PHPA has carboxylic groups and thearfore interact with cationic surfactant. The nnumber of charge and the electrical conductivity decrease. Non-ionic surfactant interact via hydrogen bond.Electrical conductivity decrease.

Conductivity is a function of ion mobility and ion concentration. As PHPA is added, the presence of carboxyl groups from PHPA increase the number of ions in solution, resulting in ta factor that increase conductivity. On the other hand, PHPA may be a factor to the decrease of conductivity ,as well, due to ion mobility decrease: by increasing solution viscosity and/or by association with ions, resulting in bulkier charged species (sometimes less charged, if there is charge neutralization), with lower mobilities. It seems the second influence prevails in the present case.

The conductivity of surfactant micellar solutions depends significantly on the concentration of surfactant and the type and size of the micelles it forms in aqueous media. If the surfactant concentration is below CMC then the conductivity will most likely be due to monomeric surfactant and adding PHPA will bind cationic surfactant thereby lowering conductivity. At high surfactant concentration the effect of PHPA on conductivity will be less pronounced, however the conductivity may increase or decrease. At intermediate surfactant concentrations (i.e. 2x, 3x CMC) the micellization of the surfactant is changed by the addition of polymer, instead of CMC you get CAD (critical aggregation concentration) and the conductivity of the solution may decrease due to formation of larger micelles or by coacervation of the polymer with the cationic surfactant. For starters I would measure the conductivity and surface tension of the solution at various concentrations of surfactant and polymer. I would also try to observe if adding PHPA results in coacervate formation. Finally I suggest you search the literature for papers dealing with PHPA in surfactant solutions. I hope this helps.