Phase diagrams for reversibly associating one-end-functionalized chain molecules (with an emphasis on hydrogen bonding) are determined by computer simulations of a cubic lattice model employing canonical and grand canonical Monte Carlo methods. Due to the relatively short chain lengths used, the stability of the homogeneous state is strongly enhanced compared to mean-field random phase approximation predictions. Characteristic phenomenon such as reappearing phases and macrophase separation into two phases, at least one of which is microphase separated, are observed and discussed.