Conductive polypyrrole and acrylate nanocomposite coatings: Mechanistic study on simultaneous photopolymerization
Graphical abstract
Conductive nanocomposite coating of polypyrrole and acrylate with optimized conductive and binding properties was synthesized in a single step simultaneous photopolymerization.
Introduction
Intrinsically electronic conductive polymers have attracted great attention for their potential applications in printed circuit boards, flexible electronics, organic thin film transistors (OTFTs), sensors and various electronic devices due to their lower weight than metals, ease of preparation, and a wide range of controllable properties [1], [2], [3], [4], [5]. The past few decades have seen significant development in this field in terms of fundamental scientific research and many industrial applications. Several attempts have been made to fabricate micro-patterns, structures of conductive polymers, and their coatings on various substrates via chemical oxidation and electropolymerization processes [6], [7], [8], [9]. While some of the advantages that electropolymerization method offers are controllability on thickness of coatings and conductivity; the advantages of chemical oxidation method are feasibility of large-scale production and variability of precursors [10]. However, solubility of conductive polymers has been a major issue in both these methods in order to obtain thin films with improved adherence to various substrates.
The field of photo-induced chemistry offers a wide variety of tools that are useful in obtaining desired chemical transformations with an application of light for a broad range of applications. Among the photo-induced chemical reactions, photodoping and photopolymerization are notable techniques for the deposition of metals into polymers [11], [12]. Photodoping involves the incorporation of metals such as silver into various materials such as glass and polymer upon illumination of light. During the process, the charged metallic species migrate into the materials under the influence of intrinsic electric fields caused by the exposure of light. Photopolymerization is a process in which a liquid transforms into solid by the irradiation of generally UV light or electron beam. This phenomenon causes significant changes to physical properties of material such as viscosity, solubility, adhesion, color, and electrical conductivity. This technique for material synthesis has been found highly useful in obtaining microfabrication and coatings directly onto the substrate where there are limitations such as temperature and solubility. Complex nano- and micro-sized patterns and structures have been fabricated using photopolymerization onto printed circuit boards, miniature wiring boards, and biomaterial scaffolds [13], [14].
Recent studies on photopolymerization of pyrrole in the presence of electron acceptors, for example silver salts, excited by UV light have shown interesting results for the incorporation of metal nanoparticles into polypyrrole [15], [16], [17]. Previously, some reports on multiphoton-sensitized polymerization of pyrrole, self-sensitized photopolymerization of pyrrole, and photopolymerization of pyrrole using ruthenium, cobalt, ferrocene and copper complexes as electron acceptors were published [18], [19], [20], [21]. The photopolymerization method has been successfully used to manufacture composites of polypyrrole/metal nanoparticles for applications such as gas sensors and humidity sensors [22], [23]. However, so far very few reports have been published on the use of photopolymerization because of lower yields and inferior conductivity of polypyrrole obtained in this method as compared to chemical and electrochemical methods. One of the major advantages of photopolymerization is that it can be readily applied with the ease of design and control to make polymer coatings directly onto conducting and non-conducting substrates.
In this paper, the preparation of conductive polymer coatings of polypyrrole and acrylate via simultaneous photopolymerization was reported. This method facilitates the fabrication of conductive polymer coatings for various applications such as printing conductive inks and semiconductor devices. In this method, the reaction mixture contains pyrrole with its corresponding photo-activated oxidant and acrylate monomer with its corresponding photo-initiator. This reaction mixture will be converted into a hybrid coating through photopolymerization processes of both pyrrole and acrylate occurring simultaneously. While polypyrrole serves as conductive path link, acrylate polymer acts as binder to bind polypyrrole particles as well as strongly adhere to the substrate. Due to the fact that it is a single step process, it minimizes total preparation time and eliminates the processibility of conductive polymer. In this work, Real-time Fourier Transform Infrared (RT-FTIR) spectroscopy was used to investigate polymerization conversion of pyrrole to polypyrrole in the presence of UV activator, AgNO3. Subsequently simultaneous photopolymerization, which is the combination of polypyrrole formation and acrylate polymer formation occurring together in a reaction mixture, was also studied using RT-FTIR. Finally, coatings were made on aluminum substrate and characterized using four-point probe method and conductive AFM in order to measure conductivity and surface roughness of coatings. Further, coatings prepared on epoxy substrate were analyzed using transmission electron microscope (TEM) and scanning electron microscope (SEM).
Section snippets
Materials
Pyrrole was purchased from Sigma Aldrich, distilled under vacuum, and stored in refrigerator around 0 °C prior to use. AgNO3 and methanol were also purchased from Sigma Aldrich. 1,6-hexanedioldiacrylate (SR238) and Irgacure 907 were obtained from Sartomer. EPO-TEK® 377 purchased from Epoxy Technology, Inc., (USA) of the dimensions of 1 × 1 inch was used to prepare epoxy substrates for the coating applications.
Investigation of polymerization conversions using real-time FTIR
Real-time FTIR (RT-FTIR) technique was used to determine the polymerization conversion
Photopolymerization of pyrrole
Real-time Fourier Transform Infrared (RT-FTIR) spectroscopy is one of the most valuable techniques in measuring the polymerization rates qualitatively by monitoring the changes in the IR absorption characteristics of the reactive groups such as acrylates, methacrylates, epoxies, double bonds and thiol groups. In addition, it can further be used to calculate the degree of conversion at any time during the polymerization process. It has often been effectively used to investigate the kinetics of
Conclusion
An attempt was made to prepare conductive polypyrrole coatings with optimized binding properties onto various substrates such as aluminum, glass, and epoxy via simultaneous photopolymerization of pyrrole and UV curable acrylate monomer. In order to match the polymerization processes of pyrrole and acrylate in the final coatings, their individual photopolymerization processes were investigated using RT-FTIR. It was found that the increase in AgNO3 concentration in the formulations with
Author contributions
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.
Acknowledgements
The authors would like to thank the U.S Army Research Laboratory under grant numbers W911 NF-04-2-0029, W911NF-09-20014, W911NF-10-2-0082, and W911NF-11-2-0027 for supporting this research.
References (33)
- et al.
Microstructuring of conducting polymers
Electrochim. Acta
(1999) - et al.
Application potential of conducting polymers
Electrochim. Acta
(2005) - et al.
Micropatterning of conducting polymer tracks on plasma treated flexible substrate using vapor phase polymerization-mediated inkjet printing
Synth. Met.
(2010) A physical-based simulation for the dynamic behavior of photodoping mechanism in chalcogenide materials used in the lateral programmable metallization cells
Solid State Ionics
(2016)- et al.
Preparation of polypyrrole-coated silver nanoparticles by one-step UV-induced polymerization
Mater. Lett.
(2005) - et al.
New sensing technology for detection of the common inhalational anesthetic agent sevoflurane using conducting polypyrrole films
Sens. Actuators B
(2007) - et al.
Flexible humidity sensor based on TiO2 nanoparticles-polypyrrole-poly-[3-(methacrylamino) propyl] trimethyl ammonium chloride composite materials
Sens. Actuators B
(2008) - et al.
Real-time FTIR-ATR spectroscopy to study the kinetics of ultrafast photopolymerization reactions induced by monochromatic UV light
Vib. Spectrosc.
(1999) - et al.
Synthesis and structural study of polypyrroles prepared in the presence of surfactants
Synth. Met.
(2003) - et al.
Large area electronics using printing methods
Proc. IEEE
(2005)
Printed circuit patterns of conducting polymer
Mol. Cryst. Liq. Cryst.
Conducting polymer coatings in electrochemical technology − part 2 − application areas
Trans. Inst. Met. Finish.
Laterally controlled template electrodeposition of polyaniline
Isr. J. Chem.
Micropatterning of conducting polymer thin films on reactive self-assembled monolayers
Chem. Mater.
Patterning of conducting polymers using charged self-Assembled monolayers
Langmuir
The effect of polymer morphology on the performance of a corrosion inhibiting polypyrrole/aluminum flake composite pigment
Electrochim. Acta
Cited by (22)
A review of polymerization fundamentals, modification method, and challenges of using PPy-based photocatalyst on perspective application
2022, Journal of Environmental Chemical EngineeringCitation Excerpt :The ECP takes over COP in controlling the thickness and uniformity of synthesis film of PPy via changing the input parameters, including solvent (aqueous or nonaqueous solvent), current density, electric potential, or electrodeposition period [61,63]. Interestingly, PPy can be synthesized via various methods, as shown in Table 3 [64–71]. The polymerization method and conditions, along with dopant type and concentration can impact the structural, thermal, and morphological properties of prepared PPy [77].
Corrosion failure process of organic conductive coating on Mg-RE alloy with PEO in the simulated Xisha atmospheric solution
2022, Materials Chemistry and PhysicsBoosting visible photocatalytic degradation of 2,4-dichlorophenol and phenol efficiency by stable core@shell hybrid Ag<inf>3</inf>PO<inf>4</inf>@polypyrrole
2022, Colloids and Surfaces A: Physicochemical and Engineering AspectsInvestigation on mechanical and conductive properties of polypyrrole/UV cured acrylate nanocomposite coatings
2021, Progress in Organic CoatingsCitation Excerpt :They have demonstrated valuable properties for applications including electrochemical sensors, energy storage devices, and 2D or 3D printable electronics [33,34]. In our previous work, we presented that the conductive polypyrrole nanocomposite coatings can be obtained via a novel method called simultaneous photopolymerization [35]. In this method, the polymerizations of pyrrole and acrylate monomers occur simultaneously under UV radiation to form conductive composite coating.
Influence of photoinitiator and temperature on photocross-linking kinetics of acrylated epoxidized soybean oil and properties of the resulting polymers
2021, Industrial Crops and ProductsCitation Excerpt :Although, the theoretical value of the reaction enthalpy is needed for the reaction process investigation, it is not always accessible for novel and complicated systems containing a mixture of various materials (Castell et al., 2007). RT-FTIR is a likewise spread technique used for the monitoring of UV-curing reactions due to its relatively simple execution and ability to monitor prompt reactions occurring in a short time scale (Kasisomayajula et al., 2016). RT-FTIR is used to measure the conversion of the selected functional groups during the UV irradiation, in case of (meth)acrylates, the change of acrylic CC group signal at 1637 cm−1 is monitored (Meereis et al., 2016).
Digital light processing for the fabrication of 3D intrinsically conductive polymer structures
2018, Synthetic MetalsCitation Excerpt :However, the magnitude of the peaks differs due the quantity of each bond. The FTIR spectrum of photopolymerized PPy exhibits several characteristic bands at 3440 cm−1 (N–H stretching), 1530 cm−1 (C–C and C=C ring stretching), 1448 cm−1 (C–N stretching), 1297 cm−1 (C–H and C–N stretching), 1170 cm−1 (ring breathing vibration) and 1041 cm−1 (C–H in-plane and out-of-plane deformation) [26,29,41–43]. The strong absorbance band at 1702 cm−1 corresponds to the presence of a carbonyl group produced by the nucleophilic attack of water on pyrrole [41,42].