Polyacetylene films with vertically aligned fibril morphology were synthesized in homeotropic nernatic LC (N-LC) solvent, by using a magnetic field of 5 T as an external perturbation. Next, helical polyacetylene films with vertically aligned and screwed fibril morphology were synthesized in macroscopically aligned chiral nernatic LC (N-*-LC) under magnetic field. Scanning electron micrograph (SEM) indicated that the lengths of fibrils from the substrate were 5-20 mu m, depending on polymerization time, acetylene pressure and catalyst concentration. (c) 2005 Elsevier B.V. All rights reserved.