Thermosensitive association of a diblock co-polymer consisting of poly(3 dimethyl(methacryloxyethyl) ammonium propane sulfonate) (PdMMAEAPS), as an upper critical solution temperature (UCST) block, and poly(N,N'-diethylacrylamide) (PdEA), as a lower critical solution temperature (LCST) block has been investigated by using IR spectroscopy. The v(C=O) and v(SO3) bands of the PdMMAEARS block and the amide I band of PdEA block critically changed at the UCST and LCST respectively indicating that the segmental interaction of each block is altered at each transition. The double temperatures responsiveness of a UCST block and LCST block containing diblock copolymer Micelles from at temperatures both below the UCST and above the LCST of the blocks.