Homo- and Co-polymers of norbornene containing aryl- and hetaryl-azo dyes; synthesis and sensing properties

Abstract

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 °C, and possessed glass transition temperatures ranging from 93 to 133 °C. In THF solutions, the aryl -azo dye containing homopolymers, displayed אmax = 417 nm while the hetaryl-azo dye containing homopolymers displayed אmax = 495 nm. The copolymers displayed a אmax 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. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.