Reversible colour phase transitions and annealing properties of Langmuir-Blodgett polydiacetylene films

Abstract

The reversible colour phase transition between the blue phase and the red phase is investigated for pre-annealed Langmuir-Blodgett (LB) polydiacetylene (PDA) films. LB PDA films are pre-annealed before polymerization in order to improve the characteristics of the films. The main absorption peaks for the LB PDA films are observed at 640 nm without the pre-annealing, but the pre-annealed films under appropriate conditions have new main absorption peaks at 704 nm. The new peaks at 704 nm exhibit stronger reversibility of the colour phase transition than the peaks at 640 nm. Moreover, X-ray diffraction measurements show that the pre-annealed films have extremely ordered layer structures compared with the films that have not been pre-annealed.