Synthesis of dioxyheterocycle-based polymers

A method of polymerization for the preparation of conjugated polymers and copolymers comprising dioxypyrrole and/or dioxyfuran repeating units involves the halogen, N-haloimide, or N-haloamine promoted polymerization of monomers and/or oligomers comprising one or more dioxypyrrole and/or dioxyfuran units. The polymerization can be carried out over a wide range of temperatures and can be carried out with or without a solvent. The monomers allow the preparation of polymers having an oligomeric repeating unit comprising a conjugated unit other than a dioxypyrrole or dioxyfuran that is bound to two dioxypyrrole or dioxyfuran units.

BACKGROUND OF INVENTION

Conjugated conducting polymers displaying moderate charge mobilities, an ability to be redox doped to highly conducting compositions, and an ability to change optical properties reversibly, can be used as color changing materials, conductors, and antistatic coatings in electronic components, photovoltaic devices, and light emitting devices. One class of conducting polymers, polyheterocycles, which include polythiophenes, polypyrroles, and polyfurans, have been developed for their use in electrochromic devices, photovoltaic devices, and light emitting diodes. Appending a 3,4-alkylenedioxy bridge on the heterocycle allows a modified polyheterocycle, where the bridge does not cause an undesirable conformational change in the backbone of the polymer, and the electron donating effect of the oxygen substituents increases the HOMO of the conjugated polymer, reducing both its oxidation potential and its electronic band gap. Poly(3,4-dioxythiophene)s have been extensively studied, poly(3,4-dioxypyrrole)s are somewhat less well known, and poly(3,4-dioxyfuran)s are not well documented.

Poly(3,4-dioxypyrrole)s are materials that display high electronic band gaps and low oxidation potentials, and have properties that make them excellent candidates as sensors, supercapacitors, and electrochromic devices where high conductivity and processability are needed. The syntheses and properties of a wide variety of poly(3,4-dioxypyrrole)s have been reported, for example, in: Walczak et al.,Adv. Mater.2006, 18, 1121-31; Schottland et al.,Macromolecules2000, 33, 7051-61; Sonmez et al.,Macromolecules2003, 36, 639-47; Thomas et al.,Adv. Mater.2000, 12, 222-5; and Walczak et al.,Macromolecules2007, 40, 7777-85.

More recently, the polymerization of 2,5-diodo-3,4-alkylenedioxypyrrole in bulk or using a suitable solvent has been disclosed in Reynolds et al., U.S. Pat. No. 7,649,076 and Walczak et al.,Macromolecules2008, 41, 691-700. By this method, high molecular weight polymer can be prepared without the use of metals, oxidants, solvents, or other additives. Additionally, reaction can be carried out in aqueous solution and tolerates substitution by a wide variety of functionalities, including those that cannot be synthesized by an oxidative polymerization process. This polymerization, as shown in Scheme 1, requires a three-step synthesis that starts from a 3,4-dioxypyrrole-2,5-diacid and requires isolation and purification of the intermediate 2,5-di-iodo-3,4-dioxypyrrole monomer. However, the isolation and purification steps reduce overall yield and throughput. Furthermore, the polymerization process is limited to the types of 3,4-dioxypyrrole monomers reported in Reynolds et al. Hence, a method that does not require the use of 2,5-di-iodo-3,4-dioxypyrrole and can expand the range of 3,4-dioxypyrrole-based monomers that can be polymerized efficiently is desirable.

BRIEF SUMMARY

Embodiments of the invention are directed to conjugated polymers and methods of their preparation. Conjugated polymers have a multiplicity of 3,4-dialkoy of 3,4-alkylenedioxy pyrrole or furan repeating units. The polymers can also include additional conjugated repeating units that are isolated by 3,4-dialkoy of 3,4-alkylenedioxy pyrrole or furan repeating units. The additional conjugated repeating units include 1,2-ethenediyl, 1,4-butadienediyl, 1,4-benzenediyl, 2,6-naphthalendiyl, 9,10-anthracenediyl, 2,7-fluorenediyl, 2,5-furandiyl, 2,5-thiophenediyl, 2,5-pyrroldiyl, 2,1,3-benzothiadiazole-4,7-diyl, 2,7-carbazolediyl, 2,6-pyridinediyl, 1,4-bis(2′,2″-thiophenyl)benzene-5′,5″-diyl, and/or 4,7-bis-(2′,2″thiophenyl)-2,1,3-benzothiadiazole-5′,5″-diyl units. In embodiments of the invention, the end-groups of the conjugated polymers can be a halogen, hydrogen or C(O)OR7, where R7is hydrogen, lithium, sodium, potassium, cesium, or ammonium. In other embodiments of the invention, the end-groups can have selected functionality.

According to an embodiment of the invention, one or more monomers and/or oligomer that includes a terminal 3,4-dialkoy of 3,4-alkylenedioxy pyrrole or furan substituted at a 2- and/or 5-position with a H, chlorine, bromine, iodine, or C(O)OR7, where R7is hydrogen, lithium, sodium, potassium, cesium, or ammonium, is polymerized or copolymerized upon addition of a halogen, N-haloimide or N-haloamine. Optionally, an acid can be included. Optionally the polymerization mixture can be irradiated with ultraviolet light. The polymerization can be carried out as the neat monomer(s) and/or oligomer(s) or a solvent can be included. Polymerizing or copolymerizing can be carried out over a wide range of temperatures and can be carried out under mild conditions, for example, 0 to 100° C. End-capping 3,4-dialkoy of 3,4-alkylenedioxy pyrrole or furan monomers can be included, where one substituent is a 2- or 5-H, chlorine, bromine, iodine, or C(O)OR7, where R7is hydrogen, lithium, sodium, potassium, cesium, or ammonium for incorporation into the polymer or copolymer and another functionality that is designed to provided an additional end-group that can be used to provide functionality for subsequent condensation, addition, or complexation with other monomers, oligomers, polymers, resins, surfaces, salts, or particles to form coupled polymers, block copolymers, multiblock copolymers, networks, aggregates, functionalized resins, functionalized surfaces, or functionalized particles.

DETAILED DISCLOSURE

An embodiment of the invention is directed to a method for the preparation of a conjugated polymer, where the conjugated polymer is: a poly(dioxypyrrole), either a poly(3,4-dialkyloxypyrrole), poly(3,4-alkylenedioxypyrrole), or poly(3,4-alkylenedioxypyrrole-co-3,4-dialkyloxypyrrole); a poly(dioxyfuran), either a poly(3,4-dialkyloxyfuran), poly(3,4-alkylenedioxyfuran), or poly(3,4-alkylenedioxyfuran-co-3,4-dialkyloxyfuran); or a poly(dioxypyrrole-co-dioxyfuran), either a poly(3,4-alkylenedioxypyrrole-co-3,4-dialkyloxyfuran), a poly(3,4-alkylenedioxyfuran-co-3,4-dialkyloxypyrrole), a poly(3,4-alkylenedioxypyrrole-co-3,4-alkylenedioxyfuran), or poly(3,4-dialkyloxypyrrole-co-3,4-dialkyloxyfuran) via the halogen, N-haloimide, or N-haloamine promoted homopolymerization or copolymerization of monomers comprising 2,5-disubstituted-3,4-dialkyloxypyrrole, 2,5-disubstituted-3,4-alkylenedioxypyrrole, 2,5-disubstituted-3,4-dialkyloxyfuran, 2,5-disubstituted-3,4-alkylenedioxyfuran, any oligomers thereof, or any combination of monomers and oligomers thereof. In an embodiment of the invention, the polymerization involves halogen, N-haloimide, or N-haloamine promoted homopolymerization or copolymerization of: 2,5-disubstituted-3,4-alkylenedioxypyrrole and/or 2,5-disubstituted-3,4-alkylenedioxyfuran comprising monomers or oligomers of the structure:

where: x is 1 to 10; R1, R2, R3, and R4are independently hydrogen, methyl, ethyl, C3through C20straight or branched chain alkyl, aryl, or alkylaryl; R5and R6are independently methyl, ethyl, C3through C20straight or branched chain alkyl, aryl, or alkylaryl; p is 2 through 6, m is 1 through p−1, n is 0 through p−2; when x is 1, Z is II or C(O)OR7, wherein R7is hydrogen, lithium, sodium, potassium, cesium, or ammonium where 1 to 4 of the substituents on the ammonium N is H, C1to C8alkyl, aryl, or alkyl aryl groups; when x>1, Z is H, chlorine, bromine, iodine, or C(O)OR7; and A is O or NR, wherein R is hydrogen, methyl, ethyl, C3through C20straight or branched chain alkyl, aryl, alkylaryl, or CH2X where X is C(O)R8, CH2YR9, or CR10═CR11R12, where R8is hydrogen, methyl, ethyl, C3through C20straight or branched chain alkyl, aryl, OR13, or NR14R15, where R13, R14, and R15, are independently hydrogen, methyl, ethyl, C3through C20straight or branched chain alkyl, aryl or alkylaryl, where Y is O, OC(O), NR16, or NR17C(O), and where R9, R10, R11, R12, R16, and R17are independently hydrogen, methyl, ethyl, C3through C8straight or branched chain alkyl, aryl, or alkylaryl. The polymerization can be carried out over a wide range of temperatures, for example, about 20 to about 100° C., and can be carried out in the presence of air or in an inert atmosphere. The polymerization can be carried out in a neat liquid phase, as an amorphous solid, in solution, for example, in dichloromethane (DCM), dibromomethane, or tetrahydrofuran (THF), or in an emulsion of an organic solvent and water. As desired or required, the polymerization mixture can be irradiated with UV radiation or include an acid, for example, a Lewis acid, for example, FeCl3. The resulting homopolymers or copolymers have repeating units that are indicated between the parentheses of structures I and/or II and end-units that comprise chlorine, bromine, or iodine; depending on the halogen, N-haloimide, or N-haloamine, for example, N-halosuccinimide. To achieve high molecular weight homopolymers or copolymers, at least two equivalents of the halogen, N-haloimide, or N-haloamine per mole of monomer or oligomer I and/or II are required.

Another embodiment of the invention is directed to polymers comprising oligomeric bis-dioxypyrrole and/or bis-dioxyfuran repeating units in a homopolymer or copolymer, such that all L units are separated by two or more dioxypyrrole or dioxyfuran units. The oligomeric bis-dioxypyrrole or bis-dioxyfuran repeating units result from polymerization of reaction mixtures that include oligomers of the structures:

In an embodiment of the invention L is a substituted 2,5-thiophenediyl having the structure:

Examplary trimeric bis-dioxypyrroles, according to embodiments of the invention, include:

In embodiments of the invention, polymers are prepared from the homopolymerization of any trimer or the copolymerization of one or more trimers of the structures III or IV, for example, two or more different trimers of structure III, a trimer of structure III and a trimer of structure IV, or two trimers of the structure IV with a trimer of the structure III, or any other combination. In other embodiments of the invention, polymers are prepared from the copolymerization of one or more trimers of the structures III or IV with one or more dioxypyrrole monomers or oligomers of structures I and II. In an embodiment of the invention, the conjugated polymers have repeating units common with those of structures I, II, III, and/or IV from which they are prepared, and can have end-groups selected from H, C(O)OR7, Cl, Br, and/or I.

In embodiments of the invention, an end-capping monomer of the structure is:

In an embodiment of the invention, the homopolymers or copolymers prepared from I, II, III, and/or IV, can be employed as macromers for their homopolymerization or their copolymerization with other monomers or oligomers from I, II, III, or IV to form higher molecular weight homopolymers, di- to multiblock copolymers, semi-random copolymers or semi-regular copolymers. In an embodiment of the invention, polymers prepared with one or more of I, II, III, and IV with VII and/or VIII have functionality for condensation, addition, or complexation with other monomers, oligomers, polymers, resins, surfaces, salts, or particles to form coupled polymers, block copolymers, multiblock copolymers, networks, aggregates, functionalized resins, functionalized surfaces, or functionalized particles.

Reynolds et al., U.S. Pat. No. 7,649,076 teaches the catalyst free polymerization of 2,5-dihalo-3,4-alkylenedioxypyrroles and 2,5-dihalo-3,4-alkylenedioxyfurans. This method involves isolation of the dihalo monomers, in the manner taught by Zong et al.J. Org. Chem.2001, 66, 6873-82, as illustrated inFIG. 2. After isolation, the polymerization is carried out, as indicated inFIG. 2. The polymerization method has been successfully applied for the preparation of homopolymers and copolymers, either block or random copolymers. However, a polycondensation method for production of regioregular copolymers from discrete α,ω-dihalo oligomers does not readily occur. Using the method of Zong et al., it is not possible to prepare α,ω-dihalo oligomers, such as the trimers of structure III where Z is iodine, because a significant amount of decarboxylation of the diacid occurs during the first step of base catalyzed ester hydrolysis to the diacid, which leads to a mixture of products even when the hydrolysis is carried out at relatively low temperatures. Preparation of N-alkyl substituted 3,4-alkylenedioxypyrrole monomers that can be used to prepare polymers, according to embodiments of the present invention, are taught in Reynolds et al., U.S. Pat. No. 7,799,932, and incorporated herein by reference.

It was discovered that N-halosuccinimides promote electrophilic halogenation of a model 3,4-propylenedioxypyrrole (ProDOP) 9 and halodecarboxylation of a model 3,4-propylenedioxypyrrole carboxylic acid 8, as shown inFIG. 3, and that N-halosuccinimides promote halodecarboxylation of a model 3,4-propylenedioxypyrrole carboxylic acid potassium salt 10, as shown inFIG. 4. While attempting to extend the N-halosuccinimides promoted electrophilic halodecarboxylation to ProDOP-dicarboxylates, either acids or potassium salts, polymerization resulted, according to an embodiment of the invention, and polymerization can be carried out effectively using N-iodosuccinimide (>2 equivalents) or iodine (>2 equivalents) to high molecular weight polymer, as shown inFIG. 5. Results for polymerization of monomeric and trimeric dicarboxylic acids and di(potassium carboxylates) are given in Table 1, below. The polymerization occurs at relatively low temperatures, for example, 40 to 60° C. or below, in dichloromethane (DCM) or chloroform. Potassium carboxylates, such as 14 and 17, have low solubility in DCM and the reaction can be carried out in an emulsion formed with water and DCM. Other solvents, for example THF, can be used.

TABLE 1Polymerization of various ProDOP-dicarboxylates via halodecarbonylation-dehalogenation polycondensation using various halogen (X) sourcesMn/MwyieldaentrymonomerX-Sourcepolymer(kDa)(%)1NIS NBS NCS7a 7.7/13.6 7b 66.3/8.9 7c 5.0/6.371b83b39b2NIS NBS NCS16a 6.9/17.4 16b 0.9/1.1 16c 1.1/1.56076c79c3NIS I2Br27a 6.2/10.0 7a 22.9/58.1 7b 1.3/1.967 6620c4I2Br216a 15.9/35.7 16b 0.9/1.955 48aThe yields were calculated based on the potassium salts except for entry 2, by the method of Walczak et al.,Macromolecules2008, 41, 691-700.bThe crude mixture was employed after acidic work-up of the respective potassium salt.cThe polymer was not precipitated but was washed with water and methanol, and dried under vacuum.

Polymerizations using N-iodosuccinimide (NIS) require longer reaction times than did those using iodine, at otherwise equivalent conditions. N-Chlorosuccinimide (NCS) and N-bromosuccinimide (NBS), and bromine produce lower molecular weight polymers. The polymerization typically starts spontaneously, but, if needed or desired, can be promoted by irradiation with UV-light using a standard UV-lamp, typically requiring only a few minutes of irradiation, for example, 1 to 3 minutes, to promote polymerization. A catalytic amount of FeCl3can be added to the monomer mixture to promote the polymerization. The polymer that is produced is halogen doped, which can be easily dedoped by the addition of hydrazine.

Although no specific relationship has been determined between the number of equivalents of halogen from the halogen source and the molecular weight of the polymer, when less than two equivalents of halogen is employed, the resulting molecular weight of the polymer is less than when more than two equivalents are employed. End-groups of the polymer are indicated as X in Table 1, and are halogens or a starting carboxylate groups. Conditions of the polymerization affect the degree of polymerization obtained and allow the use of the oligomers or polymers that are produced in one polymerization to be used as macromers for the formation of larger homopolymers or block copolymers. As shown inFIG. 6, polymer 7a with a molecular weight of about 7 kDa, can be used as a macromer to produce a polymer of 11 kDa. The macromer 7a, as shown inFIG. 6, was prepared in DCM, reduced with hydrazine, precipitated in MeOH, and stored under argon for several months before carrying out its polymerization in dibromomethane, at a temperature in excess of the boiling point of DCM.

Employing N-protonated 2,5-disubstituted-3,4-alkylenedioxypyrroles results in polymers, although generally of lower molecular weight than those of N-alkylated 2,5-disubstituted-3,4-alkylenedioxypyrrole, as indicated in Table 2, below. However, compared to the FeCl3oxidative polymerization of 3,4-dioxypyrroles, as taught in Kim et al.,Chem. Lett.2004, 33, 46-7, a polymerization by any embodiment of the present invention, can provide higher molecular weights and permits polymerizations starting from 3,4-dioxypyrroles carboxylates, which are the normal precursors to unsubstituted 3,4-dioxypyrroles used in FeCl3oxidative polymerizations. Furthermore, the halodecarbonylation-dehalogenation polycondensation method, according to embodiments of the invention, displays higher tolerance to functionality and lower sensitivity toward water than is observed with other methods for the polymerization of 3,4-dioxypyrroles.

TABLE 2Polymerization of N—H-3,4-alkydioxypyrroles via halodecarbonylation-dehalogenation polycondensation using NIS and iodinemonomerI-SourcepolymerMn/Mw (kDa)yielda(%)NIS3.7/5.231bI22.1/2.836baYields were calculated as in Table 1.bPolymer was isolated by removal of the solvent in vacuo, washing with water and methanol, and drying under vacuum.

Polymeric materials comprising 3,4-dioxypyrroles possess characteristic optical and electrochemical properties, as indicated in the spectroelectrochemistry data for polymer 7a that is shown inFIG. 7. This polymeric material: is almost colorless in solution and the solid state; can be employed as a film on an ITO-coated glass or other transparent electrode; and displays almost no absorption in the visible region of the light spectrum. As shown inFIG. 7a, upon electrochemical oxidation, polymer 7a remains highly transmissive in the visible region with absorption in the near infrared region. Minimum color changing polymer, such as 7a, may be used for applications in organic electronics, such as in electrochromic devices and windows. The cyclic voltammetry on ITO, ofFIG. 7b, shows that polymer 7a has a low oxidation potential (+0.18V vs. Ag/Ag+), for this electron rich polymeric system. Under conditions of the electrochemical experiment, polymer 7a delaminated from the ITO slide upon electrochemical oxidation, consistent with a high solubility of the doped polymer in the solvent, acetonitrile, that was used.

Polymers prepared according to embodiments of the invention can comprise materials that are advantageous for electrochromic windows, mirrors or displays. Additionally, these polymers can comprise materials for field effect transistors, supercapacitors, batteries, or other electronic devices. The polymers, according to embodiments of the invention, can comprise materials used in electronic paper, camouflage, anti-stat conductors, or photovoltaic devices.

Methods and Materials

All reagents and starting materials were purchased from commercial sources and used without further purification unless otherwise noted. All reactions were carried out under argon atmosphere unless otherwise noted. All1H-NMR and13C-NMR spectra were generated using a Mercury 300 or Inova 500 NMR Spectrometer. Elemental analyses were carried out by the CHN elementary analysis service in the Chemistry Department of the University of Florida. FTIR measurements were carried out using a Perkin-Elmer Spectrum One FTIR outfitted with a LiTaO3detector. Gel permeation chromatography (GPC) was performed using a Waters GPCV2000 liquid chromatography system with an internal differential refractive index detector (DRI) with two Waters Styragel HR-5E columns in series (10 μm PD, 7.8 mm i.d., 300 mm length) and a mobile phase of tetrahydrofuran (THF) with a flow rate of 1.0 mL/min, by injection of samples have a concentration of 0.05-0.08% w/v. Retention times were calibrated against narrow molecular weight polystyrene standards.

Dioxypyrrole potassium salts and diacids were synthesized from their respective diesters, as previously reported in Arroyave et al.,J. Org. Chem.2011, 76, 8621-28.

The potassium dicarboxylate 14 of 6 (0.133 g, 0.1449 mmol, 1 equiv.), 10 mL of water, and 20 mL of dichloromethane DCM were added to and shaken in a 100-mL separatory funnel. To the mixture was added 20 mL of 0.5M HCl and the mixture shaken. After separation of the layers, the DCM layer was removed. The remaining aqueous layer was combined and shaken with an additional 20 mL of DCM and 10 mL of 0.5M HCl and upon separation, the DCM layer was removed and combined with the first DCM layer. The combined DCM solution was washed three times with deionized water, and dried using sodium sulfate. The DCM was removed in vacuo, and the resulting solid was dried under vacuum for an additional two hours. The product was obtained as a mixture of diacid 6a, monoacid 6b and non-substituted dioxypyrrole oligomer 6c. The product was used without further purification.1H-NMR (300 MHz, DCCl3): δH9.77 (br, 1.23H), 6.33 (s, 0.17H), 6.31 (s, 0.05H), 4.26 (m, 11.52H), 4.05 (m, 4.43H), 3.71 (m, 0.84H), 2.26 (m, 4H), 1.62 (m, 4.25H), 1.45-1.19 (br, m, 38.15H), 0.86 (t, 6H, J=6.14).13C-NMR (75 MHz, DCCl3): δC159.7, 141.9, 139.9, 135.4, 117.3, 107.7, 105.5, 73.8, 72.2, 64.8, 46.4, 34.3, 32.1, 31.7, 29.9, 29.8, 29.6, 29.5, 26.9, 22.9, 14.3.FIGS. 8 and 9are traces of the1H-NMR spectrum and the13C-NMR spectrum, respectively.

Polymerization Method Using N-halosuccinimides

General Polymerization Method Using Iodine