Mechanism Of Polycondensation Research Articles

Shining light on green chemistry: BODIPY-infused porphyrin nanocomposite-enzymatic photocatalyst boosts selective aldehydes hydrogenation and organic transformation under solar spectrum

Photo-bio enzyme coupled biotransformation solar radiation driven processes grasp promising in the production of solar driven organic chemicals. Here we reported the synthesis and development of (NH2)4TPP@BODIPY photocatalyst, which was constructed from 5,10,15,20 tetrakis (4 amino phenyl) porphyrin and BODIPY {5,5-difluoro-3,7-bis((E)-4-nitrobenzylidene)-10-(4-nitrophenyl)-5,7-dihydro-3H-4l4,5l4-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinine} molecule through poly-condensation mechanism resulting in the composite formation which manifest excellent light harvesting properties and photocatalytic reactions with suitable satisfactory band gap and formation of huge electrons channels which bears the organic transformation (98 %) and photo-regeneration of NADH (66.92 %) in 60 min which further enhances reduction of aldehyde resulting alcohol production. The highly selective aldehyde hydrogenation process is proposed via coordination of alcohol dehydrogenase with (NH2)4TPP@BODIPY assistant reduces from the coupling process; regeneration of nicotinamide adenine dinucleotide (NADH). Our results show an excellent benchmark for the NAD+ co-factor coupled solar-driven alcohol production via (NH2)4TPP@BODIPY photocatalyst.

Refined kinetic model for the simulation of polycarbonate synthesis via continuous melt transesterification

This paper establishes a kinetic model for the polymerization and condensation occurring during the melt transesterification of bisphenol A (BPA) and diphenyl carbonate (DPC). The model is based on molecular fragments and functional groups, treating polymers as an assembly of four types of chain segments. This study delves into the reaction mechanisms underlying the polycondensation of BPA and DPC, offering fresh perspectives on the process. Kinetic equations pertinent to the polycondensation mechanism were deduced from the analysis and then rigorously tested against experimental data to ascertain their validity. Kinetic constants emerged through the fitting of this experimental data, lending credence to the model’s accuracy. Utilizing the Aspen Plus software, the model was applied to simulate the annual production of 100,000 tons of polycarbonate (PC). The simulation facilitated the optimization of the operating conditions for each reactor, yielding valuable insights for scaling up to industrial production.

Shining bright: B@S-codoped graphitic carbon nitride nanorods illuminate enhanced catalytic C-N bond formation under visible-light

Graphitic carbon nitride as a photocatalyst seeking attention nowadays, due to its thermal stability, band structure, and chemical properties. Herein, we reported a boron sulfur co-doped graphitic carbon nitride (B@S-g-C3N4) photocatalyst synthesized by a one-pot thermal polycondensation mechanism. However, it was observed that due to co-doping in native carbon nitride structure the photocatalytic behavior and the band structure enhanced which was capable of fascinating the demand of organic transformations i.e. photocatalytic and charge transfer capability. The synthesized B@S-g-C3N4 photocatalyst was characterized by UV–vis DRS, FT-IR, XRD, SEM, EDX, HR-TEM, XPS and electrochemical properties. In addition, the synthesized B@S-g-C3N4 photocatalyst is a metal-free carbon nitride photocatalyst proven to be highly effective in performing organic transformations (conversion yield 98 %) like C-N bond formation under visible light source.

Mechanistic Details of the Titanium-Mediated Polycondensation Reaction of Polyesters: A DFT Study

In this work, the mechanism of polyester polycondensation catalysed by titanium catalysts was investigated using density functional theory (DFT). Three polyester polycondensation reaction mechanisms, including the Lewis acid mechanism (M1), the coordination of the ester alkoxy oxygen mechanism (M2) and the coordination of the carboxy oxygen mechanism (M3), were investigated. Three reaction mechanisms for the polycondensation reaction of diethyl terephthalate (DET) were investigated using Ti(OEt)4 and cationic Ti(OEt)3+ as the catalyst. The results show that the polycondensation reaction of the Lewis acid mechanism exhibits similar energy barriers to the catalyst-free condition (42.6 kcal/mol vs. 47.6 kcal/mol). Mechanism M3 gives the lowest energy barrier of 17.5 kcal/mol, indicating that Ti(OEt)4 is the active centre for the polycondensation reaction. The catalytic efficiency of Ti(OEt)3+ is lower than that of Ti(OEt)4 catalysts due to its higher DET distortion energy (67.6 kcal/mol vs. 37.4 kcal/mol) by distortion–interaction analysis.

Study of triboelectric properties and biocompatibility of some selected polyesters: Toward implantable triboelectric nanogenerator devices

Herein, exploration of potential synthesis routes for developing key components for efficient, implantable, and bio-absorbable triboelectric nanogenerators was performed. Further, their triboelectric charging, thermal and infrared spectroscopic properties along with biocompatibility were investigated. To obtain polymers with improved triboelectric charging efficiency, copolymers of sorbitol and sebacic acid (PSS) and hexanediol and citric acid (PHC) were synthesized using polycondensation mechanism. Whereas a copolymer of citric acid, glutaric acid, 1,2-propanediol and 1,6-hexanediol (CHGP) was synthesized via sequential ring-opening, and polycondensation mechanisms. The synthesis pathways of PSS and PHC were used as described earlier, while CHGP copolymer was synthesized through a novel route. The triboelectric measurements of the synthesized copolymers demonstrated higher triboelectric surface charge – an order of magnitude higher than commercially available acid- and ester-terminated poly(d,l-lactide-co-glycolides) (PLGA) elastomers. The measured values are up to two orders of magnitude higher than well-known triboelectric materials such as polydimethylsiloxane and polytetrafluorethylene. Thermal analysis of polymers performed through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) displayed a typical degradation and phase change behavior, associated with copolymers. Moreover, revealing the effect of crosslinking in CHGP polymer on glass transition temperature (Tg), melting temperature (Tm) was analyzed. Finally, human skin fibroblasts were used to study the cytotoxicity of the polymers by using standard MTT cell proliferation assay. All of the investigated polymers exhibited some cytotoxicity, which was more expressed in case of CHGP. The fibroblast cell viability was notably higher in the presence of PSS and PHC. The distinctive collective properties of the investigated polymers enable the potential use as components of the implantable TENG devices in the future.

All-Polyhydroxyalkanoate Triblock Copolymers via a Stereoselective-Chemocatalytic Route

Biodegradable polyhydroxyalkanoate (PHA) homopolymers and statistical copolymers are ubiquitous in microbially produced PHAs, but the step-growth polycondensation mechanism the biosynthesis operates on presents a challenge to access well-defined block copolymers (BCPs), especially higher-order tri-BCP PHAs. Here we report a stereoselective-chemocatalytic route to produce discrete hard-soft-hard ABA all-PHA tri-BCPs based on the living chain-growth ring-opening polymerization of racemic (rac) 8-membered diolides (rac-8DLR; R denotes the two substituents on the ring). Depending on the composition of the soft B block, originated from rac-8DLR (R = Et, nBu), and its ratio to the semicrystalline, high-melting hard A block, derived from rac-8DLMe, the resulting all-PHA tri-BCPs with high molar mass (Mn up to 238 kg mol-1) and low dispersity (Đ = 1.07) exhibit tunable mechanical properties characteristic of a strong and tough thermoplastic, elastomer, or a semicrystalline thermoplastic elastomer.

Sequence-controlled alternating block polychalcogenophenes: synthesis, structural characterization, molecular properties, and transistors for bromine detection.

Sequence-controlled polychalcogenophenes have attracted much interest in terms of synthesis, structure and function in polymer science. For the first time, we developed a new class of alternating block conjugated copolymers denoted as poly(alt-AB)x-b-(alt-AC)y where both blocks are constituted by an alternating copolymer. 3-Hexylthiophene (S), 3-hexylselenophene (Se) and 3-hexyltellurophene (Te) are used as A, B and C units to assemble three sequence-controlled polychalcogenophenes P(SSe)b(STe), P(SSe)b(SeTe) and P(STe)b(SeTe) which are prepared by adding two different Grignard monomers in sequence to carry out Ni(dppp)Cl2-catalyzed Kumada polymerization. The molecular weight, dispersity, and length of each block (x = y) and main-chain sequence can be synthetically controlled via the catalyst transfer polycondensation mechanism. The polymer structures, i.e. alternating block main chain with high side-chain regioregularity, are unambiguously confirmed by 1H-NMR and 13C-NMR. The optical and electrochemical properties of the polymers can be systematically fine-tuned by the composition and ratio of the chalcogenophenes. From GIWAXS measurements, all the polymers exhibited predominantly edge-on orientations, indicating that the packing behaviors of the alternating block polychalcogenophenes with high regioregularity are inherited from the highly crystalline P3HT. P(SSe)b(STe) exhibited a hole OFET mobility of 1.4 × 10-2 cm2 V-1 s-1, which represents one of the highest values among the tellurophene-containing polychalcogenophenes. The tellurophene units in the polymers can undergo Br2 addition to form the oxidized TeBr2 species which results in dramatically red-shifted absorption due to the alternating arrangement to induce strong charge transfer character. The OFET devices using the tellurophene-containing polychalcogenophenes can be applied for Br2 detection, showing high sensitivity, selectivity and reversibility.

Solar Light Responsive Graphitic Carbon Nitride Coupled Porphyrin Photocatalyst that Uses for Solar Fine Chemical Production.

Photocatalysis is a defendable manner for production of several organic chemicals, energy and its storage from solar energy. For the evolution of metal free, cost-effective catalyst a 2D composite has been appear as a photocatalyst. Here, we had reported the synthesis of a light harvesting composite as a photocatalyst which was assembled by a poly-condensation mechanism between graphitic carbon nitride and tetrakis(4-nitrophenyl) porphyrin and the resulting composite manifest the excellent light harvesting properties, suitable energy band and low charge recombination. The photocatalyst [(NO2 )4 TPP@g-C3 N4 ] enables the efficient photocatalytic production of nicotinamide adenine dinucleotide (NADH) from consumed NAD+ also the production of organic chemicals like 4-methoxybenzylimines from 4-methoxybenzylamines. The photocatalytic efficiency of the photocatalyst was estimated by the percentage of NADH regeneration and the percentage yield of organic transformations. It shows the tetrakis(4-nitrophenyl) porphyrin could enhance the charge transfer capacity of graphitic carbon nitride which shows excellent photocatalysis activities and organic transformations.

Enhanced Room-Temperature Ethanol Detection by Quasi 2D Nanosheets of an Exfoliated Polymeric Graphitized Carbon Nitride Composite-Based Patterned Sensor.

A novel room-temperature gas sensor composed of polymeric graphitic carbon nitride composite was fabricated and used for the detection of ethanol vapor under ambient conditions. Polymeric carbon nitride (PCN) microstructures composed of fluffy nanosheets were synthesized via a thermal polycondensation mechanism using melamine as the precursor, followed by vigorous chemical exfoliation. These sheet-like microstructures were employed as active materials in the form of composites, along with carbon paste consisting of graphite nanoplatelets and carbon black. The active sensing layer was fabricated on a PET sheet and assembled on an interdigitated gold electrode. The as-fabricated sensor exhibited excellent sensing efficiency (>100% response at 10 ppm) along with high selectivity and stability. In particular, for ultralow concentrations such as 1 ppm (>10% response), this resistive-based sensor exhibited a swift response time provided under ambient conditions. The exfoliated PCN composite sensor was found to be working with appreciable efficiency at moderate relative humidity (%) with the least fluctuation in response signals also demonstrating long-term stability for 30 days with consistent response signals.

Key progresses of MOE key laboratory of macromolecular synthesis and functionalization in 2021

In 2021, The MOE Key Laboratory of Macromolecular Synthesis and Functionalization in Zhejiang University had achieved several important results. First, a series of versatile organoboron catalysts were synthesized for ring-opening (co)polymerizations. Second, a catalyst-free polycondensation mechanism was proposed for the production of polyesters with high molecular weights. Third, a co-assembly method that can fabricate films and coatings with controllable structures and properties on various substrates was demonstrated, providing a platform for the construction of novel surface coatings. Forth, facile methods for producing high-productivity poly(propylene carbonate) and semicrystalline polyester have been discovered. And linear non-conjugated polyesters exhibiting yellow-green clusteroluminescence were developed for the first time. Fifth, a supramolecular prodrug nano-assembly strategy has been developed for reactive nitrogen species potentiated chemotherapy. Sixth, a series of tough and stiff supramolecular hydrogels with shape memory properties have been used for information encryption. Seventh, reversible fusion and fission of wet-spun graphene oxide fibers has been successfully achieved. Eighth, three non-conjugated polypeptides were synthesized and the mechanism of clusteroluminescence was studied. Ninth, a series of conducting covalent organic frameworks with high electrical conductivity and carrier mobility have been used as high-performance chemiresistor, electrocatalyst, and organic field-effect transistor. Tenth, the exploration of non-fused electron acceptors, and their photostable mechanism are exemplified for developing high-performance, low-cost and eco-friendly polymer solar cells. Finally, gel-grown long-range ordering bulk-heterojunctions has achieved improved X-ray detector performance.

Mechanism and Kinetics of Lipase-Catalyzed Polycondensation of Glycerol and Sebacic Acid: Influence of Solvent and Temperature.

The mechanism for theCandida antacticalipase B (CALB)-catalyzed polycondensation of glycerol and sebacic acid in polar solvents was proposed based on the profile of formation and consumption of the glyceridic species in the reaction media and on the occurrence of the acyl migration reaction. The acyl migration is mainly responsible for the esterification of the secondary hydroxyl of glycerol and in an opposite way to the regioselective CALB-catalyzed esterification of primary hydroxyls. The enzymatic esterification of glycerol primary hydroxyls occurs preferentially up to carboxylic acid conversions of approximately 0.60-0.75 with rate constants in the range of 0.07-1.44 L mol-1 h-1, depending on the solvent. Above carboxylic acid conversions of 0.60-0.75, acyl migration occurs in parallel to enzymatic esterification with rate constants of approximately 0.04-0.12 h-1 and is the rate-limiting step of the polymerization. The hydrogen bonding accepting ability of the solvents is the main parameter that dictates the enzymatic catalysis rate. However, the magnitude of the polymer-solvent interaction governs the polymer chain growth. Acetonitrile has a lower hydrogen bonding accepting ability and a less favorable polymer-solvent interaction compared with the other polymer-solvent pairs, and polycondensation achieves the highest enzymatic rate constant of approximately 0.84-1.44 L mol-1 h-1; however, low molar mass polymers with Mn = 1.4 kDa were formed. On the other hand, acetone has intermediate hydrogen bonding accepting ability and optimal intermediate polymer-solvent interactions and, therefore, an intermediate enzymatic rate constant of approximately 0.41-0.52 L mol-1 h-1, and the highest molar mass polymers with Mn = 4.9-9.4 kDa were obtained.

Multicomponent approach for the synthesis of functional copolymers via tandem polycondensations of isatoic anhydride, bisaldehydes and bisprimary amines in trifluoroethanol

A novel multicomponent polymerization strategy based on the tandem reactions of isatoic anhydride with bisaldehyde and bisamine monomers under mild metal catalyst-free conditions was developed. • Multicomponent synthesis of poly(dihydroquinazolinone)s was achieved. • MCP utilizes isatoic anhydride, bisaldehyde and bisamine monomers. • Obtained polymers show pH-dependent phase changes. A novel multicomponent polymerization (MCP) strategy based on tandem reactions of isatoic anhydride with bisprimary amine and bisaldehyde monomers under mild metal catalyst-free conditions was developed, leading to tailor-made copolymers carrying dihydroquinazolinone groups in the main chains. Trifluoroethanol was employed as a solvent during polymerization due to its high solvating ability of growing chains as well as its strong Brønsted acid character that allows high activation of tandem polycondensations. Functional copolymers in the range from 8.5 kDa to 23.2 kDa molecular weights (M n ) were synthesized with moderately high monomer conversions. By simple alteration of bisaldehyde and bisamine monomers, a structurally diverse functional copolymer library was obtained. The polycondensation mechanism proceeds on the liberation of CO 2 and H 2 O byproducts and together with the solvent reusability, this multicomponent polymerization allows a green approach to functional polymer synthesis. The obtained results demonstrated that the corresponding cationic polymers display post-polymerization modification feature and pH-dependent phase changes that suggest their potential use in various material applications.

Metal Oxide-Related Dendritic Structures: Self-Assembly and Applications for Sensor, Catalysis, Energy Conversion and Beyond.

In the past two decades, we have learned a great deal about self-assembly of dendritic metal oxide structures, partially inspired by the nanostructures mimicking the aesthetic hierarchical structures of ferns and corals. The self-assembly process involves either anisotropic polycondensation or molecular recognition mechanisms. The major driving force for research in this field is due to the wide variety of applications in addition to the unique structures and properties of these dendritic nanostructures. Our purpose of this minireview is twofold: (1) to showcase what we have learned so far about how the self-assembly process occurs; and (2) to encourage people to use this type of material for drug delivery, renewable energy conversion and storage, biomaterials, and electronic noses.

Synthesis, characterization, and properties of poly (arylene ether nitrile) with high crystallinity and high molecular weight

Crystalline poly (arylene ether nitrile) (PEN) has superior performance such as solvent resistance, excellent mechanical properties, heat resistance, and so on. However, it is of great difficulty to obtain crystalline PEN with high molecular weight. In this work, a series of crystalline copolymers named HQ/BPA-PEN were synthesized from hydroquinone, bisphenol A and 2,6-dichlorobenzonitrile through nucleophilic substitution polycondensation mechanism, and properies can be adjusted by changing the mole ratios of bisphenol A and hydroquinone. All the HQ/BPA-PEN copolymers show the excellent thermal properties (Tg > 180 °C, Td5%>480 °C) and superior mechanical properties (tensile strength>100 MPa). Among them, HQ/BPA-PEN85 copolymer (molar ratio of HQ/BPA was 85:15) obtained high Tg 188.75 °C, intrinsic viscosity 2.61, tensile strength 134.18 MPa and crystallinity of 43.71%. Therefore, this crystalline HQ/BPA-PEN has potential applications in the fields of high temperature resistant materials and electronic materials.

Microstructural Characteristics and Impact Fracture Behaviors of a Novel High-Strength Low-Carbon Bainitic Steel with Different Reheated Coarse-Grained Heat-Affected Zones

To obtain the correlation of microstructural characteristics and toughness in a novel high-strength low-carbon bainitic structural steel with medium and heavy plate after multipass welding, a welding thermal simulation experiment was conducted to simulate different subregions in the reheated coarse-grained heat-affected zones (CGHAZ). The microstructure evolution was then analyzed and factors that influence the fracture behavior were studied. The results show that the brittle zone appeared in subcritical reheated CGHAZ, and the fractured morphology was cleavage fracture. Supercritical reheated CGHAZ had the highest impact toughness, and the fractured morphology was primarily the ductile fracture with dimples formed via the micropore polycondensation mechanism. With an increase in the secondary pass welding thermal cycle peak temperature (tp2), the average length size of martensite and austenite (M-A) decreased from 9 to 2 μm. The coarsening of M-A constituents was the main reason for decrease in the crack initiation absorbed energy. A large number of retained austenite and cementite precipitates in subcritical reheated CGHAZ clearly worsened the impact toughness, and the massive austenite and cementite precipitates more than offset the beneficial effects of high-angle boundaries. This phenomenon led to disappearance of the effect of high-angle grain boundary of prior austenite and lath bainite on arresting crack propagation. In supercritical reheated CGHAZ, crack propagation absorbed energy was increased because of grain refinement, fine precipitates, lamellar residual austenite at corners, and high-angle grain boundary.

Evolution of the polydispersity of ammonium polyphosphate in a reactive extrusion process: Polycondensation mechanism and kinetics

Ammonium polyphosphate (APP) was prepared by the co-rotating twin-screw extrusion of monoammonium phosphate (MAP) and urea for potential application as a slow-release fertilizer. A fundamental study to establish a possible polycondensation mechanism was carried out using thermal analysises and the screw pullout technique. A two-step mechanism, MAP polycondensation and pyrophosphate polycondensation, was verified. Furthermore, a urea-phosphate intermediate was identified by X-ray photoelectron spectroscopy (XPS), allowing us to break the system down into basic reactions. To support the mechanism, a kinetics model of the overall conversion reaction was established based on ion chromatography (IC) data. The inactivation effect of the intermediate polyphosphate was found to increase the polydispersity index (PDI, defined as the ratio of the weight-average molecular weight to the number-average molecular weight, Mw/Mn) of APP. The resulting multiformity led to an optimized phosphorus release curve over the crop growth cycle. This work adds to earlier studies on APP synthesis, allowing synthetic control at the molecular weight distribution (MWD) level rather than the general polymerization level.

Optical rotation kinetics study of the polycondensation of chiral sol-gel precursors

We show that the polycondensation of chiral sol-gel precursors can be efficiently followed up by optical rotation measurements. Three silanes were studied, namely, the hexaethoxysilane derivatives of l-threonine, l-isoleucine, and dimethyl-l-tartrate. Two main sol-gel polycondensation mechanisms were identified, namely, linear kinetics product growth and second-order cluster–cluster growth. Dynamic light scattering measurements are used to support the proposed mechanisms.

Synthesis and characterization of electro-optic waveguide material polyurethane-imides

The electro-optic (EO) polymers of Y-type polyurethane-imides (PUI-1 and PUI-2) were synthesized by reaction of monomer azo-based chromophores, phenyl diisocyanate and aromatic dianhydride, based on polycondensation mechanism. Molecular structure characteristics for the polymers were evidenced by 1HNMR, FTIR, elemental analysis and gel permeation chromatography. The polymers exhibited a glass transition temperature (Tg) of 185 °C and 192 °C and a temperature of 5% weight loss at 256 °C and 325 °C and showed EO coefficient, γ33, of 43 pm/V and 51 pm/V at 1550 nm wavelength. A type of single-mode embedded PUI polymeric inverted rib waveguide Mach-Zehnder (MZ) interferometer electro-optic modulators was fabricated and measured, and exhibiting favorable electro-optical modulation response and the average propagation loss of the waveguide was less than 2.0 dB/cm at 1550 nm. The experimental results indicated that the PUI were promising candidates for the preparation of comprehensive performance excellent EO polymer waveguide materials, due to their large nonlinear optic effects, thermal stability, good processability and low optical propagation loss.

High‐Molecular‐Weight Polynucleotides by Transferase‐Catalyzed Living Chain‐Growth Polycondensation

AbstractWe present terminal deoxynucleotidyl transferase‐catalyzed enzymatic polymerization (TcEP) for the template‐free synthesis of high‐molecular‐weight, single‐stranded DNA (ssDNA) and demonstrate that it proceeds by a living chain‐growth polycondensation mechanism. We show that the molecular weight of the reaction products is nearly monodisperse, and can be manipulated by the feed ratio of nucleotide (monomer) to oligonucleotide (initiator), as typically observed for living polymerization reactions. Understanding the synthesis mechanism and the reaction kinetics enables the rational, template‐free synthesis of ssDNA that can be used for a range of biomedical and nanotechnology applications.

High-Molecular-Weight Polynucleotides by Transferase-Catalyzed Living Chain-Growth Polycondensation.

We present terminal deoxynucleotidyl transferase-catalyzed enzymatic polymerization (TcEP) for the template-free synthesis of high-molecular-weight, single-stranded DNA (ssDNA) and demonstrate that it proceeds by a living chain-growth polycondensation mechanism. We show that the molecular weight of the reaction products is nearly monodisperse, and can be manipulated by the feed ratio of nucleotide (monomer) to oligonucleotide (initiator), as typically observed for living polymerization reactions. Understanding the synthesis mechanism and the reaction kinetics enables the rational, template-free synthesis of ssDNA that can be used for a range of biomedical and nanotechnology applications.