  The effect of network chain distribution on mechanical behavior of elastomers
is one of the long standing problems in rubber mechanics. The classical theory
of rubber elasticity is built upon the assumption of entropic elasticity of
networks whose constitutive strands are of uniform length. The kinetic theories
for vulcanization, computer simulations, and indirect experimental measurements
all indicate that the microstructure of vulcanizates is made of polymer strands
with a random distribution of length. The polydispersity in strand length is
expected to control the mechanical strength of rubber as the overloaded short
strands break at small deformations and transfer the load to the longer
strands. The purpose of this contribution is to present a simple theory of
rubber mechanics which takes into account the length distribution of strands
and its effect on the onset of bulk failure.
