Paper Number
PO24
Session
Poster Session
Title
Linear and nonlinear shear rheology of pure ring polymers using cyclic poly(phthalaldehyde)
Presentation Date and Time
October 23, 2019 (Wednesday) 6:30
Track / Room
Poster Session / Ballroom C on 4th floor
Authors
- Tu, Michael Q. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Lee, Johnny Ching-Wei (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
- Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Schroeder, Charles M (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Michael Q. Tu, Johnny Ching-Wei Lee, Simon A. Rogers, and Charles M Schroeder
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Tu, Michael Q.
Text of Abstract
Ring polymers have fascinated polymer chemists and physicists for decades, yet achieving a complete understanding of the dynamics of pure ring polymer systems has remained a grand challenge due to experimental ring polymer systems suffering from linear polymer contamination. Even with recent advances in purification methods, existing ring polymer samples are thought to contain trace amounts of contaminant linear polymers, which have been shown to greatly affect the rheological response of these samples. In this work, we approach understanding the rheology of ring polymer systems by utilizing cyclic poly(phthalaldehyde), a low-ceiling temperature polymer whose metastable chemistry results in kinetically-trapped cyclic polymers above -40°C. Above this temperature, any linear chains present will degrade from free ends, resulting in a system comprised of highly pure and stable ring polymers. The synthesis is facile and can be performed at the multi-gram scale. Due to the self-immolating nature of linear chains at room temperature, no additional purification after synthesis is needed to separate linear and circular chains. We report the linear and nonlinear viscoelastic properties of highly concentrated cPPA samples (>70 wt%) of various molecular weights. The transient nonlinear start-up shear responses shows stronger shear-thinning than a previously-reported polystyrene ring melt, but exhibit drastically reduced scaling behavior in the overshoot viscosity and strain with respect to shear rate. We attribute these differences to the fact that the molecular weights of our samples are high (Mw > 200 kDa) and our samples are highly pure with respect to ring/linear purity. Overall, these results give experimental insight into the dynamics of ring polymer systems with unprecedented purity.