Molecular Weight Dependent Morphological Transitions of Bottlebrush Block Copolymer Particles: Experiments and Simulations

Eun Ji Kim, Jaeman J. Shin, Taeyang Do, Gue Seon Lee, Juhae Park, Vikarm Thapar, Jinwoong Choi, Joona Bang, Gi Ra Yi, Su Mi Hur, Jeung Gon Kim, Bumjoon J. Kim

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The molecular weights and chain rigidities of block copolymers can strongly influence their self-assembly behavior, particularly when the block copolymers are under confinement. We investigate the self-assembly of bottlebrush block copolymers (BBCPs) confined in evaporative emulsions with varying molecular weights. A series of symmetric BBCPs, where polystyrene (PS) and polylactide (PLA) side-chains are grafted onto a polynorbornene (PNB) backbone, are synthesized with varying degrees of polymerization of the PNB (NPNB) ranging from 100 to 300. Morphological transitions from onion-like concentric particles to striped ellipsoids occur as the NPNB of the BBCP increases above 200, which is also predicted from coarse-grained simulations of BBCP-containing droplets by an implicit solvent model. This transition is understood by the combined effects of (i) an elevated entropic penalty associated with bending lamella domains of large molecular weight BBCP particles and (ii) the favorable parallel alignment of the backbone chains at the free surface. Furthermore, the morphological evolutions of onion-like and ellipsoidal particles are compared. Unlike the onion-like BBCP particles, ellipsoidal BBCP particles are formed by the axial development of ring-like lamella domains on the particle surface, followed by the radial propagation into the particle center. Finally, the shape anisotropies of the ellipsoidal BBCP particles are analyzed as a function of particle size. These BBCP particles demonstrate promising potential for various applications that require tunable rheological, optical, and responsive properties.

Original languageEnglish
Pages (from-to)5513-5522
Number of pages10
JournalACS nano
Volume15
Issue number3
DOIs
Publication statusPublished - 2021 Mar 23

Keywords

  • block copolymer particle
  • bottlebrush polymer
  • ellipsoidal particle
  • molecular weight
  • onion-like particle
  • particle shape

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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