School on glass formers and glasses
Greg McKenna Lectures

16 January, 2010

Lecture 1: Structural Recovery in Glasses: Phenomenological Descriptions and Anomalous Behaviours

Abstract

The creation of the non-equilibrium glassy state results in an unstable or metastable material. The kinetics of glass formation and then the subsequent structural recovery as the material equilibrates or responds to complicated thermal histories is generally modeled using phenomenological approaches as current theory has not been fully able to describe the non-equilibrium kinetics. Here we will examine two major approaches that are referred to as the TNM (Tool-Narayanaswamy-Moynihan) and KAHR (Kovacs, Aklonis, Hutchinson, Ramos) models of glassy behavior. Important concepts such as fictive temperature and departure from equilibrium will be used in the discussion. The success and failures of these models will be considered and their implications for the interpretation of such observations as the dynamic heat capacity near to the glass transition will be discussed. Finally, a brief discussion of the so-called Caruthers model or thermoviscoelastic model of glass kinetics will also be presented.

References and suggested reading

  1. G.B. McKenna, “Glass Formation and Glassy Behavior,” in Comprehensive Polymer Science: Vol.2 Polymer Properties, ed. By C. Booth and C. Price, Pergamon, Oxford, 311-363 (1989).
  2. A.Q. Tool, “Relation Between Inelastic Deformability and Thermal Expansion of Glass in Its Annealing Range,” J. Amer. Ceram. Soc., 29, 240-253 (1946); A.Q. Tool, “Viscosity and the Extraordinary Heat Effects in Glass,” J. Research National Bureau of Standards (USA), 37, 73- 90 (1946).
  3. O.S. Narayanaswamy, “A Model of Structural Relaxation in Glass, “J.Am.Ceram.Soc., 54, 491-498 (1971).
  4. C.T. Moynihan, P.B. Macedo, C.J. Montrose, P.K. Gupta, M.A. DeBolt, J.F. Dill, B.E. Dom, P.W.Drake, A.J. Esteal, P.B. Elterman, R.P. Moeller, H. Sasabe and J.A. Wilder, “Structural Relaxation in Vitreous Materials,” Ann. N.Y. Acad. Sci., 279, 15-35 (1976).
  5. A. J. Kovacs, J.J. Aklonis, J.M. Hutchinson and A.R. Ramos, “”Isobaric Volume and Enthalpy Recovery of Glasses. II. A Transparent Multiparameter Model,” J. Polym. Sci., Polym. Phys. Ed., 17, 1097-1162 (1979).
  6. I. M. Hodge, “Enthalpy Relaxation and Recovery in Amorphous Materials,” J. Non-Crystalline Solids, 169, 211-266 (1984).
  7. S. R. Lustig, R.M. Shay and J.M. Caruthers, “Thermodynamic Constitutive Equations for Materials with Memory on a Material Time Scale,” Journal of Rheology, 40, 69-106 (1996).
  8. S.L. Simon and G.B. McKenna, “Interpretation of the Dynamic Heat Capacity Observed in Glass-Forming Liquids,” J. Chem. Phys., 107, 8678-8685 (1997).

 

 

18 January, 2010

Lecture 2: Structural Recovery in Glasses: Aging and Rejuvenation

Abstract

Associated with the changes in structure that occur in the non-equilibrium glass are changes in the dynamic responses, such as the viscoelastic response or the dielectric response. The changes in these latter properties are referred to as physical aging and are well understood in the linear response regime. On the other hand, in the nonlinear response regime, there is a much lower level of understanding, possibly because of the nonlinear mechanics that is involved in the experiments that have been used to evidence erasure or rejuvenation responses. In this lecture, we will summarize the linear aging response regime and show where the classical picture is valid and where there may be problems with it. We will then discuss the issues surrounding aging in the nonlinear response regime and that is often referred to as rejuvenation. It will be shown from a range of novel mechanical testing experiments that rejuvenation of the glass is only apparent and alternative interpretations are required. Recent computer simulations consistent with this view will be briefly mentioned as well. Finally, the understanding of structural recovery and physical aging in molecular glasses will be discussed in terms of its relevance to the apparent aging of colloidal glasses.

References and suggested reading

  1. L.C.E. Struik, Physical Aging in Polymers and Other Amorphous Materials, Elsevier, Amsterdam (1976).
  2. G.B. McKenna, “Mechanical Rejuvenation in Polymer Glasses: Fact or Fallacy?,” J. Phys. Cond. Matter, 15, S737-S763 (2003).
  3. R. S. Duran and G.B. McKenna, "A Torsional Dilatometer for Volume Change Measurements on Deformed Glasses: Instrument Description and Measurements on Equilibrated Glasses," J. Rheol., 34, 813-839 (1990).
  4. J.M. Hutchinson, “Physical Aging of Polymers,” Prog. Polym. Sci., 20, 703-760 (1995).
  5. B.A. Isner and D.J. Lacks, “Generic Rugged Landscapes under Strain and the Possibility of Rejuvenation in Glasses,” Phys. Rev. Lett., 96, 025506-1 – 025506-4 (2006).
  6. G.B.McKenna, T. Narita and F. Lequeux, “Soft Colloidal Matter: A Phenomenological Comparison of the Aging and Mechanical Responses with Those of Molecular Glasses,” J. Rheol., 53, 489-516 (2009).

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20 January, 2010

Lecture 3: Free Volume, configurational entropy and other aspects of the glass transition: Perspectives from engineering / expermental view

Abstract

The glass transition is often debated as a thermodynamic vs. kinetic transition and the free volume view of the subject is most often associated with the kinetic interpretation. In the present lecture, we will examine two major free volume models and discuss their ability to describe the phenomenology of the glass transition event. For example, how does composition affect Tg? How does one predict the effect of chemical crosslinking on the glass transition? Can one distinguish between the models? And are the predictions better than those from, e.g., the configurational entropy model of Gibbs and DiMarzio? These and other aspects of the free volume models will be considered.

References and suggested reading

  1. G.B. McKenna, “Glass Formation and Glassy Behavior,” in Comprehensive Polymer Science: Vol. 2. Polymer Properties, ed. By C. Booth and C. Price, Pergamon, Oxford, 311-363 (1989).
  2. M. L. Williams, R. F. Landel, and J. D. Ferry, “The Temperature Dependence of Relaxation Mechanisms in Amorphous Polymers and Other Glass-forming Liquids,” J. Am. Chem. Soc., 77, 3701-3706 (1955).
  3. R. Simha and T. Somcynsky, “On the statistical thermodynamics of spherical and chain molecule fluids,” Macromolecules, 2, 342-350 (1969).
  4. T. Somcynsky and R. Simha, “Hole theory of liquids and glass transition,” J. Appl. Phys., 42, 4545-4548 (1971).
  5. E.A. DiMarzio and J.H. Gibbs, “Chain stiffness and the lattice theory of polymer phases,” J. Chem. Phys., 28, 807-813 (1958).
  6. Gibbs J.H. and DiMarzio E.A., “Nature of the glass transition and the glassy state,” J. Chem. Phys., 28, 373-383 (1958).