Hexagonal packed cylinder phase

Fig. 4.17 Small-angle X-ray scattering patterns for 38wt% aqueous solutions of PE04oPB010 (a) BCC phase observed between 5 and 50°C (b) FCC structure between 50 and 75 °C (c) hexagonally-packed cylinder phase above 75 °C (Pople et al. 1997).

Fig. 5.25 Phase diagrams for PS-PEO diblocks in diethyl phthalate (Ciervais and Gallot 1973a), a selective solvent for PS. SEO-3 M = 34.7kgmol 59% PEO.This sample forms a non-crystalline lamellar phase (lam) and a lamellar crystalline phase (crystal). SEO-9 Ma - 75 kg mol-1, 70.5% PEO. This sample forms a non-crystalline hexagonal-packed cylinder phase (hex) and a crystal phase.

The morphology of the ABA-type linear block copolymers is strongly influenced by the volume fraction of the two components. For example, in PS-EB-PS-type block copolymer as the volume fraction of PS is increased, the shape of the dispersed PS phase changes from spherical (comprising body-centered cubic spheres of PS dispersed in continuous soft phase) to cylindrical form (hexagonal packed cylinders of PS) [10,133,134]. When the volume fraction of the two phases... 

Fig. 1 Morphologies of diblock copolymers cubic packed spheres (S), hexagonal packed cylinders (C or Hex), double gyroid (G or Gyr), and lamellae (L or Lam). Inverse phases not shown. From [8], Copyright 2000 Wiley...

The term star-block copolymer is used for a star architecture in which each arm is a diblock. The influence of chain topology on mechanical and morphological properties was investigated for copolymers composed of PS and PB with a constant styrene content of = 0.74 by Michler s group (Fig. 32) [101,102], While hexagonally packed cylinders of PB in a PS matrix were observed in a symmetric PS-fo-PB-fr-PS triblock copolymer, an L phase... 

Fig. 2.11 Schematic representation of the transition from hexagonally packed cylinders to disorder following cessation of large-amplitude shear, deduced from SANS experiments on an asymmetric PEP-PEE diblock (Bates et al. 1994). Shear was used to stabilize a hex phase above the equilibrium ODT, and the relaxation back to the equilibrium disordered phase was followed after the shear was stopped. Close to the ODT, the transition r, —> u was postulated, while at a higher temperature, (ri) > rr ) r, was indicated.

Fig. 16. A Lyotropic phase of hexagonally packed cylinders. B Mesoporous silica prepared therefrom (B) [60]...

While the theory is simple to solve for spatially uniform phases, it has been extremely difficult to obtain solutions with a given desired symmetry such as that of the hexagonally packed cylinders. What has been done in the past is to further approximate the mean-field free energy of the system by expanding it in terms of the Fourier components of the local A and B densities, (/> (k) - (f)g k) = Landau-Ginzburg free energy of the system. 

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