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Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body

Publication ,  Journal Article
Saito, I; Sheridan, RJ; Zauscher, S; Brinson, LC
Published in: Macromolecules
January 28, 2025

Understanding the mechanical properties of polymer nanocomposite materials is essential for industrial use. Particularly, the determination of the polymer modulus at the nanofiller-polymer interphase is important for optimizing the interfacial mechanical properties. Nanoindentation via Atomic Force Microscopy (AFM) is well-established for measuring the modulus of the interphase region with nanoscale spatial resolution. However, indentation into heterogeneous materials presents a confounding issue often referred to as the “substrate effect”, i.e., the structural stress field caused by the rigid body is convoluted with the actual modulus of the interphase region. While finite element analysis (FEA)-based methods can be used to deconvolute the interphase modulus from measured apparent modulus-distance profiles, the experimental validation of this method is still needed. Here, we provide this validation using AFM nanoindentation on a layered model composite that consists of three layers with different moduli to recapitulate the properties of the matrix, the filler, and the interphase of real polymer nanocomposites. By systematically varying the thickness of the “artificial” interphase layer and the AFM probe radius, we obtain modulus-distance profiles over a wide range of indentation conditions. We validate a method to deconvolute the substrate effect using an empirically derived master curve obtained from FEA analysis. Furthermore, we showed that the effect of the artificial interphase on modulus- distance profiles can be distinguished only if the interphase layer is thick enough compared to the contact radius of the probe. Finally, we established an innovative and quantitative framework to predict the interphase thickness from mechanical nanoindentation measurements and discussed the lower, practical limit for interphase thickness determination. In summary, we provide a broadly applicable method to extract interphase mechanical properties of multiphase soft materials and practical guidelines for choosing optimal characterization conditions.

Duke Scholars

Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

January 28, 2025

Volume

58

Issue

2

Start / End Page

980 / 988

Related Subject Headings

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

Citation

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MLA
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Saito, I., Sheridan, R. J., Zauscher, S., & Brinson, L. C. (2025). Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body. Macromolecules, 58(2), 980–988. https://doi.org/10.1021/acs.macromol.4c01993
Saito, I., R. J. Sheridan, S. Zauscher, and L. C. Brinson. “Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body.” Macromolecules 58, no. 2 (January 28, 2025): 980–88. https://doi.org/10.1021/acs.macromol.4c01993.
Saito I, Sheridan RJ, Zauscher S, Brinson LC. Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body. Macromolecules. 2025 Jan 28;58(2):980–8.
Saito, I., et al. “Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body.” Macromolecules, vol. 58, no. 2, Jan. 2025, pp. 980–88. Scopus, doi:10.1021/acs.macromol.4c01993.
Saito I, Sheridan RJ, Zauscher S, Brinson LC. Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body. Macromolecules. 2025 Jan 28;58(2):980–988.
Journal cover image

Published In

Macromolecules

DOI

EISSN

1520-5835

ISSN

0024-9297

Publication Date

January 28, 2025

Volume

58

Issue

2

Start / End Page

980 / 988

Related Subject Headings

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