Lignin derived photo-responsive coatings
Coating compositions that provide hydrophilic and self-cleaning properties upon exposure to an electromagnetic spectrum are disclosed. Coatings can include lignin-coumarate derivatives and/or lignin-azobenzene derivatives. When exposed to the electromagnetic spectrum, these compounds isomerize to cis-configuration which are hydrophilic in nature as compared to when these compounds are in their hydrophobic trans-state.
1. A coating composition comprising:
a lignin derivative of formula I,
wherein X is one of —N═N— or —CH═CH—C(═O)—O-(alkylene)-O—C(═O)—CH═CH—;
each Z is one of H, alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, nitro, cyano, halogen, or cycloalkyl; and
each R is one of —O— or —NH—;
wherein the lignin derivative of formula I is hydrophobic and exposing the lignin derivative of formula I to an electromagnetic spectrum to isomerize the derivative to a cis configuration in order to impart hydrophilicity.
2. The coating composition of claim 1 , wherein X is —N═N—; each Z is one of H, alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, nitro, cyano, halogen, or cycloalkyl; and R is —NH—.
3. The coating composition of claim 1 , wherein X is —CH═CH—C(═O)—O-(alkylene)-O—C(═O)—CH═CH—; each Z is, one of H, alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, nitro, cyano, halogen, or cycloalkyl; and R is —O—.
4. The coating composition of claim 1 , wherein the lignin derivative is present at about 0.5 weight percent to about 20 weight percent of the coating composition.
5. The coating composition of claim 1 , further comprising a pigment comprising titanium dioxide, zinc oxide, tin oxide, tungsten oxide, or any combination thereof.
6. The coating composition of claim 1 , wherein the coating is a decorative coating, an industrial coating, a protective coating, a self-cleaning coating, a biocidal coating, or any combination thereof.
7. The coating composition of claim 1 , further comprising a solvent, a binder, a pigment, a rheology modifier, a plasticizer, or any combination thereof.
8. The coating composition of claim 1 , wherein the coating is a latex emulsion, a non-aqueous dispersion, or a powder.
9. The coating composition of claim 1 , wherein the electromagnetic spectrum has a wavelength of about 300 nanometers to about 1400 nanometers.