Self-assembled membranes of amphiphilic diblock copolymers enable comparisons of cohesiveness with lipid membranes over the range of hydrophobic thicknesses $d=3\mathrm{}–15\mathrm{nm}$. At zero mechanical tension the breakdown potential $V_c$ for polymersomes with $d=15\mathrm{nm}$ is $9\mathrm{V}$, compared to $1\mathrm{V}$ for liposomes with $d=3\mathrm{nm}$. Nonetheless, electromechanical stresses at breakdown universally exhibit a $V_c^2$ dependence, and membrane capacitance shows the expected strong $d$ dependence, conforming to simple thermodynamic models. The viscous nature of the diblock membranes is apparent in the protracted postporation dynamics.

• Received 24 May 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.208301