PT  - JOURNAL ARTICLE
AU  - Giulia Giubertoni
AU  - Michiel Hilbers
AU  - Hajo Groen
AU  - Anne Van der Weide
AU  - Daniel Bonn
AU  - Sander Woutersen
TI  - Rheo-2DIR spectroscopy reveals strain-induced hydrogen-bond redistribution in polyurethane
AID  - 10.1101/2022.10.04.510759
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.10.04.510759
4099  - http://biorxiv.org/content/early/2022/10/04/2022.10.04.510759.short
4100  - http://biorxiv.org/content/early/2022/10/04/2022.10.04.510759.full
AB  - The 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.Competing Interest StatementThe authors have declared no competing interest.