Lamellae orientation in dynamically sheared diblock copolymer melts

Conference · Fri Dec 31 04:00:00 EST 1993

OSTI ID:141760

Koppi, K A; Tirrell, M; Bates, F S ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

Two distinct lamellae orientations have been identified by small angle neutron scattering in dynamically sheared poly(ethylene--propylene)-poly(ethylethylene) diblock copolymer melts. Near the order--disorder transition and at low shear frequencies, the lamellae arrange with unit normal perpendicular to the flow direction and parallel to the velocity gradient direction (parallel lamellae). Higher frequency processing leads to lamellae with unit normal perpendicular to both the flow and velocity gradient directions (perpendicular lamellae). The crossover from low to high frequency behavior occurs at a frequency roughly equal to the inverse of the relaxation time for local domain deformations. At temperatures well below the order-disorder transition, the parallel orientation is obtained at all shearing frequencies. The perpendicular orientation is proposed to arise from shear-induced disordering, followed by reordering in the perpendicular direction due to the effect of vorticity.

• OSTI ID: 141760
• Report Number(s): CONF-930304--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPOLYMERS
LAMELLAE
ORDER-DISORDER TRANSFORMATIONS
ORIENTATION
PHASE STUDIES
POLYETHYLENES
POLYPROPYLENE