  The scission kinetics of bottle-brush molecules in solution and on an
adhesive substrate is modeled by means of Molecular Dynamics simulation with
Langevin thermostat. Our macromolecules comprise a long flexible polymer
backbone with $L$ segments, consisting of breakable bonds, along with two side
chains of length $N$, tethered to each segment of the backbone. In agreement
with recent experiments and theoretical predictions, we find that bond cleavage
is significantly enhanced on a strongly attractive substrate even though the
chemical nature of the bonds remains thereby unchanged.
  We find that the mean bond life time $<\tau>$ decreases upon adsorption by
more than an order of magnitude even for brush molecules with comparatively
short side chains $N=1 \div 4$. The distribution of scission probability along
the bonds of the backbone is found to be rather sensitive regarding the
interplay between length and grafting density of side chains. The life time
$<\tau>$ declines with growing contour length $L$ as $<\tau>\propto L^{-0.17}$,
and with side chain length as $<\tau>\propto N^{-0.53}$. The probability
distribution of fragment lengths at different times agrees well with
experimental observations. The variation of the mean length $L(t)$ of the
fragments with elapsed time confirms the notion of the thermal degradation
process as a first order reaction.
