Time-temperature indicator based on oligomeric spiroaromatics

摘要: The present invention relates to a time temperature indicator for indicating change over comprising one dimeric or trimeric spiropyran of the formula I II wherein R1-R4 independently another is hydrogen, —C1C6 alkoxy, halogen, CF3, alkyl —NO2, R5 —C1-C6 —COOH, —COO—C1-C6 alkyl, —CF3 phenyl; R11 hydrogen and form together phenyl ring; Ra Rb with 5-6 membered ring L divalent linker; L′ trivalent linker.