The thermophysical properties viz. density rho, speed of sound u, and specific conductivity kappa of pure room temperature ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) and its binary formulations with Triton X-45 and Triton X-100 have been studied over the entire composition range at different temperatures (293.15 to 323.15) K. Excess molar volume V-E, deviation in isentropic compressibility Delta K-S, partial molar excess volume V-i(E), deviation in partial molar isentropic compressibility Delta K-S,K-i, deviation in specific conductivity Delta kappa have also been estimated and analysed. Spectroscopic properties (IR, H-1 and C-13 NMR) of these mixtures have been investigated in order to understand the structural and interactional behaviour of formulations studied. The magnitude of interactions between the two components increases with addition of number of oxyethylene groups in Tritons and with rise in temperature. Spectroscopic measurements indicate that interactions are mainly taking place through the five member ring of room temperature ionic liquid and six member ring of Tritons. (c) 2012 Elsevier Ltd. All rights reserved.