Structure and phase behavior of block copolymer melts near the sphere-cylinder boundary

Ferass M. Abuzaina, Amish J. Patel, Simon Mochrie, Suresh Narayanan, Alec Sandy, Bruce Garetz, Nitash P. Balsara

Research output: Contribution to journalArticle

Abstract

The phase behavior of a poly(styrene-block-isoprene) copolymer (SI) with styrene volume fraction f = 0.18 was studied by small-angle X-ray scattering (SAXS), optical birefringence, and rheology conducted under quiescent conditions and under the influence of shear flow. This sample is located at the border between ordered spheres and ordered cylinders. Near the order-disorder transition, SI block copolymers with f < 0.18 form ordered spheres while those with f > 0.18 form ordered cylinders. Our sample exhibits a phase transition from ordered cylinders to disordered micelles at 70 ± 2°C. The cylinder phase obtained by a quiescent quench is highly defective and thus cannot be detected using birefringence. However, birefringence measurements made in the presence of shear flow and high-resolution SAXS measurements on both quiescent and sheared samples confirm the presence of ordered cylinders. The data obtained from our sample differs qualitatively from all previously published data on SI copolymers with f = 0.18. We show that the phase behavior, near the sphere-cylinder boundary, depends on all three thermodynamic parameters: f, χ, and N and not just f and χN, as is usually the case. This dependence on f, χ, and N is ascribed to fluctuation effects and the presence of micelles in the disordered phase. By combining the data presented here with previous results in the literature, we estimate the range of compositions over which disordered micelles are obtained in SI copolymer melts.

Original languageEnglish (US)
Pages (from-to)7090-7097
Number of pages8
JournalMacromolecules
Volume38
Issue number16
DOIs
StatePublished - Aug 9 2005

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Micelles
Phase behavior
Birefringence
Block copolymers
Styrene
Copolymers
Shear flow
X ray scattering
Isoprene
Order disorder transitions
Engine cylinders
Rheology
Volume fraction
Phase transitions
Thermodynamics
Chemical analysis

ASJC Scopus subject areas

  • Materials Chemistry

Cite this

Abuzaina, F. M., Patel, A. J., Mochrie, S., Narayanan, S., Sandy, A., Garetz, B., & Balsara, N. P. (2005). Structure and phase behavior of block copolymer melts near the sphere-cylinder boundary. Macromolecules, 38(16), 7090-7097. https://doi.org/10.1021/ma047540r

Structure and phase behavior of block copolymer melts near the sphere-cylinder boundary. / Abuzaina, Ferass M.; Patel, Amish J.; Mochrie, Simon; Narayanan, Suresh; Sandy, Alec; Garetz, Bruce; Balsara, Nitash P.

In: Macromolecules, Vol. 38, No. 16, 09.08.2005, p. 7090-7097.

Research output: Contribution to journalArticle

Abuzaina, FM, Patel, AJ, Mochrie, S, Narayanan, S, Sandy, A, Garetz, B & Balsara, NP 2005, 'Structure and phase behavior of block copolymer melts near the sphere-cylinder boundary', Macromolecules, vol. 38, no. 16, pp. 7090-7097. https://doi.org/10.1021/ma047540r
Abuzaina, Ferass M. ; Patel, Amish J. ; Mochrie, Simon ; Narayanan, Suresh ; Sandy, Alec ; Garetz, Bruce ; Balsara, Nitash P. / Structure and phase behavior of block copolymer melts near the sphere-cylinder boundary. In: Macromolecules. 2005 ; Vol. 38, No. 16. pp. 7090-7097.
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