Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 29, 1997 | public
Journal Article

Pathways to Macroscale Order in Nanostructured Block Copolymers

Abstract

Polymeric materials undergo dramatic changes in orientational order in response to dynamic processes, such as flow. Their rich cascade of dynamics presents opportunities to create and combine distinct alignments of polymeric nanostructures through processing. In situ rheo-optical measurements complemented by ex situ x-ray scattering reveal the physics of three different trajectories to macroscopic alignment of lamellar diblock copolymers during oscillatory shearing. At the highest frequencies, symmetry arguments explain the transient development of a bimodal texture en route to the alignment of layers parallel to the planes of shear. At lower frequencies, larger-scale relaxations introduce rearrangements out of the deformation plane that permit the formation of lamellae perpendicular to the shear plane. These explain the change in the character of the pathway to parallel alignment and the emergence of perpendicular alignment as the frequency decreases.

Additional Information

© 1997 American Association for the Advancement of Science. This research was carried out with the support of NSF (grant CTS 9421015), the Air Force Office of Scientific Research (Liquid Crystals MURI), Chevron, and Raychem.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023