Lamellar Dilation in (AB)-g-A Copolymacromer Melts: A Dissipative Particle Dynamics Study

Homopolymer addition is a widely used strategy to dilate the microdomain spacing of block copolymers, yet the attainable dilation is often limited by macrophase separation in conventional blends at elevated homopolymer loading. In this work, we investigate an architectural route to suppress macrophase separation while retaining homopolymer-driven dilation: a covalently hybridized bottlebrush copolymer (CH-BBC), a copolymacromer-like bottlebrush architecture in which symmetric AB diblock side chains and A-type homopolymer side chains are covalently grafted to a common backbone. Using dissipative particle dynamics (DPD) simulations, we directly compare the phase behavior of CH-BBC melts with that of composition-matched blends of symmetric AB diblocks and A-type homopolymers. Across the explored window, CH-BBC exhibits microphase morphologies and disorder without an observable two-phase region, whereas the corresponding blends show extensive two-phase coexistence at elevated homopolymer loading. Lamellar analysis and one-dimensional density decompositions further reveal that CH-BBC enables substantially larger microphase dilation and stronger selective swelling of the A-rich domain because tethered A-type homopolymer segments preferentially occupy and dilate the A-rich domain interior while diblock A segments remain localized near interfaces.