We report experimental observations on the ordered surface patterns resulting from the crystallization of annealed thin films of microphase-separated low-molecular-weight hydrogenated poly(butadiene- $b$-ethyleneoxide) diblock copolymers. For crystal growth rates higher than about 1 nm $/$sec the resulting orientation of the crystalline lamellae was perpendicular to the substrate. Alignment of these lamellae on large length scales was found when crystallization occurred at boundaries created by a dewetting process.

• Received 25 March 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.3844