  We study the connection between polymers at the theta temperature on the
lattice and Schramm-Loewner chains with constant step length in the continuum.
The latter realize a useful algorithm for the exact sampling of tricritical
polymers, where finite-chain effects are excluded. The driving function
computed from the lattice model via a radial implementation of the zipper
method is shown to converge to Brownian motion of diffusivity kappa=6 for large
times. The distribution function of an internal portion of walk is well
approximated by that obtained from Schramm-Loewner chains. The exponent of the
correlation length nu and the leading correction-to scaling exponent Delta_1
measured in the continuum are compatible with nu=4/7 (predicted for the theta
point) and Delta_1=72/91 (predicted for percolation). Finally, we compute the
shape factor and the asphericity of the chains, finding surprising accord with
the theta-point end-to-end values.
