentenueva S/N , 18071 Granada , Spain
| | - Alicia Germán-Bellod
- Departamento de Física Aplicada, Facultad de Ciencias , Universidad de Granada , Avenida Fuentenueva S/N , 18071 Granada , Spain
| | | | | | - Joachim Dzubiella
- Research Group for Simulations of Energy Materials , Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner-Platz 1 , D-14109 Berlin , Germany
- Physikalisches Institut, Albert-Ludwigs-Universität Freiburg , Hermann-Herder Straße 3 , D-79104 Freiburg , Germany
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10
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Landsgesell J, Nová L, Rud O, Uhlík F, Sean D, Hebbeker P, Holm C, Košovan P. Simulations of ionization equilibria in weak polyelectrolyte solutions and gels. SOFT MATTER 2019; 15:1155-1185. [PMID: 30706070 DOI: 10.1039/c8sm02085j] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
This article recapitulates the state of the art regarding simulations of ionization equilibria of weak polyelectrolyte solutions and gels. We start out by reviewing the essential thermodynamics of ionization and show how the weak polyelectrolyte ionization differs from the ionization of simple weak acids and bases. Next, we describe simulation methods for ionization reactions, focusing on two methods: the constant-pH ensemble and the reaction ensemble. After discussing the advantages and limitations of both methods, we review the existing simulation literature. We discuss coarse-grained simulations of weak polyelectrolytes with respect to ionization equilibria, conformational properties, and the effects of salt, both in good and poor solvent conditions. This is followed by a discussion of branched star-like weak polyelectrolytes and weak polyelectrolyte gels. At the end we touch upon the interactions of weak polyelectrolytes with other polymers, surfaces, nanoparticles and proteins. Although proteins are an important class of weak polyelectrolytes, we explicitly exclude simulations of protein ionization equilibria, unless they involve protein-polyelectrolyte interactions. Finally, we try to identify gaps and open problems in the existing simulation literature, and propose challenges for future development.
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Affiliation(s)
- Jonas Landsgesell
- Institute for Computational Physics, University of Stuttgart, Allmandring 3, Stuttgart, Germany.
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11
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Chudoba R, Heyda J, Dzubiella J. Tuning the collapse transition of weakly charged polymers by ion-specific screening and adsorption. SOFT MATTER 2018; 14:9631-9642. [PMID: 30457144 DOI: 10.1039/c8sm01646a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The experimentally observed swelling and collapse response of weakly charged polymers to the addition of specific salts displays quite convoluted behavior that is not easy to categorize. Here we use a minimalistic implicit-solvent/explicit-salt simulation model with a focus on ion-specific interactions between ions and a single weakly charged polyelectrolyte to qualitatively explain the observed effects. In particular, we demonstrate ion-specific screening and bridging effects cause collapse at low salt concentrations whereas the same strong ion-specific direct interactions drive re-entrant swelling at high concentrations. Consistently with experiments, a distinct salt concentration at which the salting-out power of anions inverts from the reverse to direct Hofmeister series is observed. At this so called isospheric point, the ion-specific effects vanish. Furthermore, with additional simplifying assumptions, an ion-specific mean-field model is developed for the collapse transition which quantitatively agrees with the simulations. Our work demonstrates the sensitivity of the structural behavior of charged polymers to the addition of specific salt beyond simple screening and shall be useful for further guidance of experiments.
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Affiliation(s)
- Richard Chudoba
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin, Germany.
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12
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Adroher-Benítez I, Moncho-Jordá A, Odriozola G. Conformation change of an isotactic poly (N-isopropylacrylamide) membrane: Molecular dynamics. J Chem Phys 2018; 146:194905. [PMID: 28527458 DOI: 10.1063/1.4983525] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, isotactic Poly (N-Isopropylacrylamide)-PNIPAM-in neat water and in electrolyte solutions is studied by means of molecular dynamics simulations. This is done for an infinitely diluted oligomer and for an assembly of several PNIPAM chains arranged into a planar membrane configuration with a core-shell morphology. We employed two different force fields, AMBER (assisted model building with energy refinement) and OPLS-AA (all atom - optimized potentials for liquid simulations) in combination with extended simple point charge water. Despite the more water insoluble character of isotactic oligomers, our results support the existence of a coil to globule transition for the isolated 30-mer. This may imply the existence of an oligomer rich phase of coil-like structures in equilibrium with a water rich phase for temperatures close but below the coil to globule transition temperature, TΘ. However, the obtained coil structure is much more compact than that corresponding to the syndiotactic chain. Our estimations of TΘ are (308±5) K and (303±5) K for AMBER and OPLS-AA, respectively. The membrane configuration allows one to include chain-chain interactions, to follow density profiles of water, polymer, and solutes, and accessing the membrane-water interface tension. Results show gradual shrinking and swelling of the membrane by switching temperature above and below TΘ, as well as the increase and decrease of the membrane-water interface tension. Finally, concentration profiles for 1M NaCl and 1M NaI electrolytes are shown, depicting a strong salting-out effect for NaCl and a much lighter effect for NaI, in good qualitative agreement with experiments.
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Affiliation(s)
- Irene Adroher-Benítez
- Departamento de Física Aplicada e Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - Arturo Moncho-Jordá
- Departamento de Física Aplicada e Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - Gerardo Odriozola
- Área de Física de Procesos Irreversibles, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana, Ave. San Pablo 180 Col., Reynosa-Tamaulipas, 02200 Ciudad de México, Mexico
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13
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Nöjd S, Holmqvist P, Boon N, Obiols-Rabasa M, Mohanty PS, Schweins R, Schurtenberger P. Deswelling behaviour of ionic microgel particles from low to ultra-high densities. SOFT MATTER 2018; 14:4150-4159. [PMID: 29744516 DOI: 10.1039/c8sm00390d] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The swelling of ionic microgel particles is investigated at a wide range of concentrations using a combination of light, X-ray and neutron scattering techniques. We employ a zero-average contrast approach for small-angle neutron scattering experiments, which enables a direct determination of the form factor at high concentrations. The observed particle size initially decreases strongly with the particle concentration in the dilute regime but approaches a constant value at intermediate concentrations. This is followed by a further deswelling at high concentrations above particle overlap. Theory and experiments point at a pivotal contribution of dangling polymer ends to the strong variation in size of ionic microgels, which presents itself mainly through the hydrodynamics properties of the system.
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Affiliation(s)
- Sofi Nöjd
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Peter Holmqvist
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Niels Boon
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Marc Obiols-Rabasa
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
| | - Priti S Mohanty
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden. and School of Chemical Technology, Kalinga Institute of Industrial Technology (KIIT), Bhubaneswar, India
| | - Ralf Schweins
- Large Scale Structures Group, Institut Laue-Langevin, Grenoble, 38042, France
| | - Peter Schurtenberger
- Division of Physical Chemistry, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
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14
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Maki Y, Sugawara K, Nagai D. Temperature Dependence of Electrophoretic Mobility and Hydrodynamic Radius of Microgels of Poly( N-isopropylacrylamide). Gels 2018; 4:E37. [PMID: 30674813 PMCID: PMC6209266 DOI: 10.3390/gels4020037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 04/16/2018] [Accepted: 04/19/2018] [Indexed: 11/22/2022] Open
Abstract
Electrostatic interactions in charged microgels, which are dominated by the microgel net charge, play a crucial role in colloidal stabilization and loading of small, charged molecules. In this study, the temperature dependences of electrophoretic mobility μ and hydrodynamic radius Rh were measured for a slightly ionized poly(N-isopropylacrylamide) (PNIPA) microgel in a dilute suspension. A decrease in Rh was observed in the temperature range between 30 °C and 35 °C, corresponding to the lower critical solution temperature of PNIPA, and an increase in |μ| was observed in a higher temperature range between 34 °C and 37 °C. The analysis based on electrophoresis theory for spherical polyelectrolytes indicated that the net charge of the microgel decreased as the microgel was deswollen.
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Affiliation(s)
- Yasuyuki Maki
- Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395, Japan.
| | - Kentaro Sugawara
- Division of Molecular Science, Faculty of Science and Technology, Gunma University, Kiryu 376-8515, Japan.
| | - Daisuke Nagai
- Division of Molecular Science, Faculty of Science and Technology, Gunma University, Kiryu 376-8515, Japan.
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15
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Pérez-Mas L, Martín-Molina A, Quesada-Pérez M, Moncho-Jordá A. Maximizing the absorption of small cosolutes inside neutral hydrogels: steric exclusion versus hydrophobic adhesion. Phys Chem Chem Phys 2018; 20:2814-2825. [PMID: 29323684 DOI: 10.1039/c7cp07679g] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In this work the equilibrium absorption of nanometric cosolutes (which could represent drugs, reactants, small globular proteins and other kind of biomacromolecules) inside neutral hydrogels is studied. We specially focus on exploring, for different swelling states, the competition between the steric exclusion induced by the cross-linked polymer network constituting the hydrogel, and the solvent-induced short-range hydrophobic attraction between the polymer chains and the cosolute particle. For this purpose, the cosolute partition coefficient is calculated by means of coarse-grained grand canonical Monte Carlo simulations, and the results are compared to theoretical predictions based on the calculation of the excluded and binding volume around the polymer chains. For small hydrophobic attractions or large cosolute sizes, the steric repulsion dominates, and the partition coefficient decreases monotonically with the polymer volume fraction, ϕm. However, for large enough hydrophobic attraction strength, the interplay between hydrophobic adhesion and the steric exclusion leads to a maximum in the partition coefficient at certain intermediate polymer density. Good qualitative and quantitative agreement is achieved between simulation results and theoretical predictions in the limit of small ϕm, pointing out the importance of geometrical aspects of the cross-linked polymer network, even for hydrogels in the swollen state. In addition, the theory is able to predict analytically the onset of the maximum formation in terms of the details of the cosolute-monomer pair interaction, in good agreement with simulations too. Finally, the effect of the many-body attractions between the cosolute and multiple polymer chains is quantified. The results clearly show that these many-body attractions play a very relevant role determining the cosolute binding, enhancing its absorption in more than one order of magnitude.
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Affiliation(s)
- Luis Pérez-Mas
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Avenida Fuentenueva S/N, 18001 Granada, Spain
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16
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Zhang Y, Du W, Smuda K, Georgieva R, Bäumler H, Gao C. Inflammatory activation of human serum albumin- or ovalbumin-modified chitosan particles to macrophages and their immune response in human whole blood. J Mater Chem B 2018; 6:3096-3106. [DOI: 10.1039/c7tb03096g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chitosan particles modified with different albumins cause immune response in human whole blood via platelet activation and phagocytosis.
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Affiliation(s)
- Yixian Zhang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering, Zhejiang University
- Hangzhou 310027
- China
| | - Wang Du
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering, Zhejiang University
- Hangzhou 310027
- China
| | - Kathrin Smuda
- Institute of Transfusion Medicine and Berlin-Brandenburg Center for Regenerative Therapies
- Charité-Universitätsmedizin Berlin
- 10117 Berlin
- Germany
| | - Radostina Georgieva
- Institute of Transfusion Medicine and Berlin-Brandenburg Center for Regenerative Therapies
- Charité-Universitätsmedizin Berlin
- 10117 Berlin
- Germany
| | - Hans Bäumler
- Institute of Transfusion Medicine and Berlin-Brandenburg Center for Regenerative Therapies
- Charité-Universitätsmedizin Berlin
- 10117 Berlin
- Germany
| | - Changyou Gao
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering, Zhejiang University
- Hangzhou 310027
- China
- Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine
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17
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Kim WK, Moncho-Jordá A, Roa R, Kanduč M, Dzubiella J. Cosolute Partitioning in Polymer Networks: Effects of Flexibility and Volume Transitions. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b01206] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Won Kyu Kim
- Institut
für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Arturo Moncho-Jordá
- Departamento
de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Avenida Fuente Nueva, 18071 Granada, Spain
- Instituto
Carlos I de Física Teórica y Computacional, Facultad
de Ciencias, Universidad de Granada, Avenida Fuente Nueva S/N, 18071 Granada, Spain
| | - Rafael Roa
- Institut
für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Matej Kanduč
- Institut
für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Joachim Dzubiella
- Institut
für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Institut
für Physik, Humboldt-Universität zu Berlin, Newtonstr.
15, 12489 Berlin, Germany
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18
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Adroher-Benítez I, Martín-Molina A, Ahualli S, Quesada-Pérez M, Odriozola G, Moncho-Jordá A. Competition between excluded-volume and electrostatic interactions for nanogel swelling: effects of the counterion valence and nanogel charge. Phys Chem Chem Phys 2017; 19:6838-6848. [DOI: 10.1039/c6cp08683g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The equilibrium distribution of monovalent and trivalent ions within a thermo-responsive charged nanogel is investigated using Monte Carlo simulations and Ornstein–Zernike equations.
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Affiliation(s)
- Irene Adroher-Benítez
- Departamento de Física Aplicada
- Facultad de Ciencias
- Universidad de Granada
- 18001 Granada
- Spain
| | - Alberto Martín-Molina
- Departamento de Física Aplicada
- Facultad de Ciencias
- Universidad de Granada
- 18001 Granada
- Spain
| | - Silvia Ahualli
- Departamento de Física Aplicada
- Facultad de Ciencias
- Universidad de Granada
- 18001 Granada
- Spain
| | - Manuel Quesada-Pérez
- Departamento de Física
- Escuela Politécnica Superior de Linares
- Universidad de Jaeén
- 23700 Linares
- Spain
| | - Gerardo Odriozola
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana
- 02200 México CD de México
- Mexico
| | - Arturo Moncho-Jordá
- Departamento de Física Aplicada
- Facultad de Ciencias
- Universidad de Granada
- 18001 Granada
- Spain
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19
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Maldonado-Valderrama J, Del Castillo-Santaella T, Adroher-Benítez I, Moncho-Jordá A, Martín-Molina A. Thermoresponsive microgels at the air-water interface: the impact of the swelling state on interfacial conformation. SOFT MATTER 2016; 13:230-238. [PMID: 27427242 DOI: 10.1039/c6sm01375a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poly(N-vinylcaprolactam) (PVCL) is a new temperature-responsive type of polymer microgel with improved biocompatibility as compared to more commonly used poly(N-isopropylacrylamide) (PNIPAM). Both polymers swell at low temperatures and collapse at high ones, showing a volume phase transition temperature (VPTT) around the physiological temperature. Exploring the interfacial characteristics of thermoresponsive microgels is important due to their potential application in emulsion based systems with tailored stabilities and controlled degradation profiles. In this work, we study the properties of charged PVCL particles at the air-water interface by a combination of adsorption, dilatational rheology and Langmuir monolayers. Although PVCL particles adsorb spontaneously at the air-water interface in both, swollen and collapsed conformations, the interfacial properties show significant differences depending on the swelling state. In particular, the total amount of adsorbed microgels and the rigidity of the monolayer increase as the temperature increases above the VPTT, which is connected to the more compact morphology of the microgels in this regime. Dilatational rheology data show the formation of a very loose adsorbed layer with low cohesivity. In addition, collapsed microgels yield a continuous increase of the surface pressure, whereas swollen microgels show a phase transition at intermediate compressions caused by the deformation of the loose external polymer shell of the particles. We also provide a qualitative interpretation for the surface pressure behavior in terms of microgel-microgel effective pair potentials, and correlate our experimental findings to recent rescaling models that take into account the importance of the internal polymer degrees of freedom in the rearrangement of the conformation of the microgel particles at the interface.
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Affiliation(s)
- J Maldonado-Valderrama
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - T Del Castillo-Santaella
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - I Adroher-Benítez
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - A Moncho-Jordá
- Departamento de Física Aplicada and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain.
| | - A Martín-Molina
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
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20
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Braibanti M, Haro-Pérez C, Quesada-Pérez M, Rojas-Ochoa LF, Trappe V. Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels. Phys Rev E 2016; 94:032601. [PMID: 27739781 DOI: 10.1103/physreve.94.032601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Indexed: 06/06/2023]
Abstract
We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility experiments are consistent with those obtained in Poisson-Boltzmann cell model calculations, effectively indicating that upon shrinking the number of counterions entrapped within the microgels increases. Remarkably, this behavior shows that the electrostatic energy per particle remains constant upon swelling or deswelling the microgel, resulting in a square root dependence of the net charge on the particle radius.
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Affiliation(s)
- M Braibanti
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
| | - C Haro-Pérez
- Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, Avenida San Pablo 180, 02200 Ciudad de México, Mexico
| | - M Quesada-Pérez
- Departamento de Física, Universidad de Jaén, Escuela Politécnica Superior de Linares, 23700 Linares, Spain
| | - L F Rojas-Ochoa
- Departamento de Física, CINVESTAV-IPN, Avenida Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico
| | - V Trappe
- Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
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21
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Adroher-Benítez I, Ahualli S, Bastos-González D, Ramos J, Forcada J, Moncho-Jordá A. The effect of electrosteric interactions on the effective charge of thermoresponsive ionic microgels: Theory and experiments. ACTA ACUST UNITED AC 2016. [DOI: 10.1002/polb.24109] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Irene Adroher-Benítez
- Departamento de Física Aplicada, Facultad de Ciencias; Universidad de Granada; Campus Fuentenueva S/N Granada 18071 Spain
| | - Silvia Ahualli
- Departamento de Física Aplicada, Facultad de Ciencias; Universidad de Granada; Campus Fuentenueva S/N Granada 18071 Spain
| | - Delfi Bastos-González
- Departamento de Física Aplicada, Facultad de Ciencias; Universidad de Granada; Campus Fuentenueva S/N Granada 18071 Spain
| | - José Ramos
- Grupo de Ingeniería Química, Facultad de Ciencias Químicas; Universidad del País Vasco/EHU; San Sebastián 20080 Spain
| | - Jacqueline Forcada
- Grupo de Ingeniería Química, Facultad de Ciencias Químicas; Universidad del País Vasco/EHU; San Sebastián 20080 Spain
| | - Arturo Moncho-Jordá
- Departamento de Física Aplicada and Instituto Carlos I de Física Teórica y Computacional; Universidad de Granada; Campus Fuentenueva S/N Granada 18071 Spain
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22
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González-Mozuelos P. Effective electrostatic interactions among charged thermo-responsive microgels immersed in a simple electrolyte. J Chem Phys 2016; 144:054902. [DOI: 10.1063/1.4941324] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- P. González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Mexico, Distrito Federal, C. P. 07360, Mexico
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23
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Moncho-Jordá A, Dzubiella J. Swelling of ionic microgel particles in the presence of excluded-volume interactions: a density functional approach. Phys Chem Chem Phys 2016; 18:5372-85. [DOI: 10.1039/c5cp07794j] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this work a new density functional theory framework is developed to predict the salt-concentration dependent swelling state of charged microgels and the local concentration of monovalent ions inside and outside the microgel.
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Affiliation(s)
- Arturo Moncho-Jordá
- Departamento de Física Aplicada
- Facultad de Ciencias
- Universidad de Granada
- 18071 Granada
- Spain
| | - Joachim Dzubiella
- Institut für Weiche Materie und Funktionale Materialien
- Helmholtz-Zentrum Berlin
- 14109 Berlin
- Germany
- Institut für Physik, Humboldt-Universität zu Berlin
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24
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Adroher-Benítez I, Ahualli S, Martín-Molina A, Quesada-Pérez M, Moncho-Jordá A. Role of Steric Interactions on the Ionic Permeation Inside Charged Microgels: Theory and Simulations. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00356] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Irene Adroher-Benítez
- Departamento
de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - Silvia Ahualli
- Departamento
de Física, Escuela Politécnica Superior de Linares, Universidad de Jaén, 23700 Linares, Jaén, Spain
| | - Alberto Martín-Molina
- Departamento
de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
| | - Manuel Quesada-Pérez
- Departamento
de Física, Escuela Politécnica Superior de Linares, Universidad de Jaén, 23700 Linares, Jaén, Spain
| | - Arturo Moncho-Jordá
- Departamento
de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain
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25
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Affiliation(s)
- Thiago Colla
- Faculty of Physics, University of Vienna , Boltzmanngasse 5, A-1090 Vienna, Austria
| | - Christos N. Likos
- Faculty of Physics, University of Vienna , Boltzmanngasse 5, A-1090 Vienna, Austria
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26
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Callejas-Fernández J, Ramos J, Forcada J, Moncho-Jordá A. On the scattered light by dilute aqueous dispersions of nanogel particles. J Colloid Interface Sci 2015; 450:310-315. [PMID: 25837408 DOI: 10.1016/j.jcis.2015.03.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 02/12/2015] [Accepted: 03/13/2015] [Indexed: 11/17/2022]
Abstract
This work deals with the scattered light by nanoparticles formed by a temperature sensitive polymer networks, namely nanogel particles. The scattered light is measured as a function of the scattering angle at temperatures below and above the volume phase transition temperature (VPTT) of nanogel particles. Our experimental results indicate that nanogel particles have a core-shell structure, formed by a uniform highly cross-linked core surrounded by a fuzzy shell where the polymer density decays to zero gradually for swollen configurations and sharply for shrunken states. The theoretical fitting of the experimental curves shows that the scattered light at low angle obeys a decreasing power law with the scattering vector, q(-α). The value of exponent α provides information about the radial dependence of the polymer density at the external shell of the particles for swollen nanogels, and about the degree of roughness of the surface for the case of shrunken nanogels. On the one hand, at low temperatures (below the VPPT), the nanogel particle is in the swollen state and the light scattering data show that its shell structure follows a fractal behaviour, with a polymer density that decays as r(α-3), where r is the distance to the particle centre. On the other hand, above the VPPT the results indicate that nanogel collapses into a core of uniform polymer density and a rough shell, with a fractal surface dimension of 2.5.
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Affiliation(s)
- J Callejas-Fernández
- Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain.
| | - J Ramos
- Department of Materials, Department of Bioengineering, and the Institute for Biomedical Engineering, Imperial College London, London SW7 2AZ, United Kingdom; POLYMAT, Bionanoparticles Group, Departamento de Química Aplicada, UFI/56, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 Donostia-San Sebastián, Spain
| | - J Forcada
- POLYMAT, Bionanoparticles Group, Departamento de Química Aplicada, UFI/56, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 Donostia-San Sebastián, Spain
| | - A Moncho-Jordá
- Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain
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27
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Barrios-Contreras EA, González-Tovar E, Guerrero-García GI. The dominance of small ions in the electric double layer of size- and charge-asymmetric electrolytes: a mean-field study on the charge reversal and surface charge amplification. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1018853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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28
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Colla T, Likos CN, Levin Y. Equilibrium properties of charged microgels: A Poisson-Boltzmann-Flory approach. J Chem Phys 2014; 141:234902. [DOI: 10.1063/1.4903746] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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29
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Moncho-Jordá A, Adroher-Benítez I. Ion permeation inside microgel particles induced by specific interactions: from charge inversion to overcharging. SOFT MATTER 2014; 10:5810-5823. [PMID: 24974885 DOI: 10.1039/c4sm00243a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this work we have performed a theoretical study of a system formed by ionic microgels in the presence of monovalent salt with the help of Ornstein-Zernike integral equations within the hypernetted-chain (HNC) approximation. We focus in particular on analysing the role that the short-range specific interactions between the polymer fibres of the microgel and the incoming ions have on the equilibrium ion distribution inside and outside the microgel. For this purpose, a theoretical model based on the equilibrium partitioning effect is developed to determine the interaction between the microgel particle and a single ion. The results indicate that when counterions are specifically attracted to the polymer fibres of the microgel, an enhanced counterion accumulation occurs that induces the charge inversion of the microgel and a strong increase of the microgel net charge (or overcharging). In the case of coions, the specific attraction is also able to provoke the coion adsorption even though they are electrostatically repelled, and so increasing the microgel charge (true overcharging). Moreover, we show that ion adsorption onto the microgel particle is very different in swollen and shrunken states due to the competition between specific attraction and steric repulsion. In particular, ion adsorption occurs preferentially in the internal core of the particle for swollen states, whereas it is mainly concentrated in the external shell for de-swollen configurations. Finally, we observe the existence of a critical salt concentration, where the net charge of the microgels vanishes; above this inversion point the net charge of the microgels increases again, thus leading to reentrant stability of microgel suspensions.
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Affiliation(s)
- A Moncho-Jordá
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain.
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30
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Quesada-Pérez M, Adroher-Benítez I, Maroto-Centeno JA. Size-exclusion partitioning of neutral solutes in crosslinked polymer networks: A Monte Carlo simulation study. J Chem Phys 2014; 140:204910. [DOI: 10.1063/1.4879215] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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