Hexagonally perforated layer

Fig. 2.3 Typical isothermal frequency scans for PE-PEE diblocks with indicated compositions in different ordered phases (Zhao ei at. 1996). Qualitative differences between the low frequency rheological response for distinct ordered structures similar to these are observed for other diblocks. S = BCC spheres, C = hex cylinders, G = Ia3d gyroid, HPL = hexagonal perforated layer, L = lamellae. (A) G (x) G . Structural assignments of the ordered phases were made using TEM and SAXS.

The existence of a second class of complex phases, the modulated and perforated layer structures, has largely been explored by Bates and co-workers (Forster et al. 1994 Hamley et al. 1993, 1994 Khandpur et al. 1995 Schulz et al. 1996), who used SANS and TEM to investigate shear oriented structures. The thermally-induced phase transition from the lam to the hex phase in polyolefin diblocks was studied in detail by Hamley et al. (1993, 1994) using SANS, TEM and rheology. Intermediate hexagonal modulated lamellar (HML) and hexagonal perforated layer (HPL) structures were observed on heating PEP-PEE, PE-PEP and PE-PEE diblocks, where PEP is poly(ethylene-propylene), PEE is... 

The effect of harmonics in the composition profile has been considered in Landau Brazovskii theory, as well as mean field theory. Olvera de la Cruz (1991) found a hexagonal perforated layer (HPL) structure to be stable for symmetric or nearly symmetric diblocks in addition to the classical phases. Recent work has... 

Fig. 6.6 TEM images of a catenoid lamellar hexagonal perforated layer (HPL) structure in a blend of a PS-PB diblock (M = 49.9kgmor1, 51wt% PS) and PS homopolymer M = 26 kg mol 1) and a total PS volume fraction fFS = 0.67 (Disko etal. 1993). The sample was annealed at 130 °C prior to microtoming (a) view parallel to the lamellae (b) view normal to the lamellae, showing hexagonal perforations in a PI lamella.

Park I, Lee B et al (2005) Epitaxial phase transition of polystyrene-b-polyisoprene from hexagonally perforated layer to gyroid phase in thin film. Macromolecules 38 10532-10536... 

The kinetics and mechanisms of the C G transition in a concentrated solution of PS-fc-PI in the PS-selective solvent di-n-butyl phthalate was studied [137,149]. An epitaxially transformation of the shear-oriented C phase to G, as previously estabhshed in melts [13,50,150], was observed. For shallow quenches into G, the transition proceeds directly by a nucleation and growth process. For deeper quenches, a metastable intermediate structure appears, with scattering and rheological features consistent with the hexagonally perforated layer (PL) state. The C G transition follows the same pathways, and at approximately the same rates, even when the initial C phase is not shear-oriented. 

Hexagonal modulated layers Hexagonal perforated layers Perforated layers... 

Another important aspect of adding homopolymer to a block copolymer is the ability to change morphology (without synthesis of additional polymers). Furthermore, morphologies that are absent for neat diblocks such as bicontin-uous cubic double diamond or hexagonal-perforated layer phases have been predicted in blends with homopolymers [183], although not yet observed. Transitions in morphology induced by addition of homopolymer are reviewed elsewhere [1], where a list of experimental studies on these systems can also be found. 

Figure 8 Hexagonally perforated layers (HPLs) morphology with different stacking sequences, (a) ABA stacking and (b) ABC stacking.

Hexagonally perforated layer structure in block copolymers 453... 

Hexagonally perforated layer (HPL) structure is one of the most complicated stmctures in polymers, particularly block copolymers. The HPL structure is known to be metastable and appears in limited temperature ranges between the stable lamellar and gyroid phases. HPL structure in polymers is known to be metastable and appears in limited temperature ranges between the stable lamellar and gyroid phases. Nevertheless,... 

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