Highly asymmetric lamellar microdomains, such as those required for many lithographic line patterns, cannot be straightforwardly achieved by conventional block copolymer self-assembly. We present a conceptually new and versatile approach to produce highly asymmetric lamellar morphologies by the use of binary blends of block copolymers whose components are capable of hydrogen bonding. We first demonstrate our strategy in bulk systems and complement the experimental results observed by transmission electron microscopy and small-angle X-ray scattering with theoretical calculations based on strong stretching theory to suggest the generality of the strategy. To illustrate the impact on potential lithographic applications, we demonstrate that our strategy can be transferred to thin film morphologies. For this purpose, we used solvent vapor annealing to prepare thin films with vertically oriented asymmetric lamellar patterns that preserve the bulk morphological characteristics. Due to the highly asymmetric lamellar microdomains, the line width is reduced to sub-10 nm scale, while its periodicity is precisely tuned.