Contraction of a Polyelectrolyte upon Dilution. Light-Scattering Studies on a Polycation in Saltless Water−Acetone Mixtures

Aseyev, Vladimir; Tenhu, Heikki; Klenin, S.I.

doi:10.1021/ma980552q

Cited by 20 publications

(33 citation statements)

References 12 publications

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“…Instead of varying the polymer, one could vary the solvent, e.g., by decreasing solvent quality through addition to water of miscible bad solvent, like acetone. SAX(N)S showed the coil to globule transition in dilute regime. , In the semidilute regime, in polar organic solvent of poor quality, acetonitrile, atactic poly[2-(methacryloyloxy)ethyltrimethylammonium 1,1,2,3,3,-pentacyanopropenide] ‘MPCP’ chains give two regimes with two scaling exponents α being −1/2 and −1/7 in qualitative agreement with the pearl necklace model …”

Section: Introductionmentioning

confidence: 55%

How Necklace Pearls Evolve in Hydrophobic Polyelectrolyte Chains under Good Solvent Addition: A SANS Study of the Conformation

2018

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The chain conformation in sulfonated polystyrene PSSNa of a degree of sulfonation 0.34 ≤ f ≤ 1, i.e., of various hydrophobicity, is followed in mixtures of water and increasing content of tetrahydrofuran (THF), a good solvent of the hydrophobic polystyrene moieties (which improves the solvent quality of the mixture). This is achieved by measuring the chain form factor by small-angle neutron scattering using the zero average contrast method (ZAC). Polymer concentrations 0.17 and 0.34 M correspond in our case to the semidilute regime or its limit with dilute regime depending on the chain conformation. The main result is the monitoring with added THF of the pearl necklace conformation. This heterogeneous structure, made of wormlike chain parts (strings) and pearls, was observed formerly in water: when f decreases, the string contribution decreases, and the pearls size, characterized by a maximum in Kratky q 2 S 1 (q) representation, slightly increases. Here we see that in the presence of increasing content of added THF (i) the pearls contribution decreases, as expected, and (ii) their size does not change by more than 10% in most cases (30% at the most). Among different modeling, the most complete has been done following the pearl necklace models of Schweins, Huber et al. and Lages, Huber et al.; beyond the size and distribution of pearls, it addresses the radius of gyration, the correlation distance between spheres, weakly visible, and, importantly their number N. The values of R g , as well as the modeling, suggest that while the sphere size varies a few, N decreases clearly with added good solvent. A link with the simulation of Liao et al. can be found. A second result, important in practice, is that all modeling of the scattering establishes that THF addition makes vanish an excess of low q scattering due to large compact spheres present in water. A third result is obtained after a "THF treatment" procedure, consisting of adding THF and then removing it by evaporation: (i) the spherical aggregates are washed out, and (ii) the pearl necklace conformation of the chain returns to the one in water solution before treatment. Therefore, the pearl necklace conformation of the hydrophobic polyelectrolyte in aqueous solution appears to be in an annealed equilibrium state resulting from hydrophobic attraction and electrostatic repulsion.

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Section: Introductionmentioning

confidence: 55%

How Necklace Pearls Evolve in Hydrophobic Polyelectrolyte Chains under Good Solvent Addition: A SANS Study of the Conformation

2018

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“…[117,118,121] Dimensional studies have been performed using various polyelectrolytes, such as poly-(styrene sulfonate) [117,118,121] and other ion-containing polymers. [120,122,123] [ 109] The collapse kinetics of strongly charged polyelectrolytes in poor solvents has been investigated by Langevin simulation and scaling arguments. [124] The role of the counterion, valency, solvent quality, and the shape of the counterions on the dynamics of collapse were studied in this contribution.…”

Section: Coil-globule Transition Of Polyelectrolytesmentioning

confidence: 99%

Coil‐Globule Collapse in Flexible Macromolecules

Baysal

Karasz

2003

Macro Theory & Simulations

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The transition of a solvated flexible macromolecular chain from random coil behavior in the θ‐state to a globular compact form in the collapsed state has been the subject of extensive theoretical and experimental studies. Most of the coil‐globule transition studies of macromolecules have concentrated on the prototypical polystyrene‐cyclohexane system. However, chain contractions reported in this system have been around 75% of those in the unperturbed θ‐state. This relatively small decrease in size does not satisfy the criterion for a densely packed, collapsed globule. Experimentally, the collapse from a coil to a true compact globular state has now been established for two flexible macromolecules: poly(N‐isopropylacrylamide) in water and poly(methyl methacrylate) in various solvents. In this contribution, we review recent theoretical studies covering phenomenological and Langevin models as well as computer simulations. In addition, we outline recent experimental studies of the coil‐globule transition of various flexible polymers, copolymers, and polyelectrolytes.Expansion factor, α, versus temperature for NaPSS in 4.17 M aqueous NaCl solution. (•): NaPSS‐1, (○): NaPSS‐2.imageExpansion factor, α, versus temperature for NaPSS in 4.17 M aqueous NaCl solution. (•): NaPSS‐1, (○): NaPSS‐2.

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“…20 For another polymer, it was showed by using addition of miscible bad (or marginal) solvent to water, acetone, that the polyelectrolyte chain undergoes a complete coil to globule collapse transition. 21,22 A third system dealt with anionic chains neutralized by specifically interacting alkaline earth cations, also showing a pearlstring-like conformation. 23,24 In the semi-dilute regime where many chains are interpenetrated with each others, in the case of hydrophilic polyelectrolyte, the chain is a random walk of correlation blobs, 1,2 each blob is an extended configuration of electrostatic blobs, and the correlation length ξ i.e.…”

Section: Introductionmentioning

confidence: 99%

Metastability of Large Aggregates and Viscosity, and Stability of The Pearl Necklace Conformation After Organic Solvent Treatment Of Aqueous Hydrophobic Polyelectrolyte Solutions

2014

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Aggregates-a phenomenon still not understood-as well as the pearl-necklace-like chain conformation in aqueous solutions of hydrophobic polyelectrolytes are addressed here, using treatment by an organic solvent. The second appear to be at equilibrium in water. The first appear to be metastable, and surprisingly associated with higher zero shear viscosity. The hydrophobic polyelectrolyte is poly(styrene-co-sodium styrenesulfonate) (PSS), and the solution treatment is to first add to water an organic solvent, THF, which is then evaporated and replaced by the same amount of water. To investigate polyelectrolyte solutions as a function of THF treatment, we use small angle neutron scattering in the semidilute regime, viscosimetry in the dilute and semidilute regimes (unentangled), and osmometry in the similar semidilute regime (the contribution of the counterions being dominant). First, the structure, namely, the scattering from all chains, is characterized by a maximum ("polyelectrolyte peak"). Its position, amplitude, and scattered intensity at zero angle depend, at a given sulfonation rate of PSS, on the solvent quality through the added amount of organic solvent (THF). This dependence is very pronounced when the sulfonation rate is low (more hydrophobic polyelectrolyte) and is canceled when the sulfonation rate is high (more hydrophilic polyelectrolyte). Second, the viscosity of the polyelectrolyte solutions decreases with THF treatment for the hydrophobic polyelectrolytes. Third, osmometry shows no noticeable increase of the effective charge with THF treatment. It is proposed that the large scale aggregates, especially in the case of very hydrophobic polyelectrolytes, disappear irreversibly with THF treatment, while the pearl-necklace conformation of the chain remains as in its initial state. Parallel test measurements for a fully hydrophilic polyelectrolyte, poly(sodium-2-acrylamido-2-methylpropanesulfonate)-co-(acrylamide) (P(AMAMPS)), at different sulfonation rates, show no evolution of the structure with THF treatment in the aqueous solution. The same behavior is highlighted by viscosimetry.

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Contraction of a Polyelectrolyte upon Dilution. Light-Scattering Studies on a Polycation in Saltless Water−Acetone Mixtures

Cited by 20 publications

References 12 publications

How Necklace Pearls Evolve in Hydrophobic Polyelectrolyte Chains under Good Solvent Addition: A SANS Study of the Conformation

How Necklace Pearls Evolve in Hydrophobic Polyelectrolyte Chains under Good Solvent Addition: A SANS Study of the Conformation

Coil‐Globule Collapse in Flexible Macromolecules

Metastability of Large Aggregates and Viscosity, and Stability of The Pearl Necklace Conformation After Organic Solvent Treatment Of Aqueous Hydrophobic Polyelectrolyte Solutions

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