Physical origin and the architectural pathway to the “inverted” phases of the micro-segregated diblock copolymers

Self-assembly of block copolymers has received significant attention for its potential modern lithography applications due to the ability to achieve morphologies with dimensions in the range of 10-20 nm. However, the morphology of “conventional” diblock copolymers are limited: lamellar morphologies are usually restricted to nearly symmetric widths of the domains, and hexagonal and BCC morphologies always form cylinders and spheres from the minority phase. Producing highly asymmetric lamellae or “inverted” hexagonal phases where the minority phase goes into the outside matrix and the majority phase forms inside cylinders remains an important technological challenge. Recently, such asymmetric and inverted phases were experimentally observed in ionic copolymers, copolymers with hydrogen bonds, and blends of such copolymers. We have developed a set of Self-Consistent theoretical models in conjunction with coarse-grained Monte-Carlo modelling which explain the appearance of the observed “inverted” phases. These models recognize the role of ionic interactions and hydrogen bonding in the formation of such phases and suggest optimal architectural strategies for designing copolymers forming the “inverted” microphases.