title: Evolution of collective motion in a model glass-forming liquid during physical aging.
abstract: At temperatures moderately below their glass transition temperature, the properties of many glass-forming materials can evolve slowly with time in a process known as physical aging whereby the thermodynamic, mechanical, and dynamic properties all drift towards their equilibrium values. In this work, we study the evolution of the thermodynamic and dynamic properties during physical aging for a model polymer glass. Specifically, we test the relationship between an estimate of the size of the cooperative rearrangements taking the form of strings and the effective structural relaxation time predicted by the Adam-Gibbs relationship for both an equilibrium supercooled liquid and the same fluid undergoing physical aging towards equilibrium after a series of temperature jumps. We find that there is apparently a close correlation between a structural feature of the fluid, the size of the string-like rearrangements, and the structural relaxation time, although the relationship for the aging fluid appears to be distinct from that of the fluid at equilibrium.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Shavit
authors.forename: Jack F
authors.initials: JF
authors.lastname: Douglas
authors.forename: Robert A
authors.initials: RA
authors.lastname: Riggleman
mesh_terms: D005898:Glass / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D009038:Motion; D011108:Polymers / Q000737:chemistry*; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D011108:Polymers
references.citation: Annu Rev Phys Chem. 2007;58:235-66
references.pmid: 17067282
references.citation: Phys Rev Lett. 2011 Mar 18;106(11):115702
references.pmid: 21469879
references.citation: J Phys Chem B. 2011 Dec 8;115(48):14068-76
references.pmid: 21718061
references.citation: Phys Rev Lett. 2004 Jan 30;92(4):045504
references.pmid: 14995386
references.citation: Phys Rev Lett. 2006 Jul 28;97(4):045502
references.pmid: 16907588
references.citation: Science. 2004 Feb 6;303(5659):823-6
references.pmid: 14764875
references.citation: Proc Natl Acad Sci U S A. 2009 Mar 10;106(10):3675-9
references.pmid: 19234111
references.citation: J Chem Phys. 2006 Feb 14;124(6):64901
references.pmid: 16483238
references.citation: Phys Rev Lett. 2010 May 21;104(20):205501
references.pmid: 20867036
references.citation: Science. 2005 Dec 16;310(5755):1797-800
references.pmid: 16357256
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Sep;76(3 Pt 1):031802
references.pmid: 17930264
references.citation: Annu Rev Phys Chem. 2010;61:191-217
references.pmid: 20055676
references.citation: J Chem Phys. 2012 Apr 21;136(15):154901
references.pmid: 22519344
references.citation: J Chem Phys. 2006 Oct 14;125(14):144907
references.pmid: 17042650
references.citation: Phys Rev Lett. 2002 Mar 11;88(10):105503
references.pmid: 11909369
references.citation: Phys Rev Lett. 2007 Nov 23;99(21):215501
references.pmid: 18233224
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Oct;70(4 Pt 1):041202
references.pmid: 15600400
references.citation: Phys Rev Lett. 2005 Nov 25;95(22):225504
references.pmid: 16384233
references.citation: J Chem Phys. 2007 Jun 21;126(23):234903
references.pmid: 17600442