The force–extension relationship of single polymer
chains
is an essential component underlying the development of macroscopic
constitutive models for elastomers. In this work, we present a model
for the force–extension relationship beyond the consideration
of classical entropic elasticity, by accounting for bond deformation
on the chain’s backbone. Parameters in this model are mostly
molecular parameters for bond stretching, bending, and breaking already
available in the literature, thereby limiting the parameters that
need to be extracted from fitting experimental data to a minimum.
In addition, an extension of the model is made to include the effects
of mechanophores: molecules that react under the application of a
mechanical force. This has endowed the model with the capability of
predicting the mechanophore reaction as well as chain scission. The
model is applied and compared to experimental data, in a range of
scenarios: reproducing the measured force–extension relationship
for PDMS chains, calculating the rate dependent fracture energy of
PDMS films, and predicting the force–extension relationship
caused by the unfolding of mechanophore domains. For the last example,
it was demonstrated that this type of chain has the potential to be
utilized to design elastomers with substantially enhanced strength
and toughness.