We give a detailed analysis of the intersection properties of polymers
. Using the renormalization group we provide a full crossover function
for the dependence of the number of intersections in a single polymer
on chain length and excluded volume strength. We compare our results
with Monte-Carlo data and with exact calculations for a random walk, f
inding good agreement in ail respects. Restricting to the vicinity of
the eight ternary fixed points we also calculate the number of interse
ctions between two chains placed at a fixed distance. including tile t
wo halves of a block-copolymer. The analysis of these systems confirms
the interpretation of the different contributions to the number of in
tersections in a single chain. Due to the highly nontrivial character
of the correlations in a polymer chain the correction exponents in bot
h cases however are different. None of the results can be extracted fr
om any Flory-type estimate.