Lamellar regime, block copolymers

Instead of the familiar sequence of morphologies, a broad multiphase window centred at relatively high concentrations (ca. 50-70% block copolymer) truncates the ordered lamellar regime. At higher epoxy concentrations wormlike micelles and eventually vesicles at the lowest compositions are observed. Worm-like micelles are found over a broad composition range (Fig. 67). This morphology is rare in block copolymer/homopolymer blends [202] but is commonly encountered in the case of surfactant solutions [203] and mixtures of block copolymers with water and other low molecular weight diluents [204,205]. 

Lee et al. also studied aggregates formed by a series of linear rod-coil multiblock oligomers with identical rod to coil volume fraction and found that they can regulate the supramolecular structure formed by the systematic variation of the number of repeating units [169]. This work shows very nicely the dependence of the microstructure on molecular composition as the mesophase shows a phase transition from lamellar to columnar phase with a bicontinuous cubic phase with la3d symmetry as the intermediate regime. Such a behavior has already been observed within the phase diagram of certain coil-coil block copolymers (Chapters 9, 10). 

Banaszak M, Whitmore MD. Mean field-theory of the lamellar structure of block copolymer homopolymer blends in the weak segregation regime. Macromolecules 1992 25 2757-70. 

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