  Within the Quantum Action Principle framework we show the perturbative
renormalizability of previously proposed topological lagrangian \`a la
Witten-Fujikawa describing polymers, then we perform a 2 loop computation. The
theory turns out to have the same predictive power of De Gennes theory, even
though its running coupling constants exhibit a very peculiar behaviour.
Moreover we argue that the theory presents two phases , a topological and a non
topological one.
