Monomeric Precursors Research Articles

Vinylidene Monomers Designed for Chemical Recycling

Marine pollution caused by plastic wastes increased the demand for recyclable polymer materials. In this review, we focus on the chemical recycle of vinyl polymers and polyesters, as they dominate the plastics market. Despite the easy procedure of synthesis, vinyl polymers are difficult to decompose due to the carbon backbone. Therefore, selective regeneration of monomers from polyolefins are difficult. In contrast, poly (methyl methacrylate) (PMMA) prepared by controlled radical polymerization can be depolymerized to regenerate the monomer. On the other hand, we have developed new vinyl polymers that efficiently regenerate their monomer precursors by main chain scission starting from the hydrolysis of the side group. For chemical recycling of polyesters, quantitative scission of ester bond is required. Recycling of PET has already been commercialized, but a more efficient method of the ester bond cleavage is required. Therefore, easily recyclable polyesters have been developed. In contrast, we have reported new unsaturated polyesters with chemical recyclability that recovered the monomer species. Instead of the ester bond cleavage, conjugate substitution reaction of the allyl-substituted methacrylate skeletons in unsaturated polyesters were performed under ambient condition.

Templated synthesis enhances the cobalt adsorption capacity of a porous organic polymer.

Divalent transition metals such as Co(II) are important targets for removal from water sources, due to their potential toxicity as well as their high value. In this study, we found that a series of porous organic polymers based on amide-linked tetraphenylmethane units are effective Co(II) ion adsorbents in aqueous solution. To increase the density of Co(II) binding sites, we then developed a templated synthesis in which the branched, rigid monomers are pre-assembled around Co(II) ions prior to polymerization. After polymer formation, the Co(II) template ions are removed to yield a material rich in Co(II) binding sites. Ion adsorption isotherms show that the Co(II)-templated material has an ion adsorption capacity significantly greater than those of the non-templated materials, highlighting the utility of a templated synthetic route. SEM and TEM images show the morphology of the templated polymer to be dramatically different from the non-templated polymers and to be similar in size and shape to the Co(II)-monomer precursors, emphasizing the role of the template ions in directing the formation of the resulting polymer. This guest-templated approach requires no functionalization of the generic monomer and represents a promising synthetic route to high-capacity ion adsorbents for water purification and aqueous separations.

Biocatalytic system for comparatively assessing the functional association of monolignol cytochrome P450 monooxygenases with their redox partners.

Lignin is a complex heterogenous polymer derived from oxidative radical polymerization of three monolignols, i.e., p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. These lignin monomeric precursors structurally differ in their methoxy groups of the benzene rings. In phenylpropanoid-monolignol biosynthetic pathway, the endoplasmic reticulum (ER)-resident cytochrome P450 monooxygenases, cinnamate 4-hydroxylase, coumaroyl ester 3'-hydroxylase and ferulate 5-hydroxylase, establish the key structural characteristics of monolignols. The catalysis of cytochrome P450 monooxygenase requires reducing power, which is supplied by the ER electron transfer chains, composed of cytochrome P450 oxidoreductase (CPR), cytochrome b5 reductase (CBR) and/or cytochrome b5 protein (CB5), from cofactor NADPH or NADH. While NADPH-dependent CPR serves as the typical electron donor for most P450 enzymes, in some cases, the CBR-CB5 or CPR-CB5 electron transfer system also transfers electrons to the terminal P450 enzymes. There are tremendous studies focusing on the discovery and characterization of cytochrome P450 monooxygenases. However, very limited attention has been paid to the versatility and the roles of electron transfer components in the P450 catalytic system. Due to the membrane-residence property of both P450 enzymes and electron transfer components, it is challenging to establish an effective experimental system to evaluate the functional association of P450s with their redox partners. This chapter describes a yeast cell biocatalytic system and the related experimental procedures for comparatively assessing the functional relationship of monolignol biosynthetic P450 enzymes and different redox partners in their catalysis.

Synthesis of Polydimethylsiloxane with hydrolysis and condensation methods using monomer of Dichlorodimethylsilane as vitreous humour substitute

Vitreous humour is a fluid in the eye socket, that can be disturbed due to changes in its chemical or physical structure. Polydimethylsiloxane (PDMS) that also known as a silicone oil is a liquid that is commonly used as a substitute for vitreous humour in vitreoretinal surgery. PDMS can be synthesized from the monomer of Octamethylcyclotetrasiloxane (D4). However, in Indonesia, it is still difficult to obtain D4 monomer, so an alternative is needed. In this study, a synthesis of PDMS was carried out using the monomer precursor Dichlorodimethylsilane (DCMS) through a hydrolysis method under alkaline conditions using potassium hydroxide (KOH). Then the monomer obtained from the hydrolysis process was self-polymerized by aging to form a polymer gel. The concentration of KOH was varied at 0.5, 0.6 and 1 molar. The synthesized PDMS gel have viscosity values of 0.57, 1.53 and 4.49 Pa.s, density values of 0.986, 1.004, and 1.005 g/mL, refractive index in the range of 1.4001-1.4012, and surface tension in the range 19-21 mN/m. Those values of synthesized PDMS are similar to properties of commercial PDMS. We obtained that PDMS sample that synthesized using 1 M KOH shows the fastest polymerization time.

Sono-Cavitation and Nebulization-Based Synthesis of Conjugated Microporous Polymers for Energy Storage Applications.

Conjugated microporous polymers (CMPs) are promising energy storage materials owing to their rigid and cross-linked microporous structures. However, the fabrication of nano- and microstructured CMP films for practical applications is currently limited by processing challenges. Herein, we report that combined sono-cavitation and nebulization synthesis (SNS) is an effective method for the synthesis of CMP films from a monomer precursor solution. Using the SNS, the scalable fabrication of microporous and redox-active CMP films can be achieved via the oxidative C-C coupling polymerization of the monomer precursor. Intriguingly, the ultrasonic frequency used during SNS strongly affects the synthesis of the CMP films, resulting in an approximately 30% improvement in reaction yields and ca. 1.3-1.7-times enhanced surface areas (336-542 m2/g) at a high ultrasonic frequency of 180 kHz compared to those at 120 kHz. Furthermore, we prepare highly conductive, three-dimensional porous electrodes [CMP/carbon nanotube (CNT)] by a layer-by-layer sequential deposition of CMP films and CNTs via SNS. Finally, an asymmetric supercapacitor comprising the CMP/CNT cathode and carbon anode shows a high specific capacitance of 477 F/g at 1 A/g with a wide working potential window (0-1.4 V) and robust cycling stability, exhibiting 94.4% retention after 10,000 cycles.

Polyaniline Nanofibers-Embedded Gold Nanoparticles Obtained by Template-Free Procedure with Immobilization Prospects.

In this work, template-free nanostructured conducting polymers (nCPs)-embedded gold nanoparticles (AuNPs) from aniline, thiophene and 3,4-ethylenedioxythiophene have been prepared via a one-pot sonochemical method. The synthesis of the nanocomposite (nCPs-AuNPs) was achieved in a short period of time (5–10 min), by applying high-energy ultrasound to an aqueous mixture of a CP precursor monomer and KAuCl4, in the presence of LiClO4 as dopant. The synthesis process is simpler, greener and faster in comparison to other procedures reported in the literature. Remarkably, bulk quantities of doped polyaniline PANI-AuNPs nanofibers were obtained. Subsequently, they were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR), as well as by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). PANI-AuNPs nanofibers were also employed as immobilization matrix for a benchmark enzyme, glucose oxidase (GOX). Finally, glucose was determined in real samples of white and red wines by using the so-obtained GOX-PANI-AuNPs/Sonogel-Carbon biosensor, providing outstanding recoveries (99.54%). This work may offer important insights into the synthesis of nanostructured conducting polymers and also stimulates the exploration of the applications of these nanocomposites, especially in research fields such as (bio)sensors, catalysis and composite materials.

Flame retardancy of polyurethane foams prepared from green polyols with flame retardants

AbstractPolyurethane foams (PUFs) were synthesized using bis(2‐hydroxyethylene terephthalate) (BHET), 1,4‐cyclohexanedimethanol (CHDM), and polycaprolactone diol (PCLD), and their flame retardancies were investigated. BHET and CHDM are eco‐friendly chemicals derived from waste polyethylene terephthalate, and PCLD is a precursor monomer used for synthesizing biodegradable polymers. Expandable graphite (EG) and tris(1‐chloro‐2‐isopropyl) phosphate (TCPP) were used as flame retardants. For conventional PUFs prepared with an aliphatic polyol, thermal stability was significantly enhanced with EG and TCPP through thermogravimetric analysis (TGA) and micro‐combustion calorimetry (MCC). PUFs prepared with BHET and CHDM exhibited higher thermal stability than conventional PUFs. This is attributed to the alicyclic and aromatic ring structures, which contribute to thermally stable char formation during pyrolysis. PCLD was introduced as an additional polyol, as well as a possible flame retardant, without the addition of EG and TCPP. PUFs were successfully prepared and exhibited improved resilience to burning up to 300°C due to the intrinsic thermal stability of PCLD. The limiting oxygen index (LOI) indicated that PUFs containing BHET moiety exhibited higher LOI values, whereas PUFs prepared with PCLD showed the lowest LOI value. PCLD can be used as a polyol; however, additional flame retardants are needed to obtain high flame retardancy for PUFs.

Polymerization of lactic acid produced from food waste by metal oxide-assisted dark fermentation

Lactic acid (LA) is the precursor monomer used in the production of biodegradable and eco-friendly polylactic acid (PLA) polymer. The purpose of this study was to first determine the role of nano-metal oxides in improving the production of L-LA from food waste via the dark fermentation process and then to compare the conversion of L-LA to PLA using conventional and novel catalysts. Compared to the control run without nanoparticles (NPs) addition, maximum L-LA concentration (38.86 g/L), yield (0.194 g/g- TS), and productivity (3.88 g/L-day) were achieved for iron oxide (FeOx) nanoparticles (NPs)-assisted fermentation at an optimal dosage of 15 mg/L. Nickel oxide (NiOx) and cobalt oxide (CoOx) NPs also showed similar enhancing effects for L-LA production. However, high dosages of the metal oxide NPs decreased the LA production in the medium. Moreover, a new nanocatalyst, iron phosphate (FePO4), was prepared and examined for PLA production from the as-synthesized L-LA monomeric units by ring-opening polymerization. A high yield of lactide (84.71%) was produced in a shorter reaction time (10 h) using FePO4 than the conventional tin chloride (SnCl2) catalyst. PLA polymer with molecular weights in the range of 4,900–5,200 Da was obtained using FePO4 and tin chloride dihydrates (SnCl2) catalysts under the optimized conditions. As such, this work has demonstrated a practical way to improve LA production from organic waste streams and its effective conversion to PLA for potential applications in the biomedical and bioplastic sectors.

Pulsed plasma surface modified omeprazole microparticles for delayed release application

In the present work, pulsed radio frequency (RF) plasma (PRFP) was used to functionalize omeprazole (OME) microparticles using precursor monomers methacrylic acid (MAA) and methyl methacrylate (MMA). This method had two significant factors involved – 1) ratio of monomer flow rate and 2) graded deposition by systematically varying the duty cycle of pulsed plasma. The MAA flow was set to 100 cc/min and MMA to 200 cc/min to rationalize the ratio (1:2) of monomers. Systematic variation in duty cycle (keeping ON time constant and increasing OFF time of the pulse) ensured graded deposition and functionalization of OME. The plasma functionalized OME microparticles were evaluated in-vitro via dissolution studies in pH 1.2 buffer showed a cumulative release of 3.6–9.1% within 120 min compared to complete release under 60 min in pH 6.8. Raman analysis exhibited the absence of peaks from 1800 to 1000 cm−1 and XPS studies showed an increase in oxygen-containing moieties on plasma functionalized OME surface. Thermal, NMR and HR-MS analysis confirmed successful deposition without alteration in original OME molecular structure. The decreased contact angle of post plasma treated OME resulted from hydrophilization of the OME surface. XRD data of plasma treated OME showed an improved degree of crystallinity with an increase in average crystallite size. Post plasma treated OME microparticles size through DLS corroborated well with SEM. Thus, the use of graded PRFP functionalization has proved it's potent to deliver a new, safe, and cheaper alternative to contemporary drug surface modification methods.

Temperature Gradient‐Driven Multilevel and Grayscale Patterning of Tosylate‐Doped Poly(3,4‐Ethylenedioxythiophene) Films for Flexible and Functional Electronics (Adv. Mater. Technol. 10/2021)

Patterning Conductive Polymers In article number 2100613, Tae June Kang and colleagues introduce a novel approach of patterning conductive polymers with multi-level and grayscale morphologies to prototype devices quickly and inexpensively. Selective temperature activation of the monomer precursor containing an inhibitor leads to the formation of the polymer only on the area of the desired pattern, thereby accomplishing the pattern formation.

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

Insights into the dynamic trajectories of protein filament division revealed by numerical investigation into the mathematical model of pure fragmentation.

The dynamics by which polymeric protein filaments divide in the presence of negligible growth, for example due to the depletion of free monomeric precursors, can be described by the universal mathematical equations of 'pure fragmentation'. The rates of fragmentation reactions reflect the stability of the protein filaments towards breakage, which is of importance in biology and biomedicine for instance in governing the creation of amyloid seeds and the propagation of prions. Here, we devised from mathematical theory inversion formulae to recover the division rates and division kernel information from time-dependent experimental measurements of filament size distribution. The numerical approach to systematically analyze the behaviour of pure fragmentation trajectories was also developed. We illustrate how these formulae can be used, provide some insights on their robustness, and show how they inform the design of experiments to measure fibril fragmentation dynamics. These advances are made possible by our central theoretical result on how the length distribution profile of the solution to the pure fragmentation equation aligns with a steady distribution profile for large times.

Factors affecting cuticle synthesis in apple fruit identified under field conditions

Microscopic cracks are causal in a number of commercially-important fruit skin disorders of apple, including russeting. Microcracks result from ongoing skin strain during fruit growth. Continuous cuticle deposition in developing apple fruit reduces strain and thus, microcracking. The objective was to identify factors that affect cuticle deposition under field conditions in developing apples. We fed 13C-labelled oleic acid as a precursor for cutin monomers to the surface of developing apple fruit.Cutin accounted for most of the incorporation of the oleic acid. Incorporation was limited to the surface in direct contact with the feeding solution, there was very little lateral diffusion. Increasing the concentration of the feeding solution generally increased the incorporation of 13C-labelled oleic acid. Incorporation was initially rapid, but then slowed down and approached an asymptote within three days. The duration of the incorporation period after feeding had no effect on the amount of precursor incorporated. All incorporation was essentially instantaneous. During fruit development, incorporation rate was maximal between 64 and 78 days after full bloom (DAFB), then decreased towards maturity. There was no effect of natural (foliar) shading on cutin deposition. Across five apple cultivars, incorporation of the precursor was lowest in ‘Gala’ and highest in ‘Pinova’. Those cultivars whose cuticles had higher mass per unit area also had higher incorporations of the 13C-labelled oleic acid in the cutin, but not in the wax.The potential commercial benefits of applying cutin monomer precursors in the field are discussed.

Temperature Gradient‐Driven Multilevel and Grayscale Patterning of Tosylate‐Doped Poly(3,4‐Ethylenedioxythiophene) Films for Flexible and Functional Electronics

AbstractFlexible conducting polymers are an integral part of emerging flexible and functional electronics such as rollables, photovoltaics, and wearables. Patterning the polymers into various surface morphologies is essential to fabricating such devices. Introduced here is an approach of realizing the pattern by polymerizing a precursor solution into the shape of the desired pattern on substrate. Selective temperature activation of the monomer precursor containing an inhibitor leads to the formation of the polymer only on the area of the desired pattern, thereby accomplishing the pattern formation. Even multilevel and graduated patterns, not readily realizable with the conventional lithography, can be formed autonomously. Flexible electrode arrays, a foldable supercapacitor, and an electrochromic device are fabricated to demonstrate the utility of the patterning approach and to showcase development of prototype devices quickly and inexpensively.

Development of PET Fabrics Containing N-halamine Compounds with Durable Antibacterial Property

Antibacterial textile materials are widely used in daily life, but most are disposable products with poor antibacterial durability. N-halamine can rapidly inactivate microorganisms, has good stability, and shows great potential applications in antibacterial fabrics. In this study, an N-halamine monomer precursor was synthesized and treated onto PET fabrics. The treated PET fabrics were rendered antibacterial functionality after chlorination, and exhibited good antibacterial properties with inactivation rate of 100.0 % for both E. coli O157:H7 and S. aureus. After 50 wash cycles, the chlorinated treated PET fabrics could maintain 80.0 % antibacterial efficacy, demonstrating durable antibacterial properties. Storage stability and UV irradiation tests showed that the treated PET fabrics had remarkable regenerable properties. The reduction of the breaking strength was within 12 % after treatment, which is in a satisfying range in antimicrobial finishing.

Preparation of Lactams from Cyclic Anhydrides via N‐Carboxyanhydride Intermediates

AbstractThe ring contraction‐lactamisation of anhydrides upon reaction with trimethylsilylazide in the presence of an amine catalyst has been studied. Under controlled conditions, 5,‐ 6‐ and 8‐membered ring lactams can be generated from cyclic anhydrides in an operationally simple procedure. In the case of γ‐lactams, the methodology allows for the synthesis of challenging systems incompatible with the usual disconnection involving an amine and an activated carbonyl group. The synthesis of simple larger ring lactams is hampered by inaccessible monomeric cyclic anhydride precursors ‐ a problem which can be circumvented through rigidification. Succinic anhydrides make N‐carboxyanhydrides of use in polymer chemistry and as β‐peptide precursors.

Fibril Surface-Dependent Amyloid Precursors Revealed by Coarse-Grained Molecular Dynamics Simulation.

Amyloid peptides are known to self-assemble into larger aggregates that are linked to the pathogenesis of many neurodegenerative disorders. In contrast to primary nucleation, recent experimental and theoretical studies have shown that many toxic oligomeric species are generated through secondary processes on a pre-existing fibrillar surface. Nucleation, for example, can also occur along the surface of a pre-existing fibril—secondary nucleation—as opposed to the primary one. However, explicit pathways are still not clear. In this study, we use molecular dynamics simulation to explore the free energy landscape of a free Abeta monomer binding to an existing fibrillar surface. We specifically look into several potential Abeta structural precursors that might precede some secondary events, including elongation and secondary nucleation. We find that the overall process of surface-dependent events can be described at least by the following three stages: 1. Free diffusion 2. Downhill guiding 3. Dock and lock. And we show that the outcome of adding a new monomer onto a pre-existing fibril is pathway-dependent, which leads to different secondary processes. To understand structural details, we have identified several monomeric amyloid precursors over the fibrillar surfaces and characterize their heterogeneity using a probability contact map analysis. Using the frustration analysis (a bioinformatics tool), we show that surface heterogeneity correlates with the energy frustration of specific local residues that form binding sites on the fibrillar structure. We further investigate the helical twisting of protofilaments of different sizes and observe a length dependence on the filament twisting. This work presents a comprehensive survey over the properties of fibril growth using a combination of several openMM-based platforms, including the GPU-enabled openAWSEM package for coarse-grained modeling, MDTraj for trajectory analysis, and pyEMMA for free energy calculation. This combined approach makes long-timescale simulation for aggregation systems as well as all-in-one analysis feasible. We show that this protocol allows us to explore fibril stability, surface binding affinity/heterogeneity, as well as fibrillar twisting. All these properties are important for understanding the molecular mechanism of surface-catalyzed secondary processes of fibril growth.

Tailor-Made Polyhydroxyalkanoates by Reconstructing Pseudomonas Entomophila.

Microbial polyhydroxyalkanoates (PHA) containing short- and medium/long-chain-length monomers, abbreviated as SCL-co-MCL/LCL PHAs, generate suitable thermal and mechanical properties. However, SCL-co-MCL/LCL PHAs with carbon chain longer than nine are difficult to synthesize due to the low specificity of PHA synthase PhaC and the lack of either SCL- or MCL/LCL monomer precursor fluxes. This study succeeds in reprogramming a β-oxidation weakened Pseudomonas entomophila containing synthesis pathways of SCL 3-hydroxybutyryl-CoA (3HB) from glucose and MCL/LCL 3-hydroxyalkanoyl-CoA from fatty acids with carbon chain lengths from 9 to 18, respectively, that are polymerized under a low specificity PhaC61-3 to form P(3HB-co-MCL/LCL 3HA) copolymers. Through rational flux-tuning approaches, the optimized recombinant P. entomophila accumulates 55 wt% poly-3-hydroxybutyrate in 8.4g L-1 cell dry weight. Combined with weakened β-oxidation, a series of novel P(3HB-co-MCL/LCL 3HA) copolymers with over 60 wt% PHA in 9g L-1 cell dry weight have been synthesized for the first time. P. entomophila has become a high-performing platform to generate tailor-made new SCL-co-MCL/LCL PHAs.

Broad-Spectrum Bactericidal Activity and Remarkable Selectivity of Main-Chain Sulfonium-Containing Polymers with Alternating Sequences.

Incorporation of cationic groups into polymers represents one of the most widely used strategies to prepare antibacterial materials. Sulfonium, as a typical cationic moiety, displays potent antibacterial efficacy in the form of small molecules, however, has long underperformed in polymeric systems. Herein, we developed a series of alternating polysulfoniums, where the hydrophobicity of each alternating unit can be accurately tuned by altering the monomer precursors. Excellent antibacterial activity against a broad spectrum of clinically relevant bacteria, including Methicillin-resistant Staphylococcus aureus, can be obtained in the optimal compositions with minimum bactericidal concentrations in the range of 1.25-10 μg/mL, as well as negligible hemolytic effect at polymer concentrations even up to 10000 μg/mL. Bacteria do not readily develop resistance to polysulfoniums due to the antibacterial action is possibly the membrane disrupting mechanism. This work demonstrates sulfonium-based polymers with well-defined sequences can function as a promising candidate to combat drug-resistant bacterial infection.

Liquid Stratification and Diffusion‐Induced Anisotropic Hydrogel Actuators with Excellent Thermosensitivity and Programmable Functionality

Smart hydrogel actuators with programmable anisotropic structures present fascinating prospects considering their distinctive shape transformation and controllable environmental responsiveness under external stimuli. However, the design of anisotropic hydrogels with simple and universal fabrication and programmable functionality is challenging for their valuable applications in smart actuators and soft robots. Herein, a simple, green, and devisable strategy is proposed to construct a heterogeneous porous hydrogel system by the different liquid diffusion (such as amyl alcohol, water, and ethanol) into a monomeric precursor solution of thermosensitive hydrogels. The well‐defined micro/nanoporous gradient and patterned structures related to selective liquid stratification and interfacial diffusion favor the fast response and accurate programmable deformation of hydrogels under temperature stimuli. Inspiringly, this simple diffusion‐driven tactic can be perfectly applicable for different responsive hydrogels with programmable multifunctionality by adding functional nanomaterials into the diffusible liquid. This green, general, and facile diffusion‐driven strategy provides significant guidance for fabricating environmentally responsive hydrogels with tailorable functionality for their multipurpose applications in drug delivery, bioengineering, smart actuators, and soft robots.