摘要 |
A compound which undergoes a colour change upon irradiation, and which has the general structure: X-C=C-C=C-Y-(CO)n-QZ wherein X is H, alkyl or -Y-(CO)n-QW; each Y is the same or a different divalent alkylene group; Q is O, S or NR; R is H or alkyl; W is H, alkyl or Z; each Z is the same or a different unsaturated alkyl group; and each n is 0 or 1.
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