Dynamics, fragility, and glass transition of low-molecular-weight linear homopolymers

This fundamental contribution on time-of-flight secondary ion mass spectrometry polymer depth-profiling by massive argon clusters is focused on the investigation of the influence of the Ar cluster size and the molecular weight of the investigated polymers on the efficiency of the sputtering process. For this purpose, 100-nm thin films of polymethylmethacrylate and polystyrene, with a range of molecular weights (10 3 -1.5 × 10 5 amu) spin-coated onto Si wafers, are sputtered by 10 keV Ar n + cluster ions with selected sizes (1500, 3000 and 5000 atoms/cluster) employing Bi 5 + as an analysis source. The experiments show that the sputtering yield volume (nm 3 /primary ion), Y, decreases with the increase of the molecular weight, M w , for a selected cluster size, and at constant molecular weight, Y decreases with the increase in cluster size. The experimental results are in good agreement with molecular dynamics simulations and previous studies for high molecular weight PS. Furthermore, the trend of Y versus M w seems to be related to the variation of the glass transition temperature (T g ) of the investigated polymers.

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“…a (analogous considerations can be done for PMMA, Fig. b) . The anticorrelation between Y and T g is illustrated in Fig.…”

Section: Discussionmentioning

confidence: 66%

Ar cluster sputtering of polymers: effects of cluster size and molecular weights

Cristaudo

Poleunis

Czerwinski

et al. 2014

Surface & Interface Analysis

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“…At the opposite, some systems show no dependence of the fragility index on the molecular weight. 20 According to Santangelo and Roland, 21 only polymers which exhibit a high cooperativity length at the glass transition, that is the case of PDLLA, 25 show a significant decrease of m with the M w decrease.…”

Section: Resultsmentioning

confidence: 99%

“…The dependence of the segmental dynamics on the chain length has been the focus of several studies. [20][21][22][23][24] A correlation between the fragility index and the chain length is frequently observed. At the opposite, some systems show no dependence of the fragility index on the molecular weight.…”

Section: Resultsmentioning

confidence: 99%

“…In consistence with previous studies, 5 the PDLLA exhibits a fragile behavior ( m = 155), while the oligomers exhibit lower m , which decreases from 99 (OLA2700) down to 68 (OLA1400) with the M w decrease. The dependence of the segmental dynamics on the chain length has been the focus of several studies 20–24 . A correlation between the fragility index and the chain length is frequently observed.…”

Section: Resultsmentioning

confidence: 99%

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Fragility of short‐chain poly(lactic acid)s derivatives by combining dielectric spectroscopy and fast scanning calorimetry

Moghaddam

Quelennec

Delpouve

et al. 2021

Journal of Polymer Science

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Low-molecular-mass bio-polyesters, such as lactic acid oligomers, constitute a growing category of plasticizers for poly (lactic acid), since they show good compatibility and are respectful of the environment. This study focuses on the glass transition of a series of oligomers with different molecular weights, with the aim of investigating how their associated dynamics occur. Dielectric and calorimetric results are combined to study the molecular mobility in a large temperature range. In comparison with poly (lactic acid), the oligomers exhibit a lower fragility index and smaller cooperative rearranging regions. Among oligomers, the fragility is clearly dependent on the molecular weight, whereas the variations of the cooperativity are subtler.

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“…In particular, relaxation mechanisms and mixing rules were carefully taken into account so that consistent values of the common parameters, pertinent to the same relaxation mechanisms at the different masses, are obtained. To the aim, an isofrictional correction (Andreozzi et al 2008;Colby et al 1987) is adopted to consider the different free volume amount at the chain-ends of the lightest samples. Moreover, the role of contour length fluctuation and constraint release relaxation is discussed.…”

Section: Introductionmentioning

confidence: 99%

Onset of entanglement and reptation in melts of linear homopolymers: consistent rheological simulations of experiments from oligomers to high polymers

2014

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The shear rheological behavior is investigated in this work for a series of poly(ethyl acrylate) samples, whose molar mass ranges from oligomers to high polymers. The focus was on studying the onset of entanglement effects over selected reptation models in order to ascertain their ability to reproduce the complex shear modulus of the polymers and to provide consistent values of the microscopic parameters driving the structural relaxation of the polymer system.Among ordinary reptation topological models, we found that, the Doi-Edward model, implemented with contour length fluctuation and constraint release mechanism for the tube relaxation, better reproduced the rheological response of the materials. Most importantly, we were able to simulate material functions to obtain consistent microscopic information on the materials, such as Rouse time and entanglement molar mass, over the whole range of investigated molar masses, therefore overcoming the discrepancy usually found, mostly in the mass region of partial entanglement. Finally, descriptions of the polymer entanglement features, in agreement with the experimental and microscopic model findings, are provided in the framework of the packing-length phenomenological model, and by means of analytical calculations of the polymer viscosity according to the Milner-McLeish-Likhtman model.

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Dynamics, fragility, and glass transition of low-molecular-weight linear homopolymers

Cited by 10 publications

References 21 publications

Ar cluster sputtering of polymers: effects of cluster size and molecular weights

Ar cluster sputtering of polymers: effects of cluster size and molecular weights

Fragility of short‐chain poly(lactic acid)s derivatives by combining dielectric spectroscopy and fast scanning calorimetry

Onset of entanglement and reptation in melts of linear homopolymers: consistent rheological simulations of experiments from oligomers to high polymers

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