CONDUCTIVE POLYMERIC COATINGS AND METHODS

Abstract

Embodiments of the invention include conductive polymeric coatings and methods of making the same. In an embodiment, the invention includes a method of electrodepositing a conductive polymeric coating onto a substrate surface. The method can include contacting the substrate surface with a solution comprising a monomer, a counterion, and a solvent; exposing the solution to an electrical potential, wherein the surface serves as an electrode in the application of the electrical potential; and alternating the electrical potential between a lower potential and a higher potential to form the conductive polymeric coating on the substrate surface. Other embodiments are also included herein.

Description

[0001] This application claims the benefit of U.S. Provisional Application No. 61/860,683 filed Jul. 31, 2013, the contents of which are herein incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to conductive polymeric coatings and methods of making the same.

BACKGROUND OF THE INVENTION

[0003] While many polymers are strong electrical resistors, it will be appreciated that there also various electrically conducting polymers. Such polymers have many applications in electronics, medical technologies and general industrial settings. By way of example, various conductive polymers have been applied as coatings over substrates.

SUMMARY OF THE INVENTION

[0004] Embodiments of the invention include conductive polymeric coatings and methods of making the same. In an embodiment, the invention includes a method of electrodepositing a conductive polymeric coating onto a substrate surface. The method can include contacting the substrate surface with a solution comprising a monomer, a counterion, and a solvent; exposing the solution to an electrical potential, wherein the surface serves as an electrode in the application of the electrical potential; and alternating the electrical potential between a lower potential and a higher potential to form the conductive polymeric coating on the substrate surface.

[0005] In an embodiment, the invention includes a device including a substrate and a conductive polymeric coating disposed over the substrate, wherein the conductive polymeric coating exhibits a durability that is greater than an otherwise compositionally identical conductive polymeric coating formed by a potentiostatic deposition or galvanostatic method.

[0006] This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE FIGURES

[0007] The invention may be more completely understood in connection with the following drawings, in which:

[0008] FIG. 1 is a schematic diagram of a system for coating a substrate in accordance with an embodiment herein.

[0009] While the invention is susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the invention is not limited to the particular embodiments described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments of the present invention described herein are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices of the present invention.

[0011] All publications and patents mentioned herein are hereby incorporated by reference. The publications and patents disclosed herein are provided solely for their disclosure. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate any publication and/or patent, including any publication and/or patent cited herein.

[0012] As described above, electrically conducting polymers have many applications in electronics, medical technologies and general industrial settings. As one example, relevant to medical technologies, electrically conducting polymers have been applied over portions of medical devices such as over electrodes, sensors, cases, or the like.

[0013] However, it has been observed that electrically conducting polymers when applied as coatings may exhibit durability that is less than desirable for some applications. For example, it has been observed that the application of frictional force to the surface of some electrically conductive polymeric coatings can result in portions of the coating coming off the surface to which the coating was disposed on. In some cases, the entire coating may come off.

[0014] Embodiments herein include electrically conductive polymeric coatings that exhibit improved durability. Embodiments herein also include methods of electrodepositing conductive polymeric coatings onto substrates.

[0015] In an embodiment, a method of electrodepositing a conductive polymeric coating onto a substrate surface is included. The method can include contacting the substrate surface with a solution comprising a monomer(s), a counter ion and a solvent.

[0016] The monomer can include one or more distinct monomers. The monomer(s) can include those that polymerize to form an electrically conductive polymer. In some embodiments, the monomer can include 3,4-ethylenedioxythiophene. In some embodiments, a counter ion can also be included. In some embodiments, the counter ion can include a polystyrenesulfonate salt. In some embodiments, the monomer comprises a mixture of 3,4-ethylenedioxythiophene and a counter ion of polystyrenesulfonate salt. It will be appreciated that beyond the monomer, suitable counter ion and a suitable solvent, the solution can further include various other components including, but not limited to, additional monomers, additives, salts, co-solvents, and the like

[0017] The molar ratios of the monomer and the counterion can be varied depending on the desired end properties of the coating. By way of example, in some embodiments, the ratio of 3,4-ethylenedioxylthiophene to polystyrenesulfonate can vary from 1:2 to 2:1. In yet other exemplary embodiments, the ratio of 3,4-ethylenedioxylthiophene to polystyrenesulfonate can be 1:1.

[0018] In some embodiments, the resulting conductive polymeric coating comprises poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS).

[0019] The substrate surface can include various materials. In some embodiments, the substrate surface includes an electrically conductive material. In some embodiments, the substrate surface comprising a metal. In some embodiments, the substrate surface comprising platinum. In some embodiments, the substrate surface comprises platinized stainless steel (stainless steel coated with platinum). In some embodiments, the substrate surface comprises platinum-iridium such as platinum-iridium (90:10). In some embodiments, the surface can be textured and in other embodiments the surface can be substantially smooth.

[0020] The method can also include exposing the solution to an electrical potential, wherein the surface serves as an electrode in the application of the electrical potential. The method can also include alternating the electrical potential between a lower potential and a higher potential to form the conductive polymeric coating on the substrate surface.

[0021] In some embodiments, alternating the electrical potential between a lower potential and a higher potential comprises changing the electrical potential in a step change pattern. The step change pattern can include a single change from the lower potential to the higher potential, or from the higher potential to the lower potential. In other embodiments, the step change pattern can include multiple incremental changes from the lower potential to a higher potential, or from the higher potential to a lower potential.

[0022] In some embodiments, alternating the electrical potential between a lower potential and a higher potential comprises changing the electrical potential gradually at a particular rate of change. It will be appreciated that various rates of change can be used. In some embodiments, the rate of change is from about 5 mV/s to about 200 mV/s. In some embodiments, the rate of change is from about 20 mV/s to about 100 mV/s. In some embodiments, the rate of change is from about 40 mV/s to about 60 mV/s. In some embodiments, the rate of change is from about 45 mV/s to about 55 mV/s. In some embodiments, the rate of change is about 50 mV/s.

[0023] In some embodiments, the lower potential is between -1.5 V and 1.0 V. In some embodiments, the lower potential is between -0.5 V and 0.7 V. In some embodiments, the lower potential less than about 0.7 V. In some embodiments, the lower potential less than about 0 V. In some embodiments, the lower potential is about -0.2 V.

[0024] In some embodiments, the higher potential is between 0.5 V and 3.0 V. In some embodiments, the higher potential is between 0.7 V and 2.0 V. In some embodiments, the higher potential is between about 1.0 V and 1.6 V. In some embodiments, the higher potential is between about 1.2 V and 1.5 V. In some embodiments, the higher potential is about 1.4 V.

[0025] In some embodiments, alternating the electrical potential comprises alternating the electrical potential between the lower potential and the higher potential a plurality of times. In some embodiments, alternating the electrical potential comprises alternating the electrical potential between the lower potential and the higher potential from between 1 and 500 times. In some embodiments, alternating the electrical potential comprises alternating the electrical potential between the lower potential and the higher potential from between 2 and 200 times. In some embodiments, alternating the electrical potential comprises alternating the electrical potential between the lower potential and the higher potential from between 10 and 50 times.

[0026] In yet other embodiments, a combination of potentiostatic and potentiodynamic processes can be alternatingly applied to ultimately achieve durable coated surface properties. By way of example, a potentiostatic (constant voltage) process could be used first followed by a potentiodynamic process. Alternatively, a potentiodynamic process could be used first followed by a potentiostatic process. In some embodiments, a method can include alternating between potentiostatic and potentiodynamic processes.

[0027] In some embodiments, further operations can be performed after initial deposition of the electrically conductive polymeric coating. By way of example, in some embodiments, an additional coating layer, such as a top coat, can be applied. In other embodiments, various compounds can be applied in order to improve properties of the coating such as, but not limited to, the conductivity of the coating.

[0028] Coatings in accordance with embodiments herein can exhibit superior properties in comparison to otherwise similar or compositionally identical coatings that are applied in different ways. By way of example, in some embodiments, the conductive polymeric coating adheres more strongly than an otherwise compositionally identical polymeric coating formed by a potentiostatic or galvanostatic application method. In some embodiments, the conductive polymeric coating exhibits a resistance to frictional removal that is greater than an otherwise compositionally identical polymeric coating formed by a potentiostatic or galvanostatic application method. In some embodiments, the conductive polymeric coating exhibits a durability that is greater and a conductivity that is lower than an otherwise compositionally identical polymeric coating formed by a potentiostatic or galvanostatic application method.

[0029] Referring now to FIG. 1 a schematic diagram of a system 100 for coating a substrate in accordance with an embodiment herein is shown. The system 100 includes a container 102 into which components of the system can be placed. A substrate 104 is shown with a conductive polymeric layer 106 disposed thereon. A solution 108 is in contact with the substrate 104 and/or the conductive polymeric layer 106. The system 100 also includes an electrode 110 for applying the electric potential. The substrate 104 itself can serve as the other electrode. The system 100 can also include a controller 112 for applying the electric potential as described herein. In some embodiments, the controller 112 can be a potentiostat/galvanostat.

[0030] The present invention may be better understood with reference to the following examples. These examples are intended to be representative of specific embodiments of the invention, and are not intended as limiting the scope of the invention.

EXAMPLES

Coated Rod Durability Test Method

[0031] This test method was developed to compare the durability of coatings on a cylindrical rod. A texture analyzer system (model TA XT Plus, available from Stable Microsystems, Godalming, Surrry, UK) equipped with a load cell was used to control the speed and distances. The platinum coated stainless steel rod to be tested (3'' length×0.125'' diameter) was placed in a hemostasis valve with a silicone compression seal (hemostasis Valve Y Connector; part No. 80398, available from Qosina Inc, Edgewood, N.Y.). The diameter of the hemostasis valve allows for uniform force to be applied to the circumference of the coated cylindrical sample rod to be tested.

[0032] The tests were performed using a fluid circulation system adapted to the hemostasis valve. The hemostasis valve was modified with a fitting on the sidearm and exit. Tubing was attached to the fittings and the opposite ends were positioned in a fluid reservoir. A peristaltic pump was then placed between the reservoir and sidearm port to deliver fluid to the hemostasis valve returning to the reservoir via the exit port. Fluid was recirculated continuously throughout the test run with no visible leaks at the compression fitting when fluid pressure was applied on the test part.

Example 1

Potentiodynamic Deposition of Conductive Polymeric Layer

[0033] All electrochemical experiments were carried out using SP-150 potentiostat/galvanostat (BioLogic). The electrochemical cell was a conventional three-electrode system with a platinum mesh as the counter electrode and Ag/AgCl/KCl (3.5M) as the reference electrode.

[0034] Platinum-coated stainless steel rods (3'', 1/8'', matte finish) were used as substrates. The area 0.5'' from the top was not coated (i.e., only 2.5'' of the rod was coated).

[0035] The solution used for polymerization contained 3,4-ethylenedioxythiophene (0.25 mL) and sodium polystyrene sulfonate (1 g) in 250 mL of water. Potentiodynamic polymerization was carried out by cycling in the potential range from -0.2 to 1.4 V at scan rate of 50 mV/s (20 cycles). Potentiostatic electrodeposition was performed with several voltages: 1.1, 1.2, 1.3 and 1.4 V for 10 min. During galvanostatic polymerization 2, 3, 5 and 10 mA current was used for 10 min.

[0036] During potentiostatic (1.2, 1.3 and 1.4 V) and galvanostatic (3, 5 and 10 mA) electrodeposition dark-blue precipitate started to form around the working electrode after about 3 min and settled to the bottom. No precipitate formed during potentiodynamic method or at 1.1 V or at 2 mA.

[0037] The resulting coatings were rinsed with DI water and tested for durability by using the test method described above. The durability was assessed qualitatively.

[0038] The coatings deposited by potentiodynamic method appeared to be the most durable and uniform.

[0039] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a mixture of two or more compounds. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

[0040] It should also be noted that, as used in this specification and the appended claims, the phrase "configured" describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration to. The phrase "configured" can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, constructed, manufactured and arranged, and the like.

[0041] All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

[0042] The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

1. A method of electrodepositing a conductive polymeric coating onto a substrate surface comprising: contacting the substrate surface with a solution comprising a monomer, a counter ion, and a solvent; exposing the solution to an electrical potential, wherein the surface serves as an electrode in the application of the electrical potential; and alternating the electrical potential between a lower potential and a higher potential to form the conductive polymeric coating on the substrate surface.

2. The method of claim 1, wherein alternating the electrical potential between a lower potential and a higher potential comprises changing the electrical potential in a step change pattern.

3. The method of claim 1, wherein alternating the electrical potential between a lower potential and a higher potential comprises changing the electrical potential gradually at a particular rate of change.

4. The method of claim 3, wherein the rate of change is from about 5 mV/s to about 200 mV/s.

5. (canceled)

6. (canceled)

7. The method of claim 3, wherein the rate of change is from about 45 mV/s to about 55 mV/s.

8. (canceled)

9. The method of claim 1, wherein the lower potential is between -1.5 V and 1.0 V.

10. The method of claim 1, wherein the lower potential is between -0.5 V and 0.7 V.

11. (canceled)

12. (canceled)

13. (canceled)

14. The method of claim 1, wherein the higher potential is between 0.5 V and 3.0 V.

15. The method of claim 1, wherein the higher potential is between 0.7 V and 2.0 V.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

21. (canceled)

22. The method of claim 1, wherein alternating the electrical potential comprises alternating the electrical potential between the lower potential and the higher potential from between 10 and 50 times.

23. The method of claim 1, the monomer comprising a monomer that polymerizes to form an electrically conductive polymer.

24. The method of claim 1, the conductive polymeric coating comprising poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonate) (PEDOT:PSS).

25. The method of claim 1, the monomer comprising 3,4-ethylenedioxylthiophene.

26. The method of claim 1, the counter ion comprising a polystyrenesulfonic acid or salt thereof.

27. The method of claim 1, the monomer comprising 3,4-ethylenedioxylthiophene and the counter ion comprising a polystyrenesulfonate salt.

28. The method of claim 1, the solution further comprising an additive.

29. The method of claim 28, the additive comprising sodium dodecyl sulfate.

30. (canceled)

31. (canceled)

32. (canceled)

33. (canceled)

34. The method of claim 1, the substrate surface comprising a metal.

35. (canceled)

36. (canceled)

37. A device comprising: a substrate; a conductive polymeric coating disposed over the substrate; wherein the conductive polymeric coating exhibits a durability that is greater than an otherwise compositionally identical conductive polymeric coating formed by a potentiostatic or galvanostatic deposition method.

38. The device of claim 37, the conductive polymeric coating comprising PEDOT:PSS.

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