Transition behavior of polyelectrolyte brushes depending on polymer chain density

Brush layers of polyelectrolytes, ionized poly(L-lysine) (PLL) or poly(L-glutamic acid) (PLGA), at desired densities were prepared by the Langmuir-Blodgett (LB) deposition of amphiphiles bearing PLL or PLGA segments as hydrophilic groups, and subjected to the surface force measurements. Abrupt changes in the surface force, the surface potential, and the transfer ratio of the brush layers were observed at a critical density. The present data is in good agreement with our previous report on the jump in the compressibility of the brushes, and supports the existence of the density dependent transition of polyelectrolytes in solutions.