POS1-0874
Synthesis of High Density Nanospheres via Early-stage Curvature Stabilization from Polymerization-induced Microphase Separation of Bottlebrush Block Copolymer
When and Where
Nov 30, -0001
12:00am - 12:00am
Presenter(s)
Seungjin Ha (KAIST)
Co-Author(s)
Abstract
Bottlebrush block copolymers (BBCPs) possess densely grafted side chains that create steric crowding, promoting extended backbone conformations and energetically favoring flat interdomain interfaces. Consequently, generating highly curved nanostructures requires substantial conformational asymmetry to compensate for the curvature penalty. Previous studies have shown that architecturally induced conformational asymmetry can drive the formation of spherical morphologies in diblock BBCPs. However, polymer self-assembly originated sphere morphology generally exhibits low sphere volume fractions and broad size distributions due to energetical penalty of stabilizing high curvature. Moreover, the discrete core domains in sphere morphology hinders efficient core crosslinking, resulting in collapse after selective etching of matrix domain.
Here, we combine polymerization-induced microphase separation (PIMS) under near-neat conditions with copolymerization of crosslinker to kinetically arrest highly curved interfaces before they relax toward lower-curvature morphologies. As polymerization occurs from BBCP macro-chain-transfer agent (CTA), simultaneous microphase separation occurs. Crosslinking kinetically arrests the highly curved interface at an early stage, preserving the curvature throughout polymerization. Polymer monoliths with sphere nanodomains having core fraction higher than 70% is obtained, exceeding those accessible in annealing based approach with linear and BBCPs. The spheres have short-ranged body-centered cubic (BCC) packing with domain spacing up to 150 nm. The conformational asymmetry at the point of kinetic arrest can be tuned by varying polymerization mixture composition and macro-CTA architecture, demonstrating that the resulting morphology is governed by the asymmetry established during early-stage arrest. This approach provides the kinetic pathway that circumvents the energetic limitation corresponding to highly curved interfaces with BBCPs.
Here, we combine polymerization-induced microphase separation (PIMS) under near-neat conditions with copolymerization of crosslinker to kinetically arrest highly curved interfaces before they relax toward lower-curvature morphologies. As polymerization occurs from BBCP macro-chain-transfer agent (CTA), simultaneous microphase separation occurs. Crosslinking kinetically arrests the highly curved interface at an early stage, preserving the curvature throughout polymerization. Polymer monoliths with sphere nanodomains having core fraction higher than 70% is obtained, exceeding those accessible in annealing based approach with linear and BBCPs. The spheres have short-ranged body-centered cubic (BCC) packing with domain spacing up to 150 nm. The conformational asymmetry at the point of kinetic arrest can be tuned by varying polymerization mixture composition and macro-CTA architecture, demonstrating that the resulting morphology is governed by the asymmetry established during early-stage arrest. This approach provides the kinetic pathway that circumvents the energetic limitation corresponding to highly curved interfaces with BBCPs.
