POS2-0308
Nanomechanical Characterization of Fibrillar Structures in Liquid Crystalline Polymers under Uniaxial Stretching by In Situ AFM Nanomechanics
Topic
S2. High-End Characterization/Polymer Physics/Properties
When and Where
Sep 29, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Hae Jung SON
Boseok KANG
Presenter(s)
Yuto MIZUNO (Institute of Science Tokyo)
Co-Author(s)
Abstract
Main-chain liquid crystalline polymers (LCPs) exhibit excellent mechanical properties owing to highly oriented fibrillar structures. Although microfibrils have been proposed as fundamental stress-transfer units, the nanoscale stress-transfer mechanism within the fibrillar hierarchy remains unclear. In this study, local deformation and nanomechanical responses in fibrillar LCPs were investigated using in situ AFM nanomechanics.
An aromatic copolyester LCP composed of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid was examined. PeakForce QNM nanomechanical mapping combined with a custom-built tensile stage enabled repeated observation of the same nanoscale region (0.5 μm × 0.5 μm), allowing direct comparison of local strain and modulus evolution under macroscopic strains up to approximately 7%.
AFM height images revealed fibrillar structures on the LCP surface. Upon stretching, fibrillar morphology gradually changed without apparent fibril fracture. Simultaneously, local Young’s modulus decreased with increasing macroscopic strain, showing an average reduction of approximately 30% near the highest strain level.
Despite uniform macroscopic tensile loading, heterogeneous local strain distributions were observed within the same observation area. At approximately 7% macroscopic strain, local strains ranged from +14% extension to −14% contraction, substantially exceeding the applied macroscopic strain. Local mechanical responses depended strongly on local deformation modes. Regions undergoing local stretching generally exhibited decreases in Young’s modulus, whereas increases in modulus were observed only in locally contracted regions during global tensile deformation.
These results indicate redistribution of local stress-transfer states during stretching and suggest that variations in interfibrillar interactions contribute significantly to the heterogeneous mechanical response of fibrillar LCP structures.
An aromatic copolyester LCP composed of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid was examined. PeakForce QNM nanomechanical mapping combined with a custom-built tensile stage enabled repeated observation of the same nanoscale region (0.5 μm × 0.5 μm), allowing direct comparison of local strain and modulus evolution under macroscopic strains up to approximately 7%.
AFM height images revealed fibrillar structures on the LCP surface. Upon stretching, fibrillar morphology gradually changed without apparent fibril fracture. Simultaneously, local Young’s modulus decreased with increasing macroscopic strain, showing an average reduction of approximately 30% near the highest strain level.
Despite uniform macroscopic tensile loading, heterogeneous local strain distributions were observed within the same observation area. At approximately 7% macroscopic strain, local strains ranged from +14% extension to −14% contraction, substantially exceeding the applied macroscopic strain. Local mechanical responses depended strongly on local deformation modes. Regions undergoing local stretching generally exhibited decreases in Young’s modulus, whereas increases in modulus were observed only in locally contracted regions during global tensile deformation.
These results indicate redistribution of local stress-transfer states during stretching and suggest that variations in interfibrillar interactions contribute significantly to the heterogeneous mechanical response of fibrillar LCP structures.
