Poly(trimethylene oxy-2 methyl trimethylene p-p' bibenzoate) is a linear thermotropic liquid crystal polymer that may or may not develop anomalous orientation depending on the applied strain rate. X-ray diffraction patterns show that macromolecular chains tend to align perpendicularly to the deformation direction for the slowest analysed strain rates and in parallel to the deformation direction for the highest rates. The study of the strain-stress curves reveals that plastic deformation of this polymer can be controlled by two different microscopic mechanisms whose relative contributions to the overall strain are rate dependent. (C) 2001 Elsevier Science Ltd. All rights reserved.