Morphology of lipid-like structured weak polyelectrolyte poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers induced by confinements

Abstract

Combined with quantum calculations and mesoscale simulations, the self-assembly of twelve lipid-structured PEO-b-PMMA copolymers (BCPs) with six types of molecular topologies was investigated. The BCPs with MMA species as the connecting center of the other arms present ample mesoscale structures, such as micelles and lamellae or curved lamellar phases, and even macrophase separation occurs for the long-chained BCPs. The excluded volume effect of confinements helps form vesicle-like structures, which proved to be a possible method of confinement to regulate phase morphologies or segment distributions and, ultimately, the properties of materials. An analysis of the phase formation process of short-chained BCP with two hydrophilic EO segments and one hydrophobic MMA segment indicated that four stages were found in both neutral and non-neutral wall confinement, all of which present a hexagonal columnar phase. Surprisingly, when the repulsion effect of the wall to the EO segment is greater than that of the MMA segment, such BCP self assembles into a crossed columnar phase, and the intersection angle of the orientation of these two sets of cylinder arrays is 75 degrees, which can be used to produce heterogeneous nanotube arrays. For the short-chained BCP with four arms joined at MMA species and EO segments in the outer region, we found a novel method of exchanging the repulsive preference of the wall to the EO or MMA species that can control the adsorption or desorption of the lamellar phase with the interval of EO or MMA segments.