In Situ Study of Structure Formation under Stress in Stretchable Conducting Nanocomposites

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Flexible sensors often suffer from decreased conductivity after repeated mechanical stress.
• Understanding the structural behavior of conductive fillers within polymer matrices is crucial for improving sensor durability.

Purpose of the Study:

• To investigate the structural evolution of conducting nanofillers (carbon black and carbon nanotubes) in polydimethylsiloxane (PDMS) under cyclic tensile stress.
• To elucidate the relationship between nanofiller network formation, interfacial interactions, and the electrical properties of flexible conducting films.

Main Methods:

• Incorporation of carbon black and carbon nanotubes into PDMS beyond the percolation threshold.
• Application of cyclic tensile stress and annealing to nanocomposite films.
• Simultaneous in situ stretching, vis-à-vis conductometry, and synchrotron-based ultra-small angle X-ray scattering (USAXS) experiments.
• Systematic variation of carbon nanotube surface chemistry to probe interfacial interactions.

Main Results:

• Cyclic stress and annealing lead to irreversible changes in nanofiller network geometry.
• The fractal dimensions of nanofillers are critical for molecular-level interactions and network stability.
• The observed structural rearrangements directly correlate with the electrical conductivity and stability of the flexible films.

Conclusions:

• The long-term electrical performance of flexible conducting films is governed by the irreversible formation of nanofiller network structures under mechanical and thermal stimuli.
• Tailoring nanofiller geometry and interfacial properties is key to enhancing the conductivity and durability of flexible sensors.