Variable-temperature tapping mode atomic force microscopy was used to follow thermal transitions in nanoscale phase separated triblock copolymers containing partially crystalline poly(octadecyl methacrylate) or poly(docosyl methacrylate) and glassy (poly(tert-butyl acrylate)) segments. Melting/crystallization and devitrification/vitrification transitions in phase separated domains were followed with the aid of "phase shift thermograms" constructed from cantilever phase shift maps acquired at different temperatures. This type of analysis turned out to be particularly useful in following melting/crystallization and devitrification/vitrification transitions occurring in the same temperature range and thus difficult or impossible to resolve using differential scanning calorimetry.