  We consider three different continuum polymer models, that all depend on a
tunable parameter r that determines the strength of the excluded-volume
interactions. In the first model chains are obtained by concatenating hard
spherocylinders of height b and diameter rb (we call them thick self- avoiding
chains). The other two models are generalizations of the tangent hard-sphere
and of the Kremer-Grest models. We show that, for a specific value r*, all
models show an optimal behavior: asymptotic long-chain behavior is observed for
relatively short chains. For r < r*, instead, the behavior can be parametrized
by using the two-parameter model that also describes the thermal crossover
close to the {\theta} point. The bonds of thick self-avoiding chains cannot
cross each other and, therefore, the model is suited for the investigation of
topological properties and for dynamical studies. Such a model also provides a
coarse-grained description of double-stranded DNA, so that we can use our
results to discuss under which conditions DNA can be considered as a model
good-solvent polymer.
