Glass transition phenomena observed in stereoregular PMMAs using molecular modeling

Soldera, Armand; Metatla, Noureddine

doi:10.1016/j.compositesa.2004.10.019

Cited by 26 publications

(18 citation statements)

References 31 publications

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“…These latter parameters are specifically computed to accurately mimic the liquid phase. A better determination of T g s is obtained using OPLS comparatively to the use of AMBER whose non-bond parameters have been determined from crystal structures: difference in T g s between the two configurations of PMMA has been shown to be better depicted using OPLS [33,34].…”

Section: Simulated Dilatometrymentioning

confidence: 99%

Computation of densities, bulk moduli and glass transition temperatures of vinylic polymers from atomistic simulation

Metatla

Soldera

2006

Molecular Simulation

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Section: Simulated Dilatometrymentioning

confidence: 99%

Computation of densities, bulk moduli and glass transition temperatures of vinylic polymers from atomistic simulation

Metatla

Soldera

2006

Molecular Simulation

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“…Simulations also allow us to explore and validate specific mechanisms for motion directly: for example, the association of the R-relaxation with motion of the chain backbone, and connection of the -relaxation to the rotation of the ester side group. At the same time, only a few works have been done on PMMA MD simulations [19][20][21] and therefore we also propose a force field for this purpose and validate it against QENS data.…”

Section: Introductionmentioning

confidence: 98%

Local Dynamics of Syndiotactic Poly(methyl methacrylate) Using Molecular Dynamics Simulation

2006

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The local dynamics of syndiotactic poly(methyl methacrylate) (PMMA) are investigated by explicit atom molecular dynamics (MD) simulations and quasielastic neutron scattering at temperatures well above the glass transition temperature. Using MD, we are able to isolate specific local motions well above T g . These include rotations of the R-methyl and ester methyl, rotations of the entire ester side group and segmental motion of the chain backbone. This capacity is unique to simulation as proton motion at high temperatures necessarily involves multiple motions. The force field used is validated by direct comparison to structural and dynamic neutron scattering measurements, and by comparison via temperature extrapolation of activation energies and rotational times for methyl group rotations. We find that the rotation of the ester side group is consistent with the -relaxation at low temperatures: the activation energy closely matches that assigned from dielectric spectroscopy (DS), and relaxation times are also consistent with these measurements. Although the ester protons rotate continuously with no preferred spatial orientation, the rotation of the ester oxygen around the C 1 -C bond [O-C-C 1 -C 3 ] does appear to be a 2-fold jump as observed in NMR experiments. The R-relaxation is associated with the motion of the main chain. Relaxation times for these protons are not Arrhenius, but rather begin to diverge as the temperature is lowered. Rotation of the slower R-CH 3 group occurs with rates similar to the R-and -relaxations in the temperature range we investigate. Both this rotation and that of the ester side group are more prominent at smaller scales and explain why neutron scattering measurements on PMMA reveal the R-relaxation as the spatial scale is increased.

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“…The presence of polar groups such as carbonyl in polymeric macromolecules tends to draw the polymer chains together, increasing the secondary bonds 26 . The higher the attractive secondary bonds, the lower the ability of the chain to crossover the energetic barrier, and thus the higher the T g 27 . These aspects may help explain the higher T g values recorded in this study for materials Ufi Gel hard and Tokuso Rebase Fast.…”

Section: Discussionmentioning

confidence: 54%

Glass transition temperature of hard chairside reline materials after post‐polymerisation treatments

Urban¹,

Machado²,

Alves³

et al. 2010

Gerodontology

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Glass transition phenomena observed in stereoregular PMMAs using molecular modeling

Cited by 26 publications

References 31 publications

Computation of densities, bulk moduli and glass transition temperatures of vinylic polymers from atomistic simulation

Computation of densities, bulk moduli and glass transition temperatures of vinylic polymers from atomistic simulation

Local Dynamics of Syndiotactic Poly(methyl methacrylate) Using Molecular Dynamics Simulation

Glass transition temperature of hard chairside reline materials after post‐polymerisation treatments

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