Thin film and bulk morphology of PI-PS-PMMA miktoarm star terpolymers with both weakly and strongly segregated arm pairs

Sina Ariaee, Bo Jakobsen, Poul Norby, Detlef-M. Smilgies, Kristoffer Almdal, Dorthe Posselt*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

A series of three homologous ABC miktoarm star terpolymers having a polyisoprene (PI), a polystyrene (PS) and a poly(methyl methacrylate) (PMMA) arm, is synthesized by living anionic polymerization. While the volume fraction of the PI and the PS blocks are kept equal and constant, the volume fraction of the PMMA block is varied. The room temperature bulk structure is characterized using small-angle X-ray scattering and transmission electron microscopy, while the structure of thin films is investigated using scanning electron microscopy, atomic force microscopy and X-ray reflectometry. For both bulk and thin films, it is found that the sample with the lowest volume fraction of PMMA has a morphology distinctly different from the two samples with larger PMMA volume fraction. All data for both bulk and thin film samples are consistent with an alternating lamellar structure for the lowest PMMA volume fraction sample. The two higher PMMA volume fraction samples show standing rod structure, however the details of the packing in the PMMA matrix differ depending on sample thickness. Overall, a structure with PI domains screened from interacting with PMMA by a PS shell is seen for both samples. In bulk, core-shell cylinders pack hexagonally, while a 100 nm thin film of the sample with the largest volume fraction of PMMA shows a square-lattice packing. The structuring is driven by two factors: i) the strong segregation of the PI-PMMA arm pair together with the weak segregation of the two arm pairs with a PS block and ii) the geometrical constraints resulting from the star architecture. No wetting layers are observed for any of the thin film samples, neither at the air-polymner surface or at the polymer-substrate interface.
Original languageEnglish
Article number126202
JournalPolymer
Volume283
Number of pages12
ISSN0032-3861
DOIs
Publication statusPublished - 2023

Keywords

  • Living anionic polymerization
  • ABC miktoarm star terpolymer
  • Self-assembly
  • Bulk morphology
  • Thin film morphology
  • X-ray reflectometry (XRR)
  • Small angle X-ray scattering (SAXS)
  • Transmission electron microscopy (TEM)
  • Scanning electron microscopy (SEM)
  • Atomic force
  • Microscopy (AFM)

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