Chemically induced transition phenomena in polyurethanes as seen from generalized mode Grüneisen parameters

Müller, Ulrich; Philipp, Martine; Bactavatchalou, Ravindrakumar; Sanctuary, Roland; Baller, Jörg; Zieliński, Bartosz; Possart, Wulff; Alnot, P.; Krüger, Jan-Kristian

doi:10.1088/0953-8984/20/20/205101

Cited by 4 publications

(24 citation statements)

References 15 publications

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“…In order to overcome the inherent tremendous experimental difficulties of measuring TOECs within liquids, we apply a key concept, which is well-known from solid state physics: the mode Grüneisen parameter 16,17,21,26,27,53,54 (see Section C.2). Brillouin spectroscopy 55,56 is used as the main experimental method.…”

Section: 2829mentioning

confidence: 99%

“…Mode Grüneisen parameters were originally introduced in solid state physics to access lattice anharmonicities of single crystals. 16,17,21,26,27,53,54 The denition of the mode Grüneisen parameter of an acoustic mode with polarization p and a wave vector q is as follows:…”

Section: C2 Mode Grüneisen Parametermentioning

confidence: 99%

“…The present article deals with the quantitative determination of TOECs across the liquid-liquid demixing transition of semi-dilute aqueous PNIPAM solutions. In order to overcome the inherent tremendous experimental difficulties of measuring TOECs within liquids, we apply a key concept, which is well-known from solid state physics: the mode Grüneisen parameter 16,17,21,26,27,53,54 (see Section C.2). Brillouin spectroscopy 55,56 is used as the main experimental method.…”

Section: A Introductionmentioning

confidence: 99%

“…16,17,21,26,27,53,54 Exceptions, which possess negative mode Grüneisen parameters, are oxide glasses 54 and water. The corresponding value of water, depicted in Fig.…”

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confidence: 99%

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Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

et al. 2013

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Elastic nonlinearities are particularly relevant for soft materials because of their inherently small linear elasticity. Nonlinear elastic properties may even take over the leading role for the transformation at mechanical instabilities accompanying many phase transitions in soft matter. Because of inherent experimental difficulties, only little is known about third order (nonlinear) elastic constants within liquids, gels and polymers. Here we show that a key concept to access third order elasticity in soft materials is the determination of mode Grüneisen parameters. We report the first direct observation of third order elastic constants across mechanical instabilities accompanying the liquid-liquid demixing transition of semi-dilute aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions. Immense elastic nonlinearities, leading to a strong strain-softening in the phase-separating PNIPAM solutions, are observed. Molecular mechanisms, which may be responsible for these immense elastic nonlinearities, are discussed. The importance of third order elastic constants in comparison to second order (linear) elastic constants in the demixing PNIPAM solutions evidences the need to focus more on the general role played by nonlinear elasticity at phase transitions within synthetic and biological liquids and gels. A IntroductionFor so condensed matter, knowledge about its continuum mechanics plays a decisive role in understanding the molecular cohesion and organization.1-21 When so matter is subjected to a sufficiently small static strain, the mechanical response is controlled by linear elastic, but not viscoelastic, properties.21 If liquids, gels or polymers are excited by a dynamical mechanical probe, their viscoelastic properties become relevant. This relevance increases with the complexity of the molecular structure in terms of inter-and intramolecular degrees of freedom. At sufficiently high probe frequencies, oen lying in the upper MHz or GHz regime, the mechanical relaxation processes are dynamically clamped and the mechanical response of the system is purely elastic again. Hence, for so materials the mechanical response may be of linear elastic nature when probed either statically or at sufficiently high probe frequencies. In such case, it can be described by Hooke's law, using the second order elastic constants (SOECs) provided by the linear elastic stiffness tensor of 4 th order.Of course linear elasticity only describes one aspect of the complex mechanical behaviour of so matter. The regime of linear elastic response is oen soon abandoned for so materials as the stress or strain amplitude is increased in stress-strain or dynamic mechanical experiments (e.g. ref. 4-6, 8 and 11-14). In order to quantify this nonlinear elastic response of the material within the frame of continuum mechanics, Hooke's law must be extended. Usually the consideration of third order elastic constants (TOECs), but no higher order elastic constants, is sufficient to describe the nonlinear elastic response. 21,22Because of the usually...

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Section: 2829mentioning

confidence: 99%

Section: C2 Mode Grüneisen Parametermentioning

confidence: 99%

Section: A Introductionmentioning

confidence: 99%

“…16,17,21,26,27,53,54 Exceptions, which possess negative mode Grüneisen parameters, are oxide glasses 54 and water. The corresponding value of water, depicted in Fig.…”

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Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

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“…Therefore the proportionality discussed above is no more expected for thermosets. Astonishingly, the Lorentz-Lorenz relation has been experimentally verified to be applicable to many classes of materials under different thermodynamic conditions, including isothermal curing of adhesives [17,18]. In other words, the specific refractivity remains almost constant even in the case of molecular network formation in polymers.…”

Section: Theoretical Backgroundmentioning

confidence: 97%

Effect of mixing sequence on the curing of amine-hardened epoxy/ alumina nanocomposites as assessed by optical refractometry

Philipp

Gervais²,

Sanctuary

et al. 2008

Express Polym. Lett.

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Abstract. High performance refractometry has been proven to be a useful tool to elucidate the isothermal curing process of nanocomposites. As a model system an amine-hardening epoxy filled with non-surface-treated alumina nanoparticles was selected. The tremendous resolution of this experimental technique is used to study morphological changes within nanocomposites via the refractive index. It is shown that these morphological changes are not simply due to the curing process but also depend on the sequence of mixing the nanoparticles either first into the resin or first into the hardener. Independent of the resin/hardener composition, the type of the mixing sequence discriminates systematically between two distinct refractive index curves produced by the curing process. The difference between the two refractive index curves increases monotonically with curing time, which underlines the importance of the initial molecular environment of the nanoparticles.

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Vapor Sorption–Desorption Phenomena of HD and GB Simulants from Polyurethane Thin Films on Aluminum Oxide via a Quartz Crystal Microbalance

et al. 2022

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Protection and decontamination of surfaces after exposure to chemical warfare agents (CWAs) are of considerable interest to the homeland defense and battlespace operation communities. In this work, polyurethane was spin-coated onto aluminum oxide quartz crystal microbalance (QCM) sensors. Polyurethane film thickness was varied by altering the concentration of the polymer/chloroform solution used for spin-coating. Atomic force microscopy confirmed the formation of smooth, homogeneous films on the QCM sensor surface. Aluminum oxide QCM sensors coated with polyurethane were exposed to saturated vapors of dichloropentane (DCP), a mustard gas (HD) simulant, and dimethyl methylphosphonate (DMMP), a sarin gas (GB) simulant, and the mass uptake, diffusion coefficient, volume fraction, and partition coefficient of the simulant in the film were determined from QCM data. Results showed that both DCP and DMMP readily sorbed into the films although the mass uptake of DCP was greater than that of DMMP owing to DCP’s higher vapor pressure. Additionally, the CWA simulant uptake increased with polyurethane film thickness. Sorption diffusion coefficients were 1 × 10 –13 cm 2 /s and 1 × 10 –12 cm 2 /s for DCP and DMMP vapor, respectively. Simulant desorption was also measured and showed that some DMMP remained in the film/substrate system, while DCP sorption was fully reversible. Reversible desorption for both CWA simulants was relatively quick and independent over the range of film thicknesses studied, with average desorption diffusion coefficients of 2 × 10 –9 cm 2 /s and 1 × 10 –11 cm 2 /s for DCP and DMMP, respectively. Collectively, this study is expected to inform protection and decontamination strategies of equipment and structures upon exposure to CWAs.

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Chemically induced transition phenomena in polyurethanes as seen from generalized mode Grüneisen parameters

Cited by 4 publications

References 15 publications

Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

Effect of mixing sequence on the curing of amine-hardened epoxy/ alumina nanocomposites as assessed by optical refractometry

Vapor Sorption–Desorption Phenomena of HD and GB Simulants from Polyurethane Thin Films on Aluminum Oxide via a Quartz Crystal Microbalance

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