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Gresham IJ, Johnson EC, Robertson H, Willott JD, Webber GB, Wanless EJ, Nelson ARJ, Prescott SW. Comparing polymer-surfactant complexes to polyelectrolytes. J Colloid Interface Sci 2024; 655:262-272. [PMID: 37944374 DOI: 10.1016/j.jcis.2023.10.101] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/12/2023] [Accepted: 10/19/2023] [Indexed: 11/12/2023]
Abstract
HYPOTHESIS Understanding the complex interactions between polymers and surfactants is required to optimise commercially relevant systems such as paint, toothpaste and detergent. Neutral polymers complex with surfactants, forming 'pearl necklace' structures that are often conceptualised as pseudo-polyelectrolytes. Here we pose two questions to test the limits of this analogy: Firstly, in the presence of salt, do these polymer-surfactant systems behave like polyelectrolytes? Secondly, do polymer-surfactant complexes resist geometric confinement like polyelectrolytes? EXPERIMENTS We test the limits of the pseudo-polyelectrolyte analogy through studying a poly(N-isopropylacrylamide) (PNIPAM) brush in the presence of sodium dodecylsulfate (SDS). Brushes are ideal for interrogating pseudo-polyelectrolytes, as neutral and polyelectrolyte brushes exhibit distinct and well understood behaviours. Spectroscopic ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and neutron reflectometry (NR) were used to monitor the behaviour and structure of the PNIPAM-SDS system as a function of NaCl concentration. The ability of the PNIPAM-SDS complex to resist geometric confinement was probed with NR. FINDINGS At a fixed SDS concentration below the zero-salt CMC, increasing NaCl concentration <100 mM promoted brush swelling due to an increase in osmotic pressure, not dissimilar to a weak polyelectrolyte. At these salt concentrations, the swelling of the brush could be described by a single parameter: the effective CMC. However, at high NaCl concentrations (e.g., 500 mM) no brush collapse was observed at all (non-zero) concentrations of SDS studied, contrary to what is seen for many polyelectrolytes. Study of the polymer-surfactant system under confinement revealed that the physical volume of surfactant dominates the structure of the strongly confined system, which further differentiates it from the polyelectrolyte case.
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Affiliation(s)
- Isaac J Gresham
- School of Chemical Engineering, UNSW Sydney, Sydney, 2052, NSW, Australia
| | - Edwin C Johnson
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, 2308, NSW, Australia
| | - Hayden Robertson
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, 2308, NSW, Australia
| | - Joshua D Willott
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, 2308, NSW, Australia
| | - Grant B Webber
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, 2308, NSW, Australia
| | - Erica J Wanless
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, 2308, NSW, Australia
| | | | - Stuart W Prescott
- School of Chemical Engineering, UNSW Sydney, Sydney, 2052, NSW, Australia.
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2
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Lin M, Raghuwanshi VS, Browne C, Simon GP, Garnier G. Tailoring the humidity response of cellulose nanocrystal-based films by specific ion effects. J Colloid Interface Sci 2023; 629:694-704. [PMID: 36183648 DOI: 10.1016/j.jcis.2022.09.101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 09/15/2022] [Accepted: 09/19/2022] [Indexed: 11/21/2022]
Abstract
HYPOTHESIS The optical properties and humidity response of iridescent films made of cellulose nanocrystal (CNC) and polyethylene glycol (PEG) can be tailored by the incorporation of electrolytes chosen based on specific ion effects (SIE). EXPERIMENTS A series of inorganic salts comprising five different cations and five anions based on the Hofmeister series were mixed with CNC/PEG suspensions, followed by an air-dried process into iridescent solid films. These films were tested in changing relative humidity (RH) environments from 30% to 90% and their photonic properties and mass change monitored. The underlying structures and the mechanism of their formation were quantified in terms of interparticle distance derived from small angle X-ray scattering experiment and pitch size quantified by scanning electron microscope (SEM). FINDINGS The specific color and color range of CNC/PEG based films are controlled by a specific anion effect achieved by selection of the salt while the specific cation effect is negligible. The salting-in type anions with the same valency result in a red-shift color when films are in the dried state. The salting-in type leads to a greater color changing range during RH changes than the salting-out type. The resultant mass gain/loss trend is consistent with the color change. In contrast, cations do not show any relationships between salting-in effect and the measured properties as observed for anions. The observed SIE can be used to engineer CNC/polymer-based humidity and bio-diagnostic colorimetric indicator devices.
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Affiliation(s)
- Maoqi Lin
- Bioresource Processing Research Institute of Australia (BioPRIA), Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Vikram Singh Raghuwanshi
- Bioresource Processing Research Institute of Australia (BioPRIA), Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Christine Browne
- Bioresource Processing Research Institute of Australia (BioPRIA), Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
| | - George P Simon
- Department of Materials Science and Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Gil Garnier
- Bioresource Processing Research Institute of Australia (BioPRIA), Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia.
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3
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Umapathi R, Kumar K, Ghoreishian SM, Rani GM, Park SY, Huh YS, Venkatesu P. Effect of Imidazolium Nitrate Ionic Liquids on Conformational Changes of Poly( N-vinylcaprolactam). ACS OMEGA 2022; 7:39742-39749. [PMID: 36385857 PMCID: PMC9648054 DOI: 10.1021/acsomega.2c03650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 09/27/2022] [Indexed: 06/16/2023]
Abstract
Detailed information about molecular interactions and conformational changes of polymeric components in the presence of ionic liquids (ILs) is essential for designing novel polymeric ionic liquid-based biomaterials. In biomaterials science and technology, thermoresponsive polymers (TRPs) are widely viewed as potential candidates for the fabrication of biorelated medical devices. Here, we synthesized thermoresponsive poly(N-vinyl-caprolactam) (PVCL) polymer and investigated the effects of imidazolium-based ILs (1-ethyl-3-methyl imidazolium nitrate and 1-butyl-3-methylimidazolium nitrate) with common anion and different cations on the phase transition behavior of PVCL aqueous solution. The impact of ILs on the phase transition behavior of PVCL was monitored by using UV-visible absorption spectra, steady-state fluorescence spectroscopy, thermal fluorescence spectroscopy, and temperature dependent dynamic light scattering. Results showed significant changes in the absorbance, molecular interactions, agglomeration, and coil to globule transition behaviors of PVCL in the presence of two ILs. PVCL aqueous solution showed significant conformational changes after the addition of ILs.
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Affiliation(s)
- Reddicherla Umapathi
- NanoBio
High-Tech Materials Research Center, Department of Biological Sciences
and Bioengineering, Inha University, Incheon 22212, Republic of Korea
| | - Krishan Kumar
- NanoBio
High-Tech Materials Research Center, Department of Biological Sciences
and Bioengineering, Inha University, Incheon 22212, Republic of Korea
- Department
of Chemistry, University of Delhi, Delhi 110 007, India
| | - Seyed Majid Ghoreishian
- NanoBio
High-Tech Materials Research Center, Department of Biological Sciences
and Bioengineering, Inha University, Incheon 22212, Republic of Korea
| | | | - So Young Park
- NanoBio
High-Tech Materials Research Center, Department of Biological Sciences
and Bioengineering, Inha University, Incheon 22212, Republic of Korea
| | - Yun Suk Huh
- NanoBio
High-Tech Materials Research Center, Department of Biological Sciences
and Bioengineering, Inha University, Incheon 22212, Republic of Korea
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4
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Qi HK, Yang X, Yang QH, Luo MB. Effect of grafting density on the adsorption of end-grafted polymer chains. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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5
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Peña JA, Du XJ, Xing JF. One-step grafting reaction of thermoresponsive polymer brushes over silica nanoparticles. Colloid Polym Sci 2022. [DOI: 10.1007/s00396-022-05012-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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Ehtiati K, Moghaddam SZ, Klok HA, Daugaard AE, Thormann E. Specific Counterion Effects on the Swelling Behavior of Strong Polyelectrolyte Brushes. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c00411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Koosha Ehtiati
- Department of Chemistry, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
| | - Saeed Z. Moghaddam
- Department of Chemistry, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
| | - Harm-Anton Klok
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire des Polyméres, Institut des Matériaux and Institut des Sciences et Ingénierie Chimiques, Bâtiment MXD, Station 12, CH-1015 Lausanne, Switzerland
| | - Anders E. Daugaard
- Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Esben Thormann
- Department of Chemistry, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
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7
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Gregory KP, Elliott GR, Robertson H, Kumar A, Wanless EJ, Webber GB, Craig VSJ, Andersson GG, Page AJ. Understanding specific ion effects and the Hofmeister series. Phys Chem Chem Phys 2022; 24:12682-12718. [PMID: 35543205 DOI: 10.1039/d2cp00847e] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Specific ion effects (SIE), encompassing the Hofmeister Series, have been known for more than 130 years since Hofmeister and Lewith's foundational work. SIEs are ubiquitous and are observed across the medical, biological, chemical and industrial sciences. Nevertheless, no general predictive theory has yet been able to explain ion specificity across these fields; it remains impossible to predict when, how, and to what magnitude, a SIE will be observed. In part, this is due to the complexity of real systems in which ions, counterions, solvents and cosolutes all play varying roles, which give rise to anomalies and reversals in anticipated SIEs. Herein we review the historical explanations for SIE in water and the key ion properties that have been attributed to them. Systems where the Hofmeister series is perturbed or reversed are explored, as is the behaviour of ions at the liquid-vapour interface. We discuss SIEs in mixed electrolytes, nonaqueous solvents, and in highly concentrated electrolyte solutions - exciting frontiers in this field with particular relevance to biological and electrochemical applications. We conclude the perspective by summarising the challenges and opportunities facing this SIE research that highlight potential pathways towards a general predictive theory of SIE.
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Affiliation(s)
- Kasimir P Gregory
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia. .,Department of Materials Physics, Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - Gareth R Elliott
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Hayden Robertson
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Anand Kumar
- Flinders Institute of Nanoscale Science and Technology, College of Science and Engineering, Flinders University, South Australia 5001, Australia
| | - Erica J Wanless
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
| | - Grant B Webber
- School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Vincent S J Craig
- Department of Materials Physics, Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - Gunther G Andersson
- Flinders Institute of Nanoscale Science and Technology, College of Science and Engineering, Flinders University, South Australia 5001, Australia
| | - Alister J Page
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
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8
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Gregory KP, Wanless EJ, Webber GB, Craig VSJ, Page AJ. The electrostatic origins of specific ion effects: quantifying the Hofmeister series for anions. Chem Sci 2021; 12:15007-15015. [PMID: 34976339 PMCID: PMC8612401 DOI: 10.1039/d1sc03568a] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/15/2021] [Indexed: 12/23/2022] Open
Abstract
Life as we know it is dependent upon water, or more specifically salty water. Without dissolved ions, the interactions between biological molecules are insufficiently complex to support life. This complexity is intimately tied to the variation in properties induced by the presence of different ions. These specific ion effects, widely known as Hofmeister effects, have been known for more than 100 years. They are ubiquitous throughout the chemical, biological and physical sciences. The origin of these effects and their relative strengths is still hotly debated. Here we reconsider the origins of specific ion effects through the lens of Coulomb interactions and establish a foundation for anion effects in aqueous and non-aqueous environments. We show that, for anions, the Hofmeister series can be explained and quantified by consideration of site-specific electrostatic interactions. This can simply be approximated by the radial charge density of the anion, which we have calculated for commonly reported ions. This broadly quantifies previously unpredictable specific ion effects, including those known to influence solution properties, virus activities and reaction rates. Furthermore, in non-aqueous solvents, the relative magnitude of the anion series is dependent on the Lewis acidity of the solvent, as measured by the Gutmann Acceptor Number. Analogous SIEs for cations bear limited correlation with their radial charge density, highlighting a fundamental asymmetry in the origins of specific ion effects for anions and cations, due to competing non-Coulombic phenomena.
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Affiliation(s)
- Kasimir P Gregory
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle Callaghan New South Wales 2308 Australia
| | - Erica J Wanless
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle Callaghan New South Wales 2308 Australia
| | - Grant B Webber
- School of Engineering, The University of Newcastle Callaghan New South Wales 2308 Australia
| | - Vincent S J Craig
- Department of Applied Mathematics, Research School of Physics, Australian National University Canberra ACT 0200 Australia
| | - Alister J Page
- Discipline of Chemistry, School of Environmental and Life Sciences, The University of Newcastle Callaghan New South Wales 2308 Australia
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9
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Flemming P, Münch AS, Fery A, Uhlmann P. Constrained thermoresponsive polymers - new insights into fundamentals and applications. Beilstein J Org Chem 2021; 17:2123-2163. [PMID: 34476018 PMCID: PMC8381851 DOI: 10.3762/bjoc.17.138] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 08/10/2021] [Indexed: 12/15/2022] Open
Abstract
In the last decades, numerous stimuli-responsive polymers have been developed and investigated regarding their switching properties. In particular, thermoresponsive polymers, which form a miscibility gap with the ambient solvent with a lower or upper critical demixing point depending on the temperature, have been intensively studied in solution. For the application of such polymers in novel sensors, drug delivery systems or as multifunctional coatings, they typically have to be transferred into specific arrangements, such as micelles, polymer films or grafted nanoparticles. However, it turns out that the thermodynamic concept for the phase transition of free polymer chains fails, when thermoresponsive polymers are assembled into such sterically confined architectures. Whereas many published studies focus on synthetic aspects as well as individual applications of thermoresponsive polymers, the underlying structure-property relationships governing the thermoresponse of sterically constrained assemblies, are still poorly understood. Furthermore, the clear majority of publications deals with polymers that exhibit a lower critical solution temperature (LCST) behavior, with PNIPAAM as their main representative. In contrast, for polymer arrangements with an upper critical solution temperature (UCST), there is only limited knowledge about preparation, application and precise physical understanding of the phase transition. This review article provides an overview about the current knowledge of thermoresponsive polymers with limited mobility focusing on UCST behavior and the possibilities for influencing their thermoresponsive switching characteristics. It comprises star polymers, micelles as well as polymer chains grafted to flat substrates and particulate inorganic surfaces. The elaboration of the physicochemical interplay between the architecture of the polymer assembly and the resulting thermoresponsive switching behavior will be in the foreground of this consideration.
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Affiliation(s)
- Patricia Flemming
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Alexander S Münch
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Petra Uhlmann
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- University of Nebraska-Lincoln, NE 68588, Lincoln, USA
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10
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Gresham IJ, Murdoch TJ, Johnson EC, Robertson H, Webber GB, Wanless EJ, Prescott SW, Nelson ARJ. Quantifying the robustness of the neutron reflectometry technique for structural characterization of polymer brushes. J Appl Crystallogr 2021. [DOI: 10.1107/s160057672100251x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Neutron reflectometry is the foremost technique for in situ determination of the volume fraction profiles of polymer brushes at planar interfaces. However, the subtle features in the reflectometry data produced by these diffuse interfaces challenge data interpretation. Historically, data analyses have used least-squares approaches that do not adequately quantify the uncertainty of the modeled profile and ignore the possibility of other structures that also match the collected data (multimodality). Here, a Bayesian statistical approach is used that permits the structural uncertainty and multimodality to be quantified for polymer brush systems. A free-form model is used to describe the volume fraction profile, minimizing assumptions regarding brush structure, while only allowing physically reasonable profiles to be produced. The model allows the total volume of polymer and the profile monotonicity to be constrained. The rigor of the approach is demonstrated via a round-trip analysis of a simulated system, before it is applied to real data examining the well characterized collapse of a thermoresponsive brush. It is shown that, while failure to constrain the interfacial volume and consider multimodality may result in erroneous structures being derived, carefully constraining the model allows for robust determination of polymer brush compositional profiles. This work highlights that an appropriate combination of flexibility and constraint must be used with polymer brush systems to ensure the veracity of the analysis. The code used in this analysis is provided, enabling the reproduction of the results and the application of the method to similar problems.
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11
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Gresham IJ, Humphreys BA, Willott JD, Johnson EC, Murdoch TJ, Webber GB, Wanless EJ, Nelson ARJ, Prescott SW. Geometrical Confinement Modulates the Thermoresponse of a Poly( N-isopropylacrylamide) Brush. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02775] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Isaac J. Gresham
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Ben A. Humphreys
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Joshua D. Willott
- Membrane Science and Technology, Mesa+ Institute for Nanotechnology, University of Twente, Enschede 7500 AE, The Netherlands
| | - Edwin C. Johnson
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Timothy J. Murdoch
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Grant B. Webber
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | - Erica J. Wanless
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan 2308, Australia
| | | | - Stuart W. Prescott
- School of Chemical Engineering, UNSW Sydney, Sydney, New South Wales 2052, Australia
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12
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Johnson EC, Gresham IJ, Prescott SW, Nelson A, Wanless EJ, Webber GB. The direction of influence of specific ion effects on a pH and temperature responsive copolymer brush is dependent on polymer charge. POLYMER 2021. [DOI: 10.1016/j.polymer.2020.123287] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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13
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Flemming P, Janke A, Simon F, Fery A, Münch AS, Uhlmann P. Multiresponsive Transitions of PDMAEMA Brushes for Tunable Surface Patterning. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:15283-15295. [PMID: 33306910 DOI: 10.1021/acs.langmuir.0c02711] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) is an attractive polymer for switchable surface coatings based on its multiresponsiveness toward environmental triggers (temperature, pH-value, ionic strength). In this in situ study, we present the complex and tunable thermoresponsiveness of PDMAEMA Guiselin brushes (9 nm, dry thickness), which were prepared via an efficient grafting-to approach. Combining in situ atomic force microscopy (AFM) visualizing the surface topography (x-y plane) and spectroscopic ellipsometry monitoring the swelling behavior of the polymer film (layer thickness, z-direction) offers for the first time a three-dimensional insight into thermoresponsive transitions on the nanoscale. While PDMAEMA films exhibit LCST behavior in the presence of monovalent counterions, it can easily be switched toward an UCST thermoresponsiveness via the addition of small quantities of multivalent ions. In both cases, the transition temperature as well as the sharpness and reversibility of the transition can be tuned via a second external trigger, the ionic strength. Whereas homogeneous surfaces were observed both below and above the LCST in monovalent salt solutions, the UCST transition was characterized by the in situ formation of a nanostructured surface of pinned PDMAEMA micelles with entrapped multivalent counterions. Moreover, it was demonstrated for the first time that the characteristic dimensions of the nanopattern (the diameter and height of the pinned micelles) could be tuned in situ by the pH- and induced UCST thermoresponsiveness of PDMAEMA. This approach therefore provides a novel bottom-up strategy to create and control polymeric nanostructures in an aqueous environment.
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Affiliation(s)
- Patricia Flemming
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
- Technische Universität Dresden, Dresden 01062, Germany
| | - Andreas Janke
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
| | - Frank Simon
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
- Technische Universität Dresden, Dresden 01062, Germany
| | - Alexander S Münch
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
| | - Petra Uhlmann
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden 01069, Germany
- University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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14
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Kent EW, Lewoczko EM, Zhao B. Effect of Buffer Anions on Pearl-Necklace Morphology of Tertiary Amine-Containing Binary Heterografted Linear Molecular Bottlebrushes in Acidic Aqueous Buffers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13320-13330. [PMID: 33135416 DOI: 10.1021/acs.langmuir.0c02435] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Molecular bottlebrushes can exhibit a multitude of distinct conformations under different conditions, and precise control of their morphology can facilitate better use of such materials in potential applications. Herein, we report a study on the effect of buffer anions on the pearl-necklace morphology of linear binary heterografted molecular brushes consisting of pH-responsive poly(2-N,N-diethylamino)ethyl methacrylate) (PDEAEMA) with a pKa of 7.40 and thermoresponsive poly(ethoxydi(ethylene glycol) acrylate) (PDEGEA) with a lower critical solution temperature of 9 °C as side chains in various acidic aqueous buffers at 0 °C. The molecular brushes, denotated as BMB, were prepared by a grafting-to approach using copper(I)-catalyzed azide-alkyne cycloaddition reaction. Dynamic light scattering studies showed that the apparent hydrodynamic size of BMB in aqueous buffers with a pH of 6.50 at 1 °C decreased with increasing valency of buffer anions, from acetate anions with a charge of 1-, to phosphate anions carrying charges of 2- and 1- and citrate anions bearing charges of 3- and 2- at pH = 6.50. Atomic force microscopy revealed that BMB exhibited a pearl-necklace morphology from all three aqueous buffers with a pH of 6.50 when spin-cast at 0 °C. Analysis of AFM images showed that the average length of BMB and the number of beads per brush molecule decreased with increasing valency of buffer anions while the size and height of the beads increased. The pearl-necklace morphology of BMB was believed to be the result of microphase separation of the neutral PDEGEA and the charged PDEAEMA side chains along the brush backbone. Multivalent kosmotropic buffer anions formed bridging linkages between protonated tertiary amine moieties and thus "crosslinked" the charged PDEAEMA side chains, resulting in the shrinkage of BMB and enhanced microphase separation of two side chain polymers.
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Affiliation(s)
- Ethan W Kent
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Evan M Lewoczko
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Bin Zhao
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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15
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Bruce EE, Okur HI, Stegmaier S, Drexler CI, Rogers BA, van der Vegt NFA, Roke S, Cremer PS. Molecular Mechanism for the Interactions of Hofmeister Cations with Macromolecules in Aqueous Solution. J Am Chem Soc 2020; 142:19094-19100. [PMID: 33124825 DOI: 10.1021/jacs.0c07214] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ion identity and concentration influence the solubility of macromolecules. To date, substantial effort has been focused on obtaining a molecular level understanding of specific effects for anions. By contrast, the role of cations has received significantly less attention and the underlying mechanisms by which cations interact with macromolecules remain more elusive. To address this issue, the solubility of poly(N-isopropylacrylamide), a thermoresponsive polymer with an amide moiety on its side chain, was studied in aqueous solutions with a series of nine different cation chloride salts as a function of salt concentration. Phase transition temperature measurements were correlated to molecular dynamics simulations. The results showed that although all cations were on average depleted from the macromolecule/water interface, more strongly hydrated cations were able to locally accumulate around the amide oxygen. These weakly favorable interactions helped to partially offset the salting-out effect. Moreover, the cations approached the interface together with chloride counterions in solvent-shared ion pairs. Because ion pairing was concentration-dependent, the mitigation of the dominant salting-out effect became greater as the salt concentration was increased. Weakly hydrated cations showed less propensity for ion pairing and weaker affinity for the amide oxygen. As such, there was substantially less mitigation of the net salting-out effect for these ions, even at high salt concentrations.
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Affiliation(s)
- Ellen E Bruce
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt, Germany
| | - Halil I Okur
- Department of Chemistry, and National Nanotechnology Research Center (UNAM), Bilkent University, 06800 Ankara, Turkey.,Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sina Stegmaier
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt, Germany
| | | | | | - Nico F A van der Vegt
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt, Germany
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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Competitive specific ion effects in mixed salt solutions on a thermoresponsive polymer brush. J Colloid Interface Sci 2020; 586:292-304. [PMID: 33189318 DOI: 10.1016/j.jcis.2020.10.092] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/21/2020] [Accepted: 10/22/2020] [Indexed: 11/22/2022]
Abstract
HYPOTHESIS Grafted poly(ethylene glycol) methyl ether methacrylate (POEGMA) copolymer brushes change conformation in response to temperature ('thermoresponse'). In the presence of different ions the thermoresponse of these coatings is dramatically altered. These effects are complex and poorly understood with no all-inclusive predictive theory of specific ion effects. As natural environments are composed of mixed electrolytes, it is imperative we understand the interplay of different ions for future applications. We hypothesise anion mixtures from the same end of the Hofmeister series (same-type anions) will exhibit non-additive and competitive behaviour. EXPERIMENTS The behaviour of POEGMA brushes, synthesised via surface-initiated ARGET-ATRP, in both single and mixed aqueous electrolyte solutions was characterised with ellipsometry and neutron reflectometry as a function of temperature. FINDINGS In mixed fluoride and chloride aqueous electrolytes (salting-out ions), or mixed thiocyanate and iodide aqueous electrolytes (salting-in ions), a non-monotonic concentration-dependent influence of the two anions on the thermoresponse of the brush was observed. A new term, δ, has been defined to quantitively describe synergistic or antagonistic behaviour. This study determined the specific ion effects imparted by salting-out ions are dependent on available solvent molecules, whereas the influence of salting-in ions is dependent on the interactions of the anions and polymer chains.
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17
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Moghaddam SZ, Thormann E. Surface forces and friction tuned by thermo-responsive polymer films. Curr Opin Colloid Interface Sci 2020. [DOI: 10.1016/j.cocis.2019.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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18
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Yuan H, Liu G. Ionic effects on synthetic polymers: from solutions to brushes and gels. SOFT MATTER 2020; 16:4087-4104. [PMID: 32292998 DOI: 10.1039/d0sm00199f] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The ionic effects on synthetic polymers have attracted extensive attention due to the crucial role of ions in the determination of the properties of synthetic polymers. This review places the focus on specific ion effects, multivalent ion effects, and ionic hydrophilicity/hydrophobicity effects in synthetic polymer systems from solutions to brushes and gels. The specific ion effects on neutral polymers are determined by both the direct and indirect specific ion-polymer interactions, whereas the ion specificities of charged polymers are mainly dominated by the specific ion-pairing interactions. The ionic cross-linking effect exerted by the multivalent ions is widely used to tune the properties of polyelectrolytes, while the reentrant behavior of polyelectrolytes in the presence of multivalent ions still remains poorly understood. The ionic hydrophilicity/hydrophobicity effects not only can be applied to make strong polyelectrolytes thermosensitive, but also can be used to prepare polymeric nano-objects and to control the wettability of polyelectrolyte brush-modified surfaces. The not well-studied ionic hydrogen bond effects are also discussed in the last section of this review.
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Affiliation(s)
- Haiyang Yuan
- Hefei National Laboratory for Physical Sciences at the Microscale, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Department of Chemical Physics, University of Science and Technology of China, No. 96, Jinzhai Road, Hefei 230026, P. R. China.
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Flemming P, Müller M, Fery A, Münch AS, Uhlmann P. Mechanistic Investigation of the Counterion-Induced UCST Behavior of Poly(N,N-dimethylaminoethyl methacrylate) Polymer Brushes. Macromolecules 2020. [DOI: 10.1021/acs.macromol.9b02666] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Patricia Flemming
- Leibniz-Institut für Polymerforschung Dresden e.V, Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Martin Müller
- Leibniz-Institut für Polymerforschung Dresden e.V, Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Andreas Fery
- Leibniz-Institut für Polymerforschung Dresden e.V, Hohe Straße 6, 01069 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - Alexander S. Münch
- Leibniz-Institut für Polymerforschung Dresden e.V, Hohe Straße 6, 01069 Dresden, Germany
| | - Petra Uhlmann
- Leibniz-Institut für Polymerforschung Dresden e.V, Hohe Straße 6, 01069 Dresden, Germany
- University of Nebraska-Lincoln, 68588 Lincoln, Nebraska, United States
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Pharmaceutical excipient salts effect on micellization and drug solubilization of PEO-PPO-ph-PPO-PEO block copolymer. Colloids Surf B Biointerfaces 2020; 189:110857. [PMID: 32066087 DOI: 10.1016/j.colsurfb.2020.110857] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 01/14/2020] [Accepted: 02/10/2020] [Indexed: 11/22/2022]
Abstract
Hydrophobic modification PEO-PPO copolymer BP123 was synthesized, with two aromatic rings in the centre linked to PEO-PPO blocks, and the identical PEO and PPO block numbers were possessed with commercial copolymer P123. The influence of three common pharmaceutical excipient salts sodium chloride (NaCl), sodium citrate (NaCA) and sodium benzoate (NaBZ) on self-assembly behaviors of BP123 and P123 was investigated via cloud point, surface tension, pyrene fluorescence and dynamic light scattering. Solubilization for hydrophobic drug simvastatin (SV) and in vitro drug release behavior were assessed accordingly. In the presence of NaCl or NaCA, cloud point and critical micellization concentration (CMC) decreased, micelles became more hydrophobic, micellar size and drug solubilization increased, drug release rate slowed, and the impact of NaCA was more significant than NaCl. Oppositely, cloud point and CMC increased with the addition of NaBZ. NaBZ could participate in the formation of micelles by hydrophobic aromatic ring, which greatly raised solubilization of SV. Moreover, a different performance occurred when NaBZ was added to BP123 or P123, due to the hydrophobic benzene rings in BP123, which prominently enhanced the interaction with hydrophobic drug, leading to obvious delay of drug release for BP123. This work is conducive to turning copolymer property in diverse pharmaceutical applications and in drug delivery systems as drug carriers.
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21
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Reversible stimuli-responsive nanomaterials with on-off switching ability for biomedical applications. J Control Release 2019; 314:162-176. [DOI: 10.1016/j.jconrel.2019.10.036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 10/17/2019] [Accepted: 10/18/2019] [Indexed: 12/14/2022]
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The Hofmeister series: Specific ion effects in aqueous polymer solutions. J Colloid Interface Sci 2019; 555:615-635. [PMID: 31408761 DOI: 10.1016/j.jcis.2019.07.067] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 12/21/2022]
Abstract
Specific ion effects in aqueous polymer solutions have been under active investigation over the past few decades. The current state-of-the-art research is primarily focused on the understanding of the mechanisms through which ions interact with macromolecules and affect their solution stability. Hence, we herein first present the current opinion on the sources of ion-specific effects and review the relevant studies. This includes a summary of the molecular mechanisms through which ions can interact with polymers, quantification of the affinity of ions for the polymer surface, a thermodynamic description of the effects of salts on polymer stability, as well as a discussion on the different forces that contribute to ion-polymer interplay. Finally, we also highlight future research issues that call for further scrutiny. These include fundamental questions on the mechanisms of ion-specific effects and their correlation with polymer properties as well as a discussion on the specific ion effects in more complex systems such as mixed electrolyte solutions.
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24
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Makelane H, Waryo T, Feleni U, Iwuoha E. Dendritic copolymer electrode for second harmonic alternating current voltammetric signalling of pyrene in oil-polluted wastewater. Talanta 2019; 196:204-210. [DOI: 10.1016/j.talanta.2018.12.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 12/10/2018] [Accepted: 12/12/2018] [Indexed: 01/25/2023]
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Goh K, Li H, Lam K. Effects of salt- and oxygen-coupled stimuli on the reactive behaviors of hemoglobin-loaded polymeric membranes. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2018.11.139] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Johnson EC, Murdoch TJ, Gresham IJ, Humphreys BA, Prescott SW, Nelson A, Webber GB, Wanless EJ. Temperature dependent specific ion effects in mixed salt environments on a thermoresponsive poly(oligoethylene glycol methacrylate) brush. Phys Chem Chem Phys 2019; 21:4650-4662. [DOI: 10.1039/c8cp06644b] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The temperature induced swelling/collapse transition of poly(oligoethylene glycol methacrylate) (POEGMA) brushes has been investigated in electrolyte solutions comprised of multiple anions.
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Affiliation(s)
- Edwin C. Johnson
- Priority Research Centre for Advanced Particle Processing and Transport
- University of Newcastle
- Callaghan
- Australia
| | - Timothy J. Murdoch
- Priority Research Centre for Advanced Particle Processing and Transport
- University of Newcastle
- Callaghan
- Australia
| | | | - Ben A. Humphreys
- Priority Research Centre for Advanced Particle Processing and Transport
- University of Newcastle
- Callaghan
- Australia
| | | | | | - Grant B. Webber
- Priority Research Centre for Advanced Particle Processing and Transport
- University of Newcastle
- Callaghan
- Australia
| | - Erica J. Wanless
- Priority Research Centre for Advanced Particle Processing and Transport
- University of Newcastle
- Callaghan
- Australia
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Humphreys BA, Prescott SW, Murdoch TJ, Nelson A, Gilbert EP, Webber GB, Wanless EJ. Influence of molecular weight on PNIPAM brush modified colloidal silica particles. SOFT MATTER 2018; 15:55-64. [PMID: 30534695 DOI: 10.1039/c8sm01824c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The effect of molecular weight and temperature on the phase transition and internal structure of poly(N-isopropylacrylamide) brush modified colloidal silica particles was investigated using dynamic light scattering (DLS) and small angle neutron scattering (SANS) between 15 and 45 °C. Dry particle analysis utilising transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) all confirmed the thickness of the polymer brush shell increased as a function of polymerisation time. Hydrodynamic diameter and electrophoretic mobility results revealed that the brush modified particles transitioned from swollen shells to a collapsed conformation between 15 and 35 °C. The dispersions were electrosterically stabilised over the entire temperature range investigated, with minimal thermal hysteresis recorded. Modelling of the hydrodynamic diameter enabled the calculation of a lower critical solution temperature (LCST) which increased as a function of brush thickness. The internal structure determined via SANS showed a swollen brush at low temperatures (18 and 25 °C) which decayed radially away from the substrate, while a collapsed block-like conformation with 60% polymer volume fraction was present at 40 °C. Radial phase separation was evident at intermediate temperatures (30 and 32.5 °C) with the lower molecular weight sample having a greater volume fraction of polymer in the dense inner region at these temperatures.
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Affiliation(s)
- Ben A Humphreys
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, NSW 2308, Australia.
| | | | - Timothy J Murdoch
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Andrew Nelson
- Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, NSW 2234, Australia
| | - Elliot P Gilbert
- Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, NSW 2234, Australia
| | - Grant B Webber
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Erica J Wanless
- Priority Research Centre for Advanced Particle Processing and Transport, University of Newcastle, Callaghan, NSW 2308, Australia.
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