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Stretchability of Elastomers

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Yikai Yin, Yanming Wang, Xiaohan Zhang, Lihua Jin, Shaswat Mohanty

Conducting, semiconducting and insulating polymers offer potential to realize intrinsically stretchable electronic devices.  However, existing semiconducting polymers are brittle.  They need to be blended with elastomers to become stretchable but doing so may degrade their electronic properties.  How to make stretchable polymers with satisfactory electronic properties remains a significant challenge.

We use a multiscale modeling approach to understand the relationship between molecular configurations of polymers and their mechanical behavior during stretching.  A major goal is to predict the fracture toughness of an elastomer from the molecular bond properties (bond strength, density, distribution, etc.).

At the smallest length/time scale, we perform coarse-grained molecular dynamics (CGMD) simulations of polymer molecules using the LAMMPS program (see figure below illustrating the simulation procedure).

simulation_procedure

The following figures show the stress-strain curves and number of broken bonds as a function of strain during loading/unloading cycles.

stress strain curve

 

The stress-strain relations from CGMD is used to construct a finite element model for the elastomer containing a crack.

FEA model

We also perform experiments to measure the fracture toughness of elastomers with different cross-linking bond densities.

 

fracture experiment