We study polydiacetylene films that are pertinent to the problems of mirror symmetry breaking induced by the effects of compression and circularly polarized ultra-violet (UV) light. The subphase is only pure water. After polymerization, polymerized 10, 12-tricosadiynoic acid (PTDA) LB films that deposited at the surface pressure of 20 mN m(-1) showed obviously chiral properties, however, no obvious Cotton effect was obtained for PTDA LB films that deposited at the surface pressure of 10 mN m(-1). In addition, TDA LB films could be polymerized to a designed chirality by using chiral circular polarized ultra-violet light (CPUL). (C) 2007 Elsevier B.V. All rights reserved.