Diffusion mechanism for physical aging of polycarbonate far below the glass transition temperature studied by means of dielectric spectroscopy

Cangialosi, Daniele; Wübbenhorst, Michael; Groenewold, Jan; Mendes, Eduardo; Picken, Stephen J.

doi:10.1016/j.jnoncrysol.2005.03.070

Cited by 34 publications

(57 citation statements)

References 24 publications

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“…This assumption arises from the fact that a decrease of the size of free volume holes rather than their number occurs. This would rule out the possibility of diffusion of free volume holes towards the interface, as recently proposed by several studies [14,16,17]. The diffusion mechanism would likely provoke the decrease of the number of free volume holes.…”

Section: Resultsmentioning

confidence: 74%

“…4 the loss part of the permittivity is presented as a function of the frequency at the beginning of the aging process and after aging during 1.1 × 10 4 s for the nanocomposite labelled as V10, as an example, and pure PMMA. The dielectric strength of PMMA β process, showing up in the available frequency window, clearly decreases during the course of aging for both the nancomposites and PMMA as a consequence of reduced orientation polarization due to relaxed molecular dipoles [16,17]. Furthermore, the decrease of the dielectric strength of PMMA β process is more marked in the nanocomposites than in pure PMMA.…”

Section: Resultsmentioning

confidence: 95%

“…Despite this, a number of experiments in polymer films with thickness in the micron range clearly display accelerated physical aging in comparison to the bulk counterpart [13][14][15][16][17]. The typical length scale of these systems is therefore far too large to justify any argument invoking the role of surface or finite size effects.…”

Section: Introductionmentioning

confidence: 99%

“…The latter technique was also employed to assess the effect of silica particles on PMMA molecular mobility. Similarly to polymer thin films [13][14][15][16][17], physical aging in PMMA/silica nanocomposites speeds up in comparison to pure PMMA and such acceleration is more pronounced for nanocomposites with larger ratio area of silica/volume of polymer. Furthermore no effect on mobility due to the presence of silica particles was found.…”

Section: Introductionmentioning

confidence: 99%

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Physical aging in PMMA/silica nanocomposites: Enthalpy and dielectric relaxation

Boucher

Cangialosi

Alegría

et al. 2011

Journal of Non-Crystalline Solids

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We have investigated the physical aging below the glass transition temperature, namely the slow evolution occurring in non-equilibrium glasses, of poly(methyl methacrylate)/silica (PMMA/silica) nanocomposites. To do so we have followed the time evolution of the enthalpy and that of the dielectric strength of PMMA β process during isothermal annealing. The results indicate that physical aging is generally accelerated in all nanocomposites in comparison to pure PMMA, despite the lack of effect of the nanoparticles on PMMA molecular dynamics. Furthermore, the shorter is the interparticle distance, and hence the higher is the area/ volume of silica in PMMA, the more pronounced is such acceleration. The acceleration of the physical aging together with the invariance of PMMA dynamics in the nanocomposites in comparison to pure PMMA poses serious questions on the idea that the molecular mobility is the only responsible parameter for the rapidity of physical aging. Thus, an interpretation based on the free volume holes diffusion towards the external surface, in this case represented by the polymer/silica interface, is provided.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Physical aging in PMMA/silica nanocomposites: Enthalpy and dielectric relaxation

Boucher

Cangialosi

Alegría

et al. 2011

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

show abstract

“…In addition to the T g -confinement effects, there has been much interest in the effect of confinement on the "physical aging" of polymer films and nanocomposites [19][20][21][22][23][24][25]. Physical aging is the observed continuous change in properties as a function of thermal history or annealing time below T g .…”

Section: Introductionmentioning

confidence: 99%