PHASE-BEHAVIOR OF PURE DIBLOCKS AND BINARY DIBLOCK BLENDS OF POLY(ETHYLENE)-POLY(ETHYLETHYLENE)

We have determined the phase behavior of a series of model poly(ethyle ne)-poly(ethylethylene) (PE-PEE) diblock copolymers with poly(ethylene ) block volume fractions (f(PE)) ranging from 0.25 to 0.46. Four order ed microstructures make contact with the ODT: spheres arranged on a bo dy-centered cubic lattice (<lm(3)over bar m> space group), cylinders p acked on a hexagonal lattice, a bicontinuous structure of space group <la(3)over bar d>, and lamellae. A fifth ordered phase, tentatively id entified as hexagonally perforated layers (HPL), separates the cylindr ical and lamellar morphologies at moderate or greater degrees of segre gation. Binary blends of f(PE) = 0.37 and 0.46 diblocks were used to i nvestigate the bicontinuous cubic phase region in greater detail; thes e experiments indicate that this phase extends as much as 100 degrees C below the ODT for (f(PE)) values in the blend from 0.385 to 0.420.