A series of thermo-responsive oligo(ethylene glycol) methacrylate (OEGMA, Mn, = 300 g/mol)-pentafluorostyrene (PFS) copolymers was prepared, and the effect of composition on polymer conformation changes and size of the self-assembled particles in solution was studied. Furthermore, the relationship between self-aggregation mechanistic steps in water and rheological properties is reported. Water-soluble OEGMA-PFS copolymers were synthesized at different molar ratios via free radical polymerization, and their phase transition behavior was investigated in detail by dynamic light scattering (DLS), H-1 NMR, simultaneous rheometry-FTIR spectroscopy, and transmission electronic microscopy (TEM). All copolymers exhibited sharp and reversible LCST in water. LCST and particle size of the self-assemblying copolymers can be precisely tuned by varying monomer molar ratio. Simultaneous rheometry-FTIR spectroscopy showed that above the LCST, copolymers with higher OEGMA content form micron-sized and hydrated particles, resulting in a pseudo-hydrogel structure. When the hydrophobic character increases, a more significant dehydration of OEGMA side chains leads to a strengthening of polymer chain interactions, resulting in the formation of nanosized and phase-segregated particles. These results are also relevant with a view of using these structures as a template for the preparation of chemically or physically stabilized nanoparticles to be employed for a variety of applications, such as immobilization, controlled release and flocculation in water treatment. (C) 2017 Published by Elsevier Ltd.