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Structure and Electronic Properties of Conjugated Polymers and Nanocomposites

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Computational and Theoretical Chemistry".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 15336

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Dr. Ştefan Ţǎlu

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The Directorate of Research, Development and Innovation Management (DMCDI), The Technical University of Cluj-Napoca, Constantin Daicoviciu Street, no. 15, 400020 Cluj-Napoca, Cluj County, Romania
Interests: mechanical and tribological characterization of macro–micro–nanostructures; topographical and morphological characterization of three-dimensional surfaces at micro/nanoscale; experimental techniques for micro/nanomechanical and micro/nanotribological characterization; development of new mathematical tools in the investigation of 3D surface quality; theoretic and applied research in advanced materials science in engineering; fractal and multifractal geometry analysis and applications
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Special Issue Information

Dear Colleagues,

This Special Issue publishes papers about the structure and electronic properties of conjugated polymers and nanocomposites because of the wide range of potential applications in multidisciplinary fields, such as chemistry, biology, and engineering. The theoretical studies focus on the understanding of these materials with novel electronic structure, optical, electrical, magnetic, catalytic, and mechanical properties at the atomic level. The materials include conjugated polymers, nanocomposites, nanomaterials, biomaterials, and catalysts, in addition to the study of surfaces and interfaces by microscopy such as SEM and AFM of these materials. Nanocomposites, as multi-phasic materials, have extraordinary properties, distinctive design capacity, eco-friendly nature, easy fabrication, cost-effectiveness, with numerous applications due to their advanced properties. Furthermore, combined experimental and theoretical evaluation of the electronic structure of conjugated polymers and nanocomposites can contributed to a better understanding of several physicochemical properties of these materials, enabling new and interesting technological applications.

The scope of this Special Issue includes but is not limited to:

Understanding the structure, electronic property, performance relationships, and their underlying mechanisms;
Designing new conjugated polymers and nanocomposites for energy, catalysis, biology, and other applications;
Application of new computer programs for computer modeling and simulation in analyses of these materials;
Recent developments of the functionalities of conjugated polymers and nanocomposites;
Computer modeling and simulation to predict properties;
Combined experimental and theoretical evaluation of conjugated polymers and nanocomposites.

Dr. Ştefan Ţǎlu
Guest Editor

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Keywords

conjugated polymers
nanocomposites
structure and electronic properties
surfaces and interfaces
physical–chemical properties and advanced functionality
methods, tools, computerized simulation
design of innovative conjugated polymers and nanocomposites
fabrication and applications

Published Papers (8 papers)

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Research

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12 pages, 4011 KiB

Open AccessEditor’s ChoiceArticle

Toward High-Performance Electrochromic Conjugated Polymers: Influence of Local Chemical Environment and Side-Chain Engineering

by Kaiwen Lin, Changjun Wu, Guangyao Zhang, Zhixin Wu, Shiting Tang, Yingxin Lin, Xinye Li, Yuying Jiang, Hengjia Lin, Yuehui Wang, Shouli Ming and Baoyang Lu

Molecules 2022, 27(23), 8424; https://doi.org/10.3390/molecules27238424 - 1 Dec 2022

Cited by 12 | Viewed by 1289

Abstract

Three homologous electrochromic conjugated polymers, each containing an asymmetric building block but decorated with distinct alkyl chains, were designed and synthesized using electrochemical polymerization in this study. The corresponding monomers, namely T610FBTT810, DT6FBT, and DT48FBT, comprise the same backbone structure, i.e., an asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole unit substituted by two thiophene terminals, but were decorated with different types of alkyl chain (hexyl, 2-butyloctyl, 2-hexyldecyl, or 2-octyldecyl). The effects of the side-chain structure and asymmetric repeating unit on the optical absorption, electrochemistry, morphology, and electrochromic properties were investigated comparatively. It was found that the electrochromism conjugated polymer, originating from DT6FBT with the shortest and linear alkyl chain, exhibits the best electrochromic performance with a 25% optical contrast ratio and a 0.3 s response time. The flexible electrochromic device of PDT6FBT achieved reversible colors of navy and cyan between the neutral and oxidized states, consistent with the non-device phenomenon. These results demonstrate that subtle modification of the side chain is able to change the electrochromic properties of conjugated polymers. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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13 pages, 1695 KiB

Open AccessCommunication

Novel Push-Pull Benzodithiophene-Containing Polymers as Hole-Transport Materials for Efficient Perovskite Solar Cells

by Aleksandra N. Mikheeva, Ilya E. Kuznetsov, Marina M. Tepliakova, Aly Elakshar, Mikhail V. Gapanovich, Yuri G. Gladush, Evgenia O. Perepelitsina, Maxim E. Sideltsev, Azaliia F. Akhkiamova, Alexey A. Piryazev, Albert G. Nasibulin and Alexander V. Akkuratov

Molecules 2022, 27(23), 8333; https://doi.org/10.3390/molecules27238333 - 29 Nov 2022

Cited by 7 | Viewed by 1764

Abstract

Donor-acceptor conjugated polymers are considered advanced semiconductor materials for the development of thin-film electronics. One of the most attractive families of polymeric semiconductors in terms of photovoltaic applications are benzodithiophene-based polymers owing to their highly tunable electronic and physicochemical properties, and readily scalable production. In this work, we report the synthesis of three novel push–pull benzodithiophene-based polymers with different side chains and their investigation as hole transport materials (HTM) in perovskite solar cells (PSCs). It is shown that polymer P3 that contains triisopropylsilyl side groups exhibits better film-forming ability that, along with high hole mobilities, results in increased characteristics of PSCs. Encouraging a power conversion efficiency (PCE) of 17.4% was achieved for P3-based PSCs that outperformed the efficiency of devices based on P1, P2, and benchmark PTAA polymer. These findings feature the great potential of benzodithiophene-based conjugated polymers as dopant-free HTMs for the fabrication of efficient perovskite solar cells. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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13 pages, 3143 KiB

Open AccessArticle

Improvement of Dynamic Performance and Detectivity in Near-Infrared Colloidal Quantum Dot Photodetectors by Incorporating Conjugated Polymers

by Myeong In Kim, Jinhyeon Kang, Jaehee Park, WonJo Jeong, Junho Kim, Sanggyu Yim and In Hwan Jung

Molecules 2022, 27(21), 7660; https://doi.org/10.3390/molecules27217660 - 7 Nov 2022

Cited by 1 | Viewed by 1735

Abstract

Colloidal quantum dots (CQDs) have a unique advantage in realizing near-infrared (NIR) photodetection since their optical properties are readily tuned by the particle size, but CQD-based photodetectors (QPDs) presently show a high dark current density (J_d) and insufficient dynamic characteristics. To overcome these two problems, we synthesized and introduced two types of conjugated polymers (CPs) by replacing the p-type CQD layer in the QPDs. The low dielectric constant and insulating properties of CPs under dark conditions effectively suppressed the J_d in the QPDs. In addition, the energy-level alignment and high-hole mobility of the CPs facilitated hole transport. Therefore, both the responsivity and specific detectivity were highly enhanced in the CP-based QPDs. Notably, the dynamic characteristics of the QPDs, such as the −3 dB cut-off frequency and rising/falling response times, were significantly improved in the CP-based QPDs owing to the sizable molecular ordering and fast hole transport of the CP in the film state as well as the low trap density, well-aligned energy levels, and good interfacial contact in the CP-based devices. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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9 pages, 2356 KiB

Open AccessArticle

Conjugated Polymers-Based Ternary Hybrid toward Unique Photophysical Properties

by Bandar Ali Al-Asbahi, Mohamad S. AlSalhi, Mohammad Hafizuddin Hj. Jumali, Amanullah Fatehmulla, Saif M. H. Qaid, Wafa Musa Mujamammi and Hamid M. Ghaithan

Molecules 2022, 27(20), 7011; https://doi.org/10.3390/molecules27207011 - 18 Oct 2022

Cited by 6 | Viewed by 1151

Abstract

The improvement of optical and optoelectronic properties of the individual poly [2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]–End capped with Dimethyl phenyl (OC1C10–PPV–DMP), and poly (9,9′-di- n -octylfluorenyl-2,7-diyl) (F8) was revealed by blending them in ternary hybrid with optimal ratio (F8/2 wt.% MEH-PPV/2 wt.% OC1C10–PPV–DMP). All individual and optimal ternary solutions were prepared via the solution-blending method followed by depositing them onto glass and ITO substrates using spin-coating technique. The semi-crystalline phase of the ternary hybrid and the strong mixing between the conjugated polymers were evidenced by observing the X-ray diffraction patterns that related to F8 into the hybrid diffractogram. The optical and optoelectronic properties of all prepared thin films were investigated in terms of absorption and emission spectra, Commission International d′Eclairage (CIE) coordinates, and current–voltage (I-V) characterizations. Emission peaks at the entire range of visible spectrum can be revealed from the ternary hybrid of the three individual conjugated polymers, producing white emission as evidenced from the emission spectrum and CIE coordinates of the hybrid. Among all fabricated organic light-emitting diodes (OLEDs) devices, the ternary hybrid-based-OLED revealed the best performance in terms of current and turn-on voltage. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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28 pages, 5172 KiB

Open AccessArticle

Head-to-Tail and Head-to-Head Molecular Chains of Poly(p-Anisidine): Combined Experimental and Theoretical Evaluation

by Lilian Rodrigues de Oliveira, Douglas de Souza Gonçalves, Adriano de Souza Carolino, William Marcondes Facchinatto, Diogo de Carvalho Menezes, Cleverton Oliveira Dias, Luiz Alberto Colnago, Yurimiler Leyet Ruiz, Ştefan Ţălu, Henrique Duarte da Fonseca Filho, Puspitapallab Chaudhuri, Pedro Henrique Campelo, Yvonne Primerano Mascarenhas and Edgar Aparecido Sanches

Molecules 2022, 27(19), 6326; https://doi.org/10.3390/molecules27196326 - 26 Sep 2022

Cited by 1 | Viewed by 1594

Abstract

Poly(p-anisidine) (PPA) is a polyaniline derivative presenting a methoxy (–OCH₃) group at the para position of the phenyl ring. Considering the important role of conjugated polymers in novel technological applications, a systematic, combined experimental and theoretical investigation was performed to obtain more insight into the crystallization process of PPA. Conventional oxidative polymerization of p-anisidine monomer was based on a central composite rotational design (CCRD). The effects of the concentration of the monomer, ammonium persulfate (APS), and HCl on the percentage of crystallinity were considered. Several experimental techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), multifractal analysis, Nuclear Magnetic Resonance (¹³C NMR), Fourier-transform Infrared spectroscopy (FTIR), and complex impedance spectroscopy analysis, in addition to Density Functional Theory (DFT), were employed to perform a systematic investigation of PPA. The experimental treatments resulted in different crystal structures with a percentage of crystallinity ranging from (29.2 ± 0.6)% (PPA1_HT) to (55.1 ± 0.2)% (PPA16_HT-HH). A broad halo in the PPA16_HT-HH pattern from 2θ = 10.0–30.0° suggested a reduced crystallinity. Needle and globular-particle morphologies were observed in both samples; the needle morphology might have been related to the crystalline contribution. A multifractal analysis showed that the PPA surface became more complex when the crystallinity was reduced. The proposed molecular structures of PPA were supported by the high-resolution ¹³C NMR results, allowing us to access the percentage of head-to-tail (HT) and head-to-head (HH) molecular structures. When comparing the calculated and experimental FTIR spectra, the most pronounced changes were observed in ν(C–H), ν(N–H), ν(C–O), and ν(C–N–C) due to the influence of counterions on the polymer backbone as well as the different mechanisms of polymerization. Finally, a significant difference in the electrical conductivity was observed in the range of 1.00 × 10⁻⁹ S.cm⁻¹ and 3.90 × 10⁻¹⁴ S.cm⁻¹, respectively, for PPA1_HT and PPA16_HT-HH. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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14 pages, 2185 KiB

Open AccessArticle

Temperature Dependence of the Electrical Properties of Na₂Ti₃O₇/Na₂Ti₆O₁₃/POMA Composites

by Salomão Dos Santos Costa, Juliana Pereira da Silva, Matheus Moraes Biondo, Edgar Aparecido Sanches, Marcos Marques Da Silva Paula, Francisco Xavier Nobre, José Anglada Rivera, Yohandys Alexis Zulueta, Milton S. Torikachvili, David Vieira Sampaio, Marcos Vinicius Dias Vermelho, Ştefan Ţălu, Lianet Aguilera Dominguez and Yurimiler Leyet

Molecules 2022, 27(18), 5756; https://doi.org/10.3390/molecules27185756 - 6 Sep 2022

Cited by 1 | Viewed by 1546

Abstract

The temperature dependence of the electrical properties of composites formed by biphasic sodium titanate and poly(o-methoxyaniline) (Na₂Ti₃O₇/Na₂Ti₆O₁₃/POMA) with different concentrations of POMA (0%, 1%, 10%, 15%, 35% and 50%) in the ceramic matrix was determined from measurements of complex impedance. The structural details were studied by means of X-ray diffraction, confirming the formation of the Na₂Ti₃O₇/Na₂Ti₆O₁₃/POMA composites. The displacement of the (200) reflection from 2θ = 10.45° to 11.15° in the composites with 10 and 15% of POMA suggested the partial replacement of H⁺ for Na⁺ in the Na₂Ti₃O₇ structure. The thermal properties were investigated by Thermogravimetry and Differential Thermal Analysis. The Thermogravimetry curves of the composites with POMA content of 1, 10 and 15% presented profiles similar to that of pure sodium titanate sample. The composites with 35 and 50% of POMA showed a process at temperatures around 60–70 °C, which was associated with water absorbed by the polymer. The analysis of the complex impedance spectroscopy measurements revealed that the electrical resistivity of the composites in the range from 0 to 35% increased by two orders of magnitude, with different values for each concentration. This positive temperature coefficient of resistivity was less noticeable in the composite with highest POMA mass content (50%). The rapid increase in resistivity caused an increase in the relaxation time calculated from the time domain. The electrical response of the 50% of POMA compound changes in relation to what was observed in the other compounds, which suggests that there is a saturation limit in the increase in resistivity with POMA content. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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21 pages, 6479 KiB

Open AccessArticle

PANI–WO₃·2H₂O Nanocomposite: Phase Interaction and Evaluation of Electronic Properties by Combined Experimental Techniques and Ab-Initio Calculation

by Adriano de Souza Carolino, Matheus Moraes Biondo, Ştefan Ţălu, Henrique Duarte da Fonseca Filho, Pedro Henrique Campelo, Jaqueline de Araújo Bezerra, Cicero Mota, Hidembergue Ordozgoith da Frota, Vanderlei Salvador Bagnato, Natalia Mayumi Inada and Edgar Aparecido Sanches

Molecules 2022, 27(15), 4905; https://doi.org/10.3390/molecules27154905 - 31 Jul 2022

Cited by 1 | Viewed by 1569

Abstract

The development of conjugated polymer-based nanocomposites by adding metallic particles into the polymerization medium allows the proposition of novel materials presenting improved electrical and optical properties. Polyaniline Emeraldine-salt form (ES–PANI) has been extensively studied due to its controllable electrical conductivity and oxidation states. On the other hand, tungsten oxide (WO₃) and its di-hydrated phases, such as WO₃·2H₂O, have been reported as important materials in photocatalysis and sensors. Herein, the WO₃·2H₂O phase was directly obtained during the in-situ polymerization of aniline hydrochloride from metallic tungsten (W), allowing the formation of hybrid nanocomposites based on its full oxidation into WO₃·2H₂O. The developed ES–PANI–WO₃·2H₂O nanocomposites were successfully characterized using experimental techniques combined with Density Functional Theory (DFT). The formation of WO₃·2H₂O was clearly verified after two hours of synthesis (PW₂ nanocomposite), allowing the confirmation of purely physical interaction between matrix and reinforcement. As a result, increased electrical conductivity was verified in the PW₂ nanocomposite: the DFT calculations revealed a charge transfer from the p-orbitals of the polymeric phase to the d-orbitals of the oxide phase, resulting in higher conductivity when compared to the pure ES–PANI. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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Review

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34 pages, 23990 KiB

Open AccessReview

Conjugated Polymer-Based Nanocomposites for Pressure Sensors

by Qin-Teng Lai, Qi-Jun Sun, Zhenhua Tang, Xin-Gui Tang and Xin-Hua Zhao

Molecules 2023, 28(4), 1627; https://doi.org/10.3390/molecules28041627 - 8 Feb 2023

Cited by 12 | Viewed by 3627

Abstract

Flexible sensors are the essential foundations of pressure sensing, microcomputer sensing systems, and wearable devices. The flexible tactile sensor can sense stimuli by converting external forces into electrical signals. The electrical signals are transmitted to a computer processing system for analysis, realizing real-time health monitoring and human motion detection. According to the working mechanism, tactile sensors are mainly divided into four types—piezoresistive, capacitive, piezoelectric, and triboelectric tactile sensors. Conventional silicon-based tactile sensors are often inadequate for flexible electronics due to their limited mechanical flexibility. In comparison, polymeric nanocomposites are flexible and stretchable, which makes them excellent candidates for flexible and wearable tactile sensors. Among the promising polymers, conjugated polymers (CPs), due to their unique chemical structures and electronic properties that contribute to their high electrical and mechanical conductivity, show great potential for flexible sensors and wearable devices. In this paper, we first introduce the parameters of pressure sensors. Then, we describe the operating principles of resistive, capacitive, piezoelectric, and triboelectric sensors, and review the pressure sensors based on conjugated polymer nanocomposites that were reported in recent years. After that, we introduce the performance characteristics of flexible sensors, regarding their applications in healthcare, human motion monitoring, electronic skin, wearable devices, and artificial intelligence. In addition, we summarize and compare the performances of conjugated polymer nanocomposite-based pressure sensors that were reported in recent years. Finally, we summarize the challenges and future directions of conjugated polymer nanocomposite-based sensors. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)

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