The conformationat change and the alignment behavior of poly-4BCMU were investigated in compression, de-compression and re-compression process using LB method. In compression process, the conformation of poly-4BCMU changed from random-coil conformation to rigid-rod one. With the increase of surface pressure, poly-4BCMU with rigid-rod conformation gathered into bundles and they aligned perpendicular to the compressing direction. Once stopping the compression and releasing the surface pressure, the bundle textures released packing. In this process (de-compression process), the conformational change never occurred. Discrete slender fibrils gathered again in re-compression process, resulting in the formation of close-packed bundles with high molecular ordering. (C) 2009 Elsevier B.V. All rights reserved.