# US 10,246,557 B2 · pH sensitive quantum dots for use as cure indicators > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,246,557 B2 - Document ID: US10246557B2 - Status: Granted - Kind: B2 - Application number: 14/955,388 - Filed: 2015-12-01 - Published: 2017-06-01 - Granted: 2019-04-02 - Earliest claimed: 2015-12-01 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Katherine L. Frank; Andrew M. Zweig - Web page: https://patentgrep.com/patent/US10246557B2 ## CPC - C08G 75/14: Polysulfides - C08G 75/02: Polythioethers - G01N 21/80: Indicating pH value - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES ## Abstract Disclosed is a curable sealant composition including: (i) a thiol-terminated prepolymer and/or monomers thereof, wherein the thiol-terminated prepolymer is a polythioether or a polysulfide; (ii) an “ene” crosslinker having a molecular weight of about 100 to about 5000; and (iii) a pH indicator molecule including a quantum dot functionalized with a pH-responsive ligand. Methods for determining a sufficient cure state of a composition by combining the thiol-terminated prepolymer and/or monomers thereof and the “ene” crosslinker with a pH indicator molecule, including a quantum dot functionalized with a pH-responsive ligand, and (ii) then subjecting a resultant mixture of (i) to curing conditions until the mixture changes its color are also disclosed. ## Claims ### Claim 1 A curable sealant composition comprising: (i) a curable composition comprising at least one thiol-terminated prepolymer, wherein the thiol-terminated prepolymer is selected from the group consisting of a polythioether and a polysulfide and a curing agent, wherein the curing agent comprises an “ene” crosslinker; and (ii) a pH indicator molecule comprising a quantum dot functionalized with a pH-responsive ligand comprising a pH-responsive moiety, wherein energy transfer between the pH-responsive moiety and the quantum dot occurs when the pH-responsive moiety is protonated or deprotonated. ### Claim 2 (depends on 1) The curable sealant composition of claim 1, wherein the quantum dot is a CdSe/ZnS core/shell quantum dot. ### Claim 3 (depends on 1) The curable sealant composition of claim 1, wherein the pH-responsive ligand is protonated. ### Claim 4 (depends on 1) The curable sealant composition of claim 1, wherein the pH-responsive ligand is a tertiary amine. ### Claim 5 (depends on 4) The curable sealant composition of claim 4, wherein the tertiary amine is selected from the group consisting of 2-(diethylamino)ethane-1-thiol, 2-(diisopropylamino)ethane-1-thiol, 2-(dibutylamino)ethane-1-thiol, 2-(pyrrolidin-1-yl)ethane-1-thiol, 2-(piperidin-1-yl)ethane-1-thiol and 2-(dimethylamino)ethane-1-thiol. ### Claim 6 (depends on 1) The curable sealant composition of claim 1, wherein the pH-responsive ligand is a mercaptopyridine derivative. ### Claim 7 (depends on 6) The curable sealant composition of claim 6, wherein the mercaptopyridine derivative is selected from the group consisting of 2-mercaptopyridine, 2-mercaptopyridine N-oxide, and 4-mercaptopyridine. ### Claim 8 (depends on 1) The curable sealant composition of claim 1, wherein the pH-responsive ligand comprises a mercaptoalkane carboxylic acid. ### Claim 9 (depends on 8) The curable sealant composition of claim 8, wherein the mercaptoalkane carboxylic acid is selected from the group consisting of mercaptoacetic acid, mercaptooctanoic acid, mercaptohexanoic acid, mercaptodecanoic acid, mercaptopropanoic acid, and combinations thereof. ### Claim 10 (depends on 1) The curable sealant composition of claim 1, wherein the pH-responsive ligand is hydrophobic. ### Claim 11 (depends on 1) The curable sealant composition of claim 1, further comprising a photosensitizes. ### Claim 12 (depends on 1) The curable sealant composition of claim 1, wherein the polythioether has the following formula (I): HS—R1—[—S—(CH2)p—(—R2—O—)m—(CH2)q—S—R1[n—SH (I) wherein R1 is a C2-C6 alkyl and R2 is a C2-C6 alkyl; m is independently selected from a value ranging from 1 to 50; n is independently selected from a value ranging from 1 to 60; p is independently selected from a value ranging from 2 to 6; and q is independently selected from a value ranging from 1 to 5. ### Claim 13 (depends on 1) The curable sealant composition of claim 1, wherein the polysulfide has the following formula: HSCH2 CH2 OCH2 OCH2 CH2 S[SCH2 CH2 OCH2 OCH2 CH2 S]9 [—SCH2 CH(SH)CH2 S—]n SCH2 CH2 OCH2 O—CH2 CH2 SH wherein m is from about 5 to about 50, n is from 0 to about 1, and n/m is from about 0.002 to about 0.02, when greater than 0. ### Claim 14 (depends on 1) The curable sealant composition of claim 1, further comprising at least one filler. ### Claim 15 (depends on 14) The curable sealant composition of claim 14, wherein the at least one filler is present in an amount of about 20 to about 40 percent by weight. ### Claim 16 (depends on 14) The curable sealant composition of claim 14, wherein the at least one filler is selected from the group consisting of clay, talc, calcium carbonate, fumed silica, carbon black, plasticizers, solvents, stabilizers, cure accelerators, cure retardants, adhesion promoters, and preservatives. ### Claim 17 (depends on 1) The curable sealant composition of claim 1, further comprising at least one non-polysulfide or non-polythioether prepolymer. ### Claim 18 (depends on 1) The curable sealant composition of claim 1, further comprising at least one non-polysulfide or non-polythioether monomer. ### Claim 19 (depends on 1) The curable sealant composition of claim 1, wherein the “ene” crosslinker is selected from the group consisting of diethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,4-butanediol diacrylate, bisphenol A bimethacrylate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and pentaerythritol tetraacrylate. ### Claim 20 (depends on 1) The curable sealant composition of claim 1, wherein the “ene” crosslinker ranges from 0.7 to 1.5 moles per mole of thiol in the at least one thiol-terminated prepolymer.