A minimal model is presented for helix-coil type transitions in solutions of self-assembled supramolecular polymers. The diagram of states calculated using this model shows that there are essentially two ordering regimes, one where the polymerization transition and the helical transition coincide and one where they are separate. In both regimes a strong coupling exists between the growth and the helical transition of the supramolecular polymers. Comparison of the theory with experimental data confirms that the minimal model provides an adequate description of helix-coil type transitions in self-assembled polymers and that these transitions can be highly cooperative.