Poly(<i>N</i>-isopropylacrylamide) Microgels under Alcoholic Intoxication: When a LCST Polymer Shows Swelling with Increasing Temperature

Backes, Sebastian; Krause, Patrick; Tabaka, Weronika; Witt, Marcus U.; Mukherji, Debashish; Kremer, Kurt; Klitzing, Regine von

doi:10.1021/acsmacrolett.7b00557

Cited by 55 publications

(83 citation statements)

References 45 publications

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“…This behavior reveals a preferential solvation of the chains by ethanol molecules not only above the transition temperature, as reported by Backes at all. [21], but also in the temperature range where PNIPAM is soluble. It is noteworthy that this effect of ethanol molecules selection in the first solvation shell occurs in a binary mixture where the cosolvent content is so low.…”

Section: Temperature Dependence Of Polymer Structure and Solvationmentioning

confidence: 99%

“…As a result, in the last years several experimental and numerical studies have been carried out to investigate PNIPAM chains and microgels solution behavior [1,10]. The LCST/VPTT control can be achieved by variations of chemical [11] and stereochemical [12,13,14] composition of the polymer and by variations of the aqueous suspension medium, concerning ionic strength [15,16,17] and cosolute [18,19] or cosolvent addition, the latter being one of the simplest and less expensive ways to decrease the transition temperature [20,21,22]. In particular, the presence of ethanol as water cosolvent has a drastic impact on PNIPAM solution behavior, since this polymer, soluble in ethanol at all temperatures and in water at T ≤ 305 K, is actually insoluble in ethanol/water mixtures having an ethanol mass fraction approximately from 20% to 60%, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration

Tavagnacco

Zaccarelli

Chiessi

2020

Journal of Molecular Liquids

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Poly(N-isopropylacrylamide), PNIPAM, is a widely studied polymer, which serves as a key constituent of nanostructured soft materials with responsive properties. Upon increasing temperature the PNIPAM polymer chain undergoes a reversible coil-to-globule transition at T ∼305K, which is reflected by a volume phase transition in cross-linked architectures, such as microgels, valuable for many practical applications. The addition of a cosolvent is a simple method to tune the transition temperature according to the specific purpose. In this study, we use atomistic molecular dynamics simulations to explore the solution behavior of a PNIPAM chain in a mixture of water and ethanol, acting as cosolvent, at low alcohol concentration. Our simulations reproduce the occurrence of the coil-to-globule transition of the polymer chain at 289 K, a temperature lower than that measured in water, in full agreement with experimental findings. By monitoring the temperature evolution of structural and dynamical properties of the PNIPAM-water-ethanol ternary system, we detect a localization of ethanol molecules at the polymer interface, mainly due to interactions between isopropyl and ethyl groups. We observe that the transition occurs without a release of adsorbed ethanol molecules, but with a loss of water molecules from the surrounding of PNIPAM hydrophobic moieties that favours the aggregation of ethanol molecules close to the polymer. Our results support the idea that both the decreased chemical potential of water in the bulk of the mixture and the competition between water and ethanol molecules in the interactions with the polymer play a driving role in the transition.

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Section: Temperature Dependence Of Polymer Structure and Solvationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration

Tavagnacco

Zaccarelli

Chiessi

2020

Journal of Molecular Liquids

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“…Poly( N ‐isopropylacrylamide) (PNIPAM) is a water‐soluble polymer displaying a lower critical solution temperature at T ≃ 32 °C in aqueous solution. PNIPAM has attracted much interest as a stimuli‐responsive material, for example, in the design of microgels, with potential applications in drug delivery, as well as a model system to study fundamental problems in polymer physics such as the coil‐to‐globule transition or co‐nonsolvency …”

Section: Introductionmentioning

confidence: 99%

The Swelling of Poly(Isopropylacrylamide) Near the θ Temperature: A Comparison between Linear and Cross‐Linked Chains

Lopez

Scotti

Brugnoni

et al. 2018

Macro Chemistry & Physics

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Thermoresponsive polymeric gels are a class of smart materials with the ability to absorb or release large amounts of solvent when changes in their environment occur. Scaling theories of gel swelling (de Gennes' c∗ theorem and Obukhov's model) predict that the swelling of a gel correlates with that of a linear chain with equal degree of polymerization to that of a network strand. Data on linear and cross‐linked poly(N‐isopropylacrylamide) (PNIPAM) in aqueous solutions of different molar masses under θ temperature and good solvent conditions are examined. The Kuhn length of PNIPAM is evaluated to be LK = 4 ± 1 nm, in strong disagreement with previous estimates by single molecule force spectroscopy. The excluded volume strength (B) varies with the reduced temperature (τ) as B ≃ 4.7τ nm. While the power law exponent for the equilibrium swelling as a function of degree of cross‐linking is close to the scaling predictions, the degree of swelling observed in cross‐linked networks is two to three orders of magnitude larger than that expected from scaling models. The large differences between theoretical predictions and experimental results probably arise from the highly inhomogeneous nature of PNIPAM gels.

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“…Micro-and nanogel particles are one of the most interesting approaches to create smart materials, as they can be made responsive to many different stimuli, including pH [5,6], temperature [5,7,8], electromagnetic radiation [9], ionic strength or electric fields [7,10]. Their responses include large structural changes, typically swelling/collapse transitions, and a complex rheology [11,12].…”

Section: Introductionmentioning

confidence: 99%

The influence of an applied magnetic field on the self-assembly of magnetic nanogels

Novikau

Sánchez

Kantorovich

2020

Journal of Molecular Liquids

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Using Langevin dynamics simulations, we investigate the self-assembly of magnetic nanogels in the presence of applied magnetic fields of moderate strength. We find that even weak fields lead to drastic changes in the structure factors of both, the embedded magnetic nanoparticles and of whole nanogel particles. Nanogels assemble by uniting magnetic particle clusters forming inter-gel bridges. At zero field the average amount of such bridges for a pair of nanogels is close to one, whereas even for weak fields it fastly doubles. Rapid growth of cluster size at low values of the applied field is followed by a broad region of slow increase, caused by the mechanical constraints imposed the polymer matrix. The influence of the latter manifests itself in both, the slow growth of the magnetisation curve at intermediate fields and the slow decay of the total Zeeman energy.

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Poly(N-isopropylacrylamide) Microgels under Alcoholic Intoxication: When a LCST Polymer Shows Swelling with Increasing Temperature

Cited by 55 publications

References 45 publications

Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration

Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration

The Swelling of Poly(Isopropylacrylamide) Near the θ Temperature: A Comparison between Linear and Cross‐Linked Chains

The influence of an applied magnetic field on the self-assembly of magnetic nanogels

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