## Abstract

The equilibrium phase behavior of 43 linear poly(isoprene-b-styrene-b- ethylene oxide) (ISO) triblock copolymer melts, with molecular weights that place these materials near the order-disorder transition, is reported. Ordered phase morphologies were characterized using small-angle X-ray scattering, transmission electron microscopy, dynamic mechanical spectroscopy, and static birefringence measurements. Interpretation of these results was aided by a modeling technique that facilitates resolution of reciprocal and real-space experimental data, leading to definitive three-dimensional morphological structures. Three distinct multiply continuous network morphologies are identified across a range of compositions between 0.1 ≤ f _{o} ≤ 0.3, situated between two-domain and three-domain lamellae, where f _{o} represents the volume fraction of O blocks. Two cubic network phases, Q ^{230} (core-shell double gyroid, Ia3d space group symmetry) and Q ^{214} (alternating gyroid, I4 _{1}32 space group symmetry), flank an orthorhombic network phase, denoted O ^{70} (Fddd space group symmetry), which is positioned around the isopleth composition f _{s} ≈ f _{I}. These results provide a powerful strategy for designing network phases in linear ABC triblock copolymers when χ _{AB} ≈ χ _{BC} < χ _{AC}, where χ represents the Flory-Huggins interaction parameter.

Original language | English (US) |
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Pages (from-to) | 8325-8341 |

Number of pages | 17 |

Journal | Macromolecules |

Volume | 37 |

Issue number | 22 |

DOIs | |

State | Published - Nov 2 2004 |