29 August 1997
Vol 277, Issue 5330

About The Cover

Polymers that join two regions with different chemical compositions can separate into phases on a nanometer scale. This particular layered material responded to shear flow in a dynamic manner; it became well aligned (its x-ray scattering pattern is shown at the bottom) but only after proceeding through a transient of mutually perpendicular domains (four-spot pattern, upper left). See 1248 and the special section on Materials Science beginning on 1213. [Image: Z.-R. Chen and J. A. Kornfield]