  We investigate the dynamics and the pathways of the collapse of a single,
semiflexible polymer in a poor solvent via 3-D Brownian Dynamics simulations.
Earlier work indicates that the condensation of semiflexible polymers
generically proceeds via a cascade through metastable racquet-shaped,
long-lived intermediates towards the stable torus state. We investigate the
rate of decay of uncollapsed states, analyze the preferential pathways of
condensation, and describe likelihood and lifespan of the different metastable
states. The simulation are performed with a bead-stiff spring model with
excluded volume interaction and exponentially decaying attractive potential.
The semiflexible chain collapse is studied as functions of the three relevant
length scales of the phenomenon, i.e., the total chain length $L$, the
persistence length $L_p$ and the condensation length $L_0 = \sqrt{k_B T
L_p/u_0}$, where $u_0$ is a measure of the attractive potential per unit
length. Two dimensionless ratios, $L/L_p$ and $L_0/L_p$, suffice to describe
the decay rate of uncollapsed states, which appears to scale as $(L/L_p)^{1/3}
(L_0/L_p)$. The condensation sequence is described in terms of the time series
of the well separated energy levels associated with each metastable collapsed
state. The collapsed states are described quantitatively through the spatial
correlation of tangent vectors along the chain. We also compare the results
obtained with a locally inextensible bead-rod chain and with a phantom
bead-spring model. Finally, we show preliminary results on the effects of
steady shear flow on the kinetics of collapse.
