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18 pages, 7203 KiB

Open AccessArticle

Study on the Catalytic Performance of Nickel(II) Complexes with Distinct Triazine Support Structures in Ethylene Oligomerization via Different Experiment Designs

by Xiaobing Wei, Jiahui Li, Dan Li, Lijun Guo, Yanling Xiao and Cuiqin Li

Molecules 2025, 30(9), 1977; https://doi.org/10.3390/molecules30091977 - 29 Apr 2025

Abstract

Covalent organic frameworks hold great promise for heterogeneous catalysis because of their porous structure for gas adsorption and tunable functionality. Two triazine support materials (MAmPA-COF and MAoPA-COF) were prepared by using melamine as the linked monomer and meta-phthalaldehyde (MPA) [...] Read more.

Covalent organic frameworks hold great promise for heterogeneous catalysis because of their porous structure for gas adsorption and tunable functionality. Two triazine support materials (MAmPA-COF and MAoPA-COF) were prepared by using melamine as the linked monomer and meta-phthalaldehyde (MPA) or ortho-phthalaldehyde (OPA) as the sub-construction monomer. Two nickel(II) complexes (Ni@MAmPA-COF and Ni@MAoPA-COF) based on the synthesized COFs were prepared to use for ethylene oligomerization. The nickel(II) complexes had good catalytic activities in ethylene oligomerization. Moreover, the substituent position of the aldehyde group in the sub-construction monomer had a certain influence on the specific surface area, morphology and catalytic activity. The morphology of Ni@MAmPA-COF was spherical, while Ni@MAoPA-COF exhibited layered stacking shapes and had a large specific surface area. Ni@MAoPA-COF has a higher catalytic activity and higher selectivity for low-carbon olefins in ethylene oligomerization due to its larger specific surface area and smaller pore width. Ni@MAoPA-COF has good recyclability and still had excellent catalytic activity after three cycles. Based on the gray correlation analysis and single factor experiment, the reaction pressure was the most important factor affecting the activity of Ni@MAoPA-COF in ethylene oligomerization, and the molar ratio of Al/Ni was the main important factor affecting the selectivity. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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18 pages, 2347 KiB

Open AccessArticle

Bioconversion of Liquid and Solid Lipid Waste by Yarrowia lipolytica Yeast: A Study of Extracellular Lipase Biosynthesis and Microbial Lipid Production

by Katarzyna Wierzchowska, Karolina Szulc, Bartłomiej Zieniuk and Agata Fabiszewska

Molecules 2025, 30(4), 959; https://doi.org/10.3390/molecules30040959 - 19 Feb 2025

Viewed by 544

Abstract

This study investigated the capabilities of Yarrowia lipolytica strains to grow in media with different hydrophobic wastes from the meat industry. The yeast growth, cellular lipid accumulation, production of lipases, and degree of utilization of liquid and solid lipid wastes were studied in [...] Read more.

This study investigated the capabilities of Yarrowia lipolytica strains to grow in media with different hydrophobic wastes from the meat industry. The yeast growth, cellular lipid accumulation, production of lipases, and degree of utilization of liquid and solid lipid wastes were studied in shaken cultures in media with organic and inorganic nitrogen sources. The effects of the type of waste, initial concentration of carbon source, Yarrowia strain, and inoculum size were investigated in two experimental sets using the Latin Square 5 × 5 design method. Post-frying rapeseed oil from chicken frying was selected as the carbon source to promote biomass growth. In contrast, the solid lipid fraction from meat broths promoted efficient lipid accumulation and yeast lipolytic activity. An initial concentration of the carbon source at 8% m/v stimulated efficient lipid biosynthesis and lipase production, while 2.5% v/v inoculum provided optimal conditions for the growth and utilization of hydrophobic substrates. No significant differences were observed in the particle dispersion of the liquid and solid wastes in the culture media (span = 2.51–3.23). The maximum emulsification index (62%) was observed in the culture of the Y. lipolytica KKP 323 strain in the medium with post-frying rapeseed oil from chicken frying, which was correlated with biosurfactant synthesis. It was concluded that the type of waste, its structure, and its composition affected various physiological yeast responses. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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21 pages, 4325 KiB

Open AccessArticle

Effect of the Incorporation of an Innovative Monomer with a Quaternary Ammonium Group into a Temporary Soft Liner on Its Biological and Physicochemical Properties

by Patrycja Kula, Izabela Barszczewska-Rybarek, Anna Mertas and Grzegorz Chladek

Molecules 2025, 30(4), 941; https://doi.org/10.3390/molecules30040941 - 18 Feb 2025

Viewed by 424

Abstract

The colonizing of temporary soft lining materials in the oral cavity by yeast-like fungi, particularly Candida albicans, poses a significant risk of complications during prosthetic treatment. Various experimental materials incorporating antimicrobial additives, such as drugs, natural oils, and inorganic particles, have been [...] Read more.

The colonizing of temporary soft lining materials in the oral cavity by yeast-like fungi, particularly Candida albicans, poses a significant risk of complications during prosthetic treatment. Various experimental materials incorporating antimicrobial additives, such as drugs, natural oils, and inorganic particles, have been tested. However, these components are not chemically bonded to a polymer network, making them prone to being easily released into the surrounding environment. This study aimed to evaluate experimental soft lining materials containing liquid components with 2-(methacryloyloxy)ethyl-2-decylhydroxyethylmethylammonium bromide, a monomethacrylate monomer with a quaternary ammonium group, added at concentrations of 8.54%, 8.75%, and 14.90% by weight. The adherence of Candida albicans, cytotoxicity, glass transition temperature (Tg), sorption (WS), solubility (WSL), Shore A hardness (SHA), tensile strength (TS), and tensile bond strength (TBS) were tested. Two tested materials did not show cytotoxicity for the 2-day undiluted extracts. The Candida albicans adhesions were reduced for two materials. The SHA values compared to the control were varied but all decreased with time. WS and WSL increased compared to the control. The TBS values were at an acceptable level. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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25 pages, 3048 KiB

Open AccessArticle

Novel Quaternary Ammonium Urethane-Dimethacrylates for Copolymers with Low Water Sorption and Solubility

by Patryk Drejka, Patrycja Kula and Izabela Barszczewska-Rybarek

Molecules 2025, 30(4), 769; https://doi.org/10.3390/molecules30040769 - 7 Feb 2025

Viewed by 655

Abstract

Six novel urethane-dimethacrylates with quaternary ammonium groups (QAUDMAs) were successfully synthesized from 2-(methacryloyloxy)ethyl-2-hydroxyethylmethylalkylammonium bromide (QAHAMA-n, where n was 8 and 10) and diisocyanate (isophorone diisocyanate (IPDI), 4,4′-methylenedicyclohexyl diisocyanate (CHMDI), and 4,4′-diphenylmethane diisocyanate (MDI)). Their chemical structures were confirmed through nuclear magnetic resonance spectroscopy [...] Read more.

Six novel urethane-dimethacrylates with quaternary ammonium groups (QAUDMAs) were successfully synthesized from 2-(methacryloyloxy)ethyl-2-hydroxyethylmethylalkylammonium bromide (QAHAMA-n, where n was 8 and 10) and diisocyanate (isophorone diisocyanate (IPDI), 4,4′-methylenedicyclohexyl diisocyanate (CHMDI), and 4,4′-diphenylmethane diisocyanate (MDI)). Their chemical structures were confirmed through nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). The refractive index (RI) and density (d_m) were also determined. The novel QAUDMAs were compounded with common dental dimethacrylates and subsequently photopolymerized. The resulting copolymers, comprising QAUDMA 40 wt.%, bisphenol A glycerolate dimethacrylate (Bis-GMA) 40 wt.%, and triethylene glycol dimethacrylate (TEGDMA) 20 wt.%, were tested for water sorption (WS) and solubility (SL). The WS and SL values decreased following these orderings based on the diisocyanate: IPDI > CHMDI > MDI for WS, and MDI > CHMDI > IPDI for SL. The WS values ranged from 11.50 to 13.82 µg/mm³, and were significantly lower than the recommended maximum for dental materials, 40 µg/mm³. The SL values that met the recommended maximum, 7.5 µg/mm³, ranged from 2.67 to 6.75 µg/mm³. Only the copolymer having the QAHAMA-8- and MDI-derived QAUDMA had the SL slightly exceeding 7.5 µg/mm³, at 7.89 µg/mm³. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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18 pages, 11458 KiB

Open AccessArticle

Construction of Hydrogen-Bonded Self-Assembled Structures of Sodium 4-[(4-Chlorobenzoyl) Amino] Benzoate for Dispersion and Lubrication in Polypropylene

by Yapeng Dong, Fuhua Lin, Tianjiao Zhao, Meizhen Wang, Xinyu Hao, Dingyi Ning, Yanli Zhang, Kexin Zhang, Dan Zhou, Xiangyang Li, Jun Luo and Bo Wang

Molecules 2025, 30(3), 527; https://doi.org/10.3390/molecules30030527 - 24 Jan 2025

Viewed by 545

Abstract

Among numerous nucleating agents, organic carboxylate nucleating agents have been demonstrated to markedly improve the crystallization of polypropylene (PP). However, poor dispersion in the PP matrix affects the modification effect. In this work, erucamide (ECM) and sodium 4-[(4-chlorobenzoyl) amino] benzoate (SCAB) form a [...] Read more.

Among numerous nucleating agents, organic carboxylate nucleating agents have been demonstrated to markedly improve the crystallization of polypropylene (PP). However, poor dispersion in the PP matrix affects the modification effect. In this work, erucamide (ECM) and sodium 4-[(4-chlorobenzoyl) amino] benzoate (SCAB) form a hydrogen-bonded self-assembled structure to obtain the SCAB-ECM composite nucleating agent in order to improve the dispersion of SCAB in the PP matrix and to exert internal lubrication on the PP matrix. The molecular structure of the SCAB-ECM composite was investigated by using Fourier transform infrared spectroscopy (FT-IR), and the result showed that SCAB and ECM could form a hydrogen-bonded self-assembled structure after physical blending. The scanning electron microscopy (SEM) results visualized that ECM promoted the dispersion of SCAB due to the formation of hydrogen-bonded self-assembled structures by SCAB and ECM. The crystallization behavior was studied using differential scanning calorimetry (DSC). At the crystallization temperature of 135 °C, the K of PP, PP/ECM, PP/SCAB, and PP/SCAB-ECM were 0.0002, 0.0004, 1.1616, and 1.8539, respectively. The crystallization properties of PP/SCAB-ECM were the best, which was attributed to the fact that SCAB formed a hydrogen-bonded self-assembled structure with ECM, which promoted the dispersion of SCAB in the PP matrix. The results of the rheological behavior demonstrated that the ECM can act as a lubrication effect, which was also proved by flexural strength results. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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14 pages, 3787 KiB

Open AccessArticle

Fluorescently Tagged Poly(methyl methacrylate)s

by Fabia Grisi, Rubina Troiano, Donatella Fiore, Patrizia Gazzerro, Mariateresa Lettieri, Vincenzo Venditto and Stefania Pragliola

Molecules 2024, 29(24), 5940; https://doi.org/10.3390/molecules29245940 - 16 Dec 2024

Viewed by 793

Abstract

Plastic pollution is a global problem affecting the environment and, consequently, people’s well-being. Careful and timely end-of-life plastic recycling is certainly a way, albeit a partial one, to remedy the problem. The immediate identification and selection of the different types of plastic materials [...] Read more.

Plastic pollution is a global problem affecting the environment and, consequently, people’s well-being. Careful and timely end-of-life plastic recycling is certainly a way, albeit a partial one, to remedy the problem. The immediate identification and selection of the different types of plastic materials in the recycling process certainly facilitate its recovery and reuse, allowing the damage caused by plastic emission into the environment to be limited. Recently, new technologies for automatic sorting of plastics based upon fluorescent tagging have been considered. This article reports the synthesis and characterization of fluorescent copolymers of poly(methyl methacrylate) (PMMA) that could be potentially used as fluorescent markers of commercial PMMA. Poly(methylmetacrylate-co-2-(9-carbazolyl)ethyl methacrylate) (P(MMA-co-CEMA)) and poly(methylmetacrylate-co-7-methacryloyloxycoumarin) (P(MMA-co-MAOC)) samples containing a small number of fluorescent units (<4%) were synthesized by free-radical polymerization. All copolymer samples show chemico-physical properties like those of pure PMMA and produce fluorescence emission under 290 nm wavelength excitation. P(MMA-co-CEMA)s and P(MMA-co-MAOC)s were also tested as fluorescent dyes for PMMA identification. The experimental results demonstrate that PMMA/P(MMA-co-CEMA) and PMMA/P(MMA-co-MAOC) blends prepared using 1% by weight of fluorescent copolymer show a homogeneous morphology completely similar to pure PMMA and are still optically active. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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21 pages, 32757 KiB

Open AccessArticle

Molecular Dynamics Simulations of HEMA-Based Hydrogels for Ophthalmological Applications

by Katarzyna Filipecka-Szymczyk, Malgorzata Makowska-Janusik and Wojciech Marczak

Molecules 2024, 29(23), 5784; https://doi.org/10.3390/molecules29235784 - 7 Dec 2024

Cited by 1 | Viewed by 925

Abstract

The structural and dynamic properties of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(N-vinylpyrrolidone-co-2-hydroxyethyl methacrylate) [P(VP-co-HEMA)], dry and as hydrogels, were studied by molecular dynamics simulations. The P(VP-co-HEMA) chains differed in the number of VP mers, distributed randomly [...] Read more.

The structural and dynamic properties of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(N-vinylpyrrolidone-co-2-hydroxyethyl methacrylate) [P(VP-co-HEMA)], dry and as hydrogels, were studied by molecular dynamics simulations. The P(VP-co-HEMA) chains differed in the number of VP mers, distributed randomly or in blocks. In all considered configurations, HEMA and VP side chains proved relatively rigid and stable. Water concentration had a significant impact on their dynamic behavior. Oxygen atoms of hydroxyl and carbonyl groups of HEMA and carbonyl groups of VP are preferred sites of hydrogen bonding with water molecules. The copolymer swelling results in diffusion channels, larger in systems with high water content. In low-hydrated materials, water shows subdiffusion, while normal diffusion predominates in the high-hydrated ones. The VP side chains in copolymers with HEMA do not enhance the mobility of water. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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11 pages, 4314 KiB

Open AccessArticle

Mechanistic Study of Atomic Oxygen Erosion on Polyimide Under Electric Fields: A Molecular Dynamics and Density Functional Theory Approach

by Shengrui Zhou, Li Zhang, Liang Zou, Bilal Iqbal Ayubi and Yiwei Wang

Molecules 2024, 29(22), 5353; https://doi.org/10.3390/molecules29225353 - 14 Nov 2024

Viewed by 1000

Abstract

Polyimide (PI) is widely used in aerospace applications due to its superior insulating properties. However, the high concentration of atomic oxygen (AO) in low Earth orbit leads to significant performance degradation in PI, and the underlying mechanism of AO erosion under an electric [...] Read more.

Polyimide (PI) is widely used in aerospace applications due to its superior insulating properties. However, the high concentration of atomic oxygen (AO) in low Earth orbit leads to significant performance degradation in PI, and the underlying mechanism of AO erosion under an electric field remains unclear. This study utilizes molecular dynamics simulations to model AO erosion on PI under various electric field strengths and explores the corresponding degradation mechanisms. The results indicate that the presence of an electric field exacerbates the degradation of PI by AO. AO erosion elevates the polymer’s temperature, and the combined effects of thermal and electric stresses increase the polymer’s free volume, loosening its structure and accelerating degradation. The quantity of AO-induced erosion products increases with rising electric field strength, causing more large carbon chains to detach from the polymer surface. Density functional theory (DFT) calculations further reveal that the electric field reduces the frontier orbital energy gap in PI molecules, making AO erosion reactions more thermodynamically favorable. This work provides an atomic-level insight into the degradation mechanism of PI under AO erosion in electric fields and offers a theoretical basis for future studies on polymer resistance to AO erosion in space environments. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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12 pages, 4443 KiB

Open AccessArticle

Rheological Property Modification of a Molten-State Polyamide through the Addition of an α-Olefin–Maleic Anhydride Copolymer

by Xianzhu Mei, Quoc-Viet Do, Takaaki Narita, Misaki Yamaguchi and Masayuki Yamaguchi

Molecules 2024, 29(16), 3730; https://doi.org/10.3390/molecules29163730 - 6 Aug 2024

Cited by 1 | Viewed by 1211

Abstract

The rheological properties of a polyamide (PA) resin with low crystallinity were modified by melt-mixing it with a small amount of an alternative α-olefin–maleic anhydride copolymer as a reactive compound. Because PA has a low melting point, rheological characterization was performed over [...] Read more.

The rheological properties of a polyamide (PA) resin with low crystallinity were modified by melt-mixing it with a small amount of an alternative α-olefin–maleic anhydride copolymer as a reactive compound. Because PA has a low melting point, rheological characterization was performed over a wide temperature range. Owing to the reaction between PA and the alternative α-olefin–maleic anhydride copolymer, the blend sample behaved as a long-chain branched polymer in the molten state. The thermo-rheological complexity was obvious owing to large flow activation energy values in the low modulus region, i.e., the rheological time–temperature superposition principle was not applicable. The primary normal stress difference under steady shear was greatly increased in the wide shear rate range, leading to a large swell ratio at the capillary extrusion. Furthermore, strain hardening in the transient elongational viscosity, which is responsible for favorable processability, was clear. Because this is a simple modification method, it will be widely employed to modify the rheological properties of various polyamide resins. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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16 pages, 2330 KiB

Open AccessArticle

Effect of Particle Heterogeneity in Catalytic Copper-Containing Single-Chain Polymeric Nanoparticles Revealed by Single-Particle Kinetics

by Anjana Sathyan, Emmanouil Archontakis, A. J. H. Spiering, Lorenzo Albertazzi and Anja R. A. Palmans

Molecules 2024, 29(8), 1850; https://doi.org/10.3390/molecules29081850 - 18 Apr 2024

Cited by 1 | Viewed by 1357

Abstract

Single-chain polymeric nanoparticles (SCPNs) have been extensively explored as a synthetic alternative to enzymes for catalytic applications. However, the inherent structural heterogeneity of SCPNs, arising from the dispersity of the polymer backbone and stochastic incorporation of different monomers as well as catalytic moieties, [...] Read more.

Single-chain polymeric nanoparticles (SCPNs) have been extensively explored as a synthetic alternative to enzymes for catalytic applications. However, the inherent structural heterogeneity of SCPNs, arising from the dispersity of the polymer backbone and stochastic incorporation of different monomers as well as catalytic moieties, is expected to lead to variations in catalytic activity between individual particles. To understand the effect of structural heterogeneities on the catalytic performance of SCPNs, techniques are required that permit researchers to directly monitor SCPN activity at the single-polymer level. In this study, we introduce the use of single-molecule fluorescence microscopy to study the kinetics of Cu(I)-containing SCPNs towards depropargylation reactions. We developed Cu(I)-containing SCPNs that exhibit fast kinetics towards depropargylation and Cu-catalyzed azide-alkyne click reactions, making them suitable for single-particle kinetic studies. SCPNs were then immobilized on the surface of glass coverslips and the catalytic reactions were monitored at a single-particle level using total internal reflection fluorescence (TIRF) microscopy. Our studies revealed the interparticle turnover dispersity for Cu(I)-catalyzed depropargylations. In the future, our approach can be extended to different polymer designs which can give insights into the intrinsic heterogeneity of SCPN catalysis and can further aid in the rational development of SCPN-based catalysts. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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10 pages, 2553 KiB

Open AccessArticle

Development of Ring-Expansion RAFT Polymerization of tert-Butyl Acrylate with a Cyclic Trithiocarbonate Derivative toward the Facile Synthesis of Cyclic Polymers

by Jin Motoyanagi, Hiroki Fujii and Masahiko Minoda

Molecules 2024, 29(8), 1839; https://doi.org/10.3390/molecules29081839 - 18 Apr 2024

Cited by 2 | Viewed by 1521

Abstract

Polymers with cyclic topology have no terminal structure and, therefore, exhibit various unique physical and functional properties compared to those of linear analogs. In this paper, we report an innovative methodology for the synthesis of cyclic polymers via ring-expansion RAFT (RE-RAFT) polymerization of [...] Read more.

Polymers with cyclic topology have no terminal structure and, therefore, exhibit various unique physical and functional properties compared to those of linear analogs. In this paper, we report an innovative methodology for the synthesis of cyclic polymers via ring-expansion RAFT (RE-RAFT) polymerization of vinyl monomers using a cyclic trithiocarbonate derivative (CTTC) as a RAFT agent. RE-RAFT of tert-butyl acrylate (TBA) was performed to yield a mixture of polymers exhibiting a bimodal size exclusion chromatography (SEC) trace. Both the peak top molecular weights shifted to higher-molecular-weight regions as the monomer conversion increased. The structure of the resulting polymer mixture was examined by ¹H NMR and MALDI-TOF-MS. Detailed studies indicated that the obtained polymer of higher molecular weight was one of the large-sized cyclic polymers generated by the fusion of smaller-sized cyclic polymers during the RE-RAFT polymerization process. This approach opens the door to the simple synthesis of well-controlled cyclic polymers with complex structures, such as alternating and multi-block repeat unit sequences. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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23 pages, 13534 KiB

Open AccessArticle

Benchmark Study of Epoxy Coatings with Selection of Bio-Based Phenalkamine versus Fossil-Based Amine Crosslinkers

by Pieter Samyn, Joey Bosmans and Patrick Cosemans

Molecules 2023, 28(11), 4259; https://doi.org/10.3390/molecules28114259 - 23 May 2023

Cited by 7 | Viewed by 2903

Abstract

The phenalkamines (PK) derived from cardanol oil can be used as a bio-based crosslinker for epoxy coatings as an alternative for traditional fossil amines (FA). First, the reaction kinetics of an epoxy resin with four PK and FA crosslinkers are compared by differential [...] Read more.

The phenalkamines (PK) derived from cardanol oil can be used as a bio-based crosslinker for epoxy coatings as an alternative for traditional fossil amines (FA). First, the reaction kinetics of an epoxy resin with four PK and FA crosslinkers are compared by differential scanning calorimetry, illustrating a fast reaction rate and higher conversion of PK at room temperature in parallel with a moderate exothermal reaction. Second, the performance of coatings with various concentrations of PK and PK/FA ratios indicates good mixing compatibility between crosslinkers resulting in higher hardness, scratch resistance, hydrophobicity, and abrasive wear resistance of coatings with PK. The superior performance is confirmed over a broad range of resin/crosslinker ratios, facilitating the processing with viscosity profiles depending on the PK type. Although fossil- and bio-based crosslinkers have different chemical structures, the unique linear relationships between intrinsic mechanical properties (i.e., ductility and impact resistance) and coating performance indicate that the degree of crosslinking is a primary parameter controlling coating performance, where PK simultaneously provides high hardness and ductility. In conclusion, the optimization of the processing range for bio-based PK as a crosslinker for epoxy coatings delivers suitable processing conditions and superior mechanical performance compared to traditional amine crosslinkers. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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12 pages, 5815 KiB

Open AccessArticle

Co-Crystallization between Aliphatic Polyesters through Co-Inclusion Complexation with Small Molecule

by Jia-Yao Chen, Xue-Wen Zhang, Tian-Yu Wu and Hai-Mu Ye

Molecules 2023, 28(10), 4091; https://doi.org/10.3390/molecules28104091 - 15 May 2023

Cited by 1 | Viewed by 1646

Abstract

Crystalline/crystalline blends of polymer have shown advantages in the preparation of new polymeric materials. However, the regulation of co-crystallization in a blend is still full of challenges due to the preferential self-crystallization driven by thermodynamics. Here, an inclusion complex approach is proposed to [...] Read more.

Crystalline/crystalline blends of polymer have shown advantages in the preparation of new polymeric materials. However, the regulation of co-crystallization in a blend is still full of challenges due to the preferential self-crystallization driven by thermodynamics. Here, an inclusion complex approach is proposed to facilitate the co-crystallization between crystalline polymers, because the crystallization process displays a prominent kinetics advantage when polymer chains are released from the inclusion complex. Poly(butylene succinate) (PBS), poly(butylene adipate) (PBA) and urea are chosen to form co-inclusion complexes, where PBS and PBA chains play as isolated guest molecules and urea molecules construct the host channel framework. The coalesced PBS/PBA blends are obtained by fast removing the urea framework and systematically investigated by differential scanning calorimetry, X-ray diffraction, proton nuclear magnetic resonance and Fourier transformation infrared spectrometry. It is demonstrated that PBA chains are co-crystallized into PBS extended-chain crystals in the coalesced blends, while such a phenomenon has not been detected in simply co-solution-blended samples. Though PBA chains could not be totally accommodated in the PBS extended-chain crystals, their co-crystallized content increases with the initial feeding ratio of PBA. Consequently, the melting point of the PBS extended-chain crystal gradually declines from 134.3 °C to 124.2 °C with an increasing PBA content. The PBA chains playing as defects mainly induce lattice expansion along the a-axis. In addition, when the co-crystals are soaked in tetrahydrofuran, some of the PBA chains are extracted out, leading to damage to the correlative PBS extended-chain crystals. This study shows that co-inclusion complexation with small molecules could be an effective way to promote co-crystallization behavior in polymer blends. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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18 pages, 5492 KiB

Open AccessArticle

The Synergistic Effect of Triazine and Phosphaphenanthrene Units on the Physico-Chemical Behavior of Polyimides

by Irina Butnaru and Mariana-Dana Damaceanu

Molecules 2023, 28(10), 4072; https://doi.org/10.3390/molecules28104072 - 13 May 2023

Cited by 4 | Viewed by 1898

Abstract

With the aim to develop polymers with appealing, multifunctional characteristics, a series of polyimides were designed by anchoring 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) units on the main polymer chains containing 1,3,5-triazine and several flexible moieties, such as ether, hexafluoroisopropylidene, or isopropylidene. A detailed study was [...] Read more.

With the aim to develop polymers with appealing, multifunctional characteristics, a series of polyimides were designed by anchoring 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) units on the main polymer chains containing 1,3,5-triazine and several flexible moieties, such as ether, hexafluoroisopropylidene, or isopropylidene. A detailed study was conducted to establish structure–property correlations, with a focus on the synergistic effectiveness of triazine and DOPO moieties on the overall features of polyimides. The results evidenced good solubility of the polymers in organic solvents, their amorphous nature with short-range regular-packed polymer chains, and high thermal stability with no glass transition temperature below 300 °C. Spectrophotometric measurements revealed the existence of a strong charge transfer complex in these polymers that led to a “black” appearance, which generated broad absorption bands spanning on the overall visible range. Nevertheless, these polymers displayed green light emission associated with 1,3,5-triazine emitter. The electrochemical characteristics of the polyimides in solid state demonstrated their strong n-type doping character induced by three different structural elements with electron-acceptance capability. The useful properties of these polyimides, including optical, thermal, electrochemical, aesthetics, and opaqueness, endow them with several possible applications in the microelectronic field, such as protecting layers for the inner circuits against UV light deterioration. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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12 pages, 4672 KiB

Open AccessArticle

Rational Design of Disulfide Bridges in BbPETase^CD for Enhancing the Enzymatic Performance in PET Degradation

by Dongjian Huang, Lin Zhang and Yan Sun

Molecules 2023, 28(8), 3528; https://doi.org/10.3390/molecules28083528 - 17 Apr 2023

Cited by 8 | Viewed by 2847

Abstract

Polyethylene terephthalate (PET) is one of the most prevalent transparent thermoplastics. It is commonly utilized due to its low cost and high durability. With the massive accumulation of waste PET, however, serious environmental pollution has become a global problem. Compared to traditional chemical [...] Read more.

Polyethylene terephthalate (PET) is one of the most prevalent transparent thermoplastics. It is commonly utilized due to its low cost and high durability. With the massive accumulation of waste PET, however, serious environmental pollution has become a global problem. Compared to traditional chemical degradation, biodegradation of PET catalyzed by PET hydrolase (PETase) is more environmentally friendly and energy-efficient. BbPETase^CD from the Burkholderiales bacterium is a PETase that shows favorable properties for application in the biodegradation of PET. To enhance the enzymatic performance of this enzyme, this work focuses on the rational design of disulfide bridges in BbPETase^CD. We utilized two computational algorithms to predict the probable disulfide-bridge mutations in BbPETase^CD, and five variants were acquired from the computations. Among these, the N364C/D418C variant with one additional disulfide bond showed higher expression than the wild-type enzyme (WT) and the best enzymatic performance. The melting temperature (T_m) of the N364C/D418C variant presented an increase of 14.8 °C over that of WT (56.5 °C), indicating that the additional disulfide bond significantly raised the thermodynamic stability of the enzyme. Kinetic experiments at different temperatures also demonstrated the thermal stability increase of the variant. The variant also showed significantly increased activity over WT when using bis(hydroxyethyl) terephthalate (BHET) as the substrate. More remarkably, the N364C/D418C variant exhibited approximately an 11-fold increase over the WT enzyme in the long-term (14 days) degradation of PET films. The results prove that the rationally designed disulfide bond significantly improved the enzymatic performance of the enzyme for PET degradation. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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16 pages, 4112 KiB

Open AccessArticle

Hydrogel-Film-Fabricated Fluorescent Biosensors with Aggregation-Induced Emission for Albumin Detection through the Real-Time Modulation of a Vortex Fluidic Device

by Qi Hu, Xuan Luo, Damian Tohl, Anh Tran Tam Pham, Colin Raston and Youhong Tang

Molecules 2023, 28(7), 3244; https://doi.org/10.3390/molecules28073244 - 5 Apr 2023

Cited by 2 | Viewed by 2318

Abstract

Hydrogels have various promising prospects as a successful platform for detecting biomarkers, and human serum albumin (HSA) is an important biomarker in the diagnosis of kidney diseases. However, the difficult-to-control passive diffusion kinetics of hydrogels is a major factor affecting detection performance. This [...] Read more.

Hydrogels have various promising prospects as a successful platform for detecting biomarkers, and human serum albumin (HSA) is an important biomarker in the diagnosis of kidney diseases. However, the difficult-to-control passive diffusion kinetics of hydrogels is a major factor affecting detection performance. This study focuses on using hydrogels embedded with aggregation-induced emission (AIE) fluorescent probe TC426 to detect HSA in real time. The vortex fluidic device (VFD) technology is used as a rotation strategy to control the reaction kinetics and micromixing during measurement. The results show that the introduction of VFD could significantly accelerate its fluorescence response and effectively improve the diffusion coefficient, while VFD processing could regulate passive diffusion into active diffusion, offering a new method for future sensing research. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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33 pages, 10171 KiB

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Enzymes in “Green” Synthetic Chemistry: Laccase and Lipase

by Dieter M. Scheibel, Ioan Pavel Ivanov Gitsov and Ivan Gitsov

Molecules 2024, 29(5), 989; https://doi.org/10.3390/molecules29050989 - 24 Feb 2024

Cited by 10 | Viewed by 3360

Abstract

Enzymes play an important role in numerous natural processes and are increasingly being utilized as environmentally friendly substitutes and alternatives to many common catalysts. Their essential advantages are high catalytic efficiency, substrate specificity, minimal formation of byproducts, and low energy demand. All of [...] Read more.

Enzymes play an important role in numerous natural processes and are increasingly being utilized as environmentally friendly substitutes and alternatives to many common catalysts. Their essential advantages are high catalytic efficiency, substrate specificity, minimal formation of byproducts, and low energy demand. All of these benefits make enzymes highly desirable targets of academic research and industrial development. This review has the modest aim of briefly overviewing the classification, mechanism of action, basic kinetics and reaction condition effects that are common across all six enzyme classes. Special attention is devoted to immobilization strategies as the main tools to improve the resistance to environmental stress factors (temperature, pH and solvents) and prolong the catalytic lifecycle of these biocatalysts. The advantages and drawbacks of methods such as macromolecular crosslinking, solid scaffold carriers, entrapment, and surface modification (covalent and physical) are discussed and illustrated using numerous examples. Among the hundreds and possibly thousands of known and recently discovered enzymes, hydrolases and oxidoreductases are distinguished by their relative availability, stability, and wide use in synthetic applications, which include pharmaceutics, food and beverage treatments, environmental clean-up, and polymerizations. Two representatives of those groups—laccase (an oxidoreductase) and lipase (a hydrolase)—are discussed at length, including their structure, catalytic mechanism, and diverse usage. Objective representation of the current status and emerging trends are provided in the main conclusions. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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18 pages, 2329 KiB

Open AccessReview

Selenium in Peptide Chemistry

by Özge Pehlivan, Mateusz Waliczek, Monika Kijewska and Piotr Stefanowicz

Molecules 2023, 28(7), 3198; https://doi.org/10.3390/molecules28073198 - 4 Apr 2023

Cited by 17 | Viewed by 3927

Abstract

In recent years, researchers have been exploring the potential of incorporating selenium into peptides, as this element possesses unique properties that can enhance the reactivity of these compounds. Selenium is a non-metallic element that has a similar electronic configuration to sulfur. However, due [...] Read more.

In recent years, researchers have been exploring the potential of incorporating selenium into peptides, as this element possesses unique properties that can enhance the reactivity of these compounds. Selenium is a non-metallic element that has a similar electronic configuration to sulfur. However, due to its larger atomic size and lower electronegativity, it is more nucleophilic than sulfur. This property makes selenium more reactive toward electrophiles. One of the most significant differences between selenium and sulfur is the dissociation of the Se-H bond. The Se-H bond is more easily dissociated than the S-H bond, leading to higher acidity of selenocysteine (Sec) compared to cysteine (Cys). This difference in acidity can be exploited to selectively modify the reactivity of peptides containing Sec. Furthermore, Se-H bonds in selenium-containing peptides are more susceptible to oxidation than their sulfur analogs. This property can be used to selectively modify the peptides by introducing new functional groups, such as disulfide bonds, which are important for protein folding and stability. These unique properties of selenium-containing peptides have found numerous applications in the field of chemical biology. For instance, selenium-containing peptides have been used in native chemical ligation (NCL). In addition, the reactivity of Sec can be harnessed to create cyclic and stapled peptides. Other chemical modifications, such as oxidation, reduction, and photochemical reactions, have also been applied to selenium-containing peptides to create novel molecules with unique biological properties. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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17 pages, 2544 KiB

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Antifoaming Agent for Lubricating Oil: Preparation, Mechanism and Application

by Chenfei Ren, Xingxing Zhang, Ming Jia, Chenming Ma, Jiaxin Li, Miaomiao Shi and Yunyin Niu

Molecules 2023, 28(7), 3152; https://doi.org/10.3390/molecules28073152 - 31 Mar 2023

Cited by 7 | Viewed by 5577

Abstract

In the process of using lubricating oil, it is inevitable that bubbles will be produced, which can not only accelerate the oil’s oxidation and shorten the oil change cycle but also reduce its fluidity and lubricity, aggravate the wear of mechanical parts and [...] Read more.

In the process of using lubricating oil, it is inevitable that bubbles will be produced, which can not only accelerate the oil’s oxidation and shorten the oil change cycle but also reduce its fluidity and lubricity, aggravate the wear of mechanical parts and produce an air lock that interrupts the oil pump supply and causes an oil shortage accident. This paper mainly and comprehensively discusses the foaming process and its harm, the defoaming mechanism and defoaming method of lubricating oil, more specifically, the synthesis, application, advantages, disadvantages and current situation of three kinds of chemical defoaming agents, namely silicone defoaming agent, non-silicone defoaming agent and compound defoaming agent. Finally, the paper looks forward to the future development of special defoaming agents for lubricating oil. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Macromolecular Chemistry)

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