Homo- and Co-Polymers of Norbornene Containing Aryl- and Hetaryl-Azo Dyes; Synthesis and Sensing Properties

A series of polynorbornene homo- and copolymers containing aryl- and/or hetaryl-azo dyes were prepared through ring-opening metathesis polymerization (ROMP). Thermal studies indicated that the polymers were thermally stable up to 250 degrees C, and possessed glass transition temperatures ranging from 93 to 133 degrees C. In THF solutions, the aryl-azo dye containing homopolymers, displayed lambda(max) = 417 nm while the hetaryl-azo dye containing homopolymers displayed lambda(max) = 495 nm. The copolymers displayed a lambda(max) that encompassed both the aryl- and hetaryl-azo dye range. The monomers and polymers showed bathochromic shifts in solution when acidified. The polymers were cast into films that changed colour in the presence of both aqueous 1.2 m HCl or HCl(g). The colour change reverses when exposed to aqueous 1.2 m NaOH or NH3(g). This process was repeated several times without disintegration of the polymer film, indicating that these polymers may be useful as reusable acid sensors.