Polymers

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12 pages, 2939 KiB

Open AccessEditor’s ChoiceArticle

Ring-Opening Polymerization of rac-β-Butyrolactone Promoted by New Tetradentate Thioether-Amide Ligand-Type Zinc Complexes

by Salvatore Impemba, Gabriele Manca, Irene Tozio and Stefano Milione

Polymers 2023, 15(22), 4366; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15224366 - 09 Nov 2023

Cited by 1 | Viewed by 823

Abstract

In this work, thioether-amide ligands featuring a combination of hard amide groups with soft donor groups have been employed to develop new zinc catalysts for the ring-opening polymerization of cyclic esters. All complexes were prepared in high yields through alkane elimination reactions with [...] Read more.

In this work, thioether-amide ligands featuring a combination of hard amide groups with soft donor groups have been employed to develop new zinc catalysts for the ring-opening polymerization of cyclic esters. All complexes were prepared in high yields through alkane elimination reactions with diethyl zinc and characterized using nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) characterization provided insight into the parameters that influence catalytic activity, such as steric hindrance at the metal center, Lewis acidity and electronic density of thioether-amide ligands. In the presence of one equivalent of isopropanol, all complexes were active in the ring-opening polymerization of rac-β-butyrolactone. Quantitative conversion of 100 monomer equivalents was achieved within 1 h at 80 °C in a toluene solution. Number-average molecular weights increased linearly with monomer conversion; the values were in optimal agreement with those expected, and polydispersity index values were narrow and relatively constant throughout the course of polymerization. The most active complex was also effective in the ring-opening polymerization of ε-caprolactone and L-lactide. To propose a reliable reaction path, DFT calculations were undertaken. In the first step of the reaction, the acidic proton of the alcohol is transferred to the basic nitrogen atom of the amide ligand coordinated to the zinc ion. This leads to the alcoholysis of the Zn-N bond and the formation of an alcoholate derivative that starts the polymerization. In subsequent steps, the reaction follows the classical coordination–insertion mechanism. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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21 pages, 11311 KiB

Open AccessArticle

Thin Films of a Complex Polymer Compound for the Inhibition of Iron Alloy Corrosion in a H₃PO₄ Solution

by Yaroslav G. Avdeev, Tatyana A. Nenasheva, Andrei Yu. Luchkin, Andrei I. Marshakov and Yurii I. Kuznetsov

Polymers 2023, 15(21), 4280; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15214280 - 31 Oct 2023

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Abstract

The etching of iron alloy items in a H₃PO₄ solution is used in various human activities (gas and oil production, metalworking, transport, utilities, etc.). The etching of iron alloys is associated with significant material losses due to their corrosion. It [...] Read more.

The etching of iron alloy items in a H₃PO₄ solution is used in various human activities (gas and oil production, metalworking, transport, utilities, etc.). The etching of iron alloys is associated with significant material losses due to their corrosion. It has been found that an efficient way to prevent the corrosion of iron alloys in a H₃PO₄ solution involves the formation of thin complex compound films consisting of the corrosion inhibitor molecules of a triazole derivative (TrzD) on their surface. It has been shown that the protection of iron alloys with a mixture of TrzD + KNCS in a H₃PO₄ solution is accompanied by the formation of a thin film of coordination polymer compounds thicker than 4 nm consisting of TrzD molecules, Fe²⁺ cations and NCS⁻. The layer of the complex compound immediately adjacent to the iron alloy surface is chemisorbed on it. The efficiency of this composition as an inhibitor of iron alloy corrosion and hydrogen bulk sorption by iron alloys is determined by its ability to form a coordination polymer compound layer, as experimentally confirmed by electrochemical, AFM and XPS data. The efficiency values of inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C₆H₁₂N₄ at a temperature of 20 ± 1 °C are 97% and 98%, respectively. The kinetic parameters of the limiting processes of hydrogen evolution and permeation into an iron alloy in a H₃PO₄ solution were determined. A significant decrease in both the reaction rate of hydrogen evolution and the rate of hydrogen permeation into the iron alloy by the TrzD and its mixtures in question was noted. The inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C₆H₁₂N₄ decreased the total hydrogen concentration in the iron alloy up to 9.3- and 11-fold, respectively. The preservation of the iron alloy plasticity in the corrosive environment containing the inhibitor under study was determined by a decrease in the hydrogen content in the alloy bulk. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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21 pages, 5616 KiB

Open AccessArticle

Preparation and Characterization of Silica-Based Ionogel Electrolytes and Their Application in Solid-State Lithium Batteries

by Ji-Cong Huang, Yui Whei Chen-Yang and Jiunn-Jer Hwang

Polymers 2023, 15(17), 3505; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15173505 - 22 Aug 2023

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Abstract

In this study, tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) were used as precursors for silica, combined with the ionic liquid [BMIM-ClO₄]. Lithium perchlorate was added as the lithium-ion source, and formic acid was employed as a catalyst to synthesize silica ionogel [...] Read more.

In this study, tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) were used as precursors for silica, combined with the ionic liquid [BMIM-ClO₄]. Lithium perchlorate was added as the lithium-ion source, and formic acid was employed as a catalyst to synthesize silica ionogel electrolytes via the sol–gel method. FT-IR and NMR identified the self-prepared ionic liquid [BMIM-ClO₄], and its electrochemical window was determined using linear sweep voltammetry (LSV). The properties of the prepared silica ionogel electrolytes were further investigated through FT-IR, DSC, and ²⁹Si MAS NMR measurements, followed by electrochemical property measurements, including conductivity, electrochemical impedance spectroscopy (EIS), LSV, and charge–discharge tests. The experimental results showed that adding methyltriethoxysilane (MTES) enhanced the mechanical strength of the silica ionogel electrolyte, simplifying its preparation process. The prepared silica ionogel electrolyte exhibited a high ionic conductivity of 1.65 × 10⁻³ S/cm. In the LSV test, the silica ionogel electrolyte demonstrated high electrochemical stability, withstanding over 5 V without oxidative decomposition. Finally, during the discharge–charge test, the second-cycle capacity reached 108.7 mAh/g at a discharge–charge rate of 0.2 C and a temperature of 55 °C. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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14 pages, 2698 KiB

Open AccessArticle

Comprehensive Kinetic Study of PET Pyrolysis Using TGA

by Zaid Alhulaybi and Ibrahim Dubdub

Polymers 2023, 15(14), 3010; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15143010 - 11 Jul 2023

Cited by 2 | Viewed by 1585

Abstract

The pyrolysis of polyethylene terephthalate (PET) is a well-known process for producing high fuel value. This paper aims to study the kinetics of PET pyrolysis reactions at 4 different heating rates (2, 5, 10, and 20 K min⁻¹) using thermogravimetric analysis [...] Read more.

The pyrolysis of polyethylene terephthalate (PET) is a well-known process for producing high fuel value. This paper aims to study the kinetics of PET pyrolysis reactions at 4 different heating rates (2, 5, 10, and 20 K min⁻¹) using thermogravimetric analysis (TGA) data. TGA data show only one kinetic reaction within the temperature ranges of 650 to 750 K. Five different model-free models, namely, the Freidman (FR), Flynn–Wall–Qzawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink (STK), and distributed activation energy model (DAEM), were fitted to the experimental data to obtain the activation energy (E_a) and the pre-exponential factor (A₀) of the reaction kinetics. The Coats–Redfern (CR) model equation was fitted with the help of master plot (Criado’s) to identify the most convenient reaction mechanism for this system. E_a’s values were determined by the application of the five aforementioned models and were found to possess an average value of 212 kJ mol⁻¹. The mechanism of PET pyrolysis reaction was best described by first-order reaction kinetics; this was confirmed by the compensation. Further thermodynamic parameter analysis indicated that the reaction was endothermic in nature. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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16 pages, 4534 KiB

Open AccessArticle

Synthesis and Characterization of Poly(DL-lactide) Containing Fluorene Structures

by Chung-Fu Yu, Syang-Peng Rwei, Shung-Jim Yang, Wen-Chin Tsen and Li-Huei Lin

Polymers 2023, 15(11), 2555; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15112555 - 01 Jun 2023

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Abstract

9,9-bis[4-(2-hydroxy-3-acryloyloxypropoxy)phenyl]fluorene (BPF) hydroxyl groups (-OH) were used as initiators in the ring-opening polymerization reaction with DL-lactide monomers at different molar ratios to synthesize a Poly(DL-lactide) polymer containing bisphenol fluorene structure and acrylate functional groups (DL-BPF). The polymer’s structure and molecular weight range were [...] Read more.

9,9-bis[4-(2-hydroxy-3-acryloyloxypropoxy)phenyl]fluorene (BPF) hydroxyl groups (-OH) were used as initiators in the ring-opening polymerization reaction with DL-lactide monomers at different molar ratios to synthesize a Poly(DL-lactide) polymer containing bisphenol fluorene structure and acrylate functional groups (DL-BPF). The polymer’s structure and molecular weight range were analyzed using NMR (¹H, ¹³C) and gel permeation chromatography. DL-BPF was then subjected to photocrosslinking using the photoinitiator Omnirad 1173, resulting in the formation of an optically transparent crosslinked polymer. Characterization of the crosslinked polymer involved analyzing its gel content, refractive index, thermal stability (via differential scanning thermometry (DSC) and thermogravimetric analysis (TGA)), as well as conducting cytotoxicity tests. The crosslinked copolymer exhibited a maximum refractive index of 1.5276, a maximum glass transition temperature of 61.1 °C, and cell survival rates higher than 83% in the cytotoxicity tests. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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14 pages, 4198 KiB

Open AccessArticle

Effect of Silicone Modifier on the Physical Properties of Flexible Silica Aerogels

by Kun-Hao Luo, Min-Si Yan, Chen-An Chang, Chih-Wei Weng and Jui-Ming Yeh

Polymers 2023, 15(9), 2043; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15092043 - 25 Apr 2023

Viewed by 1279

Abstract

Research on the development of flexible silica aerogels (FSAs) has been ongoing due to their excellent thermal insulation, low density, and high elasticity. However, the physical properties of FSAs, such as density, thermal conductivity, mechanical strength, and surface wettability, are highly dependent on [...] Read more.

Research on the development of flexible silica aerogels (FSAs) has been ongoing due to their excellent thermal insulation, low density, and high elasticity. However, the physical properties of FSAs, such as density, thermal conductivity, mechanical strength, and surface wettability, are highly dependent on the preparation conditions. To achieve the desired properties of FSAs for various applications, it is necessary to develop a method to fine-tune their physical properties. In this paper, two modifiers of methyltrimethoxysilane (MTMS)/trimethylethoxysilane (TMES) were employed to fine-tune the bulk density of a series of flexible silica aerogels (FSAs), reflecting a series of FSAs with fine-tunable physical properties. First, the precursor was synthesized by a click reaction between vinyltrimethoxysilane (VTMS) and 2,2′ (ethylenedioxy) diethanethiol (EDDET). The VTMS, EDDET, and the as-prepared precursor were characterized by FT-IR and NMR spectroscopy. Subsequently, the precursor was converted into a series of FSAs (denoted by FSA, FSA-M, and FSA-T) through conventional sol-gel reactions with/without MTMS/TMES. Chemical structures of synthesized FSAs were confirmed by ¹³C and ²⁹Si solid-state NMR spectroscopy. The porous structure of FSAs was identified by BET and SEM, respectively. Physical properties, such as thermal conductivity, mechanical strength, and surface wettability of FSAs were determined by a Hot Disk, durometer/DMA in compression mode, and contact angle measurements, respectively. This study found FSAs containing none, 1 wt%, 5 wt%, and 10 wt% of MTMS increase the density of FSAs from 0.419 g/cm³ (FSA), 0.423 g/cm³ (FSA-M1), 0.448 g/cm³ (FSA-M5), and 0.456 g/cm³ (FSA-M10). It should be noted that the thermal conductivity, surface hardness, bulk mechanical strength, and hydrophobicity of FSA-Ms of increasing MTMS loading were all found to show a rising trend, while FSA-Ts exhibited lower density. FSA-T10 exhibited lower thermal conductivity, surface hardness, and bulk mechanical strength as compared to FSA. However, it was found to show higher hydrophobicity as compared to that of FSA. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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14 pages, 4878 KiB

Open AccessArticle

Sustainable Chitosan/Polybenzoxazine Films: Synergistically Improved Thermal, Mechanical, and Antimicrobial Properties

by Thirukumaran Periyasamy, Shakila Parveen Asrafali, Chaitany Jayprakash Raorane, Vinit Raj, Divya Shastri and Seong-Cheol Kim

Polymers 2023, 15(4), 1021; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15041021 - 17 Feb 2023

Cited by 6 | Viewed by 1700

Abstract

Polybenzoxazines (Pbzs) are considered as an advanced class of thermosetting phenolic resins as they overcome the shortcomings associated with novolac and resole type phenolic resins. Several advantages of these materials include curing without the use of catalysts, release of non-toxic by-products during curing, [...] Read more.

Polybenzoxazines (Pbzs) are considered as an advanced class of thermosetting phenolic resins as they overcome the shortcomings associated with novolac and resole type phenolic resins. Several advantages of these materials include curing without the use of catalysts, release of non-toxic by-products during curing, molecular design flexibility, near-zero shrinkage of the cured materials, low water absorption and so on. In spite of all these advantages, the brittleness of Pbz is a knotty problem that could be solved by blending with other polymers. Chitosan (Ch), has been extensively investigated in this context, but its thermal and mechanical properties rule out its practical applications. The purpose of this work is to fabricate an entirely bio-based Pbz films by blending chitosan with benzoxazine (Bzo), which is synthesized from curcumin and furfuryl amine (curcumin-furfurylamine-based Bzo, C-fu), by making use of a benign Schiff base chemistry. FT-IR and ¹H-NMR spectroscopy were used to confirm the structure of C-fu. The impact of chitosan on benzoxazine polymerization was examined using FT-IR and DSC analyses. Further evidence for synergistic interactions was provided by DSC, SEM, TGA, and tensile testing. By incorporating C-fu into Ch, Ch-grafted-poly(C-fu) films were obtained with enhanced chemical resistance and tensile strength. The bio-based polymer films produced inhibited the growth of Staphylococcus aureus and Escherichia coli, by reversible labile linkages, expanding Ch galleries, and releasing phenolic species, which was 125 times stronger than bare Ch. In addition, synthesized polybenzoxazine films [Ch/Poly(C-fu)] showed significant dose-dependent antibiofilm activity against S. aureus and E. coli as determined by confirmed by confocal laser scanning microscopy (CLSM). This study suggests that bio-based Ch-graft-polymer material provide improved anti-bacterial property and characteristics that may be considered as a possibility in the near future for wound healing and implant applications. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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12 pages, 3804 KiB

Open AccessArticle

Numerical Study for the Performance of Viscoelastic Fluids on Displacing Oil Based on the Fractional-Order Maxwell Model

by Jingting Huang, Liqiong Chen, Shuxuan Li, Jinghang Guo and Yuanyuan Li

Polymers 2022, 14(24), 5381; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14245381 - 08 Dec 2022

Cited by 2 | Viewed by 1032

Abstract

In the study of polymer flooding, researchers usually ignore the genetic stress properties of viscoelastic fluids. In this paper, we investigate the process of viscoelastic fluid flooding the remaining oil in the dead end. This work uses the fractional-order Maxwell in the traditional [...] Read more.

In the study of polymer flooding, researchers usually ignore the genetic stress properties of viscoelastic fluids. In this paper, we investigate the process of viscoelastic fluid flooding the remaining oil in the dead end. This work uses the fractional-order Maxwell in the traditional momentum equation. Furthermore, a semi-analytic solution of the flow control equation for fractional-order viscoelastic fluids is derived, and the oil-repelling process of viscoelastic fluids is simulated by a secondary development of OpenFOAM. The results show that velocity fractional-order derivative α significantly affects polymer solution characteristics, and increasing the elasticity of the fluid can significantly improve the oil repelling efficiency. Compared to the Newtonian fluid flow model, the fractional order derivative a and relaxation time b in the two-parameter instanton equation can accurately characterize the degree of elasticity of the fluid. The smaller the a, the more elastic the fluid is and the higher the oil-repelling efficiency. The larger the b, the less elastic the fluid is and the lower the cancellation efficiency. Moreover, the disturbance of the polymer solution to the dead end is divided into two elastic perturbation areas. The stronger the elasticity of the polymer solution, the higher the peak value of the area in the dead end and the higher the final oil displacement efficiency. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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