A reporter molecule; a fluorophore-labelled linear polymer that interacts with natural and synthetic phospholipid membranes, and whose fluorophores respond to the polymer^'s physical environment. The polymer attaches to the membrane through its aromatic fluorophores, which are sparsely spaced along its length and allow the intervening polymer to loop out into the solvent. The fluorescence intensity is greatly enhanced by the mutual proximity of the fluorophores, so physical forces that promote close association of the polymer loops (e.g. a lowered temperature or a solvent that interacts poorly with the polymer) will close up the loops, draw the fluorophores closer together and increase fluorescence, while a strongly interacting solvent or a higher temperature will cause the loops to relax, separate the fluorophores, and decrease fluorescence.