Microphase separation in model 4-miktoarm star copolymers of the AB3 type

G. Floudas*, Nikolaos Hadjichristidis, Y. Tselikas, I. Erukhimovich

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The order-disorder transition has been studied in two AB3 miktoarm stars of styrene and isoprene with SAXS and rheology. A mean-field theory has been developed to treat the most general case of miktoarm stars: AmBn (m ≠ n) which provides the phase stability criteria and the static structure factor in the disordered phase. The theory predicts a maximum in the critical value of χNt (Nt = NA + nNB) as a function of the number of arms n in ABn, for n = 3. This maximum arises from a delicate balance between the stretching free energies of the A and B blocks forming the miktoarm stars. The theoretical predictions for the phase stability and the structure factor have been tested experimentally, using SAXS, and the interaction parameter has been extracted. The latter exhibits a weak T-independence which is consistent with fluctuation effects near the transition. Further evidences for the existence of fluctuations at temperatures above and below the transition are provided by (i) the nonlinearity of the inverse peak intensity vs inverse temperature, in the disordered state, and (ii) the existence of metastable states in the ordered state. All SAXS peak parameters were discontinuous at the order-to-disorder transition, revealing a first-order transition.

Original languageEnglish (US)
Pages (from-to)3090-3096
Number of pages7
JournalMacromolecules
Volume30
Issue number10
StatePublished - May 19 1997

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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