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Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s

Publication ,  Journal Article
Chen, K; Dreger, NZ; Peng, F; Vogt, BD; Becker, ML; Cakmak, M
Published in: Macromolecules
October 23, 2018

The uniaxial mechano-optical behavior of a series of amorphous l-valine-based poly(ester urea) (VAL-PEU) with varying diol lengths was studied to elucidate the molecular mechanism associated with their thermal shape memory properties. A custom, real-time measurement system was used to capture the true stress, true strain, and birefringence during the temporary shape programming at stretching temperatures above the glass transition temperature (Tg). The mechano-optical response of VAL-PEUs exhibits an initial photoelastic behavior related to enhanced segmental correlation at low temperatures above the Tg. A characteristic temperature, defined as the liquid-liquid (Tll) transition (rubbery-viscous transition), was found at about 1.05 Tg (K) (at Tg + 15 °C) at strain rate of 0.017 s-1, above which the segmental contacts largely "melt" and the initial slope of the stress-optical curves becomes temperature independent. This temperature corresponds to the temperature where mean relaxation time for the polymer is maximized. Real-time infrared spectroscopy (IR) and in situ wide-angle X-ray scattering (WAXS) revealed a strain-induced intersegmental structural change during stretching. The intermolecular hydrogen bonding between the urea-urea and/or urea-carbonyl groups was found to adopt different bonding modes at the onset of strain hardening with a concurrent increased separation distance between adjacent segments. The hydrogen bonding strengthened supramolecular packing. The compromised shape recovery is a result of the disruption of the rigid segmental correlation, induced either by large extension at T < Tll or by progressive thermal effects at T > Tll, both of which may be minimized at Tll.

Duke Scholars

Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

October 23, 2018

Volume

51

Issue

20

Start / End Page

8114 / 8126

Related Subject Headings

  • Polymers
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences
 

Citation

APA
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ICMJE
MLA
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Chen, K., Dreger, N. Z., Peng, F., Vogt, B. D., Becker, M. L., & Cakmak, M. (2018). Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s. Macromolecules, 51(20), 8114–8126. https://doi.org/10.1021/acs.macromol.8b01176
Chen, K., N. Z. Dreger, F. Peng, B. D. Vogt, M. L. Becker, and M. Cakmak. “Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s.” Macromolecules 51, no. 20 (October 23, 2018): 8114–26. https://doi.org/10.1021/acs.macromol.8b01176.
Chen K, Dreger NZ, Peng F, Vogt BD, Becker ML, Cakmak M. Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s. Macromolecules. 2018 Oct 23;51(20):8114–26.
Chen, K., et al. “Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s.” Macromolecules, vol. 51, no. 20, Oct. 2018, pp. 8114–26. Scopus, doi:10.1021/acs.macromol.8b01176.
Chen K, Dreger NZ, Peng F, Vogt BD, Becker ML, Cakmak M. Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l -Valine-Based Poly(ester urea)s. Macromolecules. 2018 Oct 23;51(20):8114–8126.
Journal cover image

Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

October 23, 2018

Volume

51

Issue

20

Start / End Page

8114 / 8126

Related Subject Headings

  • Polymers
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences