This paper presents a report of the synthesis of temperature-sensitive microgels based on a copolymer of butyl acrylate (10%) co-polyNIPAM (90%), in the presence of and in the absence of ibuprofen (IBU), methyl paraben (MP) and propyl paraben (PP), by a surfactant-free emulsion polymerisation in water. N',N'-methylenebisacrylamide was used as a cross-linking agent and potassium persulphate as an initiator. Physicochemical properties of the microgels were determined using different techniques including dynamic light scattering and transmission electron microscopy. It is speculated that the microgel appearance is similar to a core-shell microgel, having in the core the complex IBU or MP or PP-butyl acrylate and in the shell poly(NIPAM). Permeation across a model silicone membrane and human skin was investigated over a range of temperatures (292-313 K). The transport rate of IBU and, PP from these poly(NIPAM) microgels is significantly reduced by two and one orders of magnitude, respectively, compared with the transport rate from saturated solutions. Such a reduction in flux was not however observed for MP. (C) 2003 Elsevier B.V. All rights reserved.