Photo- and Thermo-Chromic Behaviors of Polydiacetylenes with Alkylurethane Substituents

A series of polydiacetylenes with alkylurethane substituents R = (CH2)4OCONHCnH2n+1, where n=1-18, have been synthesized and their chromic behaviors have been studied by optical spectra, X-ray and DSC measurements. All of these polydiacetylenes exhibit the reversible thermochromic transitions, unless the samples are heated exceeding the limited temperatures, while the photo-excitation results in irreversible color change, only from blue to red.The length of the terminal alkyl unit in the side groups are found to affect the thermal hystereses from 0 to 60K in width.