Measurement of the Grüneisen number in polystyrene by brillouin light scattering

Brody, Edward M.; Lubell, Cathie J.; Beatty, C. L.

doi:10.1002/pol.1975.180130207

Cited by 31 publications

(15 citation statements)

References 7 publications

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Section: 22mentioning

confidence: 99%

“…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%

“…Experimental investigations of TOECs at transformation phenomena in so matter are rare; examples exist for the thermal glass transition in polymers. 17,26,27 The so-called ferroelastic phase transitions, 22 for which the mechanical stress is the order parameter, are particularly fascinating from the mechanical viewpoint. For such transitions, a linear elastic constant is interpreted as the inverse order parameter susceptibility and therefore strongly soens at the phase transition.…”

Section: A Introductionmentioning

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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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: 22mentioning

confidence: 99%

Section: 2829mentioning

confidence: 99%

Section: A Introductionmentioning

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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Acoustic Properties

Jarzynski¹,

Balizer²,

Fedderly³

et al. 2003

Encyclopedia of Polymer Science and Technology

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This article covers the use of acoustics as a molecular probe of polymer structure and describes various acoustic applications of polymers. Sound speed and sound absorption measurements in polymers are useful both as a probe of the molecular structure of polymers and as a source of engineering design properties. Enough theory and experimental details are given to make the presentation understandable, but the emphasis is on the experimental results for polymers. Most of the presentation is for small‐amplitude waves in solid polymers. References to some specialized topics are given.

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Brillouin scattering and the glass‐rubber relaxation in amorphous polymers

Patterson¹

1975

J. Polym. Sci. B Polym. Lett. Ed.

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Measurement of the Grüneisen number in polystyrene by brillouin light scattering

Cited by 31 publications

References 7 publications

Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

Immense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions

Acoustic Properties

Brillouin scattering and the glass‐rubber relaxation in amorphous polymers

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