Detection of Interchain Proximity and Segmental Motion of Polymer Glass

Xu, Jie; Li, Dawei; Chen, Jiao; Din, Lei; Wang, Xiaoliang; Tao, Fangfang; Xue, Gi

doi:10.1021/ma200962c

Cited by 21 publications

(18 citation statements)

References 24 publications

(58 reference statements)

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“…The transition from a hydrophilic to a hydrophobic character was justified considering that "well-annealed" films might achieve density values larger than in bulk, and thus have less free volume for the water molecules. Moreover, manipulation of bulk samples via dry-freezing, permitted to verify that the glass transition temperature decreases upon increase of the interchain distance, which is in line with our idea [85]. Wöll and coworkers demonstrated that the heterogeneous character of the glassy dynamics is attributed to the gradient of density and free volume in supported films [86,87].…”

Section: Reduction In T G As An Effect Of Packing Frustration On the supporting

confidence: 80%

“…Teng et al reported a separation between t eq and τ REP larger than 2-4 orders of magnitude, by measuring the decay in elastic modulus of freezedried samples of PS205 during annealing in the liquid state (T g + 50 K) [109]. Xue and coworkers had previously verified that in freeze-dried samples, the interchain distance exceeds the normal bulk values, implying a less efficient interpenetration [85].…”

Section: Slow Adsorption Kinetics Re-entanglements Dynamics and Non-mentioning

confidence: 99%

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Glassy dynamics of soft matter under 1D confinement: How irreversible adsorption affects molecular packing, mobility gradients and orientational polarization in thin films

2013

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The structural dynamics of polymers and simple liquids confined at the nanometer scale has been intensively investigated in the last two decades in order to test the validity of theories on the glass transition predicting a characteristic length scale of a few nanometers. Although this goal has not yet been reached, the anomalous behavior displayed by some systems--e.g. thin films of polystyrene exhibit reductions of Tg exceeding 70 K and a tremendous increase in the elastic modulus--has attracted a broad community of researchers, and provided astonishing advancement of both theoretical and experimental soft matter physics. 1D confinement is achieved in thin films, which are commonly treated as systems at thermodynamic equilibrium where free surfaces and solid interfaces introduce monotonous mobility gradients, extending for several molecular sizes. Limiting the discussion to finite-size and interfacial effects implies that film thickness and surface interactions should be sufficient to univocally determine the deviation from bulk behavior. On the contrary, such an oversimplified picture, although intuitive, cannot explain phenomena like the enhancement of segmental mobility in proximity of an adsorbing interface, or the presence of long-lasting metastable states in the liquid state. Based on our recent work, we propose a new picture on the dynamics of soft matter confined in ultrathin films, focusing on non-equilibrium and on the impact of irreversibly chain adsorption on the structural relaxation. We describe the enhancement of dynamics in terms of the excess in interfacial free volume, originating from packing frustration in the adsorbed layer (Guiselin brush) at t(*) ≪ 1, where t(*) is the ratio between the annealing time and the time scale of adsorption. Prolonged annealing at times exceeding the reptation time (usually t(*) ≫ 1 induces densification, and thus reduces the deviation from bulk behavior. In this Colloquium, after reviewing the experimental approaches permitting to investigate the structural relaxation of films with one, two or no free surfaces by means of dielectric spectroscopy, we propose several methods to determine gradients of mobility in thin films, and then discuss on the unexploited potential of analyses based on the time, temperature and thickness dependence of the orientational polarization via the dielectric strength.

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Section: Reduction In T G As An Effect Of Packing Frustration On the supporting

confidence: 80%

Section: Slow Adsorption Kinetics Re-entanglements Dynamics and Non-mentioning

confidence: 99%

Glassy dynamics of soft matter under 1D confinement: How irreversible adsorption affects molecular packing, mobility gradients and orientational polarization in thin films

2013

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“…For the smallest nanospheres (with a diameter of 130 nm), the compressed pellet is completely transparent and contains a continuous matrix that is the same as the high‐temperature compressed pellet. The transparency of the pellet and its accuracy of form are testimony that the polymer chains flowed and the nanospheres fused with each other under applied pressure to take the shape of its container . Priestley reported the decrease in T g through reducing size of the PS nanospheres by modulated differential scanning calorimetry (DSC) .…”

Section: Resultsmentioning

confidence: 99%

Low‐temperature processing of polymer nanoparticles for bioactive composites

Xu²,

Wang

et al. 2016

J Polym Sci B Polym Phys

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Utilizing an ingenious control over the enhanced segmental mobility of polymer chains, we proposed a novel low‐temperature processing strategy for polymeric materials, where the materials were processed substantially below their normal glass transition temperature. This state of art was achieved by the combination of the confinement effects and the stress‐induced effects on polymer nanoparticles. This method proved to be universal for various polymer systems, that is, polystyrene, polyvinyl chloride, polycarbonate, and polyphenylene oxide. Compared with the traditional high‐temperature processing, the low‐temperature processing efficiently avoids thermal degradation, and the processed polymer maintains moderate mechanical properties. In addition, this approach provides a straightforward method for the preparation of heat‐labile bioactive polymer composites without biological surface modification. The prepared lysozyme/polystyrene composite exhibits excellent bactericidal activity and striking sustained release characteristics. This facile, universal and energy‐saving low‐temperature processing strategy is expected to open avenues toward expanding manufacturing methodology and the applications of polymeric materials, especially for bioactive composites, where conventional high‐temperature processing is not applicable. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2514–2520

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“…Whereas the segmental dynamics in the surface is not only influenced by the interactions among the chain segments but also by the surrounding environment of the polymer. 4,6,7,9,13,[36][37][38][39][40][41][42][43][44] However, it is hard to explore the glass transition of the polymer surface due to the disturbance from the polymer bulk. Note that since the discovery of the deviation from bulk values of T g of nano-sized polymers, there has been intense interest in demonstrating and understanding the glass transition of the polymer surface from another angle.…”

Section: Introductionmentioning

confidence: 99%

Glass transition of poly(methyl methacrylate) nanospheres in aqueous dispersion

Feng

Chen

Mai

et al. 2014

Phys. Chem. Chem. Phys.

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Surfactant-free nanospheres and latex nanospheres of poly(methyl methacrylate) (PMMA) with diameter ranging from 20 to 220 nm are prepared by atom transfer radical polymerization (ATRP) in microemulsions and subsequent dialysis against deionized water. The glass transitions of these PMMA nanospheres are characterized using nano differential scanning calorimetry (nano-DSC) in aqueous dispersions. The glass transition temperature (Tg) of the surfactant-free PMMA nanospheres and nonionic PMMA latex nanospheres with diameters below 150 nm is less than that of the PMMA bulk, and Tg decreases with the decrease of the diameter. In contrast, Tg of the anionic PMMA latex nanospheres is size-independent and is near to that of the PMMA bulk. The influence of the environment surrounding the PMMA nanospheres on glass transitions as well as comparisons to our prior studies with polystyrene (PS) nanospheres in aqueous dispersions are discussed.

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Detection of Interchain Proximity and Segmental Motion of Polymer Glass

Cited by 21 publications

References 24 publications

Glassy dynamics of soft matter under 1D confinement: How irreversible adsorption affects molecular packing, mobility gradients and orientational polarization in thin films

Glassy dynamics of soft matter under 1D confinement: How irreversible adsorption affects molecular packing, mobility gradients and orientational polarization in thin films

Low‐temperature processing of polymer nanoparticles for bioactive composites

Glass transition of poly(methyl methacrylate) nanospheres in aqueous dispersion

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