Cationic double-azobenzene-chain lipid 5 undergoes efficient trans --> cis photoisomerization in MeCN solution and in 1:9 coliposomes with bisether lipid 2 at temperatures above 20 degrees C. However, in 1:1 5/2 coaggregates, or in pure liposomal 5, the extent of photoisomerization is very sensitive to temperature; for example, it is limited to less than or equal to 10% below 40 degrees C. Dispersed 1:9 coliposomes of 5 and 2 spontaneously segregate into domains rich in the individual lipids. Thermal cis --> trans isomerization of 5 in MeCN solution and in 1:9 5/2 coliposomes proceeds readily between 20 and 60 degrees C with activation energies of 19-20 kcal/mol. The photoisomerization of 5 in pure liposomes or in 1:1 5/2 coliposomes is less efficient than that of its single-azobenzene-chain analogue, 1, under comparable conditions.