  We consider the rupture dynamics of a homopolymer chain pulled at one end at
a constant loading rate. Our model of the breakable polymer is related to the
Rouse chain, with the only difference that the interaction between the monomers
is described by the Morse potential instead of the harmonic one, and thus
allows for mechanical failure. We show that in the experimentally relevant
domain of parameters the dependence of the most probable rupture force on the
chain length may be non-monotonic, so that the medium-length chains break
easier than the short and the long ones. The qualitative theory of the effect
is presented.
