Azeotropic or azeotrope-like compositions of the present technology include methyl chloride and at least one hydrofluorocarbon or hydrofluoro-olefin. In some examples, the at least one hydrofluorocarbon or hydrofluoro-olefin can be selected from the group consisting of 1,1,1,2-tetrafluoroethane and 1,3,3,3-tetrafluoropropene. The azeotropic or azeotrope-like compositions can be used as solvents or diluents in polymerization processes, including slurry polymerization processes.