Correlation between fragility and cooperativity in segmental dynamics of glass-forming para-substituted polystyrenes

Sasaki, Takashi; Ichimura, Mizuki; Irie, Satoshi

doi:10.1038/pj.2015.50

Cited by 14 publications

(10 citation statements)

References 60 publications

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“…Hence, it is reasonable to conclude that IL microscopic parameters (quantified by λ and D/D blk ) plays a considerable role in tuning the m and DH of the PNC system. Importantly, our report provides an evidence of anti-correlation between fragility and dynamical heterogeneity which is contrary to most recent reports in other types or glasses or PNCs [5,25]. These results also points to the predominance of kinetic fragility in our entropic PNC systems which was alluded to occur in some amorphous polymers earlier [26] but has not been observed in most other PNC systems.…”

Section: Resultscontrasting

confidence: 99%

“…Another key dynamical parameter, which has been widely used to describe glasses and supercooled liquids, including polymers and PNCs, is dynamic heterogeneity (DH) [22][23][24]. In the case of enthalpic PNCs, m seems to correlate with DH (increases for attractive and decreases for repulsive interactions) quantified in terms of a temperature dependent dynamical length scale, ξ, which seems to grow moderately on approaching the glass transition [5,19,24,25]. On the other hand some studies suggest that DH decreases with increasing fragility [26] in amorphous polymers.…”

Section: Introductionmentioning

confidence: 99%

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Nanoparticle–polymer interfacial layer properties tune fragility and dynamic heterogeneity of athermal polymer nanocomposite films

Begam

Chandran

et al. 2018

Soft Matter

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Enthalpic interactions at the interface between nanoparticles and matrix polymers is known to influence various properties of the resultant polymer nanocomposites (PNC). For athermal PNCs, consisting of grafted nanoparticles embedded in chemically identical polymers, the role and extent of the interface layer (IL) interactions in determining the properties of the nanocomposites is not very clear. Here, we demonstrate the influence of the interfacial layer dynamics on the fragility and dynamical heterogeneity (DH) of athermal and glassy PNCs. The IL properties are altered by changing the grafted to matrix polymer size ratio, f , which in turn changes the extent of matrix chain penetration into the grafted layer, λ. The fragility of PNCs is found to increase monotonically with increasing entropic compatibility, characterised by increasing λ. Contrary to observations in most polymers and glass formers, we observe an anti-correlation between the dependence on IL dynamics of fragility and DH, quantified by the experimentally estimated Kohlrausch-Watts-Williams parameter and the non-Gaussian parameter obtained from simulations.

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Section: Resultscontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanoparticle–polymer interfacial layer properties tune fragility and dynamic heterogeneity of athermal polymer nanocomposite films

Begam

Chandran

et al. 2018

Soft Matter

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“…The dispersion of the data is noticeable for α 1 and α 2 compared with α 3 and α 4 , which suggests that the assumptions of α 3 and α 4 are more appropriate than those of α 1 and α 2 . The above behavior of m may be related to the relationship between the fragility and the dynamic length scale at T g [ 29 , 55 , 56 , 57 ]. The coupling energy ε , which denotes the ability of dynamical coupling between segments, can be regarded as the cohesive energy [ 58 ].…”

Section: Resultsmentioning

confidence: 99%

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

2021

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The non-Arrhenius behavior of segmental dynamics in glass-forming liquids is one of the most profound mysteries in soft matter physics. In this article, we propose a dynamically correlated network (DCN) model to understand the growing behavior of dynamically correlated regions during cooling, which leads to the viscous slowdown of supercooled liquids. The fundamental concept of the model is that the cooperative region of collective motions has a network structure that consists of string-like parts, and networks of various sizes interpenetrate each other. Each segment undergoes dynamical coupling with its neighboring segments via a finite binding energy. Monte Carlo simulations showed that the fractal dimension of the DCNs generated at different temperatures increased and their size distribution became broader with decreasing temperature. The segmental relaxation time was evaluated based on a power law with four different exponents for the activation energy of rearrangement with respect to the DCN size. The results of the present DCN model are consistent with the experimental results for various materials of molecular and polymeric liquids.

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“…Many works investigate the relationships between the glass transition temperature, the fragility index, and the cooperativity in polymers. Sasaki et al, for instance, show that in PS derivatives the size of the cooperative rearranging regions (CRR) increases with increasing fragility. Recent investigations showed that m is a key parameter to evaluate the molecular arrangement and the relaxation dynamics of amorphous phases, for it is supposed to be strongly dependent on the packing efficiency of the macromolecules as well as on the stiffness of their backbone .…”

Section: Results and Discussionmentioning

confidence: 99%

Molecular Mobility in Amorphous Biobased Poly(ethylene 2,5-furandicarboxylate) and Poly(ethylene 2,4-furandicarboxylate)

et al. 2018

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Among all the emergent biobased polymers, poly(ethylene 2,5-furandicarboxylate) (2,5-PEF) seems to be particularly interesting for packaging applications. This work is focused on the investigation of the relaxation dynamics and the macromolecular mobility in totally amorphous 2,5-PEF as well as in the less studied poly(ethylene 2,4-furandicarboxylate) (2,4-PEF). Both biopolymers were investigated by differential scanning calorimetry and dielectric relaxation spectroscopy in a large range of temperatures and frequencies. The main parameters describing the relaxation dynamics and the molecular mobility in 2,5-PEF and 2,4-PEF, such as the glass transition temperature, the temperature dependence of the α and β relaxation times, the fragility index, and the apparent activation energy of the secondary relaxation, were determined and discussed. 2,5-PEF showed a higher value of the dielectric strength as compared to 2,4-PEF and other well-known polyesters, such as poly(ethylene terephthalate), which was confirmed by molecular dynamics simulations. According to the Angell’s classification of glass-forming liquids, amorphous PEFs behave as stronger glass-formers in comparison with other polyesters, which may be correlated to the packing efficiency of the macromolecular chains and therefore to the free volume and the barrier properties.

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Correlation between fragility and cooperativity in segmental dynamics of glass-forming para-substituted polystyrenes

Cited by 14 publications

References 60 publications

Nanoparticle–polymer interfacial layer properties tune fragility and dynamic heterogeneity of athermal polymer nanocomposite films

Nanoparticle–polymer interfacial layer properties tune fragility and dynamic heterogeneity of athermal polymer nanocomposite films

A Dynamically Correlated Network Model for the Collective Dynamics in Glass-Forming Molecular Liquids and Polymers

Molecular Mobility in Amorphous Biobased Poly(ethylene 2,5-furandicarboxylate) and Poly(ethylene 2,4-furandicarboxylate)

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