Polydiacetylene water sensors
View Patent ↗Moisture sensing color change compositions are built of nanofibers of suitable small dimension based on diacetylene monomers that are polymerized in situ in a dried film containing a hygroscopic polymer that is bound to the nanofibers either directly or through crosslinkers.
1. A method of making a sensor that changes color on exposure to moisture, comprising:
coating a solution of a carboxylate salt on a substrate;
drying the coated substrate;
exposing the dried substrate to a solution of water-soluble polyvinyl alcohol; and
irradiating the coated substrate with ultraviolet radiation;
wherein the carboxylate salt is a potassium, rubidium, or cesium salt of a carboxylic acid comprising a carboxylate head and an aliphatic tail, and
wherein the aliphatic tail comprises two conjugated triple bonds.
2. The method of claim 1 , wherein the salt is a potassium salt.
3. The method of claim 1 , wherein the carboxylic acid has 16-30 carbon atoms.
4. The method of claim 3 , wherein carboxylic acid has 18-28 carbon atoms.
5. A water sensor that changes color from blue in the dry state to red in the presence of water, comprising:
a substrate;
a polymerized diacetylene carboxylate salt coated on the substrate; and
a water-soluble polymer disposed on the substrate over the polymerized diacetylene carboxylate salt;
wherein the carboxylate salt is a potassium, rubidium, or cesium salt of a carboxylic acid comprising a carboxylate head and an aliphatic tail, and
wherein the aliphatic tail comprises two conjugated triple bonds.
6. The water sensor according to claim 5 , wherein the water-soluble polymer comprises polyvinyl alcohol.
7. The water sensor according to claim 5 , wherein the carboxylate salt is a potassium salt.