  We study the conformational properties of polymers in presence of extended
columnar defects of parallel orientation. Two classes of macromolecules are
considered: the so-called partially directed polymers with preferred
orientation along direction of the external stretching field and semiflexible
polymers. We are working within the frames of lattice models: partially
directed self-avoiding walks (PDSAWs) and biased self-avoiding walks (BSAWs).
Our numerical analysis of PDSAWs reveals, that competition between the
stretching field and anisotropy caused by presence of extended defects leads to
existing of three characteristic length scales in the system. At each fixed
concentration of disorder we found a transition point, where the influence of
extended defects is exactly counterbalanced by the stretching field. Numerical
simulations of BSAWs in anisotropic environment reveal an increase of polymer
stiffness. In particular, the persistence length of semiflexible polymers
increases in presence of disorder.
