The collapse of a polymer interacting with the solvent but without explicit monomer-monomer interactions are modeled with Hamiltonian. Such model depicts the behavior of hydrophobic polymers in water which found the presence of both cold and warm denaturation temperatures in some proteins and broadly thermosensitive homopolymers such as poly(N-isopropylacrylamide). When polymers are swollen in low and high temperature phases, there is an intermediate phase where the most favorable configurations are compact.