Paper Number
RS26 

Session
Techniques and Methods: Rheometry & Spectroscopy/Microscopy

Title
Meso-scale topology variation during stress relaxation of main-chain liquid crystal elastomers via digital image correlation

Presentation Date and Time
October 12, 2022 (Wednesday) 2:10

Track / Room
Track 6 / Mayfair

Authors (Click on name to view author profile)

  1. Forster, Aaron (National Institute of Standards and Technology)
  2. Van Blitterswyk, Jared (NIST)
  3. Nguyen, Thao D. (Johns Hopkins University)

Author and Affiliation Lines (in printed abstract book)
Aaron Forster1, Jared Van Blitterswyk1 and Thao D. Nguyen2
1National Institute of Standards and Technology, Gaithersburg, MD; 2Johns Hopkins University, Baltimore, MD

Speaker / Presenter 
Forster, Aaron

Keywords
experimental methods; microscopy; rheometry techniques

Text of Abstract
Liquid crystal elastomers (LCEs) are cross-linked elastomer networks with liquid crystalline regions (i.e. mesogens) integrated into the polymer chains. External fields such as stress, electromagnetic, or thermal may be used to locally orient the mesogen phases in the principle direction of the applied external field. Stress remains one of the easiest methods to induce large scale mesogen rotation, leading to a non-linear stress-strain response that allows LCEs to dissipate large amounts of energy. The non-linear response reflects the interplay between the amorphous polymer chains/crosslinks and the mesogens. Two predominant time-scales are identified as a fast relaxation of the polymer network and a slower relaxation of the mesogens. However, the evolution of mesogen re-orientation can be highly heterogeneous and depends on chemistry, initial nematic order, applied load and loading rate. In this work, the stress relaxation behavior of polydomain and monodomain LCEs is measured as a function of applied strain and time. Digital image correlation is used to measure the full-field displacement and strain at the surface of the LCE. We report on the development of a rich dataset of structural relaxations as the elastomer relaxes to the applied stress. This technique is readily accessible for the study of the viscoelastic behavior of LCE materials.