To provide insights into the aggregation behavior, hydration tendency and variation in phase transition temperature produced,by the addition of ionic liquids (ILs) to poly(N-isopropylacrylamide) (PNIPAM) aqueous solution, systematic physicochemical studies, and moleenlar dynamic simulations were carried out. The influence of ILs-possessing the same [Cl](-) anion and a set of cations [C(n)mim](+) with increasing alkyl chain length such as 1-l-ethyl-3-methylimidaiohum ([Emim](+)), 1-ally1-31nethylimidatoliuni ([Amim](+)); 1-butyl-3-methyliinidazolium ([Bmim](+)), 1-hexy1-3-methylintidazolium ([Hmirr](+)),24-benzyl-3-methylimidazolium ([Bzmim](+)), and 1-decyl3-methylirnidazoliurn: ([Dmin](+)) on the phase transition of PNIPAM-was monitored by the aid of UV-visible absorption spectra, fluorescence intensity spectra, viscosity (eta), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, to, interpret the direct images and surfaee morphologies of the PNIPAM-IL aggregates, we performed field emission scanning electron micros Copy (FESEM). The Overall specific ranking of ILs in preserving the hydration layer around the PNIPAM aquetius solution was [Emim][Cl] > [Amim] [Cl]> [Bmin] [Cl] > [Hmim][Cl] > [Bzmim] [Cl] > [Dmim][Cl]. Moreover,to investigate the molecular mechanism Behind the Change in the tower critical soltitiOn temperature (LCST) of the polymer in the presence of the ILs, a molecular dynamics (MD) study was performed. The MD simulation has clearly shown the reduction in hydration shell,of the polymer after interacting with the ILs at their respective LCST. MD Study revealed significant changes in polymer conformtion because of IL interactions and strongly supports the experiMental observation of polymer phase transition at a temperature lower than typical LCST for all the studied ILs. The driving force for concomitant sharp configurational transition has been attributed to the displacement of water Molecules On the polymer surface by -the ILs because of their hydrophobic interaction with the polymer.