Fluorescence techniques, particularly time-resolved anisotropy measurements, TRAMS, have confirmed that poly(N-vinylcaprolactam), PNVCap, undergoes a conformational transition from an expanded coil to a compact globule at its lower critical solution temperature, LCST. TRAMS and cloud point measurements have revealed the onset of the LCST as 38 degrees C. The nature of the conformational change for PNVCap is distinct from that of another thermoresponsive polymer, poly(N- isopropylacrylamide), PNIPAM: the discontinuity in the thermal dependence of the rate of macromolecular motion occurs over a range of ca. 15 degrees C for PNVCap while that for PNIPAM takes place between 31 and 33 degrees C. Furthermore, there is a reduction in the magnitude of the conformational change of PNVCap when compared to that of PNIPAM. Pyrene solubilisation experiments provide support for a model for PNVCap above the LCST, consisting of a globular structure with a hydrophobic core which is stabilised by more hydrophilic units on the surface. (c) 2005 Published by Elsevier B.V.