| abstract |
The present invention relates to a time-temperature indicator indicating a temperature change over time, comprising one dimeric or trimeric spiropyran indicator of formula (I) or (II).n n n Formula In n n n n n n n Formula IIn n n n n n n n In the above formulas (I) and (II),n n n R 1 To R 4 are independently of each other hydrogen, —C 1 -C 6 alkoxy, halogen, CF 3 , —C 1 -C 6 alkyl, or —NO 2 ;n n n R 5 is hydrogen, halogen, —C 1 -C 6 alkoxy, —COOH, —COO-C 1 -C 6 alkyl, —CF 3 or phenyl; R 11 is hydrogen, or R 11 and R 5 together form a phenyl ring;n n n R a is —C 1 -C 6 alkyl;n n n R b is —C 1 -C 6 alkyl or, together with R a , forms a 5- or 6-membered ring;n n n L is a divalent linker;n n n L 'is a trivalent linker. |