Crossover from Independent to Cooperative Segmental Dynamics in Polymers: Experimental Realization in Poly(Vinyl Chloride)

Colmenero, Juan; Arbe, Arantxa; Coddens, G.; Frick, B.; Mijangos, Carmen; Reinecke, Helmut

doi:10.1103/physrevlett.78.1928

Cited by 71 publications

(64 citation statements)

References 9 publications

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“…The crossover time, which corresponds to t c in Ngai's coupling model, is observed in pure PEO, and it has also been seen in other homopolymer melts. [26][27][28][29] For this specific system, QENS measurements in this time range have not previously been made; however, molecular dynamics simulations did not show this crossover. 12 We observe that the fast process is independent of the environment, whereas the slow process is not.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of PEO in Blends with PMMA: Study of the Effects of Blend Composition via Quasi-Elastic Neutron Scattering

et al. 2008

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We address the dynamic behavior of poly(ethylene oxide) [PEO] in miscible blends with poly(methyl methacrylate) [PMMA] by using quasi-elastic neutron scattering [QENS] with isotopic labeling. The data reveal two dynamic processes in the picosecond-nanosecond time scales: a slow process that is consistent with previous measurements of the segmental relaxation and a composition independent fast process occurring on the picosecond time scale. The composition dependence of the slow process differs from previous measurements, particularly at low PEO content. The fast process is similar to the fast process observed in pure polymers and is insensitive to blending with PMMA. Relaxation times extracted from Kolraush-Williams-Watts [KWW] fits to the data are used to test the applicability of the chain connectivity and coupling models as a function of spatial scale. Both models describe slow process relaxation times within a small range of spatial scales near the Kuhn length of PEO. The effective concentration, when obtained as a fit parameter in chain connectivity model fits, is not a constant, but it decreases with increasing spatial scale.

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Section: Resultsmentioning

confidence: 99%

Dynamics of PEO in Blends with PMMA: Study of the Effects of Blend Composition via Quasi-Elastic Neutron Scattering

et al. 2008

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“…Here t c is a cross-over time, whose typical value is 2 × 10 -12 s for molecular and polymeric glass formers (Colmenero et al, 1997;Ngai, 2007), and p is a shape parameter of the α relaxation given by ( Alvarez et al, 1991;Alvarez et al, 1993). The theoretical precursor time τ CM calculated using Eq.…”

Section: Resultsmentioning

confidence: 99%

Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic

Tripathi

Romanini

Tamarit

et al. 2015

International Journal of Pharmaceutics

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We employ dielectric spectroscopy to monitor the relaxation dynamics and crystallization kinetics of the Biclotymol antiseptic in its amorphous phase. The glass transition temperature of the material as determined by dielectric spectroscopy is T g = 290±1 K. The primary (α) relaxation dynamics is observed to follow a Vogel-Fulcher-Tammann temperature dependence, with a kinetic fragility index m = 86±13, which classifies Biclotymol as a relatively fragile glass former. A secondary relaxation is also observed, corresponding to an intramolecular dynamic process of the non-rigid Biclotymol molecule. The crystallization kinetics, measured at four different temperatures above the glass transition temperature, follows an Avrami behavior with exponent virtually equal to n = 2, indicating one-dimensional crystallization into needle-like crystallites, as experimentally observed, with a time-constant nucleation rate. The activation barrier for crystallization is found to be E a = 115±22 kJ mol -1 .

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“…Since t c ) 2 × 10 -12 s, 15,16 the ratio [τ 0 /t c ] is not large, and consequently [τ 0 /t c ] n /(1-n ) , and hence τ(n ), do not vary much within the range of n engendered by the range of PMMA concentration. In the extreme case, 1 Shown by the dotted line is the independent relaxation time for neat PEO calculated using n ) 0.67, the value reported by Lutz et al 1 Also shown are the most probable relaxation times calculated from eq 5 for the lower (O, n ) 0.84), midrange (0, n ) 0.83), and higher concentrations of PEO (4, n ) 0.81).…”

Section: Peo Dynamics In D 4 Peo/pmma Blendsmentioning

confidence: 99%

Unusual Component Dynamics in Poly(ethylene oxide)/Poly(methyl methacrylate) Blends As Probed by Deuterium NMR

Ngai

Roland

2004

Macromolecules

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We analyze recent deuterium NMR data on blends of poly(ethylene oxide) (PEO) with poly-(methyl methacrylate) (PMMA), using a model for the blend dynamics based on the coupling model. This model has previously been shown to describe the relaxation properties of blends whose component dynamics are strongly composition dependent. We show herein that the unusual feature of PEO/PMMA blends, an invariance of the PEO dynamics to composition, is a natural consequence of the high frequency and temperature of the NMR experiments. To wit, when the independent relaxation time of our model approaches the characteristic time for intermolecular cooperativity (∼2 ps), the effect of local environment on the component dynamics becomes negligible. A similar situation pertains for poly(vinyl methyl ether) mixed with polystyrene, at temperatures sufficiently high that the segmental relaxation times become small. On the other hand, for blends of 1,4-polyisoprene with poly(vinylethylene), the component dynamics retain their dependence on composition, even at high temperatures. The reason for the differing behavior is brought out by an analysis using our blend model.

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Crossover from Independent to Cooperative Segmental Dynamics in Polymers: Experimental Realization in Poly(Vinyl Chloride)

Cited by 71 publications

References 9 publications

Dynamics of PEO in Blends with PMMA: Study of the Effects of Blend Composition via Quasi-Elastic Neutron Scattering

Dynamics of PEO in Blends with PMMA: Study of the Effects of Blend Composition via Quasi-Elastic Neutron Scattering

Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic

Unusual Component Dynamics in Poly(ethylene oxide)/Poly(methyl methacrylate) Blends As Probed by Deuterium NMR

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