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Lorentz - 2008 Atomistic Modelling of Deformed Polymer Glasses Alexey Lyulin Group Polymer Physics, Eindhoven Polymer Laboratories and Dutch Polymer Institute, Technische Universiteit Eindhoven, The Netherlands

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Lorentz - 2008 Participants TU EindhovenTU AthensMPI-P Mainz Thijs MichelsDoros TheodorouNico v.d. Vegt B. Vorselaars C. TzoumanekasV. Harmandaris T. Mulder L. Peristeras E. de Caluwe H.E.H. Meijer L. Govaert IMPB RAN, PuschinoICP RAN, MoscowTver University N.K. BalabaevM.A. MazoA.S. Pavlov E.F. OlejnikI. Neratova

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Lorentz - 2008 Motivation Brittle Polystyrene Polycarbonate vs. Tough

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Lorentz - 2008 Another puzzle

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Lorentz - 2008 Stress-strain behaviour Intrinsic microscopic response vs chemical structure unclear (e.g. H.E.H. Meijer et al., TU/e and DPI) PC PS extension PC PS compression

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Lorentz - 2008 Thermal and mechanical rejuvenation Thermal: heating up above T g, then quenching H.G.H. van Melick, PhD thesis, Eindhoven, 2002

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Lorentz - 2008 Thermal and mechanical rejuvenation H.G.H. van Melick, PhD thesis, Eindhoven, 2002 Mechanical: deformation above the yield point, then compression

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Lorentz - 2008 Thermal and mechanical rejuvenation Thermal: heating up above T g, then quenching Mechanical: deformation above the yield point, then compression Bulk mechanics similar Microscopically the same ???? No !

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Lorentz - 2008 PS vs PC as model amorphous polymers PS fails brittle, PC tough PS shows more post-yield stress drop, large strain softening What is the relation with molecular structure and chain dynamics ?

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Lorentz - 2008 T ~ T g P = 1 atm Equilibration PS PC

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Lorentz - 2008 Characteristic ratio PS PC SANS: Boothroyd et al., 8.7-9.6 simulations: Han and Boyd, 10.2 Sun and Faller, 6.5 SANS: Gawrisch, Brereton, Fischer, 1.9-2 simulations: Hutnik, Argon, Suter, 1.6 (Wittmer, Meyer, Baschnagel, Johner, Obukhov, Mattioni, Müller, Semenov, PRL, 2004)

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Lorentz - 2008 Cooling down below T g Cooling time, c 10 ps (quenched) 25 ns (annealed)

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Lorentz - 2008 Orientational mobility b polystyrenepolycarbonate

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Lorentz - 2008 Equilibrated films, T =540 K 8x80, 38 Å 16x80, 65 Å 32x80, 112 Å

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Lorentz - 2008 Orientational mobility film bulk

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Lorentz - 2008 P 2 relaxation-time distribution (CONTIN analysis) AVL, M.A.J. Michels, J. Non-Cryst. Solids 2006 -process -process PC

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Lorentz - 2008 Temperature dependence of P 2 relaxation times polystyrene polycarbonate ~ 50 ps ~ 500 ps << T = 300K

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Lorentz - 2008 Uniaxial extension PS: 4 chains x N=160, 8 chains x N=80 PC: 64 chains x N=10, 8 chains x N=80 L =0 L =65% L =110% AVL, N.K. Balabaev, M.A. Mazo, M.A.J. Michels, Macromolecules 2004 Å/ps

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Lorentz - 2008 PC: T << T g PS:

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Lorentz - 2008 Simulation vs. experiment PC PS H.G.H. van Melick et al., Polymer 2003 AVL, B. Vorselaars, M. Mazo, N. Balabaev, M.A.J. Michels, Europhys. Lett. 2005

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Lorentz - 2008 Simulation vs. experiment quenched annealed polystyrene AVL, M.A.J. Michels, Phys. Rev. Lett., 2007 H.G.H. van Melick, PhD thesis, Eindhoven, 2002 polystyrene

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Lorentz - 2008 Three time scales cooling: c ~ 10 ps (quenched) << 25000 ps (annealed) deformation: y ~ 1000 ps - relaxation: ~ 50 ps (PS) <<500 ps (PC) (PS) c (quenched) (PC)>> c (quenched) c (annealed) >> , y for both polymers

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Lorentz - 2008 Stretching - compression loop: quenched samples mechanical overaging because of the process - faster for PS, slower for PC - effect is larger for PC

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Lorentz - 2008 Stretching - compression loop: annealed samples

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Lorentz - 2008 Energy partitioning AVL, M.A.J. Michels, Phys. Rev. Lett., 2007 Energy distribution mechanically rejuvenated glass is different from thermally rejuvenated glass

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Lorentz - 2008 Summary, questions T g, overaging and rejuvenation for typical polymer glasses have been simulated; Key factors are ratios between three time scales: - relaxation; - cooling time; - deformation time; Fast relaxation for PS, slow for PC; Thermal and mechanical rejuvenation are microscopically different Direct measurement of segmental mobility under mechanical deformation

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