Glass transition of polystyrene nanospheres under different confined environments in aqueous dispersions

Feng, Shuo; Li, ZhiYun; Liu, Ran; Mai, BiYun; Wu, Qing; Liang, Guodong; Gao, Haiyang; Zhu, Fangming

doi:10.1039/c3sm27576k

Cited by 40 publications

(77 citation statements)

References 67 publications

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“…Glassy polymer nanofilms [8] are probably the most prominent examples of the latter, and for the emblematic case of polystyrene there is a considerable body of experimental evidence supporting the fact that the glass transition temperature decreases as the film thickness is reduced below several tens of nanometers, when there is at least one free interface. Interestingly, the same behavior has been observed for nanopores [7], and spherical nanoparticles [9][10][11], among other geometries. Besides, experiments and numerical studies have shown that the mobility of glassy materials is higher near a free interface compared to the bulk [12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionsupporting

confidence: 71%

Cooperative strings and glassy dynamics in various confined geometries

et al. 2020

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Previously, we developed a minimal model based on random cooperative strings for the relaxation of supercooled liquids in the bulk and near free interfaces, and we recovered some key experimental observations. In this article, after recalling the main ingredients of the cooperative string model, we study the effective glass transition and surface mobility of various experimentally-relevant confined geometries: freestanding films, supported films, spherical particles, and cylindrical particles, with free interfaces and/or passive substrates. Finally, we introduce a novel way to account for a purely attractive substrate, and explore the impact of the latter in the previous geometries.

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Section: Introductionsupporting

confidence: 71%

Cooperative strings and glassy dynamics in various confined geometries

et al. 2020

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“…This was found for PMMA/silica nanocomposites where silica nanoparticles were previously silanized to avoid strong hydrogen bonding with the polymer [10,14]. This can be as large as 70 K for PS nanospheres with diameter *20 nm [51]. However once such content is increased, T g depression was observed [22].…”

Section: Thermal Glass Transitionmentioning

confidence: 97%

“…Finally, it is worth recalling that a number of polymer nanocomposites exhibit no experimentally detectable deviations from bulk T g . More recently, a number of works showed negative T g deviations in PS [38,51,193,194] and PMMA [50] nanospheres. This was the case for low silica contents in the polymer.…”

Section: Thermal Glass Transitionmentioning

confidence: 99%

“…This was the case for low silica contents in the polymer. In the works of Feng et al [50,51], it was demonstrated how the presence of a surfactant on the surface of the nanosphere and its nature (ionic or nonionic) has a crucial effect on the magnitude (if any) of deviations from bulk T g . Nanocomposites exhibiting no evidence of deviation from bulk T g are those of PVAc with neat silica [3] and poly(ether imide) (PEI) with carbon fiber [35].…”

Section: Thermal Glass Transitionmentioning

confidence: 99%

“…However once such content is increased, T g depression was observed [22]. In particular, surfactant free PS nanospheres and, to a minor extent, those recovered by an ionic surfactant exhibit negative deviations of the T g [51]. Several works have been devoted to the study of the glass transition in polymer nanospheres.…”

Section: Thermal Glass Transitionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Confinement Geometry on Out-of-Equilibrium Glassy Dynamics

Cangialosi

2015

Non-Equilibrium Phenomena in Confined Soft Matter

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Glassy dynamics under nanoscale confinement have been subject of under intense debate in soft matter physics in the last 20 years. Scientific impetus in the field was provided by the increasing employment of glasses confined at the nanoscale. Furthermore, investigation of confined glasses may deliver information of the still unsolved problem of the glass transition. Within this context, the present chapter critically discusses the experimental findings in the field. Special attention is devoted to literature dealing with polymers under 1-D confinement, that is, thin polymer film. Results on different confinement geometries, such as polymer nanocomposites and nanospheres, are discussed as well. In discussing these results, we emphasize how the out-of-equilibrium dynamics, that is, the glass transition temperature (T g ) and the spontaneous evolution towards equilibrium in the so-called physical aging regime, is in numerous cases decoupled from the equilibrium dynamics, namely the rate of spontaneous fluctuations in the glass former. In particular, arguments based exclusively on the modification of the rate of spontaneous fluctuations in confinement are not able to provide a comprehensive description of the deviation of the T g and the rate of physical aging. In the search for the factors affecting the out-of-equilibrium dynamics in confinement, we show solid experimental evidence that this is mainly determined by the amount of free interface. In this sense the crucial role of irreversible chain adsorption is highlighted. Finally a framework, based on free volume holes diffusion (FVHD), to describe the entire phenomenology of glassy dynamics in confinement is reviewed. This is able to catch the enhancement of the out-of-equilibrium dynamics, that is, the T g depression and the speed-up of physical aging in confinement, with no need to invoke any acceleration of the rate of spontaneous fluctuations of the polymer.

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Physical Aging of Polymers

Cangialosi

2018

Encyclopedia of Polymer Science and Technology

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This article provides an overview of the most important aspects of physical aging of polymers. First, we briefly introduce basic concepts of the glass transition, that is, the way a nonequilibrium glass is formed. Subsequently, after presenting the way physical aging can be monitored, we describe the main well‐established signatures of physical aging, that is, its nonexponential and nonlinear nature. The next part of the article is dedicated to recent advancements in the physical aging of bulk polymers. In this context, recent experimental activity is discussed, where the existence of multiple mechanisms for equilibrium recovery is presented. In addition, important aspects of physical aging in polymers altered by geometrical confinement are scrutinized in light of the past 20 years efforts aiming to understand glass dynamics in such conditions. It is shown how confined polymers weakly interacting with the confining medium exhibit accelerated physical aging. Importantly, such acceleration was found to be decoupled from the molecular mobility of the glass. Finally, we briefly discuss how recent advancements in physical aging of polymers in bulk and under geometrical confinement should foster experimental efforts to unveil important basic aspects of the glass transition, such as the existence of the so‐called “ideal glass.”

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Glass transition of polystyrene nanospheres under different confined environments in aqueous dispersions

Cited by 40 publications

References 67 publications

Cooperative strings and glassy dynamics in various confined geometries

Cooperative strings and glassy dynamics in various confined geometries

Effect of Confinement Geometry on Out-of-Equilibrium Glassy Dynamics

Physical Aging of Polymers

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