Ethylene propylene hexagonal phase

A hexagonal phase is found at room temperature and atmospheric pressure in some ethylene-propylene copolymers containing a small amount of diene component [86,93]. 

The cross-sectional area per chain in the hexagonal lattice of irradiated PE varies between 20.6 and 22.0 A. It is, thus, always greater than the cross-sectional area in the rotator phase in paraffins (19.5-20.0 A ), but on average somewhat smaller than that in constrained PE fibers above 7, /, (21.4-22.7 A ). An ethylene-propylene diene copolymer with approximately 64%, 32%, and 4% by weight of each component, respectively, was found to contain hexagonal crystals with a cross-sectional area per chain of 20.3 A". 

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... 

Figure 5.9 Experimental phase diagrams showing the location of the BpE phase (dashed lines) in three diblock copolymer/homopol5fmer ternary blends (a) poly(ethylene)/poly(ethylene--(ethylene-a/r-propylene)], (b) poly(ethylethylene)/poly(dimethyl-siloxane)/poly(ethylethylene-f>-(dimethylsiloxane) and (c) poly(ethylene)/poly(ethylene oxide)/ poly(ethylene-/)-ethylene oxide). The lamellar (L), hexagonal cylindrical (H) and phase-separated (PS) regimes are labeled, and the data displayed as a function of homopolymer content (0h) have been collected by a combination of rheology (x), small-angle neutron scattering (circles) and cloud-point measurements (squares). (Reprinted with permission from Hillmyer, M. A., Maurer, W. W., Lodge, T. P., Bates, F. S. and Almdal, K. J. Phys. Chem. B 103,4814, 1999. Copyright (1999) American Chemical Society.)...

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