Colloidal Unimolecular Polymer (CUP) particles were prepared by water-reduction of copolymers of methyl-methacrylate and 2-acrylamido-2-methylpropane sulfonic acid. Absence of additives like surfactant or emulsifier, easy synthesis and controllable particle size in the true-nano region (diameter 3-9nm) make the CUP systems an excellent material to study the electro-viscous effects and the effect of surface water on the rheological behavior of charged nanopolymers. In the dilute concentration regime (volume fraction < 0.10), the tertiary electroviscous effects dominated the rheology behavior and the associated water fraction on the surface of sulfonate (SO3-)-CUPs increased with increasing molecular weight or surface charge density of the CUP particles. The SO3-CUPs had a thicker and a denser surface water layer than the carboxylate (CO2-) functional CUPs.