Strong segregation limited theory was employed to deduce the expression for free energy of a curved (A-B) monolayer that is a basic repeating unit in multi-layered concentric structure. The free energy of the monolayer in different curved conditions can be evaluated. Using such cylindrical confinement model, we examined the influences of asymmetry of diblock copolymers on the layer thickness of a curved monolayer. For the diblock copolymers of f= 0.4, the optimal thickness has a slight increase and then decrease as the curvature increases; while for f = 0.6, the optimal thickness has a continuous decrease as the curvature increases. (C) 2015 Elsevier B.V. All rights reserved.