Piezochromic Polymer Materials Displaying Pressure Changes in Bar-Ranges

A piezochromic material exhibiting a pressure dependent reversible shift of the selective reflection wavelength via the entire visible range is developed. The material consists of a cholesteric mixture embedded in a cholesteric elastomer matrix bearing mesogenic side chains with similar molecular structure. The change of the selective reflection has its origin in a compressible helix structure. Thus, the pitch length is switched by pressure changes. To trigger the reversible piezochromic effect already pressure changes in bar-range are sufficient. The pressure controlled colour changes are excellent detectable by the human eye and still appear even after 100 cycles.