The self-assembled morphologies of block copolymers and their characteristic nanodomain periodicities directly impact their properties and utility in numerous applications, including nanotemplating. The composition-dependent morphologies of linear AB diblock copolymers reflect a delicate balance of the enthalpy of A/B segment repulsions, the entropy of polymer chain stretching to minimize unfavorable interfacial contacts, and the entropy of block junction localization at the microdomain interfaces. For a given monomer pair, this free energy balance sets a minimum degree of polymerization for melt self-assembly and a smallest accessible microdomain (d) spacing, which often limits the scope of block copolymer nanotemplating. As a route to circumventing these thermodynamic limits for a given copolymer chemistry, we describe the phase behaviors of densely grafted, core-shell bottlebrush (csBB) polymers, which derive from linking narrow dispersity ABA triblocks by metathesis polymerization of a norbornyl functionality situated at each chain midpoint. We quantitatively demonstrate how the stabilities of csBB microphase separated morphologies depend on polymer volume fraction, and the degrees of polymerization of the brush backbone (Nbb) and sidechain arms (Narm), while also revealing the range of nanostructures that csBBs form.

Core-Shell bottlebrush polymer self-assembly routes to sub-10 nm features

ACS Spring 2022

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