WO2025166272A1 - A polymer-based chemiresistive sensor for real-time monitoring of no2 gas emission - Google Patents

Abstract

The present disclosure provides, among other things, a copolymer, wherein the copolymer comprises: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group. Also disclosed herein are compositions and sensors comprising the copolymer, and methods of detecting an analyte, the methods comprising: contacting a sensor of the present disclosure with a sample comprising the analyte; and measuring an electrical property of the sensor in contact with the sample.

Description

A POLYMER-BASED CHEMIRESISTIVE SENSOR FOR REAL-TIME MONITORING OF NO2 GAS EMISSION

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No.

63/549,124, filed on February 2, 2024. The entire teachings of the above application are incorporated herein by reference.

BACKGROUND

[0002] Accurate and real-time monitoring of toxic gas emissions is crucial to mitigating potential health threats from increasing atmospheric pollution. In this regard, high performance, low-cost sensors for toxic gases are needed. (1-4)

SUMMARY

[0003] In some embodiments, a copolymer comprises a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

[0004] In some embodiments, a composition comprises a first polymer and a second polymer, wherein the first polymer is a copolymer of the present disclosure. In some embodiments, the second polymer is an electrically insulating polymer. In some embodiments, the second polymer comprises wherein n is an integer.

[0005] In some embodiments, a sensor comprises: a copolymer or a composition of the present disclosure; a substrate; and an electrode.

[0006] In some embodiments, methods of detecting an analyte comprise: contacting a sensor of the present disclosure with a sample comprising the analyte; and measuring an electrical property of the sensor in contact with the sample. In some embodiments, the analyte is NO2. In some embodiments, the electrical property is electrical resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.

[0008] FIGs. 1 A - IE: Example design of a thermally stable chemiresistive sensor for real-time monitoring of NO2 emission, in one embodiment. FIG. 1 A: Illustration of an example gas sensor design based on semiconducting polymer composites and chemical structures of DPP-30gT and MATRIMID® 5218. FIG. IB: AFM height image of the blend film. FIG. 1C: Illustration of the proposed NO2 sensing mechanism. FIG. ID: Proposed NO2 absorption sites for the DPP-30gT:MI blend system. FIG. IE: Respective calculated binding energies with the DPP-30gT:MI blend system.

[0009] FIG. 2 A: Example design of a thermally stable morphology from a 3 -components blend system, in one embodiment. FIG. 2B: AFM height image of DPP-30gT:MI at 1 :4 weight ratio, in one embodiment. FIG. 2C: AFM height image of DPP-30gT:MI at 1 : 1 weight ratio, in one embodiment. FIG. 2D: AFM height image of DPP-30gT:MI at 4: 1 weight ratio, in one embodiment.

[0010] FIG. 3 : AFM images of DPP-30gT :MI blend films before and after high temperature (300°C) baking. The interpenetrating morphology is retained when the blend is heated below the glass transition of the matrix.

[0011] FIG. 4A: Raman spectroscopy of DPP-30gT before and after NO2 gas exposure. FIG. 4B: Characteristic transfer curves of DPP-30gT before and after NO2 gas exposure. FIG. 4C: Characteristic transfer curves of DPP-OgT before and after NO2 gas exposure.

[0012] FIGs. 5 A - 5E: NO2 sensing performance of chemiresistors based on DPP- 30gT:MI. FIG. 5 A: Response values of DPP-30gT:MI toward 1 ppm of NO2 at various operating temperatures. FIG. 5B: Dynamic resistance changes in the DPP-30gT:MI channel toward 2-0.25 ppm of NO2 gas at 140°C. FIG. 5C: Response (Rair / Rgas) changes in the DPP- 30gT:MI channel at various concentrations (0.25 ppm, 0.5 ppm, 1.0 ppm, 1.5 ppm, 2 ppm) of NO2 gas at 140°C. FIG. 5D: Selectivity tests of NO2, H2S, NH₃, and CO2. FIG. 5E: Longterm cycling (58 cycles, >6 h) stability tests of DPP-30gT:MI sensors at 170°C.

[0013] FIG. 6A: Temperature dependent measurements (Organic Field-Effect Transistors, -IDS VS. VG) on DPP-30gT:MI thin films. FIG. 6B: Temperature dependent measurements (UV-Vis spectroscopy) on DPP-30gT:MI thin films. [0014] FIG. 7: Response time and recovery time of DPP-3 OgT:MI-based sensors toward 1 ppm NO2 gas at 140 °C.

[0015] FIGs. 8A - 8E: Demonstration of an example thermally stable and mechanically flexible sensor for real-time monitoring of NO2. FIG. 8A: Illustrations of flexible polymer chemiresistor based on a polyimide substrate, in one embodiment. FIG. 8B: Photograph of sensors in flat and bent states, in one embodiment. FIG. 8C: Dynamic resistance transitions of sensors in flat and bent states upon exposure to 1 ppm of NO2 gas at 140 °C before repeated flexing. FIG. 8D: Illustration of the thermally stable and flexible NO2 chemiresistor attached onto a car exhaust pipe, in one embodiment. FIG. 8E: Long-cycling stability tests of DPP - 30gT:MI-based sensors after 500 bending cycles at 170 °C.

[0016] FIG. 9A: Comparison of sensitivity vs. gas concentration between DPP-30gT:MI blends and state-of-the-art (data extracted from supporting references, Table 1) polymer- based chemiresi stive NO2 gas sensors. FIG. 9B: Comparison of sensitivity vs. operating temperature between DPP-30gT:MI blends and state-of-the-art (data extracted from supporting references, Table 1) polymer-based chemiresi stive NO2 gas sensors.

DETAILED DESCRIPTION

[0017] A description of example embodiments follows.

[0018] A thermally stable, mechanically compliant, and sensitive polymer-based NO2 gas sensor design is described herein. Interconnected nanoscale morphology driven from spinodal decomposition between conjugated polymers tethered with polar side chains and thermally stable matrix polymers offers judicious design of NCh-sensitive and thermally tolerant thin films. The resulting chemiresitive sensors exhibit stable NO2 sensing even at 170 °C over 6 h. Controlling the density of polar side chains along conjugated polymer backbone enables optimal design for coupling high NO2 sensitivity, selectivity, and thermal stability of polymer sensors. Thermally stable films are used to implement chemiresi stive sensors onto flexible and heat-resistant substrates and demonstrate a reliable gas sensing response even after 500 bending cycles at 170 °C. Such unprecedented sensor performance as well as environmental stability are promising for real-time monitoring of gas emission from vehicles and industrial chemical processes.

[0019] The present disclosure relates, among other things, to polymers (e.g., copolymers) comprising polar side groups. In some embodiments, a polymer of the present disclosure is used for analyte detection. Disclosed herein are also compositions comprising a polymer of the present disclosure.

[0020] The present disclosure also relates, among other things, to sensors for detecting analytes (e.g., ions, gases), comprising a polymer or composition of the present disclosure. Also disclosed herein are methods for detecting an analyte comprising contacting a sensor of the present disclosure with a sample comprising the analyte and measuring a property e.g., electrical property) of the sensor.

[0021] In embodiments, a copolymer comprises a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene (e.g., a polythiophene) functionalized with a polar side group. In some embodiments, the polar side group is a glycol.

In some embodiments, the glycol

[0022] Examples of polymers comprising diketopyrrolopyrrole are shown in Figure 1 of Li et al., The impact of device polarity on the performance of polymer-fullerene solar cells, Advanced Energy Materials, 2018, 5(22), p.1800550, the contents of which are incorporated by reference herein in their entirety.

[0023] In embodiments, a copolymer comprises a first block, wherein the first block is wherein Ri and R2 are each independently H or an alkyl, and wherein R3 and R.4 are each independently a heterocycle (e.g, a polyheterocycle, a thiophene, a polythiophene); and a second block comprising thiophene (e.g, a polythiophene) functionalized with a polar side group. In some embodiments, the polar side group is a glycol.

In some embodiments, the glycol

[0024] For non-limiting examples, the amount of the second block of the copolymer is from: about 0 % to about 50 %, about 20 % to about 50 %, or about 20 % to about 30 %. In some embodiments, the amount of the second block of the copolymer is 20 %. In other embodiments, the amount of the second block of the copolymer is 50 %.

[0025] In some embodiments, the first block is and wherein Ri and R2 are each independently an alkyl. In some embodiments, Ri and R2 are each independently a branched alkyl. In some embodiments, Ri and R2 are each independently a C3-C20 alkyl. In some embodiments, Ri and R2 are each independently

[0026] In some embodiments, the second block i , wherein Ri and

R2 are each independently H or a polar group (e.g, a glycol). In some embodiments, Ri is , wherein n is an integer (e.g., from about 1 to about 20, from about 1 to about 10, from about 1 to about 5). In some embodiments, Ri

[0027] In some embodiments, the second block i , wherein n is an integer (e.g, from about 1 to about 20, from about 1 to about 10, from about 1 to about 5).

[0028] In some embodiments, the second block i [0029] In some embodiments, the molar ratio of the first block to the second block is from about 100:0 to about 1:1 (e.g., about 10:1 to about 1:1, about 9:1 to about 1:1, about 8:1 to about 1 : 1, about 7: 1 to about 1 : 1, about 6: 1 to about 1 : 1, about 5: 1 to about 1 : 1, about 4: 1 to about 1:1, about 3:1 to about 1:1, about 9:1, about 4:1, about 7:3, about 3:2, about 1:1, etc.). In some embodiments, the molar ratio of the first block to the second block is from about 9: 1 to about 1 : 1. In some embodiments, the molar ratio of the first block to the second block is about 7:3. independently an alkyl, and wherein n and m are integers.

[0031] In some embodiments, a copolymer is wherein n and m are integers.

[0032] In some embodiments, a copolymer is wherein m is about 30 and n is about 70

(DPP-3 OgT). [0033] The present disclosure also provides compositions comprising a first polymer and a second polymer, wherein the first polymer is a copolymer of the present disclosure. In some embodiments, the second polymer is a copolymer (e.g., a matrix).

[0034] In some embodiments, a composition comprises a first polymer and a second polymer, wherein the first polymer is a copolymer comprising: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

[0035] In some embodiments, the mass ratio of the first polymer to the second polymer is from about 1 :5 to about 5: 1 (e.g., about 1 :4 to about 4: 1, about 1 :3 to about 3: 1, about 1 :2 to about 2: 1, etc.). In some embodiments, the mass ratio of the first polymer to the second polymer is about 1 : 1.

[0036] A polymer of the present disclosure includes and is not limited to: poly sulfones; poly(styrenes), including styrene-containing copolymers such as acrylonitrilestyrene copolymers, styrene-butadiene copolymers and styrene-vinylbenzylhalide copolymers; polycarbonates; cellulosic polymers, such as cellulose acetate, cellulose triacetate, cellulose acetate-butyrate, cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose, etc.; polyimides, polyetherimides, and polyamides, including aryl polyamides, aryl polyimides such as MATRIMID® 5218 and aryl poly etherimides such as ULTEM® 1000; poly ethers; poly(arylene oxides) such as poly(phenylene oxide) and poly(xylene oxide); poly(esteramide- diisocyanate); polyurethanes; polyesters (including polyarylates), such as polyethylene terephthalate), poly(alkyl methacrylates), poly(acrylates), poly(phenylene terephthalate), etc.; polysulfides; polymers from monomers having alpha-olefinic unsaturation other than mentioned above such as poly (ethylene), poly(propylene), poly(butene-l), poly(4-m ethyl pentene-1), polyvinyls, e.g., poly(vinyl chloride), poly(vinyl fluoride), poly(vinylidene chloride), poly(vinylidene fluoride), poly(vinyl alcohol), poly(vinyl esters) such as poly(vinyl acetate) and poly(vinyl propionate), poly(vinyl pyridines), poly(vinyl pyrrolidones), poly(vinyl ethers), poly(vinyl ketones), poly(vinyl aldehydes) such as poly(vinyl formal) and poly(vinyl butyral), poly(vinyl amides), poly(vinyl amines), poly(vinyl urethanes), poly(vinyl ureas), poly(vinyl phosphates), and poly(vinyl sulfates); polyallyls; poly(benzobenzimidazole); polyhydrazides; polyoxadiazoles; polytriazoles; poly (benzimidazole); poly carbodiimides; polyphosphazines; etc., and interpolymers, including block interpolymers containing repeating units from the above such as terpolymers of acrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallyl ethers; and grafts and blends containing any of the foregoing. In some embodiments, a polymer is a morphology stabilizing matrix. In some embodiments, a polymer (e.g., a first polymer, a second polymer) is an electrically insulating polymer e.g., a polymer with an electrical resistivity of at least about 10^;" Q m). In some embodiments, the electrical resistivity of a polymer is from about l()^1J O-m to about 10^;6Q m. In some embodiments, the second polymer is an electrically insulating polymer.

[0037] In some embodiments, a polymer (e.g., a second polymer) is a thermosetting polymer. In some embodiments, a polymer comprises a polyimide, an epoxy resin, a phenolic resin, a polyester resin, a polyurethane resin, a melamine formaldehyde resin, a silicone resin, an amino resin, an unsaturated polyester resin, or a combination thereof. In some embodiments, a polymer comprises a polyimide. In some embodiments, a polymer comprises wherein n is an integer (e.g, n is from about 50 to about 100). In some embodiments, a polymer comprises MATRIMID® 5218 polymer.

[0038] In some embodiments, the second polymer has a glass transition temperature of from about 120°C to about 400°C (e.g., about 200°C to about 400°C, 250°C to about 400°C, 300°C to about 400°C, etc.). In some embodiments, the second polymer has a glass transition temperature of about 325°C.

[0039] The present disclosure also provides sensors comprising a polymer (e.g. a copolymer) or composition of the present disclosure. In some embodiments, a sensor comprises a polymer or composition of the present disclosure, a substrate, and an electrode. As used herein, a sensor includes and is not limited to a transducer (e.g. a copolymer) and any electrical elements (e.g. a battery) and any processors that are integrated into the sensor.

[0040] In some embodiments, a substrate is coupled to an electrode and a composition of the present disclosure. A substrate, for example, may provide mechanical and thermal stability to a sensor. A substrate may also provide, for example, chemical resistance, electrical insulation, flexibility and lightweight properties to a sensor. In some embodiments, a substrate comprises a metal oxide or a polyimide. In some embodiments, a polyimide is MATRIMID® 5218, KAPTON®, UPILEX®, P84®, VESPEL® SP, NOMEX®, or ULTEM®.

In some embodiments, a polyimide is poly(4,4'-oxydiphenylene-pyromellitimide). In some embodiments, a metal oxide is tin oxide, zinc oxide, titanium dioxide, copper oxide, iron oxide, nickel oxide, chromium oxide, indium oxide, manganese oxide, or aluminum oxide. In some embodiments, a metal oxide is AI2O3.

[0041] In some embodiments, an electrode comprises platinum, gold, silver, copper, titanium, nickel, palladium, iridium, ruthenium, molybdenum, chromium, tungsten, tantalum, or a combination thereof. In some embodiments, an electrode comprises gold and chromium. [0042] Disclosed herein are transistors comprising a polymer or composition of the present disclosure. In some embodiments, the transistor is an organic field-effect transistor or an organic electrochemical transistor.

[0043] Also disclosed herein, among other things, are methods of detecting an analyte (e.g., a gas molecule, a small molecule), the methods comprising: contacting a sensor of the present disclosure with a sample comprising the analyte; and measuring an electrical property of the sensor in contact with the sample.

[0044] In some embodiments, measuring an electrical property of the sensor in contact with the sample includes measuring an electrical property of a component of the sensor (e.g., a composition of the present disclosure).

[0045] In some embodiments, a method of detecting an analyte comprises: contacting a sensor with a sample comprising the analyte: and measuring an electrical property of the sensor in contact with the sample, wherein the sensor comprises a composition, a substrate, and an electrode, wherein the composition comprises a first polymer and a second polymer, and wherein the first polymer is a copolymer comprising: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group. [0046] In some embodiments, the analyte is a gas. In some embodiments, the gas is carbon dioxide (CO2), sulfur dioxide (SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), nitric oxide (NO), ammonia (NH3), methane (CH4), hydrogen (H2), carbon monoxide (CO), or ozone (O3). In some embodiments, the analyte is a sulfur oxide (e.g., SO2, SO3, etc.), a nitrogen oxide (e.g., NO2, NO, etc.), or a combination thereof. In some embodiments, the analyte is SO2, SO3, NO, NO2, or a combination thereof. In some embodiments, the analyte is NO2.

[0047] In some embodiments, the electrical property is electrical resistance. [0048] In some embodiments, a method of the present disclosure further comprises contacting a sensor with a medium (e.g., air, a solution). In some embodiments, a method of the present disclosure further comprises contacting a sensor with a medium that does not comprise the analyte. In some embodiments, a sensor is contacted with a medium for from about 1 minute to about an hour (e.g., about 1 minute to about 50 minutes, about 1 minute to about 40 minutes, about 1 minute to about 30 minutes, etc.). In some embodiments, a sensor is contacted with a medium for about 20 minutes.

[0049] In some embodiments, a sample is part of a medium. In some embodiments, a sample is taken from a medium (e.g., a medium comprising an analyte). In some embodiments, a sample is within a medium. An example of a sample is an air sample comprising a gas analyte (e.g., NO2 analyte).

[0050] In some embodiments, a method of the present disclosure further comprises measuring an electrical property of a sensor in contact with a medium. In some embodiments, measuring an electrical property of a sensor in contact with a medium includes measuring an electrical property of a component (e.g., a composition of the present disclosure) of the sensor. In some embodiments, the medium is air.

[0051] In some embodiments, a sensor is contacted with a sample comprising an analyte for from about 1 minute to about an hour (e.g., about 1 minute to about 50 minutes, about 1 minute to about 40 minutes, about 1 minute to about 30 minutes, about 1 minute to about 20 minutes, etc.). In some embodiments, a sensor is contacted with a sample comprising an analyte for about 10 min.

[0052] In some embodiments, the electrical property of a sensor in contact with a sample is measured at a temperature of from about 20°C to about 170°C (e.g., about 30°C to about 170°C, about 40°C to about 170°C, about 50°C to about 170°C, about 60°C to about 170°C, etc.). In some embodiments, the electrical property of a sensor in contact with a sample is measured at a temperature of from about 140°C to about 170°C.

[0053] In some embodiments, the electrical property of a sensor in contact with a medium (e.g., a medium that does not comprises an analyte) is measured at a temperature of from about 20°C to about 170°C (e.g., about 30°C to about 170°C, about 40°C to about 170°C, about 50°C to about 170°C, about 60°C to about 170°C, etc.). In some embodiments, the electrical property of a sensor in contact with a medium is measured at a temperature of from about 140°C to about 170°C. [0054] In some embodiments, the electrical property of a sensor in contact with a sample is measured at a relative humidity of about 0.1% to about 5% (e.g., about 0.1% to about 4%, about 0.1% to about 3%, about 0.1% to about 2%, etc). In some embodiments, the electrical property of a sensor in contact with a sample is measured at a relative humidity of about 1.5%.

[0055] In some embodiments, the electrical property of a sensor in contact with a medium (e.g., a medium that does not comprises an analyte) is measured at a relative humidity of about 0.1% to about 5% (e.g., about 0.1% to about 4%, about 0.1% to about 3%, about 0.1% to about 2%, etc). In some embodiments, the electrical property of a sensor in contact with a medium is measured at a relative humidity of about 1.5%.

[0056] In some embodiments, the concentration of an analyte in a sample is from about 0 ppm to about 5 ppm (e.g., about 0.25 ppm to about 4 ppm, about 0.25 ppm to about 3 ppm, about 0.25 ppm to about 2 ppm, etc.). In some embodiments, the concentration of an analyte in a sample is from about 0.25 ppm to about 2 ppm. In some embodiments, the concentration of an analyte in a sample is about 1 ppm.

[0057] Until now, most gas sensor designs have relied on porous materials, 2D materials, and inorganic oxides as the sorbates for sensitive detection. (5,6) Unfortunately, those inorganic materials are hard to process into desired architectures in a cost-effective way, and the resulting devices are mechanically rigid and hence difficult to incorporate onto gas pipes and exhausts directly. Recently, conjugated polymers have garnered increasing attention as active materials for gas sensing, owing to their lightweight and mechanically flexible characteristics, highly desirable for facile system integration, (7-9) their high-performance sensing capabilities, (10) their facile chemical tunability for engineering device selectivity and sensitivity, as well as their solution-based processability, which is attractive for low manufacturing cost. (11-14) Conjugated polymers can be designed to bear abundant delocalized electrons along the TI conjugation as well as polar side groups, allowing electrostatic interactions with the industrial hazardous gases, typically polar small molecules (e.g., NO.v and SO.). (15-17) This facilitates controllability of sorbate-analyte interaction and, thereby, eventual enhancement in sensing performances.

[0058] As most of the industrial emissions are generated from fossil fuel combustion, real-time monitoring of toxic gases inevitably requires operating under elevated temperature conditions. Ideally, monitoring of these gases should be implemented at smoke stack or exhaust pipe levels. There, the use of conjugated polymers is commonly challenging as their functionality tends to be vulnerable under such high temperature environments. (18-21) Polymer TI- TI stacking, which is crucial to electrical conductivity, is greatly perturbed by the thermal fluctuations, leading to poor device performances. (22,23) Consequently, polymer-based gas sensors have been limited to temperatures below 100 °C. (17) To overcome inherent limitations related to extreme environments in polymer-based electronics, researchers typically employ molecular-level design and engineering strategies. (24-29) Notably, organic electronics based on polymer composites structures have been reported to sustain unusually high temperatures over 220 °C. (30,31) Among several strategies to form such composites, blending conjugated polymers with high glass-transition temperature (high 7_g) matrices has been demonstrated as a versatile and straightforward approach to combine environmental robustness with high electronic performance. (29-31) In such blends, interpenetrating spinodal-like morphologies between conjugated polymers and thermally stable matrices are used to effectively prevent the collapse of TI- TI stacks between neighboring polymer chains and thus to retain electronic functionality at the elevated temperatures.

[0059] To deploy this composite strategy into gas sensors, one intriguing class of conjugated polymers is organic mixed ionic-electronic conductors (OMIECs). (32,33) Such polymers have been actively researched for organic electrochemical transistors (OECTs), (33-35) where the voltage-driven insertion of ionic species in the polymeric bulk modulates the channel conductance. Typically, these polymers are conjugated backbones tethered with the polar side chains for ionic insertion. (35-41) This chemical structure is also an advantageous platform for investigating molecular interactions between polymers and small-molecule analytes (e.g., toxic gases) as well as for scalable synthesis. Like other polymers mentioned above, these structures also suffer from poor environmental stability, including thermal stability. The common OMIECs are stable only up to 120 °C bakes, (42,43) with the recent exception of diketopyrrolopyrrole (DPP)-based

OMIECs. (44-46) For instance, it has been shown that with systematic control over the amount of polar side chains (triethylene glycol, TEG, which is known for enhancing gas affinity) (15-17) along the backbone, optimal electrochemical modulation and unprecedented thermal stability (300 °C baking) can be achieved in DPP copolymers. (46) Motivated by the chemically tunable affinity toward polar molecules in these DPP -based copolymers, as well as their thermal stability, such OMIEC systems could be employed for sensing toxic gases (especially NO2) for real-time monitoring of industrial and domestic emissions. [0060] In the present disclosure, and as described in ref. 47, the entire content of which is incorporated herein by reference, a thermally stable and flexible NO2 gas sensor using blend composites of a DPP -based OMIEC and a polyimide matrix is demonstrated. A spinodal-like morphology between the mixed conductor and the high 7_g matrix synergistically combines high affinity toward NO2 as well as high-temperature operation stability. The blend system is readily solution-processable into thin films, thus facilitating the fabrication of chemiresi stive sensing devices, even onto flexible substrates. Chemiresi stive NO2 gas sensors with excellent response values, low detection limit, high selectivity, and long-term stability even in the temperature range, such as those found in exhaust pipes, are thus presented. The composite design showed one of the best NO2 detection performances to date, and the flexible device architecture demonstrated potential integration into exhaust pipes and chimneys. The present disclosure demonstrates both the importance of structural design of new sensing materials, especially conjugate polymers, and promising device architectures for integrated monitoring of toxic gases.

DEFINITIONS

[0061] It is to be understood that the terminology used herein is for describing particular embodiments only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains.

[0062] Although any methods and materials similar or equivalent to those described herein may be used in the practice for testing of the present disclosure, exemplary materials and methods are described herein.

[0063] When a list is presented, unless stated otherwise, it is to be understood that each individual element of that list, and every combination of that list, is a separate embodiment. For example, a list of embodiments presented as “A, B, or C” is to be interpreted as including the embodiments, “A,” “B,” “C,” “A or B,” “A or C,” “B or C,” or “A, B, or C ” [0064] 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. The conjunctive term “and/or” between multiple recited elements is understood as encompassing both individual and combined options. For instance, where two elements are conjoined by “and/or,” a first option refers to the applicability of the first element without the second. A second option refers to the applicability of the second element without the first. A third option refers to the applicability of the first and second elements together. Any one of these options is understood to fall within the meaning, and therefore satisfy the requirement of the term “and/or” as used herein. Concurrent applicability of more than one of the options is also understood to fall within the meaning, and therefore satisfy the requirement of the term “and/or.”

[0065] Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and synonyms and variants thereof such as “have” and “include”, as well as variations thereof, such as “comprises” and “comprising”, are to be construed in an open, inclusive sense, e.g., “including, but not limited to.” The transitional terms “comprising,” “consisting essentially of,” and “consisting of’ are intended to connote their generally accepted meanings in the patent vernacular; that is, (i) “comprising,” which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open- ended and does not exclude additional, unrecited elements or method steps; (ii) “consisting of’ excludes any element or step not specified in the claim; and (iii) “consisting essentially of’ limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed disclosure and disclosure. Embodiments described in terms of the phrase “comprising” (or its equivalents) also provide as embodiments those independently described in terms of “consisting of’ and “consisting essentially of.”

[0066] As used herein, an “alkyl” group or “alkane” is a straight chained or branched non-aromatic hydrocarbon which is completely saturated. Typically, a straight chained or branched alkyl group has from 1 to about 20 carbon atoms, preferably from 1 to about 10 unless otherwise defined. Examples of straight chained and branched alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, tertpentyl, neo-pentyl, iso-pentyl, sec-pentyl, 3-pentyl, sec-iso-pentyl, active-pentyl, hexyl, heptyl, octyl, ethylhexyl, and the like. A Ci-8 straight chained or branched alkyl group is also referred to as a “lower alkyl” group. An alkyl group with two open valences is sometimes referred to as an alkylene group, such as methylene, ethylene, propylene and the like. Moreover, the term “alkyl” (or “lower alkyl”) as used throughout the specification, examples, and claims is intended to include both “unsubstituted alkyls” and “substituted alkyls”, the latter of which refers to alkyl moieties having substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents, if not otherwise specified, can include, for example, an alkyl, a halogen, a hydroxyl, a carbonyl (such as a carboxyl, and alkoxycarbonyl, a formyl, or an acyl), a thiocarbonyl (such as a thioester, a thioacetate, or a thioformate), an alkoxyl, a phosphoryl, a phosphate, a phosphonate, a phosphinate, an amino, an amido, an amidine, an imine, a cyano, a nitro, an azido, a sulfhydryl, an alkylthio, a sulfate, a sulfonate, a sulfamoyl, a sulfonamido, a sulfonyl, a heterocyclyl, an aralkyl, or an aromatic or heteroaromatic moiety. It will be understood by those skilled in the art that the moieties substituted on the hydrocarbon chain can themselves be substituted, if appropriate. For instance, the substituents of a substituted alkyl may include substituted and unsubstituted forms of amino, azido, imino, amido, phosphoryl (including phosphonate and phosphinate), sulfonyl (including sulfate, sulfonamide, sulfamoyl and sulfonate), and silyl groups, as well as ethers, alkylthios, carbonyls (including ketones, aldehydes, carboxylates, and esters), -CF3, -CN and the like. Examples of substituted alkyls are described below. Cycloalkyls can be further substituted with alkyls, alkenyls, alkoxys, alkylthios, aminoalkyls, carbonylsubstituted alkyls, -CF3, -CN and the like. The term “alkyl” can mean “cycloalkyl” which refers to a non-aromatic carbocyclic ring having 3 to 10 carbon ring atoms, which are carbon atoms bound together to form the ring. The ring may be saturated or have one or more carbon-carbon double bonds. Examples of cycloalkyl include, but not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, and cycloheptyl, as well as bridged and caged saturated ring groups such as norbomyl and adamantyl.

[0067] It is understood that the specific order or hierarchy of steps in the methods or processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods or processes may be rearranged. Some of the steps may be performed simultaneously. The accompanying methods claims present elements of the various steps in a sample order, and are not meant to be limited to a specific hierarchy or order presented. A phrase such as “embodiment” does not imply that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. A phrase such as an embodiment may refer to one or more embodiments and vice-versa.

[0068] “About” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, z.e., the limitations of the measurement system. Unless explicitly stated otherwise within the disclosure, claims, result or embodiment, “about” means within one standard deviation per the practice in the art, or can mean a range of ± 20%, ± 10%, ± 5%, ±4%, ±3%, ±2% or ± 1% of a given value. It is to be understood that the term “about” can precede any particular value specified herein, except for particular values used in the Examples.

[0069] All percents are intended to be weight percent unless otherwise specified. The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.

EXEMPLIFICATION

[0070] Example 1 : Design and characterization of blend system

[0071] Synthesis of DPP copolymers

[0072] DPP-copolymers were synthesized as disclosed in ref. 46, the entire content of which is incorporated herein by reference. MATRIMID® 5218 polymer was purchased from PolyK Technologies. Octadecyltrichlorosilane (OTS) and chloroform were purchased from Sigma Aldrich. All polymers were processed from chloroform solutions.

[0073] OFET devices fabrication and characterization

[0074] Prepatterned Si/SiO2/Au substrates (W= 1500 pm, L= 80 pm) were first cleaned with piranha solution (EhSO^EEO? = 7:3) and rinsed with deionized water. OTS treatment was conducted on the cleaned substrates in a vacuum oven. All polymer materials were dissolved in chloroform (minimum 1 hour of stirring at 40 °C) prior to film processing. DPP- 30gT and MI polymer solutions of the same concentration were mixed and stirred at 1 : 1 volume ratio and spin-coated (2000 rpm, 30s) on the OTS-modified substrate. After spin coating, the film was baked at 120 °C for 30 mins inside a nitrogen filled glovebox. Electrical characterizations of OFET were carried out using a Keithley 4200 in an ambient condition. The gate voltage was applied from -40 V to 6 V, while the potential gradient between the source and drain contacts was kept at -40 V. Temperature dependent in-situ measurements were carried out using a microprobe system from Nextron. The operating temperature was increased 10 °C / min and maintained at each temperature for 30 minutes before measuring. For measuring the doping effect of NO2, NO2 gas in a measured volume was injected into the sealed measurement chamber and allowed to dope the polymer film for 30 mins prior to measurement.

[0075] Morphology characterization and spectroscopy measurement

[0076] AFM images were collected using a Bruker Dimension Icon XR SPM. The polymer films were annealed at 120°C min for 30 mins and cooled down slowly to room temperature inside a glovebox for characterizing the stability behavior of the blended film. UV-vis absorption spectra were obtained using a PerkimElmer 1050 UV-vis-NIR spectrophotometer. For in-situ measurement of UV-vis absorption spectra, the films were spin-coated on a cleaned glass substrate and the same procedure as the in-situ measurement of OFETs was followed. Raman spectroscopy was performed with a 532-nm laser using the Raman Reflex instrument.

[0077] Computational details

[0078] The Vienna Ab-initio software package (VASP) was utilized to conduct density functional theory (DFT) calculations. (48) The Perdew-Burke-Ernzerhof (PBE) functional based on the generalized gradient approximation (GGA) was used to describe the exchangecorrelation interaction. The interaction between the valence electrons and the ionic core was described by the projector augmented wave (PAW) pseudopotentials implemented in VASP. (49) The valence electron functions were treated using the plane wave basis with an energy cutoff of 500 eV. The convergence criteria for the electronic structure and geometry were 10’ ⁵ eV and 0.03 eV/A, respectively. Spin polarization was applied, and the Van der Waals force was considered through the Grimme’s DFT-D3 method. (50)

[0079] To combine efficient gas absorption and thermal stability, an active channel comprised of a blend system between a semiconducting polymer (DPP-30gT) and a high Z_g, and hence morphology stabilizing matrix, herein MATRIMID® (MI) 5218 polymer, was designed. FIG. 1 A illustrates the studied architecture of a gas sensor, where the active channel is a blend composite made of a DPP-30gT (where “30” represents the percentage on TEG-functionalized thiophene blocks) (46) copolymer and MI. The semiconductive DPP- 30gT, serving as the active material for NO2 gas absorption, was used to form a bi-continuous morphology across the film with the thermally stable MI (7_g ~ 325 °C). The matrix polymer surrounds the semiconducting domains and enables the overall environmental and thermal robustness (FIGs. IB and 2) in accordance with previous works. (30) Previous works have shown that, though beneficial for electrochemical activity, the increased density of polar side chains deters the electronic properties in mixed conducting copolymers. (46,51) DPP-30gT was selected to endow the sensor channel with (i) sufficient affinity toward NO2 molecules, (ii) a semicrystalline morphology promoting facile diffusion, and (iii) sufficient electronic charge transport needed to record the chemiresi stive sensor response (FIG. 1C). To control the blend morphology, the compositional ratio between DPP-3 OgT and MI between 0 and 100 wt % MI was varied. Upon rapid evaporation of a common solvent during the spin coating, a spinodal-like interpenetrating morphology between the two components at 1 : 1 ratio was triggered (FIG. 2C). It is hypothesized that once this interpenetrating morphology is formed, the high 7_g matrix polymer will effectively suppress the thermal fluctuations within the blend film, particularly when the films are heated below its 7_g (FIG. 3), (30,31) and thus allow stable sensing performance even at elevated temperature.

[0080] To understand the sensing mechanism in the polymer system, Raman spectroscopy was used to evaluate the chemical interaction between the polymer system and NO2. There was no specific peak shift in the DPP-30gT spectrum before and after

NO2 exposure (FIG. 4A), indicative of no specific binding between DPP-30gT and NO2. This behavior agrees with previous reports using conjugated polymers for NO2 gas sensing, where the gas molecules have been shown to simply function as dopants, thus changing the conductance of the semiconducting polymer during exposure. (15-17) The binding energy and charge transfer level around all possible absorption sites in the blend system was calculated and the lack of specific bonding between the polymers and NO2 was confirmed (FIG. ID and E). Simulations accounted for all potential binding positions in accordance with previous reports but simplified the system as one repeat unit with a shortened side chain. (15) In a fully relaxed state, the NO2 molecules were found to equilibrate around each site at distances over 3 A. In the case of bond forming interactions, distances under 2 A are expected. As shown in FIG. IE, the binding energy and charge transfer degree were greatest around the conjugated polymer compared to the matrix, which means that the insulating polymer mostly acts as a rigidifying host and does not contribute to molecular adsorption. These computation results thus support the Raman results that NO2 gas simply acts as a doping gas without any specific bonding. Note that the simulations do not capture the entire polymer system including TI- TI stacking of polymer chains, long alkyl chains, TEG side chains, and potential sites obstructed by the 7t- it stacking in a real polymer crystallite morphology. (15) Nonetheless it is anticipated that the porous nature of the blends would facilitate the NO2 diffusion, thus enhancing the device sensitivity, as illustrated in FIG. 1C. [0081] With this operating mechanism, the sensitivity of the polymer channel depends on its ability to attract NO2 molecules into the bulk, i.e., the doping level of the semiconducting component. The doping capability of NO2 toward DPP-30gT using field-effect transistor devices (FIG. 4B) was evaluated. Upon exposure to NO2 gas, the source-drain current showed to increase, indicative of channel doping. The unfunctionalized DPP analogue (no TEG side chains, DPP-OgT) shows that without the TEG groups in the polymer structure, only a slight change in the current is detected (FIG. 4C). The less hydrophilic DPP-OgT does not efficiently uptake the polar NO2 molecules, thus underscoring the importance of the side chains on the sensitivity of the sensor. Note that this shift in the drain current was attainable in a bottom-contact device configuration (where the current is measured at the bottom interface). This was more indirect evidence that the active material in the sensor allows effective diffusion of NO2 molecules into the bulk as illustrated in FIG. 1C, a property that is enabled herein by both the presence of polar pendant groups as well as amorphous domains within the film bulk. It is deduced that with the presence of TEG side chains, NO2 gas is attracted toward the polymer backbone and easily abducts the electron from the latter, thus generating mobile holes which translate into a greater electrical conductivity in the device channel. (15-17) It is thus implied that semicrystalline films are preferred here (given that the electronic performance is retained, which is the case for DPP-30gT) (46) as the amorphous regions within the active sensing area will facilitate the diffusion of gas molecules into the film bulk (FIG. 1C). (6,16)

[0082] Example 2: Gas sensor fabrication and characterization

[0083] Gas sensing characterizations were performed by transferring polymer films onto prepatterned AhCh-based sensor substrates. The sensor substrates were patterned with two parallel electrodes (90 pm wide and 160 pm apart). Specifically, DPP-30gT:MI solutions were spin-coated onto a clean Si wafer. The sensing films were subsequently removed from the Si wafer by soaking in DI water, and then transferred onto the sensor substrate. The resulting chemiresistive sensors were annealed at 150 °C for 1 hour in an N2 atmosphere to enhance intimate contact between the polymer films and electrodes. The resistance of the sensing materials on the electrodes was measured using a data acquisition system (34972A, Agilent) equipped with a 16-channel multiplexer (34902A, Agilent). A microheater was positioned on the back side of the sensor substrate to enable the operating temperature to be controlled using a DC power supply (E3647A, Agilent). Sensing characteristics were evaluated by converting the measured resistance values into response (Rair/Rgas or R_gas/Rair) where Rair and R_gas represent the resistance in air and target gas, respectively. Prior to the sensing tests, all sensors were stabilized in a baseline atmosphere (air) for 2 hours. Gas cylinders containing 50 ppm NO2, 50 ppm H2S, 1000 ppm NH3, and 5% CO2 were purchased from Airgas and diluted with air for concentration dependent measurements.

[0084] Flexible gas sensor fabrication and characterization

[0085] 5 nm thick Cr and 70 nm thick Au electrodes were deposited by thermal evaporator onto clean KAPTON® polyimide film substrates using patterned shadow mask. DPP-30gT:MI blend solutions were then directly spin-coated on the patterned flexible substrates. The bending tests were conducted manually with a bending angle of 90 degrees. The sensing tests were conducted by exposing the sample to NO2 gas for 10 min and to air for 20 min for recovery. The sensing tests were conducted under the same measurement conditions as mentioned above.

[0086] As disclosed above, chemiresistive-type sensors were fabricated and the NO2 gas sensing properties of the DPP-30gT:MI blends were evaluated. Note that all the sensing measurements were conducted under dry air conditions (1.5% relative humidity), and the sensing response is determined by measuring the difference in channel resistance when NO2 gas is present and when it is absent (A_air/A_gas). The chemiresistors’ sensing performance were assessed based on sensitivity, selectivity, reversibility, and operational stability, especially at elevated temperatures. The sensing performance was measured within a temperature range of 60 to 170 °C, a range similar to the conditions found in exhaust pipes and chimneys. FIG. 5 A shows the dynamic response of the sensor to 1 ppm of NO2 at different temperatures indicating high sensitivity of the DPP-30gT:MI channel toward NO2 gas across a wide range of heating conditions. Due to the thermally promoted hopping of charge carriers in the polymer channel, (30) the sensors showed enhanced performance with increasing temperature and showed optimal response around 140 °C. Excessive heating (above 170 °C) was found to be detrimental to the sensors response as evidenced by a decline in charge transport characteristics as well as the loss in molecular-level order (FIGs. 6A-B). ~ 140-170 °C was set as the optimal operating temperature for the blend system. Among polymer-based sensors to date, this is over 70 °C higher than the best achievable temperature for NO2 sensing, (17) promising potential for real-time and integrated (at the exhausts level) monitoring of emitted gas in industrial and residential setups. Additionally, at such temperatures, the DPP-3 OgT:MI-based sensors exhibit a dynamic response toward varying the gas concentration (2 to 0.25 ppm at 140 °C) (FIG. 5B, C). Even at extremely low NO2 concentrations (0.25 ppm), the sensors could yield dynamic responses as high as 5.7, which is desirable for practical use. The blend-based sensors also showed a response time of 1.5 min, which is among the fastest polymer-based NO2 sensors (FIG. 7). (15-17) This level or sensitivity was also accompanied by excellent selectivity toward NO2 versus other common small molecule gases. In polymer-based sensors, it is often challenging to differentiate between common gases such as NO2, EES, NH3, and CO2. (17,52-54) As shown in FIG. 5D, DPP-3 OgT:MI-based sensors exhibits excellent selectivity toward NO2 gas (Aair/Agas ~ 25.04 @ 1 ppm) compared to EES (A’air/A’gas ~ 1.06 @ 1 ppm), NEE (A’air/A’gas ~ 1.01 @ 5 ppm), and CO2 (A’air/A’gas ~ 1.04 @ 250 ppm), with a cross-selectivity value (ANO2/Ainter > 23.62, where ANO2 and Ainter denote the response toward NO2 and interfering gases, respectively). (17) Such sensitivity, selectivity, and response speeds under trace amounts (sub-ppm) of gas molecules showed potential feasibility for environmental monitoring applications using polymer-based sensors.

[0087] The feasibility of integrating the sensor devices into real -world scenarios (e.g., pipes and chimneys) was evaluated by fabricating fully flexible devices and monitoring their performance under both extreme temperatures and bending radius. Given the facile processability of the studied all-polymer active material, DPP-30gT:MI blends is readily casted onto prepattemed polyimide substrates (FIG. 8A). The gas sensing performances were evaluated under four different measurement scenarios: (i) flat state, (ii) bent state, (iii) flat state after 100 bending cycles, and (iv) flat state after 500 bending cycles (FIG. 8B, C). The flexible sensors exhibited stable and reversible sensing performances in both flat and bent states. Even after 500 bending cycles, the sensors maintained stable and reversible response as shown during 6 cyclic exposures to 1 ppm gas (FIG. 8C). This mechanical endurance was also concomitant with tolerance versus extreme temperatures. For instance, after subjecting the flexible sensor to 500 bending cycles, the operating temperature was brought to 170 °C, emulating real-world scenarios (FIG. 8D), and the performance was probed toward low (1 ppm) NO2 concentrations. As shown in FIG. 8E, the DPP-30gT:MI-based sensors exhibit robust sensing capabilities. Despite the slight downward drift in the baseline resistance over time, stable and reversible sensing behaviors occurred after subjecting the sensors to both mechanical and thermal stress. This level of tolerance to harsh conditions is highly desirable for the real-time monitoring of gas emissions using polymer-based sensors. Upon surveying the literature (Table 1 and FIGs. 9A and 9B), the sensitivity levels found in DPP-30gT:MI blends toward NO2 gas especially at such elevated temperatures were unprecedented, thus promising future polymer-based sensors.

Table 1. Comparison of DPP-3 OgT:MI-based sensing performance versus state-of-the-art polymer (and polymer composites)-!? ased chemiresi stive NO2 gas sensors. Abbreviations: polypyrrole (= PPy), polythiophene (= PT), polyaniline (= PANI), polyethylene glycol (= PEG), poly(3-hexyltiophene) (= P3HT), poly(ethyleneimine) (= PEI), imine (= IM), _

Sensing Sensitivity _T „„ „ . . ... „

„ . . - ° * LOD Cyclability Response „ ..

Sensing material temperature [AR/Ro * _r . _r„ . , .e. Ret f°Cl 100 %] lPP^ml 1^# of cycles] time [S]

PPy thin film RT 12 @ 10 ppm 10 3 218 @ 10 ppm ⁵²

PT thin film RT 33 @ 100 ppm 10 3 297 @ 10 ppm ⁵⁵

PANI-nanofibers RT 1500 @ 10 ppm 10 Nr 908 @ 10 ppm ⁵⁶

PANI thinfilm RT 1110 @ 100 _{w Nj}. 11 @ 100 ppm ⁵⁷ ppm

PEDOT-rGO 80 6.5 @ 100 ppm 1 Nr nr ^{61 D}pPy-WO₃ ^{ed RT} 72 @ 100 ppm 5 3 480 @ 10 ppm ⁶²

PT-WO3 90 400 @ 100 ppm 10 Nr nr ⁶³

PT-SnO₂ 90 300 @ 100 ppm 10 Nr nr ⁶⁴ rrP3HT-PMS Graft 50 2200 @ 5 ppm 5 3 nr ⁶⁵

PEG-P3HT 100 1980 @ 1 ppm 0.3 Nr nr ⁶⁶

PMDIT2/IM ⁶⁰ 240 @ 1 ppm 0.1 15 nr ¹⁷

DPP-30gT:MI 140 2404 @ 1 ppm 0.25 58 90 @ 1 ppm

[0088] To summarize, a thermally stable NO2 gas sensor enabled by a judicious composite design composed of a polymer mixed conductor and a thermally robust matrix is disclosed. The insulating matrix could effectively suppress the thermal fluctuations of the NCh-affme semiconductor, resulting in stable sensing performance even at elevated temperatures above 170 °C over 6 h. Moreover, the blend system showed an extremely high sensing response due to not only the chemically engineered binding sites for polar NO2 gas, but also the systematic balance of amorphous regions within the sensing volume to further boost the NO2 gas diffusion into the bulk film. Finally, typical solution processing of the blend composites onto flexible and heat resistant substrates demonstrates reliable gas sensing performance even under severe mechanical bending. It is anticipated that the structurally controllable response to various analytes available in this class of polymers, as well as their thermal stabilization through polymer blending, can serve as a valuable platform for designing a real-time monitor for toxic gases.

EMBODIMENTS

1. A copolymer, wherein the copolymer comprises: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

2. The copolymer of Embodiment 1, wherein the polar side group is a glycol.

3. The copolymer of Embodiment 2, wherein the glycol

4. The copolymer of any one of Embodiments 1-3, wherein the first block is and wherein Ri and R2 are each independently an alkyl.

5. The copolymer of Embodiment 4, wherein Ri and R2 are each independently

6. The copolymer of any one of Embodiments 1-5, wherein the second block is The copolymer of any one of Embodiments 1-6, wherein the molar ratio of the first block to the second block is from about 100:0 to about 1 : 1. The copolymer of Embodiment 7, wherein the molar ratio of the first block to the second block is from about 9: 1 to about 1 :1. The copolymer of Embodiment 7 or 8, wherein the molar ratio of the first block to the second block is about 7:3. A composition, comprising a first polymer and a second polymer, wherein the first polymer is the copolymer of any one of Embodiments 1-9. The composition of Embodiment 10, wherein the second polymer is an electrically insulating polymer. The composition of Embodiment 10 or 11, wherein the second polymer comprises a polyimide. The composition of any one of Embodiments 10-12, wherein the second polymer comprises , wherein n is an integer. The composition of any one of Embodiments 10-13, wherein the mass ratio of the first polymer to the second polymer is from about 1 : 5 to about 5: 1. The composition of any one of Embodiments 10-14, wherein the mass ratio of the first polymer to the second polymer is about 1 : 1. The composition of any one of Embodiments 10-15, wherein the second polymer has a glass transition temperature of from about 120°C to about 400°C. The composition of Embodiment 16, wherein the second polymer has a glass transition temperature of about 325°C. A sensor, comprising the copolymer of any one of Embodiments 1-9 or the composition of any one of Embodiments 10-17, a substrate, and an electrode. The sensor of Embodiment 18, wherein the substrate comprises a metal oxide or a polyimide. The sensor of Embodiment 19, wherein the polyimide is poly(4,4'-oxydiphenylene- pyromellitimide). The sensor of Embodiment 19 or 20, wherein the metal oxide is AI2O3. The sensor of any one of Embodiments 19-21, wherein the electrode comprises gold and chromium. A method of detecting an analyte, the method comprising: contacting the sensor of any one of Embodiments 18-22 with a sample comprising the analyte; and measuring an electrical property of the sensor in contact with the sample. The method of Embodiment 23, wherein the electrical property is electrical resistance. The method of Embodiment 23 or 24, wherein the method further comprises contacting the sensor with a medium that does not comprise the analyte. The method of Embodiment 25, wherein the sensor is contacted with the medium for about 20 minutes. The method of Embodiment 25 or 26, wherein the method further comprises measuring an electrical property of the sensor in contact with the medium. The method of any one of Embodiments 25-27, wherein the medium is air. 29. The method of any one of Embodiments 23-28, wherein the sensor is contacted with the sample comprising the analyte for about 10 min.

30. The method of any one of Embodiments 23-29, wherein the electrical property of the sensor in contact with the sample is measured at a temperature of from about 20°C to about 170°C.

31. The method of any one of Embodiments 23-30, wherein the electrical property of the sensor in contact with the sample is measured at a temperature of from about 140°C to about 170°C.

32. The method of any one of Embodiments 23-31, wherein the electrical property of the sensor in contact with the sample is measured at a relative humidity of about 0.1% to about 5%.

33. The method of any one of Embodiments 23-32, wherein the electrical property of the sensor in contact with the sample is measured at a relative humidity of about 1.5%.

34. The method of any one of Embodiments 23-33, wherein the concentration of the analyte in the sample is from about 0.25 ppm to about 2 ppm.

35. The method of any one of Embodiments 23-34, wherein the concentration of the analyte in the sample is about 1 ppm.

36. The method of any one of Embodiments 23-35, wherein the analyte is a gas.

37. The method of any one of Embodiments 23-36, wherein the analyte is a sulfur oxide, a nitrogen oxide, or a combination thereof.

38. The method of any one of Embodiments 23-37, wherein the analyte is SO2, SO3, NO, NO2, or a combination thereof.

39. The method of any one of Embodiments 23-38, wherein the analyte is NO2.

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[0089] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[0090] While example embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed by the appended claims.

Claims

What is claimed is:

1. A copolymer, wherein the copolymer comprises: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

2. The copolymer of claim 1, wherein the polar side group is a glycol.

3. The copolymer of claim 1, wherein the first block is wherein n is an integer.

5. The copolymer of claim 1, wherein the molar ratio of the first block to the second block is from about 9: 1 to about 1 : 1.

6. A composition, comprising a first polymer and a second polymer, wherein the first polymer is a copolymer comprising: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

7. The composition of claim 6, wherein the second polymer comprises a polyimide.

8. The composition of claim 6, wherein the second polymer comprises wherein n is an integer.

9. The composition of claim 6, wherein the mass ratio of the first polymer to the second polymer is from about 1 : 5 to about 5: 1.

10. The composition of claim 9, wherein the mass ratio of the first polymer to the second polymer is about 1 : 1.

11. A method of detecting an analyte, the method comprising: contacting a sensor with a sample comprising the analyte; and measuring an electrical property of the sensor in contact with the sample, wherein the sensor comprises a composition, a substrate, and an electrode, wherein the composition comprises a first polymer and a second polymer, and wherein the first polymer is a copolymer comprising: a first block comprising diketopyrrolopyrrole; and a second block comprising thiophene functionalized with a polar side group.

12. The method of claim 11, wherein the electrical property is electrical resistance.

13. The method of claim 11, wherein the method further comprises contacting the sensor with a medium that does not comprise the analyte.

14. The method of claim 13, wherein the method further comprises measuring an electrical property of the sensor in contact with the medium.

15. The method of claim 11, wherein the electrical property of the sensor in contact with the sample is measured at a temperature of from about 20°C to about 170°C.

16. The method of claim 11, wherein the electrical property of the sensor in contact with the sample is measured at a relative humidity of about 0.1% to about 5%.

17. The method of claim 11, wherein the concentration of the analyte in the sample is from about 0.25 ppm to about 2 ppm.

18. The method of claim 11, wherein the analyte is a gas.

19. The method of claim 11, wherein the analyte is a sulfur oxide, a nitrogen oxide, or a combination thereof.

20. The method of claim 11, wherein the analyte is NO2.