AbstractThe reversible reaction with di‐hydrazides in acidic solution or polyamines in alkaline solution is used to cause synthetic polymers containing labile carbonyl groups to gel with sharp thermoreversibility in dilute water solution. Some of the polymers described contain active methylenes, for example, partially acetoacetylated polyvinyl alcohol and polyethylenimine, and copolymer of allyl acetoacetate with acrylamide. These polymers function also as couplers for azo and azomethine dye formatio