\label{sec:conclusions}
We investigated a two-parameter model of polymer collapse that has competing interactions, first studied by Wu and Bradley \cite{Wu_1990}, and contains three previously investigated models of polymer collapse, namely ISAT, ISAW and INNSAT, as specialisations.
We find that the phase diagram for the Wu-Bradley model contains three phases: a swollen phase and two collapsed phases, one of which is maximally dense. The corresponding three phase boundaries, two of which are second order and one of which is first-order, meet seemingly at the collapse point of the ISAT model, and is in agreement with the suggestion in \cite{Nahum_2013} that the ISAT transition is an higher-order multi-critical point. The second-order phase transition line between the swollen and not maximally dense collapsed phase contains the transitions in the ISAW and INNSAT models, which we conjecture to be a line of \(\theta\)-like transitions.
We can conjecture that the two collapsed phases belong to the \(O(n \to 0)\) Goldstone phase \cite{Jacobsen_2003,Nahum_2013}, due to the presence of crossings. It is an open question whether the divergence of these two phases can be related to the appearence of a type of Ising order, as portrayed in \cite{Nahum_2013}. More work needs to be done to elucidate the nature of these phases, and to resolve the transition between them. At present, this seems to be out of reach of available algorithms.