Density and concentration fluctuations in plasticized poly(cyclohexyl methacrylate)

Fytas, G.; Floudas, G.; Ngai, K. L.

doi:10.1021/ma00206a032

Cited by 52 publications

(20 citation statements)

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“…Our results imply a stretched exponential intermediate scattering law (3) for incoherent scattering, where the Q dependence of T (Q,T) is given by f(Q)ocQ-". Therefore, Eq.…”

mentioning

confidence: 63%

“…Results from photon correlation spectroscopy (a light scattering time-domain technique) suggest that the characteristic magnitudes of the a relaxation do not depend noticeably on Q at the small-(? values covered in such experiments (£>~10~3 A" 1 ) [3]. Information about the Q behavior of the a relaxation in a mesoscopic time scale (10~, 0 -10 -7 s) can be obtained by means of quasielastic neutron scattering in a high-g range roughly between 0.1 and 5 A -1 .…”

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confidence: 98%

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Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

et al. 1992

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By means of quasielastic neutron scattering we have shown that the dynamics of the a relaxation on three different polymeric glasses shows a clear non-Debye behavior on a mesoscopic time scale. The spectral shape is found to be independent of temperature and momentum transfer (Q). The characteristic relaxation time follows a power-law Q dependence, r(Q)ccQ~n (n > 2), n being dependent on the system. We found that the Q behavior and the non-Debye behavior are directly correlated. These results have important implications concerning the physical mechanisms behind the dynamics of the a relaxation.PACS numbers: 64.70.Pf, 61.12.ExThe dynamics of the a relaxation in glass-forming systems above and near their glass-transition temperature range has been a subject of increasing interest over the past several years. It is now experimentally well established that the shape of the relaxation function characterizing the dynamics of the a relaxation shows a clear non-Debye behavior. In the time domain this behavior can be well described by means of the Kohlrausch-Williams-Watts "stretched exponential" function (pit) =exp[ -(t/ Tww)^] HI, which can be derived from different theoretical models. Here TWW is a characteristic relaxation time and p is a shape parameter ranging between 0 and 1. In the frequency domain, several empirical forms have been proposed to describe the non-Debye behavior, the most general being the Havriliak-Negami relaxation function 0*(ft>) = [l + (/COTHN) 0 ] ~~y [2]. Here a and y are two shape parameters 0~10~3 A" 1 ) [3]. Information about the Q behavior of the a relaxation in a mesoscopic time scale (10~, 0 -10 -7 s) can be obtained by means of quasielastic neutron scattering in a high-g range roughly between 0.1 and 5 A -1 . Several papers have been published recently in the field of the dynamics of glass-forming systems studied by neutron scattering techniques [4][5][6][7]. However, most of these studies aim to check the mode-coupling theories of the glass transition. In a previous paper [8] we reported preliminary results corresponding to a glass-forming polymeric system poly (vinyl methyl ether), PVME. In this Letter we report on incoherent quasielastic neutron scattering mea-surements performed on three structurally different glass-forming polymeric systems including PVME. We have focused our attention on the Q dependence of the magnitudes characterizing the dynamics of the a relaxation.The samples investigated were poly(vinyl methyl ether), polyvinyl chloride) (PVC) and poly(bisphenol A, 2hydrox...

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“…Our results imply a stretched exponential intermediate scattering law (3) for incoherent scattering, where the Q dependence of T (Q,T) is given by f(Q)ocQ-". Therefore, Eq.…”

mentioning

confidence: 63%

mentioning

confidence: 98%

Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

et al. 1992

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“…65, 66 Another example is the high molecular weight poly-(cyclohexylemethacrylate) plasticized by dioctyl phthalate. 67 More examples can be found in the review article. 68 An explanation of the property was given by the coupling model.…”

Section: Three Salient Properties In Viscoelasticitymentioning

confidence: 99%

“…The good agreement of the calculation with the left-hand-side as shown verifies the CM prediction for entangled polymers quantitatively, and as also found before. 38,55,65,67,69,74,105 The same values of (1 − n n ) and (1 − n α ) had been used in conjunction with eqs 10 and 12 to account successfully for the different TV γ -dependence of τ n and τ α but the same γ of entangled PIP with M n = 10600 g/mol (see Figure 5 in ref 25). Different TV γ -dependences of τ n and τ α with the same γ found also in PPG 23 and POB 24 are also consistent with the CM predictions as shown before in ref 25.…”

Section: Coupling Model Explanationmentioning

confidence: 99%

Thermo-Rheological, Piezo-Rheological, and TV^γ-Rheological Complexities of Viscoelastic Mechanisms in Polymers

Ngai

Plazek

2014

Macromolecules

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Experimental evidence are collected together to show in general the viscoelastic mechanisms of low and high molecular weight polymers have different dependences on temperature T, pressure P, and the same scaling product variable, TV γ , where V is the specific volume and γ is a material constant. The viscoelastic mechanisms include the Johari−Goldstein β-relaxation, the segmental α-relaxation, the sub-Rouse modes, the Rouse modes, and the terminal relaxation if the polymer chains are entangled. Appropriately called the thermo-, piezo-, and TV γ -rheological complexity of polymers, these viscoelastic anomalies are fundamental and deserve attention from the polymer physics community. Although we show that the coupling model can rationalize the origin of the complexity and explain some of the data quantitatively, the objective of this paper is to stimulate others to construct a theory that can do even better.

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“…24,25 Density fluctuations in highly concentrated polymer solutions are q-independent. 26,27 Triblock copolymer micelles above the overlap concentration show a q-independent process attributed to viscoelastic properties of a network of micelles, 28 supported by theoretical arguments. 29 Slow, q-independent modes have been found in sols nearing a sol-gel transition, 30 in dilute solutions of certain polymers, 31 and in a sponge phase in a 4-component system.…”

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confidence: 85%

Incoherent dynamic light scattering by dilute dispersions of spherical particles: wavelength-dependent dynamics

Erbe

Sigel

2013

Phys. Chem. Chem. Phys.

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Dynamic light scattering (DLS) was performed on dilute suspensions of colloidal particles, where the scattering intensity was minimised by ellipsometric optics as in ellipsometric light scattering. Measurements at minimum intensity settings are dominated by the incoherent scattering properties, i.e. the deviations from the average scattering properties. The observed relaxation dynamics does not vary with the scattering angle, but depends on the wavelength λ of the employed light. Therefore, the process has a λ-dependence beyond the dependence included in the scattering vector. Such incoherent ellipsometric DLS could be applied to determine the residence time of particles in volumes with an extension comparable to λ, and to obtain detailed information on the dynamics of complex systems which is usually hidden by the dominating diffusive process.

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Density and concentration fluctuations in plasticized poly(cyclohexyl methacrylate)

Abstract: tors (ru's). Parameter zxD in eq 4 is determined from z,D = z --z,6 where z is the coordination number, here set equal to 10.

Cited by 52 publications

References 13 publications

Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

Thermo-Rheological, Piezo-Rheological, and TV^γ-Rheological Complexities of Viscoelastic Mechanisms in Polymers

Incoherent dynamic light scattering by dilute dispersions of spherical particles: wavelength-dependent dynamics

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Density and concentration fluctuations in plasticized poly(cyclohexyl methacrylate)

Abstract: tors (ru's). Parameter zxD in eq 4 is determined from z,D = z --z,6 where z is the coordination number, here set equal to 10.

Cited by 52 publications

References 13 publications

Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

Correlation between non-Debye behavior andQbehavior of the α relaxation in glass-forming polymeric systems

Thermo-Rheological, Piezo-Rheological, and TVγ-Rheological Complexities of Viscoelastic Mechanisms in Polymers

Incoherent dynamic light scattering by dilute dispersions of spherical particles: wavelength-dependent dynamics

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Thermo-Rheological, Piezo-Rheological, and TV^γ-Rheological Complexities of Viscoelastic Mechanisms in Polymers