  Using analytic theory, numerical calculation and Langevin dynamics simulation
we demonstrate the existence of a first order unraveling transition in the
stretching of a polymer chain in a poor solvent. The chain suddenly unravels
from a "tadpole" or "ball and chain" configuration, to one where the ball
shrinks to zero size. In the force curve this appears as a discontinuous drop
in the force. This transition occurs under the conditions of most relevance for
atomic force microscope experiments, where the extension is the independent
variable. Our simulations show marked hysteresis as well as many local peaks
associated with the pullout of small portions of the chain.
