Abstract
AbstractThe remarkable elastic properties of polymers are ultimately due to their molecular structure, but the relation between the macroscopic and molecular properties is often difficult to establish, in particular for (bio)polymers that contain hydrogen bonds, which can easily rearrange upon mechanical deformation. Here we show that two-dimensional infrared spectroscopy on polymer films in a miniature stress tester sheds new light on how the hydrogen-bond structure of a polymer is related to its visco-elastic response. We study thermoplastic polyurethane, a block copolymer consisting of hard segments of hydrogen-bonded urethane groups embedded in a soft matrix of polyether chains. The conventional infrared spectrum shows that upon deformation, the number of hydrogen bonds increases, a process that is largely reversible. However, the 2DIR spectrum reveals that the distribution hydrogen-bond strengths becomes slightly narrower after a deformation cycle, due to the disruption of weak hydrogen bonds, an effect that could explain the strain-cycle induced softening (Mullins effect) of polyurethane. These results show how rheo-2DIR spectroscopy can bridge the gap between the molecular structure and the macroscopic elastic properties of (bio)polymers.
Publisher
Cold Spring Harbor Laboratory
Reference26 articles.
1. Multiple-length-scale deformation analysis in a thermoplastic polyurethane;Nature Communications,2015
2. Sui, T. ; Salvati, E. ; Ying, S. ; Sun, G. ; Dolbnya, I. P. ; Dragnevski, K. ; Prisacariu, C. ; Korsunsky, A. M. Strain softening of nano-scale fuzzy interfaces causes Mullins effect in thermoplastic polyurethane. Scientific reports 2017, 7.
3. Destruction and Reorganization of Physically Cross-Linked Network of Thermoplastic Polyurethane Depending on Its Glass Transition Temperature;ACS Applied Polymer Materials,2019
4. Siesler, H. W. Analysis/Networks/Peptides; Springer Berlin Heidelberg: Berlin, Heidelberg, 1984; pp 1–77.
5. A Rheo-Optical FTIR Spectrom-eter for Investigating Molecular Orientation and Viscoelastic Behavior in Polymers;International Journal of Polymer Analysis and Characterization,2004