Extending polysoaps in the presence of free amphiphiles

Intramolecular self-assembly affects the elastic behavior of polymers. "Denaturing" agents that weaken the resulting Secondary structure strongly modify the force laws characterizing the deformation of such polymers. This behavior is analyzed for the particular case of polysoaps: linear hydrophilic polymers incorporating, at intervals, amphiphilic monomers. In aqueous solution the amphiphiles form intrachain micelles. The deformation behavior of a linear string of spherical intrachain micelles in theta conditions and high ionic strength is analyzed as a function of the concentration of free amphiphiles X. At intermediate extensions intrachain micelles coexist with fully dissociated chain segments leading to a regime where the tension f is weakly dependent on the end to end distance R. The width of the coexistence regime shrinks as X increases. At the same time, the tension at coexistence increases. The fR diagram exhibits thus features reminiscent of a critical point approached via control of X.