Vesicles prepared from a mixture of (Sar)(25)-b-(L- Leu-Aib)(6) (SLL) and (Sar)(25)-b-(D-Leu-Aib)(6) (SDL) fused with themselves upon heating to 90 degrees C. The vesicles also fused with (Sar)(28)-b-(L-Leu-Aib)(8) vesicles upon heating to 90 degrees C. The temperature-triggered fusion was due to the phase transition of the mixed membrane of SLL and SDL at 90 degrees C and should be driven by the bending energy stored in the stereocomplex membrane upon taking a vesicular structure.