Studies of the Thermal Volume Transition of Poly(<i>N</i>-isopropylacrylamide) Hydrogels by High-Sensitivity Differential Scanning Microcalorimetry. 1. Dynamic Effects

Grinberg, Natalia V.; Dubovik, Alexander S.; Grinberg, V. Ya.; Кузнецов, Д. В.; Махаева, Е. Е.; Grosberg, Alexander Y.; Tanaka, Toyoichi

doi:10.1021/ma9810924

Cited by 71 publications

(74 citation statements)

References 25 publications

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“…30% water by weight. Curve plotted from the data of Grinberg et al (1999). the recognized authorities of the period) the conclusion that the ideal elastomer comprised of random chain networks with a Gaussian distribution of end-to-end chain lengths between cross-links.…”

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confidence: 99%

Elastin: a representative ideal protein elastomer

Urry

Hugel

Seitz

et al. 2002

Phil. Trans. R. Soc. Lond. B

281

255

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During the last half century, identification of an ideal (predominantly entropic) protein elastomer was generally thought to require that the ideal protein elastomer be a random chain network. Here, we report two new sets of data and review previous data. The first set of new data utilizes atomic force microscopy to report single-chain force-extension curves for (GVGVP) 251 and (GVGIP) 260 , and provides evidence for single-chain ideal elasticity. The second class of new data provides a direct contrast between lowfrequency sound absorption (0.1-10 kHz) exhibited by random-chain network elastomers and by elastin protein-based polymers.Earlier composition, dielectric relaxation (1-1000 MHz), thermoelasticity, molecular mechanics and dynamics calculations and thermodynamic and statistical mechanical analyses are presented, that combine with the new data to contrast with random-chain network rubbers and to detail the presence of regular non-random structural elements of the elastin-based systems that lose entropic elastomeric force upon thermal denaturation.The data and analyses affirm an earlier contrary argument that components of elastin, the elastic protein of the mammalian elastic fibre, and purified elastin fibre itself contain dynamic, non-random, regularly repeating structures that exhibit dominantly entropic elasticity by means of a damping of internal chain dynamics on extension.

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mentioning

confidence: 99%

Elastin: a representative ideal protein elastomer

Urry

Hugel

Seitz

et al. 2002

Phil. Trans. R. Soc. Lond. B

281

255

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“…These values are close to the collapse parameters of the NIPA homopolymer hydrogel synthesized at room temperature. [42,43] The obtained result implies that carrying out polymerization in a non-deeply frozen aqueous medium does not affect the thermosensitivity of NIPA homopolymers. Similar results were obtained for other stimuliresponsive cryogels [29,31,38] .…”

Section: Resultsmentioning

confidence: 90%

Thermoresponsive Copolymer Cryogel Possessing Molecular Memory: Synthesis, Energetics of Collapse and Interaction with Ligands

Burova

Grinberg

Иванов

et al. 2010

Macro Chemistry & Physics

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An imprinted thermoresponsive cryogel of copolymer of N‐isopropylacrylamide and N‐[3‐(N,N′‐dimethylamino)propyl]acrylamide was synthesized in a frozen (−10 °C) aqueous medium in presence of a molecular template, the drug substance ibuprofen. A reversible volume phase transition upon heating (thermotropic collapse) of the swollen cryogel was studied by high‐sensitivity differential scanning calorimetry. In the absence of ligands, the transition temperature, enthalpy, and width were 82.5 °C, 9.8 J · g−1 and 32.2 °C, respectively. Significant changes in the transition parameters were observed in presence of the template ligand (ibuprofen): with increasing ligand concentration the transition temperature decreased down to 30 °C, the enthalpy passed through a minimum, and the transition width notably reduced. The binding constants of ibuprofen by the cryogel subchains in the collapsed and swollen states were 119 and 5 M−1, respectively. This implies a preferential binding of ibuprofen by the shrunken cryogel. The excess absorption of ibuprofen by the cryogel related to its collapse amounted to 0.327 mmol · g−1 while for all other ligands that were structural analogs of ibuprofen this parameter did not exceed 0.016 mmol · g−1. Consequently, the imprinted cryogel possessed a selective molecular memory toward the template ligand.

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“…Such an interval between the first and second shrinking process was also found for several other stimuli-sensitive gels. [17,18] For instance, Tanaka et al [17] reported the shrinking kinetics of the thermosensitive poly(N,N-isopropylacrylamide) (poly(NIPAM)) gel and called this interval a plateau period. This period was explained in terms of the dense skin layer formed on the surface of the gel at the first stage, which might prevent a permeation of the inner fluid.…”

Section: Resultsmentioning

confidence: 99%

“…When diffusion of the polymer network took place from the inner core to the collapsed surface, the swelling degree of the inner core should increase to start an osmotic-pressure wave due to a decreased network density in the core. [17,18] No osmotic-pressure wave, however, occurred in the case of the poly(silamine) gel in spite of the very high difference in chemical potential between the swollen core and the inner surface of the collapsed skin layer. A plausible explanations for such a unique phenomenon is as follows.…”

Section: Resultsmentioning

confidence: 99%