Cononsolvency of the responsive polymer poly(N-isopropylacrylamide) in water/methanol mixtures: a dynamic light scattering study of the effect of pressure on the collective dynamics

Niebuur, Bart‐Jan; Deyerling, André; Höfer, Nicole; Schulte, Alfons; Papadakis, Christine M.

doi:10.1007/s00396-022-04987-x

Cited by 5 publications

(14 citation statements)

References 66 publications

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“…A temperature scan of a solution in H 2 O at 0.1, 130 and 200 MPa reveal that the dynamic correlation length of the fast mode shows critical behavior. The critical exponent ν in ξ ∝ | T c ( p ) – T | –ν , where T c ( p ) is the pressure-dependent critical temperature, increases from 0.7 at 0.1 MPa to 0.9 at 130 MPa and decreases to 0.5 at 200 MPa . We note that the pressure-dependent behavior of the PNIPAM chains in concentrated solutions near the phase boundaries is far from being understood, and systematic experiments at lower polymer concentrations may help to distinguish single-chain from collective effects.…”

Section: Phase Separation In Thermoresponsive Polymers In Aqueous Sol...mentioning

confidence: 85%

“…In our recent DLS study at variable pressure, we investigated the dynamics of 25 wt% aqueous PNIPAM solutions. 85 Throughout, two dynamic modes were observed: a faster one assigned to the relaxation of the chain segments within the blobs and a slower one due to the relaxation of the blobs (Figure 6a). Pressure scans in the one-phase region on an aqueous solution at 34.0 °C, i.e., slightly below the maximum of the coexistence line, revealed that the dynamic correlation length of the fast mode increases when the left or right branch of the coexistence line is approached (Figure 6b).…”

Section: Polymers In Aqueous Solutionmentioning

confidence: 99%

“…Employing DLS, the dynamics of semidilute solutions in the one-phase region was found to be pressure-dependent, and the critical behavior of the correlation length of local concentration fluctuations was found to be far from mean-field predictions for static values. 85 These deviations might be related to the very prominent large-scale dynamic inhomogeneities, but due to the lack of theoretical models or molecular dynamics simulations, the explanations remain tentative. Combining QENS with broadband dielectric spectroscopy could enlarge the accessible range in the frequency domain.…”

Section: Polymers In Aqueous Solutionmentioning

confidence: 99%

“…For clarity, only every second experimental data point is shown. Data are from ref . (b) Dynamic correlation length of the fast mode, ξ, at 34.0 °C dependent on pressure.…”

Section: Phase Separation In Thermoresponsive Polymers In Aqueous Sol...mentioning

confidence: 99%

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Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM)

Papadakis,

Niebuur,

Schulte

2023

Langmuir

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Pressure is a key variable in the phase behavior of responsive polymers, both for applications and from a fundamental point of view. In this feature article, we review recent developments, particularly applications of neutron techniques such as small-angle neutron scattering (SANS) and quasi-elastic neutron scattering (QENS), across the temperature−pressure phase diagram. These are complemented by kinetic SANS experiments following pressure jumps. In the prototype system poly(Nisopropylacrylamide) (PNIPAM), QENS revealed the pressuredependent characteristics of hydration water around the lower critical solution temperature transition. The size, water content, and inner structure of the mesoglobules formed in the two-phase region depend strongly on pressure, as shown by SANS. Beside these changes at the phase transition, the mesoglobule formation at low pressure is determined by kinetic factors, namely the formation of a polymer-rich, rigid shell, which hampers further growth by coalescence. At high pressure, in contrast, the growth proceeds by diffusion-limited coalescence without any kinetic hindrance. The disintegration of the mesoglobules evolves either via chain release from their surface or via swelling, depending on the osmotic pressure of the water. Moreover, we report on the profound influence of pressure on the cononsolvency effect. In the temperature−pressure frame, the one-phase region is hugely expanded upon the addition of the cosolvent methanol. SANS experiments unveil the enthalpic and entropic contributions to the effective Flory−Huggins interaction parameter between the segments and the solvent mixture. QENS experiments demonstrate an increase in polymer associated water with pressure, whereas methanol is released. Correspondingly, the solvent phase becomes enriched in methanol, providing a mechanism for the breakdown of cononsolvency at a high pressure. Finally, we outline future opportunities for high-pressure studies of thermoresponsive polymers, with a focus on neutron methods.

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Section: Phase Separation In Thermoresponsive Polymers In Aqueous Sol...mentioning

confidence: 85%

Section: Polymers In Aqueous Solutionmentioning

confidence: 99%

Section: Polymers In Aqueous Solutionmentioning

confidence: 99%

“…For clarity, only every second experimental data point is shown. Data are from ref . (b) Dynamic correlation length of the fast mode, ξ, at 34.0 °C dependent on pressure.…”

Section: Phase Separation In Thermoresponsive Polymers In Aqueous Sol...mentioning

confidence: 99%

See 2 more Smart Citations

Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM)

Papadakis,

Niebuur,

Schulte

2023

Langmuir

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“…Experimentally, the cononsolvency effect has predominantly been studied on poly( N -isopropylacrylamide) (PNIPAM) homopolymers in aqueous solution in the presence of methanol, namely with respect to the shift of T CP with methanol content, ,,− the chain conformation, − the energetics of the transition, the amount and dynamics of the hydration water and of methanol − as well as the segmental and chain dynamics of PNIPAM. − Only a few more complex PNIPAM-based systems in water/methanol mixtures have been investigated, mainly cross-linked micro- and nanogels. − …”

Section: Introductionmentioning

confidence: 99%

Micellar Solutions of PMMA-b-PNIPAM in Water/Methanol Mixtures: Effect of Temperature on the Micellar Size, Core–shell Structure, and Interaction

Ko,

Henschel,

Meledam

et al. 2023

Macromolecules

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In aqueous solution, diblock copolymers PMMA-b-PNIPAM having a short PMMA block and a long PNIPAM block form micelles with a PMMA core and a PNIPAM-rich shell. The same holds true for solutions in water containing small amounts of methanol. Here, we address the micellar structures for 10 g L −1 solutions of PMMA 21 -b-PNIPAM 283 in 90:10 and 80:20 v/v water/ methanol in wide temperature ranges across the respective cloud point temperature. Dynamic light scattering and synchrotron smallangle X-ray scattering reveal that the content of methanol strongly influences the temperature behavior of the overall micellar size upon heating to the cloud point temperature, the aggregation number of the micelles, their shell thickness, and their interactions. While the behavior in the 90:10 mixture is similar to that in neat water, in the 80:20 mixture, the micelles are significantly smaller and form clusters already below the cloud point temperature in water. Thus, by variation of the methanol content, the structure and interactions of the micelles can be controlled.

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Thermoresponsive and co-nonsolvency behavior of poly(N-vinyl isobutyramide) and poly(N-isopropyl methacrylamide) as poly(N-isopropyl acrylamide) analogs in aqueous media

et al. 2023

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Sets of the nonionic polymers poly(N-vinyl isobutyramide) (pNVIBAm) and poly(N-isopropyl methacrylamide) (pNIPMAm) are synthesized by radical polymerization covering the molar mass range from about 20,000 to 150,000 kg mol−1, and their thermoresponsive and solvent-responsive behaviors in aqueous solution are studied. Both polymers feature a lower critical solution temperature (LCST) apparently of the rare so-called type II, as characteristic for their well-studied analogue poly(N-isopropyl acrylamide) (pNIPAm). Moreover, in analogy to pNIPAm, both polymers exhibit co-nonsolvency behavior in mixtures of water with several co-solvents, including short-chain alcohols as well as a range of polar aprotic solvents. While the cloud points of the aqueous solutions are a few degrees higher than those for pNIPAm and increase in the order pNIPAm < pNVIBAm < pNIPMAm, the co-nonsolvency behavior becomes less pronounced in the order pNIPAm > pNVIBAm > pNIPMAm. Exceptionally, pNIPMAm does not show co-nonsolvency in mixtures of water and N,N-dimethylformamide. Graphical Abstract

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Cononsolvency of the responsive polymer poly(N-isopropylacrylamide) in water/methanol mixtures: a dynamic light scattering study of the effect of pressure on the collective dynamics

Cited by 5 publications

References 66 publications

Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM)

Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM)

Micellar Solutions of PMMA-b-PNIPAM in Water/Methanol Mixtures: Effect of Temperature on the Micellar Size, Core–shell Structure, and Interaction

Thermoresponsive and co-nonsolvency behavior of poly(N-vinyl isobutyramide) and poly(N-isopropyl methacrylamide) as poly(N-isopropyl acrylamide) analogs in aqueous media

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