Some open challenges in polymer physics

• Published in: Polymer engineering and science Vol. 62; no. 5; pp. 1325 - 1355
• Main Authors: McKenna, Gregory B., Chen, Dongjie, Mangalara, Satish Chandra Hari, Kong, Dejie, Banik, Sourya
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.05.2022; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd; Wiley Blackwell (John Wiley & Sons)
• Subjects: Analysis; cyclic macromolecules; DNA; fictive temperature; Fluoropolymers; glass and glass transition; Glass transition temperature; Heterogeneity; Hole burning; ideal glass; LAOS; macromolecular rings; Macromolecules; mechanical spectral hole burning; molecular rheology; nonlinear viscoelasticity; Physics; polymer dynamics; Polymer physics; Polymers; Properties; Rheological properties; Rheology; Temperature; Temperature dependence; ultrastable glass; Vapor deposition; Viscoelastic materials; Viscoelasticity; United States
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.25938

Three subjects in polymer and soft matter physics are outlined in the present article. The first relates to concepts of an ideal glass transition. We describe work on ultra‐stable glass, either a 20‐million‐year‐old amber or a vapor deposited amorphous fluoropolymer, which examines the temperature dependence of the dynamics in a window between a low fictive temperature and the glass transition temperature. From this “finesse” of the problem of the geological time scales in sub‐glass temperature systems strong evidence that the divergence of the relaxation times at finite temperature from WLF‐types of extrapolation is not correct. The second topic is polymer nonlinear viscoelasticity as it relates to dynamic heterogeneity. We show results from mechanical hole burning experiments that suggest that dynamic heterogeneity arises from the nature of specific relaxation mechanisms rather than heterogeneous changes in, for example, the fictive temperature. Included is a discussion of large amplitude oscillatory shear testing and how it relates to characterization of nonlinear viscoelastic materials. The last topic addressed is the rheology of circular macromolecules. Here, we take a historical perspective and describe important new results from several laboratories that seem inconsistent. New works from our own studies on circular DNA are also discussed.