We studied the thermal response of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) by comparing the differential scanning calorimetry (DSC) data of liposomes with atomic force microscopy (AFM) observations on supported planar bilayers. Planar bilayers were obtained by using the Langmuir-Blodgett (LB) technique: the first leaflet transferred at 30 mN m(-1) and the second at 25 mN m(-1). The topographic evaluation of supported POPE bilayers above room temperature showed changes between 43.8 and 59.8 degrees C. These observations are discussed in relation to the main roughness (R-a) variations and are interpreted as the result of the lamellar liquid crystalline (L-alpha) to inverted hexagonal (H-ll) phase transition. High-magnification images obtained at 45 degrees C revealed intermediate structures in the transformation. Force spectroscopy (FS) was subsequently applied to gain further structural and nanomechanical insight into the POPE planar bilayers as a function of temperature. These measurements show that the threshold force (F-y), which is the maximum force, that the sample can withstand before breaking, increases from 1.91 +/- 0.11 nN at 21 degrees C up to 3.08 +/- 0.17 nN at 43.8 degrees C. This behavior is interpreted as a consequence of the formation of intermediate structures or stalks in the transition from the L-alpha to H-ll phase.