Vapor sensor and materials therefor

• US 20040202856A1
• Filed: 04/11/2003
• Published: 10/14/2004
• Est. Priority Date: 04/11/2003
• Status: Active Grant

• Current Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Original Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Inventors: Blok, Edward J.
• Granted Patent: US 7,138,090 B2
• Time in Patent Office: Days
• US Class Current: 428/325
• CPC Class Codes: G01N 27/126 comprising organic polymers
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

The present invention relates to a composition for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e. conductometric sensors). The present invention provides sensor film compositions that have greater temperature stability and sensitivity to chemical analytes, as well as methods of making these sensor films. Sensor film compositions according to the present invention include a crosslinked siloxane polymer comprising a monomer having a hydrocarbon side group with greater than or equal to two carbon atoms and a plurality of conductive particles distributed within the polymer. Alternate preferred embodiments distribute an oil comprising siloxane having at least one side group with greater than or equal to two carbons through a crosslinked siloxane polymer, wherein the oil is distributed through a crosslinked polysiloxane copolymer. Further, conductive particles having a N₂ adsorption of between about 8 to about 25 m²/g provide enhanced sensor film performance.

Claims

1. A conductometric sensor film comprising:

a crosslinked siloxane polymer comprising a monomer having a hydrocarbon side group with greater than or equal to two carbon atoms; and

a plurality of conductive carbon black particles having a N₂ adsorption of between about 8 to about 25 m²/g, distributed within said polymer.

2. The conductometric sensor film according to claim 1, further comprising an alkyl side group substituted siloxane oil, wherein said alkyl side group has greater than or equal to two carbon atoms.

3. The conductometric sensor film according to claim 1, wherein said hydrocarbon side group is selected from the group consisting of:

alkyl, aryl, alkenes, and aromatics.

4. The conductometric sensor film according to claim 1, wherein said hydrocarbon side group comprises a hydrocarbon comprising a polar group.

5. The conductometric sensor film according to claim 1, wherein said conductive carbon black particles have a DBP value of from about 1 to about 180 ml/100 g.

6. The conductometric sensor film according to claim 1, wherein said crosslinked polymer comprises poly(vinylmethylsiloxane octylmethylsiloxane-dimethylsiloxane).

7. The conductometric sensor film according to claim 1, wherein said crosslinked siloxane polymer comprises polyphenylmethylsiloxane.

8. A sensor film composition for detecting chemical analytes comprising:

a crosslinked polymer comprising a siloxane monomer having a hydrocarbon side group with greater than or equal to two carbon atoms; and

a plurality of conductive particles distributed in said crosslinked polymer.

9. The sensor film composition according to claim 8, wherein said hydrocarbon side group is selected from the group consisting of:

alkyl, aryl, alkenes, and aromatics.

10. The sensor film composition according to claim 8, wherein said hydrocarbon side group comprises a hydrocarbon comprising a polar group.

11. The sensor film composition according to claim 8, wherein said hydrocarbon side group is selected from the group consisting of:

ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl, alkylphenyl, cyclopentyl, and phenylpropyl.

12. The sensor film composition according to claim 8, wherein said hydrocarbon side group is selected from the group consisting of:

butylated aryloxypropyl, N-pyrrolidonepropyl, cyanopropyl, benzyltrimethyl ammonium chloride, and hydroxyalkyl.

13. The sensor film composition according to claim 8, wherein said crosslinked polymer comprises poly(vinylmethylsiloxane-octylmethylsiloxane-dimethylsiloxane).

14. The sensor film composition according to claim 8, wherein said crosslinked polymer comprises polyphenylmethylsiloxane.

15. The sensor film composition according to claim 8, wherein said conductive particles are selected from the group consisting of:

gold, platinum, graphite, carbon black, nickel, conductive metal borides, nitrides and carbides, nickel, and mixtures thereof.

16. A sensor film composition for detecting chemical analytes comprising:

a polymer comprising siloxane; and

a plurality of conductive particles having a N₂ adsorption of between about 8 to about 25 m²/g;

wherein said conductive particles are distributed in said polymer.

17. The sensor film composition according to claim 16, wherein said conductive particles have a DBP value of from about 1 to about 180 ml/100 g.

18. The sensor film composition according to claim 16, wherein said plurality of conductive particles are homogeneously distributed in said polymer.

19. The sensor film composition according to claim 16, wherein said conductive particles have a N₂ adsorption of between about 10 to about 15 m²/g.

20. The sensor film composition according to claim 16, wherein said conductive particles are selected from the group consisting of:

gold, platinum, graphite, carbon black, nickel, conductive metal borides, nitrides and carbides, nickel, and mixtures thereof.

21. A sensor film composition for detecting chemical analytes comprising:

a crosslinked polymer comprising siloxane; and

an oil comprising a hydrocarbon side group substituted siloxane, wherein said hydrocarbon side group has greater than or equal to two carbon atoms, wherein said oil is distributed through said crosslinked polymer.

22. A sensor film composition according to claim 21, further comprising a plurality of conductive particles.

23. The sensor film composition according to claim 21, wherein said crosslinked polymer comprises dimethylsiloxane.

24. The sensor film composition according to claim 21, wherein said crosslinked polymer comprises a siloxane monomer having at least one hydrocarbon side group with greater than or equal to two carbon atoms.

25. The sensor film composition according to claim 21, wherein said hydrocarbon side group of said substituted siloxane oil is selected from the group consisting of:

ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, tetradecyl, octadecyl, decyl, butylated aryloxypropyl, N-pyrrolidonepropyl, cyanopropyl, benzyltrimethyl ammonium chloride, and hydroxyalkyl.

26. The sensor film composition according to claim 21, wherein said oil comprises a polyoctyl methylsiloxane.

27. A method of making a sensor film, the method comprising:

a) admixing a polymer comprising a siloxane monomer having a hydrocarbon side group with greater than or equal to two carbon atoms, and a monomer having a functional group;

a plurality of conductive particles, a curing reagent; and

a catalyst;

b) mixing said polymer, said conductive particles, said curing reagent, and said catalyst to form a matrix mixture;

c) applying said matrix mixture on a sensor probe; and

d) crosslinking said matrix mixture.

28. The method of making a sensor film according to claim 27, wherein said admixing further comprises adding an alkyl side group substituted siloxane oil.

29. The method of making a sensor film according to claim 27, wherein said crosslinking is a hydrosilyation reaction.

30. The method of making a sensor film according to claim 27, wherein said hydrocarbon side group is selected from the group consisting of:

alkyl, aryl, alkenes, aromatics, polar group modified hydrocarbons, and mixtures thereof.

31. The method of making a sensor film according to claim 27, wherein said conductive particles are selected from the group consisting of:

gold, platinum, graphite, carbon black, nickel, conductive metal borides, nitrides and carbides, nickel, and mixtures thereof.

32. The method of making a sensor film according to claim 27, wherein said conductive particles have an N₂ adsorption of between about 8 to about 25 m²/g, and a DBP value of from about 1 to about 180 ml/100 g.