Synthesis of 2d and 3D conductive polymers and derived nanocomposites

Abstract

The synthesis of 2D and 3D conductive polymers and derived nanocomposites by interfacial polymerization entails carrying out a reaction in a pure bicontinuous reaction medium using non-ionic, anionic or cationic surfactants. The technical result is an increase in the electrical conductivity of a polymer.

Description

[0001] Synthesis of 2D, 3D-conducting polymers and derivative nanocomposites.

[0002] The present invention generally relates to polymer nanostructures with conductive switching properties, methods for producing them, their use as switches in transistors, logic elements, circuits and computer memory devices.

[0003] Organic conjugated polymers have found application in light-emitting diodes (LEDs), thin-film transistors, solar cells, batteries, supercapacitors, etc.

[0004] Their specific nanostructures have unique electrical, mechanical and optical capabilities. Graphene, a two-dimensional material, has excellent electron mobility and rigidity. With the discovery of conductive polymers, current research has shown that the dimensionality of conductive polymer nanostructures is a crucial characteristic to demonstrate their unique electrical properties. Two different template synthesis methods, namely hard template [8,9] and soft template, have been effectively used to synthesize various conductive polymer nanostructures. In addition, diverse structures of polyaniline (PANI), such as nanoparticles, nanotubes, nanofibers, nanowires, nanofilms and networks], have prompted the study of the structure-property relationship of PANI.

[0005] In particular, the above-mentioned study highlighted the need to develop two-dimensional (2D) morphologies to provide superior electrical performance, especially in the desired directions, for high-density integrated electronic devices 7,29-31. By designing and fabricating specialized nanostructured material systems, scientists studying conductive polymers hope to obtain well-tailored chemical and physical properties for expanded applications in conductive polymers.

[0006] Although expensive and complex procedures such as electron beam evaporation and vapor-liquid-solid growth have been reported for the fabrication of 2D sheets, no universal strategy has been developed for the fabrication of 2D, 3D, or their composites. The removal of graphene oxide (GO) is an additional drawback of the template synthesis method for obtaining uniform PANI sheets. Currently, 2D PANI nanofilms fabricated using ice as a rigid template exhibit the highest electrical conductivity of 35 Siemens S-1, which is significantly higher than the previous values ​​reported in the past decades.

[0007] A simple and scalable synthetic process exists for creating two-dimensional (2D), three-dimensional (3D), and nanomaterials derived from nanocomposites that is distinct from interfacial polymerization used in liquid-liquid and other interfacial interactions.

[0014]

[0008] Conducting polymers (CPs) are important materials for a wide range of applications, including electronics, energy conversion and storage, sensors, and medical devices. (Skotheim, T. A., and Reynolds, J., Handbook of Conducting Polymers. 3ed.; CRC Press. (2007)

[0009] With conjugated rigid framework structures to enhance electrical conductivity, conducting polymers are generally insoluble and non-meltable, so post-polymerization processing of conducting polymers is challenging. (Skotheim, T. A., and Reynolds, J., Handbook of Conducting Polymers. 3ed.; CRC Press. (2007)

[0010] In addition, the mechanical properties of conducting polymers are severely limited by their weak intermolecular forces, which result from the lack of chain entanglement. Many methods have been developed to create conducting polymers with different morphologies. There are two types of template-based approaches: hard template and soft template.

[0011] The rigid template method combines chemical and electrochemical methods to produce small (0D and 1D) size conductive polymers (Nguyen, D. N., and Yoon, H., Polymers (2016) 8 (4), 118).

[0012] The disadvantage of this method is that it can only be used for the production of small-sized polymers: OD, 1D conductive polymers.

[0013] In the soft template approach, a micelle is used as a template for one-dimensional conductive poly(3,4-ethylenedioxythiophene) PEDOT polymers.

[0014] A poly(3,4-ethylenedioxythiophene) nanorod structure was synthesized using surfactant micelle as a template and showed application as an acid-base sensor (Jang, J., et al., Advanced Materials (2005) 17 (13), 1616).

[0015] The disadvantage of this structure is low electrical conductivity.

[0016] An interfacial polymerization approach for the synthesis of polyaniline nanofibers is known (Huang, J., and Kaner, R. B., Journal of the American Chemical Society (2004) 126 (3), 851). The disadvantage is that in conventional polymerization, excessive growth of polyaniline on these nanofiber scaffolds results in the production of irregularly shaped final micron-sized particles.

[0017] A synthetic approach for highly crystalline conducting polymers of polyaniline, polythiophene and polypyrrole is known. (Su, K., et al., SYNTHESIS OF POLYMER NANOSTRUCTURES WITH CONDUCTANCE SWITCHING PROPERTIES. Research Foundation of the City University of New York, New York, NY(US), USA, (2015), Vol. W02008 / 156492)

[0018] The disadvantage is the generation of a large amount of heat during interfacial oxidative polymerization, which can lead to an explosion. Also, this approach uses a large number of organic solvents.

[0019] A solution casting approach using FeCh as a template was developed to prepare porous pure conductive polymer film and their inorganic / organic composite films (Dai, L., et al., RSC Advances (2015) 5 (44), 34616).

[0020] The disadvantage of the method is the by-product formation of iron oxides. This approach is not applicable to all polymer-forming substances.

[0021] The electrospinning approach is considered as an effective approach to fabricate 1D CP 8 nanofibers (Sapountzi, E., et al., Sensors (2017) 17 (8), 1887).

[0022] The disadvantage of this approach is its high cost, associated with high energy consumption. And this approach is also selective.

[0023] The objective of this invention is to develop a technology for producing nanopolymers with high electrical conductivity, thermal conductivity, optical transparency and high mechanical characteristics.

[0024] The technical result is achieved by creating a new method for obtaining 2D and SD conducting polymers with high electrical conductivity properties and their use to increase the photoelectric efficiency of polymer solar cells (highest conductivity 219 S / cm).

[0025] Fig. 1 is a conceptual schematic illustration of the fabrication of suitable polymer particles (a), 2D (b), 3D and their composites (c) using continuous dual reactor systems. Fig. 2 illustrates the effect of monomer to oxidant ratio concentration on the evolution of 2D polypyrrole (PPY) nanostructures including incomplete 2D-PPY (a), complete 2O-nanosheets (b) and particle networks (c). Fig. 3 shows the evolution of conductive PPY nanosheets under different oil to water ratio conditions and the molecular model of the non-ionic interface for 60 / 10 / 30 (a), 60 / 15 / 25 (b) and 40 / 30 / 30 (c) reactors. 4 shows (a) PPY nanofilms prepared in a non-ionic continuous dual reactor, (b) 2D-PPY prepared at the pure oil / water interface, (c) a cationic continuous dual reactor, and (d) 3D-particle-linked PPY networks prepared by an anionic continuous dual reactor.Figure 5 shows the conductivity of (a) all interfaces and (b) non-ionic interface reactors with different oil to water ratios. Figure 6 shows the SEM images and illustrations of pure 2D PPY (a) and the effect of monomer to linker ratio on 3D PPY material with linker carbon chain length of 6 carbon (b, c, d). Confocal microscopy study of fluorescence quenching and CD reactivation in PPY nanocomposite materials is shown in Figure 7.

[0026] Our main method for the synthesis of 2D and 3D conducting polymers and their composites is the creation of special two-continuous reactor systems (Fig. 1). Thin-layer interfaces in two-continuous reactor systems are the main platform for controlling the morphology and properties of conductive polymer materials, including their electrical, mechanical and structural characteristics. The monomer-to-oxidant ratio, interface thickness and charge homogeneity, oxidant type and dopant element are the main criteria for creating conductive polymer nanostructures. Moreover, the monomer-linker-to-oxidant ratio is a decisive factor for controlling the morphology of 3D conducting polymer nanostructures. Interfacial polymerization is the main coupling method used in all syntheses to connect monomers and obtain 2D and 3D conducting polymers.

[0027] As shown in Fig. 1(a), the relatively low monomer to oxidant ratio (7 / 10 wt%) is one of the most important parameters used to create the PPY nanopowder structures through the manipulation interface in the nonionic pure cationic and anionic interfaces of the twin continuous reactors designed based on the phase diagrams in Figs. S1 and S6 of the Supplementary Materials. The high monomer to oxidant ratio (1.2 / 1 wt%) can be used to create the PPY nanofilms (Fig. 1(b)). In the design of 3D-PPY and nanocomposites (Fig. 1(c)) unique pyrrole linkers (Scheme S1) were designed to react with the pyrrole monomer in the twin continuous reactors to produce the layered PPY nanostructures. In the synthesis of conductive polymer nanostructures (PPY), the interface is the main driving force to control the fabrication of conductive polymer nanostructures. Four different interfaces were chosen for this study (Fig.1 (I, II, III, IV)) to study the formation of PPY nanostructure, including the pure oil / water interface (Fig. 1 (I)), the non-ionic interface (Fig. 1 (II)), the cationic interface (Fig. 1 (III)) and the anionic interface (Fig. 1 (IV)). In the bicontinuous thin film system, the task of the surfactant is to provide a uniform interfacial difference between the water and oil layers. Except for the negatively charged interface, cationic (Fig. 1(III)), non-ionic (Fig. 1(II) and pure water / oil interface (Fig. 1(I)) were able to produce 2D-PPY under optimal conditions. This can be controlled by changing the reactor composition where the oil to water ratio plays a vital role. The thickness of these layers depends on the oil and water content of the system. To study the effect of monomer to oxidant ratio on the production of PPY nanostructures, an NBCR consisting of water layers and oil layers aligned with a non-ionic interface was chosen (Fig. 1(II)).Due to the influence of oil to water ratio, PPY materials undergo a number of structural modifications. The appropriate ratio of all components, such as oil ratio from 50 to 80% by weight, water content from 5 to 20% by weight (Fig. 2) and surfactant concentration increased accordingly to 100% by weight of the NBCR system, has a decisive effect on the parameters in the production of homogeneous free-standing nanofilms (Fig. 2(6)). It has been experimentally established that excess or deficiency of monomer in the system leads to the formation of structural defects or nanopowder (Fig. 2, a, c)).

[0028] 2D PPY were generated by assembling PPY nanoballoons. At moderate level of oxidizer, FeCh (5 to 20 wt% water) (Fig. S3), PPY polymer chains have a chance to grow in 2D direction since there are significantly less nucleation sites and the PPY growth process is more prominent than the nucleation process. In case of low monomer ratio, high concentrations of oxidizers generated significantly more nucleation sites, which may be the dominant process compared with the growth process. Thus, the generation of PPY nano powder is preferable to the growth of 2D-PPY (Fig. 2(c)). 25-150 nm is the average thickness of this type of film. Since the nonionic interface does not carry charges and does not interact with monomers or oligomer chains, its influence on the polymerization process is insignificant. It acts as a barrier preventing monomer chains from penetrating into other regions and regulates the distribution of particles at the interface.Thus, the polymer chains grow in two-dimensional directions and form a film with uniform distribution at the interface. Another oxidizer (ammonium persulfate, APS) also confirms the above data (Fig. S4) in a nonionic double continuous reactor (NBCR) system.

[0029] Proper interface control is a key way to fabricate monolayer, bilayer, and even multilayer 2D free-standing nanofilms. Fig. 3 shows the effect of water content on the formation of nanofilms synthesized by nonionic interface by gradually increasing the water content from 10 to 30 wt%. Since the amount of both water and surfactant in the nonionic double continuous reactor (NBCR) system exceeds 30%, multilayer polymer sheets were found in which the monomer concentration was relatively reduced, which was a key parameter in the formation of multilayer film structures.

[0030] At both cationic and pure oil / water interfaces, although 2D-PPY nanosheets were detected, the density of 2D-PPY in the bicontinuous thin layer reactor in the absence of surfactant is relatively high due to the absence of molecular barrier formation at the interface (Fig. 4(a)) (Table S1). This allows the PPY chains to diffuse across the interfaces and form thicker and denser structured films (Fig. S7). The average thickness of this type of nanofilm is 195-220 nm. In the cationic or positively charged interface system (Fig. 4(c)) 2D-PPY film can be easily formed due to the repulsion between the positively charged interface and the PPY chains and the growth preference among the PPY polymer chains. Although 2D-PPY nanofilms are formed, the positive charge of the interface repels the pyrrole particles and leads to the formation of porous 2D nanofilms.

[0031] The presence of counterions at the interface (anionic bicontinuous reactor system) does not allow two-dimensional growth of polymer nanofilms, since they have a strong electrostatic attraction with the polymer chains (Fig. 4(d)). The average thickness of the synthesized materials is in the range from 25 μm to 220 μm.

[0032] Conjugated polymers become more conductive with the addition of dopants. In our developed reactor systems, the polymerization of pyrrole monomer occurs in the presence of ferric chloride and hydrochloric acid as dopants. The thickness of 2D polypyrrole nanofilms varies from 25 nm to 400 nm due to the factors mentioned above in the morphological studies. These parameters significantly affect the electrical properties of 2D PPY films, as shown in Fig. 5, and more detailed information can be found in Supplementary Tables S2 and S3. Table S3 presents the average conductivity values ​​obtained for four different reactors.

[0033] The special design of our reactors with four different interfaces allows us to control the electrical properties of the synthesized materials. The highest conductivity of 219 S / cm was obtained for the nanofilm prepared using the reactor system with a clean interface (DCM system) due to the absence of an interfacial barrier and easy transport of dopants into the polymer matrix. The second highest conductivity, 144.9 S / cm, was obtained by the non-ionic interface with an optimal oil-to-water ratio (50 / 10 wt.%), since it does not interfere with the transport of dopant molecules. In addition, the monomer-to-oxidizer ratio is another important parameter affecting the electrical properties of 2D-conducting polymers due to the homogeneity and relatively small thickness. The range of electrical conductivity depends on the homogeneity of 2D-conducting polymers.In the case of cationic and anionic interfaces, the morphology of the synthesized materials was more porous and non-uniform, which increased the distance between particles and led to a decrease in conductivity (Fig. 5). The conductivity of 2D-PPY nanosheets obtained using pure and neutral interfaces is ten times higher than the data published so far for 2D-conducting polymers. By controlling the interface and doping, we can tune the electrical properties of conducting polymers.

[0034] To create the 3D-PPY conducting polymer networks, special linkers (Scheme S1) were designed and mixed with a pyrrole monomer. Then, interfacial polymerization was used to co-polymerize both the monomer and the linker across the interface of thin oil and water layers in a bicontinuous system. Both the monomer and the linker were mixed in oil-thin bicontinuous layers and polymerized by introducing oxidants. The ratio between the monomer and its linker is important to obtain layers and structures of different thicknesses (Fig. 1(c) and Fig. 6). The presence of the linker in the system has a packing effect on the structure of the synthesized 3D-PPY materials. With the increase of the linker concentration in the reactor, as shown in Fig. 6(b)-(d), these layered structures tend to pack and connect with each other, forming a dense lamellar structure. Furthermore, a monomer to linker ratio of 0.5% to 4% by weight promotes the formation of a layered lamellar structure (Figs. 6 and S9).The above-mentioned morphological changes of the 3D-PPY materials were confirmed by both different linkers, the lengths of which are C6 and C10 (see Table S4 for more details). In addition, both linkers gave the same structures as layered plates. The formation of the three-dimensional layered structures was associated with the presence of bicontinuous layered structures in the reactor systems (Fig. 1 (I, II, III, IV) and 1 (c)).

[0035] Polymerization of the monomer with the linker was confirmed by FTIR study. Figure S8 shows the FTIR spectra of 2D-polypyrrole, pure linker, and 3D-PPY. Polypyrrole gives characteristic peaks for the C=C double bond at 1500 cm' 1 and stretching of vinyl C-H at -3000 cm 4 Other signals corresponding to the linker become visible after polymerization of the linker with pyrrole. Namely, the carbonyl elongation at -1700 cm' 1 and -3000 cm' 1 , corresponding to sp 3 C-H begins to appear as the number of linkers increases.

[0036] This strategy is further extended to fabricate conductive polymer nanocomposites by a one-step technology for the fabrication of free-standing conductive polymer nanocomposites combining the functionalities of conductive polymers and nanoparticles to form an integrated system. This method was applied to synthesize clean interface PPY composites with and without linker and fluorescent carbon dots (CDs). Carbon dot nanomaterials were selected as dispersed phase materials to be added into the oil phase along with monomer and linkers. Carbon dots are semiconductors and have unique photoluminescence (PL) emission, making them excellent materials for medical diagnostics bioimaging, fluorescence sensing, light emitting diodes, photovoltaic devices, etc. In addition, CDs show promising results in heavy metal detection and sensing.Thus, the presence of hazardous heavy metals in the environment can be detected by reducing the emission of carbon dots. The best emission quenching effect was demonstrated by detecting iron ions through the oxidation-reduction reaction of Fe ions. 2+ / Fe 3+ . Currently, the main limitation of carbon dots is their fluorescence self-quenching effect in dry state due to particle agglomeration, which shortens the light emission time. Our synthesis method was successfully applied to the fabrication of PPY@CD dot nanocomposites by premixing them with monomer and linkers, which improved the brightness and photoluminescence emission of CDs (Fig. S10). The intensity of PPY nanocomposites was enhanced with the addition of CDs compared with 2D-PPY@CD dot composites and pure CD particles due to the stabilization and dispersion of CDs in the PPY matrix. The synthesized PPY@CDs nanocomposites exhibited exceptional Fe ion detection capability 3+and stability due to quenching and reactivation of CD nanoparticles embedded in the structure of polymer nanoprencs. The intensity of PPY nanocomposites increased with the addition of CD due to the stabilization and dispersion of CD in the PPY matrix (Fig. S 11). Since Fe ions 3+ have a quenching effect on compact discs, the sensitivity of the polymer nanofilms was dramatically reduced by adding ferric chloride solution (Fig. S12 and Fig. 7 (middle)). Then, the PPY@CD nanocomposite was reactivated by adding ascorbic acid, and its photoluminescence returned to the original value (Fig. S12 and Fig. 7 (right).

[0037] Quenching and reactivation of PPY@CD nanocomposites proved that the synthesis method can be used to fabricate nanocomposites of conductive polymers and functional materials.

[0038] In this study, a general strategic synthesis method for the fabrication of 2D, 3D and their nanocomposites was developed for the first time. This fabrication method was developed using four different reactors with dual continuous interfaces, including pure, nonionic, cationic and anionic interfaces. Important criteria for controlling the morphology and electrical characteristics of conductive polymer materials include the nature of the interfaces, the thickness of the thin-layer interfaces, the monomer-to-oxidant ratio, the ratio between monomer, linker and oxidant, and the doping level. In the absence of a molecular layer, the pure interface provides 2D nanofilms that are significantly thicker than the cationic, nonionic and anionic interfaces.The conductivity of 2O films prepared from dual continuous systems with clean interface was the highest among four reactor systems with two different interfaces and even exceeded the value reported in the literature for conducting polymer with 2O films. With the incorporation of a unique linker, 3D-PPY materials were designed and efficiently produced in a dual continuous reactor system. In the synthesis of the nanocomposite, the components of the functional dispersion phase were introduced into the monomer and linker mixture. In order to demonstrate the stability and fabrication of the conductive polymer nanocomposites, quenching and reactivation of the C-dot photoluminescent material in the nanocomposite were used. This fabrication method will be used to synthesize additional conductive polymers and their 2D, 3D and nanocomposites. This approach represents a low-cost and environmentally friendly fabrication method that can be used for mass production.

[0039] Example 1. Synthesis of 2D-PPY. The bicontinuous microemulsion (BCME) polymerization method was used to polymerize pyrrole. In a typical experimental setup, the pyrrole monomer was freshly distilled under reduced pressure before use, and deionized water (DI) was used as the aqueous component of the microemulsion system and the oxidizing solvent for the polymerization reaction. Ferric chloride (FeCh) (concentration from 2 to 20 mg / mL) or ammonium persulfate (APS) (concentration from 1 to 15 mg / mL) were dissolved in deionized water as an oxidizing agent and hydrochloric acid (HCl) as a doping, a reagent was introduced to adjust the acidity of the aqueous fraction from pH 1 to 2. A solution of TX-100 surfactant / butanol was prepared at a weight ratio of 1:1; The monomers were dissolved in cyclohexane (80:20 wt.%). The three components were then mixed to form a bicontinuous phase and left for 8-24 hours to complete the polymerization reaction at room temperature.The resulting black films and polypyrrole powders were washed with acetone until the unreacted oil residue was completely removed. The synthesized PPY with FeCh and APS at different concentrations is shown in Figures S3 and S4.

[0040] Example 2. Synthesis of 3D-PPY. For the synthesis of 3D-PPY in a nonionic reactor system, the oil / water ratio and the amount of linker were calculated depending on the monomer concentration. The linker was pre-mixed with pyrrole. Iron chloride solution (5 mg / mL) was chosen as a catalyst. After mixing all components, the reactor was left for 24 hours. After the polymerization was completed, polypyrrole was washed with acetone and methanol. The synthesis protocol is shown in Table S4.

[0041] Example 3. Synthesis of PPY nanocomposite. A benzene / ethanol / water bicontinuous reactor system was used to create the PPY nanocomposite. In a typical preparation of the surfactant-free benzene / ethanol / water bicontinuous phase, the following composition was used; 1% benzene, 30% ethanol, and 69% water. All monomers and linkers were prepared in benzene; and the oxidizing agent and carbon dot in the aqueous phase. The ratio of oxidizing agent to S-CD was 1:100. The components were then gently mixed to form the bicontinuous phase, which was allowed to polymerize for 8-12 h at room temperature. The resulting black solid was washed with ethanol and acetone, respectively. The resulting 2D and 3D materials were further characterized using analytical tools such as AFM, SEM, TEM, and FT-IR.

Claims

CLAUSES OF THE INVENTION E Synthesis of 2D, 3D-conducting polymers and derivative nanocomposites, including the method of interfacial polymerization, characterized in that the reaction occurs in a bicontinuous reaction medium.

2. A bi-continuous reaction medium according to paragraph 1 of the formula of the invention, characterized in that the bi-continuous reaction medium is pure, without impurities.

3. A bi-continuous reaction medium according to paragraph 1 of the formula of the invention, characterized in that non-ionic surfactants are used in the bi-continuous reaction medium.

4. A bi-continuous reaction medium according to paragraph 1 of the formula of the invention, characterized in that anionic surfactants are used in the bi-continuous reaction medium.

5. A bi-continuous reaction medium according to paragraph 1 of the formula of the invention, characterized in that cationic surfactants are used in the bi-continuous reaction medium.

6. A bi-continuous reaction medium according to paragraph 1 of the formula of the invention, characterized in that the bi-continuous reaction medium contains anionic surfactants.

7. Synthesis of 2D, 3D conducting polymers and derivatives of nanocomposites according to claim 1, characterized in that polypyrrole is used as the polymer.

8. Synthesis of 2D, 3D-conducting polymers and derivative nanocomposites according to paragraph 1, characterized in that polyaniline can be used as the polymer.

9. Synthesis of 2D, 3D-conducting polymers and derivative nanocomposites according to claim 1, characterized in that polythiophene is used as the polymer.

10. Synthesis of 2D, 3D-conducting polymers and derivative nanocomposites according to paragraph 1, characterized in that carbon quantum dots are used as the nanocomposite.

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