Patent ID: 8273306

Claim:
A color-changing material comprising: a hydrogel-forming composition comprising a charged hydrogel-forming polymer, the hydrogel-forming composition containing at least one charged species; a charged colorant; a pH adjuster; and a volatile solvent; wherein the charged hydrogel-forming polymer is selected from poly(ethylene glycol)-grafted cationic hydrogels; a copolymer of 2-hydroxyethyl methacrylate (HEMA) and methacrylamide propyltrimethylammonium chloride; a crosslinked cationic copolymer of vinylpyrrolidone (VP) and 3-dimethylaminopropyl(meth)acrylamide (DMAPMA) monomer; (3-acrylamidopropyl)-trimethylammonium chloride (APTMAC1) monomer crosslinked with a neutral crosslinker N,N-methylenebisacrylamide; crosslinked hydrophobically-modified dialkyldiallylammonium salts; a vinyl ether of monoethanolamine; and copolymerization of N,N,N,N-tetrallyl piperazinium dibromide (TAP) with N,N-diallyl morpholinium bromide (DAM).