Influence of alkyl trimethylammonium bromide (CnTAB) on rheological behavior of sodium carboxymethylcellulose (NaCMC) in entangled semi-dilute solution was investigated with respect to tail length of CnTAB.Both critical aggregation concentration (cac) and viscosity were studied.cac was achieved by steady-state fluorescence using pyrene as a probe.Effect of CnTAB tail length on formation of micelles in water and NaCMC solution were quantified by calculating the Gibbs free energy.A strong thicken effect of CnTAB at high concentrations on the entangled semi-dilute solution of NaCMC was found.According to transmission electron microscopy images

both isolated micelles (ca. 5 nm) at low NaCMC concentrations and large aggregates (ca. 30 nm) at high NaCMC concentrations can be seen.Excluding the viscosity reduction by the neutralization of charges induced by NaCMC

the isolated micelles act as hard spheres

causing a viscosity change of the NaCMC solution following Einstein law.On the other hand

percolation appears at high CnTAB concentrations and the micellar aggregates spread to form a network penetrating the entanglement network of NaCMC macromolecules.It is found for the first time that the viscosity of entangled semi-dilute solution increases according to the percolation theory with mean-field calculation.This indicates that long range interaction dominates in the aggregation and percolation behavior of micellar aggregates.At the onset of micellar percolation

critical volume fraction of micelles increases while mean distance between micelle surfaces decreases with increasing tail length of CnTAB.