  We study quantum dissipative dynamics of entanglement in the spin-boson
model, described by the generalized master equation. We consider the two
opposite limits of pure-dephasing and relaxation models, measuring the degree
of entanglement with the concurrence. When the Markovian approximation is
employed, entanglement is shown to decay exponentially in both cases. On the
other hand, non-Markovian contributions alter the analytic structure of the
master equation, resulting in logarithmic decay in the pure dephasing model.
