Iron cluster and microstructure formation in metal-centered star block copolymers: Amphiphilic iron tris(bipyridine)-centered polyoxazolines

Cheolmin Park, John E. McAlvin, Cassandra L. Fraser, Edwin L. Thomas

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

The microstructure of a metal-centered six-arm star block copolymer, amphiphilic iron tris(bipyridine)-centered poly(2-ethyl-2-oxazoline)-b-poly(2-undecyl-2-oxazoline), [Fe{bpy-(PEOX-PUOX)2}3]2+, was investigated with small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Cylindrical PEOX microdomains were observed in a matrix of PUOX. A similar cylindrical morphology was noted for bpy(PEOX-PUOX)2, the metal-free macroligand subunit of which the Fe star is comprised. Thin films simple-cast from chloroform solution onto carbon substrates annealed at 160 °C for ≈ 2 days revealed in both TEM and AFM the formation of nanoscale iron clusters (≈20-40-nm diameter) distributed randomly across the surface of the film. No clusters were evident in "as-cast" films subjected to TEM analysis without the annealing step, suggesting the importance of thermal treatment for nanocrystal formation. For bulk films, larger micrometer-scale (1-2μm) iron aggregates formed and segregated to the surface of the film after thermal treatment for ≈1 week. A liquid crystal-like mesophase due to undecyl alkyl side chain ordering was evidenced by SAXS and WAXS in the bulk sample.

Original languageEnglish
Pages (from-to)1225-1230
Number of pages6
JournalChemistry of Materials
Volume14
Issue number3
DOIs
Publication statusPublished - 2002 Apr 9

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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