Polycondensation Process Research Articles

Selenium Dioxide Catalyzed Polymerization of N‐doped Poly(benzodifurandione) (n‐PBDF) and Its Derivatives

The recent discovery of highly conductive, solution‐processable, n‐doped poly(benzodifurandione) (n‐PBDF) marks a milestone in the development of conducting polymers. Currently, n‐PBDF is prepared by either duroquinone‐mediated or copper‐catalyzed polymerizations, where scalability and cost‐effectiveness may present challenges. Here, we report a general, scalable, and cost‐effective method for n‐PBDF and its derivatives, namely selenium dioxide (SeO2) catalyzed polymerization. We discovered that a catalytic amount of selenium dioxide leads to high monomer conversions (>99% by NMR). The obtained n‐PBDF exhibits a consistently narrow hydrodynamic diameter distribution and its thin films show high conductivities. Furthermore, we revealed that this polymerization involves a mechanism distinct from the previously reported radical pathway. It involves successive Riley oxidation and aldol polycondensation processes. It was also found that the reduced selenium precipitates from dimethyl sulfoxide (DMSO) when the catalytic cycle is terminated, allowing for a straightforward purification process through centrifugation and filtration. This method thus eliminates the need for the costly and slow dialysis process. Finally, we demonstrated that SeO2 catalyzed polymerization is applicable to n‐PBDF derivatives, proving the generality of this method.

Selenium Dioxide Catalyzed Polymerization of N-doped Poly(benzodifurandione) (n-PBDF) and Its Derivatives.

The recent discovery of highly conductive, solution-processable, n-doped poly(benzodifurandione) (n-PBDF) marks a milestone in the development ofconducting polymers. Currently, n-PBDF is prepared by either duroquinone-mediated or copper-catalyzed polymerizations, where scalability and cost-effectiveness may present challenges. Here, we report a general, scalable, and cost-effective method for n-PBDF and its derivatives, namely selenium dioxide (SeO2) catalyzed polymerization. We discovered that a catalytic amount of selenium dioxide leads to high monomer conversions (>99% by NMR). The obtained n-PBDF exhibits a consistently narrow hydrodynamic diameter distribution and its thin films show high conductivities. Furthermore, we revealed that this polymerization involves a mechanism distinct from the previously reported radical pathway. It involves successive Riley oxidation and aldol polycondensation processes. It was also found that the reduced selenium precipitates from dimethyl sulfoxide (DMSO) when the catalytic cycle is terminated, allowing for a straightforward purification process through centrifugation and filtration. This method thus eliminates the need for the costly and slow dialysis process. Finally, we demonstrated that SeO2 catalyzed polymerization is applicable to n-PBDF derivatives, proving the generality of this method.

How the Aliphatic Glycol Chain Length Determines the Pseudoeutectic Composition in Biodegradable Isodimorphic poly(alkylene succinate-ran-caprolactone) Random Copolyesters.

We synthesize four series of novel biodegradable poly(alkylene succinate-ran-caprolactone) random copolyesters using a two-step ring-opening/transesterification and polycondensation process with ε-caprolactone (PCL) as a common comonomer. The second comonomers are succinic acid derivatives, with variations in the number of methylene groups (nCH2) in the glycol segment, nCH2 = 2, 4, 8, and 12. The obtained copolyesters were poly(ethylene succinate-ran-PCL) (ESxCLy), poly(butylene succinate-ran-PCL) (BSxCLy), poly(octamethylene succinate-ran-PCL) (OSxCLy), and poly(dodecylene succinate-ran-PCL) (DSxCLy). We discovered a new mixed isodimorphic/comonomer exclusion crystallization in ESxCLy copolymers. The BSxCLy, OSxCLy, and DSxCLy copolymers display isodimorphic behavior. Our findings revealed a significant variation in the pseudoeutectic point position, from mixed isodimorphism/comonomer exclusion crystallization to isodimorphism with pseudoeutectic point variation from 54% to up to 90%. Moreover, we established a link between the melting temperature depression slope variation and the comonomer inclusion/exclusion balance, providing valuable insights into the complex topic of isodimorphic random copolymers.

Quaternized poly(aryl imidazolium) containing bulky binaphthyl group as proton exchange membrane for high-temperature fuel cells

The low power output and high phosphoric acid (PA) leakage are the main constraints restricting the commercialization of PA-doped high-temperature proton exchange membranes (HT-PEMs). Ionized imidazoles have been shown to be an effective strategy to improve PA retention, however, less research has been conducted on the fractional free volume (FFV) of the backbone of the main chain on PA loss. Herein, novel imidazolium ions polymer (PQBN-4-IM) material with bulky binaphthyl (BN) group was prepared as PA-doped HT-PEM using a one-step superoxid acid catalyzed polycondensation and subsequent methylation process. The rigidity and hydrophobicity of the BN group promote PQBN-4-IM PEM to produce more obvious microphase separation morphology and large FFV, which is beneficial for forming better ion transport channels and excellent PA interaction. Notably, the PA-doped PQBN-4-IM (PQBN-4-IM/PA) membrane has the highest proton conductivity (90.26 mS cm−1, 180 ℃) and peak power density (PPD) (802.5 mW cm−2, 180 ℃) than PQTP-4-IM/PA and m-PBI/PA HT-PEMs. Moreover, the PQBN-4-IM/PA membrane has higher PA retention at 80 ℃/40 % relative humidity (RH), 40 ℃/60 % RH, or immersed in water due to enhancement on ion-pair interactions by microstructure. Under the accelerated stress test (AST) of the fuel cell (FC), the PQBN-4-IM/PA membrane loses only 12.22 % of PPD after 200 cycles at 80 ℃, which exhibits higher PPD retention than that of the PQBP-4-IM/PA (70.23 %), PQTP-4-IM/PA (74.36 %) and m-PBI/PA (65.25 %) membranes, and shows excellent durability of cell performance for more than 1000 h without significant voltage decay at 160 °C. Thus, the outstanding performance suggests that the microstructure and morphology of imidazolium ions polymer membranes significantly influence proton conductivity, performance, and the durability of a cell.

In situ, Self-Healing and Self-Glazing of Geopolymers

Geopolymers are the result of the reaction of alkaline activators with reactive aluminosilicates. By dissolving these aluminosilicates and undergoing processes of polycondensation and geopolymerization, they form robust structures with distinct properties compared to other ceramics. These non-crystalline materials exhibit notable resistance to corrosion, heat, and environmental conditions, such as changes in pressure and temperature. Consequently, geopolymers, e.g., of stoichiometric composition (M2O•Al2O3•4SiO2•11H2O (or 13H2O)), find a place between cement and ceramics regarding mechanical properties. Considering the formulation of geopolymer blends, this study demonstrates that these materials have self-healing and self-glazing properties under high-temperature conditions. Through systematic experimentation and considering the specific properties of sodium-based (Na-GP) and potassium-based (K-GP) geopolymers, a combination of sodium and potassium waterglass compounds with different weight percentages were used to achieve geopolymer materials with optimum self-healing and self-glazing properties. Moreover, these samples were subjected to heat treatment under various time and temperature conditions to optimize their properties in terms of crystallization, and the best results were reported from among these variables. Based on the findings, the specific combination consisting of 75 wt.% sodium waterglass and 25 wt.% potassium waterglass were the best mixtures. This mixture was heated at a rate of 5°C per minute to a temperature of 1000°C and held isothermally for 6 hours before being cooled at the same rate. As a result, an amorphous geopolymer turned into a ceramic with irreversible, self-healing, and self-glazing capabilities.

Kinetics of chemical reactions in spray

The number of observations demonstrating a significant effect of droplet sizes on the kinetics of chemical processes has increased with the expansion of the scope of application of spray technology. The equations linking the concentrations of reagents, the volume of droplets, the initial composition of the solution, the composition of the gas medium and the speed of processes are formulated within the framework of formal chemical kinetics. Using the example of second-order reactions (coupling, exchange, condensation, polymerization, polycondensation), it is shown that size kinetic effects occur when chemical processes are accompanied by changes in the droplet sizes in equilibrium with the gas medium. The results of computer simulation of condensation reaction and polycondensation process reproducing size effects are presented. Kinetic curves obtained by modeling the polycondensation process are compared with experimental data.

Influence of soil degradation on radiation-chemical transformations of oil

Protecting soil from pollution by oil and petroleum products is an important environmental task. Sources of oil contamination of soil are not only oil fields, but also industrial facilities that directly or indirectly use petroleum products. Of interest are studies aimed at studying the processes of changes in oil during its degradation in the soil. When oil degrades, polycondensation processes occur on the soil surface, which leads to structural changes in the oil. We compared the composition and properties of oil after production and long-term presence on the soil surface. An analysis of oil-contaminated soils was carried out at a distance of 0–5 and 0–10 m from the source of pollution and from a depth of 0–15 cm. Oils degraded in the soil are also susceptible to the effects of natural radionuclide background. In this regard, the work investigated the impact of gamma radiation on oil degraded in the soil of the Surakhani oil field of Azerbaijan. Oil samples were taken from a well and from oil-contaminated soil and separated into three components: oils, resins, and asphaltenes. The results of mass spectrometric and IR spectrometric studies of the indicated fractions of crude and degraded oil samples are presented, and the patterns of formation of gaseous products during their radiolysis are established.

Intrinsically Flexible Phase Change Fibers for Intelligent Thermal Regulation.

Owing to the significant latent heat generated at constant temperatures, phase change fibers (PCFs) have recently received much attention in the field of wearable thermal management. However, the phase change materials involved in the existing PCFs still experience a solid-liquid transition process, severely restricting their practicality as wearable thermal management materials. Herein, we, for the first time, developed intrinsically flexible PCFs (polyethylene glycol/4,4'-methylenebis(cyclohexyl isocyanate) fibers, PMFs) through polycondensation and wet-spinning process, exhibiting an inherent solid-solid phase transition property, adjustable phase transition behaviors, and outstanding knittability. The PMFs also present superior mechanical strength (28 MPa), washability (>100 cycles), thermal cycling stability (>2000 cycles), facile dyeability, and heat-induced recoverability, all of which are highly significant for practical wearable applications. Additionally, the PMFs can be easily recycled by directly dissolving them in solvents for reprocessing, revealing promising applications as sustainable materials for thermal management. Most importantly, the applicability of the PMFs was demonstrated by knitting them into permeable fabrics, which exhibit considerably improved thermal management performance compared with the cotton fabric. The PMFs offer great potential for intelligent thermal regulation in smart textiles and wearable electronics.

Numerical simulations of equilibrium, kinetics, and chain length distribution in linear polycondensation proceeding in nano-scale small volumes: An apparent violation of the law of mass action

A simple polycondensation process Mi + Mj ⇄ Mi+j + Z, proceeding in dispersion of nano-scale droplets was described by analytical solutions and differential equations giving insight into equilibrium and kinetics of the process. Stochastic and deterministic simulations show that the statistical nature of polycondensation, both irreversible and reversible one, affects the way the macromolecules of different lengths are formed and distributed among droplets. The droplet distributions in respect to the number of reacting chains and the chain length distributions depend, for the given conversion, on the polycondensation equilibrium constant Kcond and the initial conditions: monomer concentration and the number of its molecules in a droplet. The apparent equilibrium constants of condensation K¯ij=[Mi+j]¯e[Z]¯e/[Mi]¯e[Mj]¯e depend on oligomer/polymer sizes as well as on the initial number of monomer molecules in a droplet. This apparent violation of the law of mass action was explained by stochasticity of involved processes. Moreover, when the polycondensation byproduct Z is being removed reversibly from the system, K¯ij depends also on average equilibrium concentration [Z]¯e. The indicated effects are observed not only for ideally dispersed systems (all droplets contain initially the same number of monomer molecules), but also when the initial numbers of monomer molecules conform the Poisson distribution. However, the chain length distribution as well as kinetics and K¯ij differ here from those observed for systems with uniform distribution.

Chemoselective Hydrogenolysis of Urethanes to Formamides and Alcohols in the Presence of More Electrophilic Carbonyl Compounds.

The development of methods for the chemical recycling of polyurethanes is recognized as an urgent issue. Herein, we report the Ir-catalyzed hydrogenolysis of the urethane C-O bond to produce formamides and alcohols, where both formamides and ester and amide functionalities are tolerated. The chemoselectivity observed is counterintuitive to the generally accepted electrophilicity order of carbonyl compounds. Hydrogenolysis of urea and isocyanurate, potential byproducts in the polycondensation process of polyurethanes, is also achieved alongside the selective degradation of polyurethanes themselves, which affords diformamides and diols. The time-course of the hydrogenative polyurethane degradation reveals that the bond cleavage occurs not from the terminal, but from any part of the polymer chain. The present catalysis offers a novel method for the recycling of polyurethane-containing polymer waste.

Radial basis function neural network and overlay sampling uniform design toward polylactic acid molecular weight prediction

Polylactic acid (PLA) is a potential polymer material as a substitute for traditional plastics, and the accurate molecular weight distribution range of PLA is strictly required in practical applications. Therefore, exploring the relationship between synthetic conditions and PLA molecular weight is crucially important. In this work, direct polycondensation combined with overlay sampling uniform design (OSUD) was applied to synthesize the low molecular weight PLA. Then a multiple regression model and two artificial neural network models on PLA molecular weight versus reaction temperature, reaction time, and catalyst dosage were developed for PLA molecular weight prediction. The characterization results indicated that the low molecular weight PLA was efficiently synthesized under this method. Meanwhile, the experimental dataset acquired from OSUD successfully established three predictive models for PLA molecular weight. Among them, both artificial neural network models had significantly better predictive performance than the regression model. Notably, the radial basis function neural network model had the best predictive accuracy with only 11.9% of mean relative error on the validation dataset, which improved by 67.7% compared with the traditional multiple regression model. This work successfully predicted PLA molecular weight in a direct polycondensation process using artificial neural network models combined with OSUD, which provided guidance for the future implementation of molecular weight-controlled polymer’ synthesis.

Synthesis and structural evolution of coal-based mesophase pitch by hydrogenation-vacuum thermal polycondensation process

As high-performance carbon materials precursor, the controlled synthesis of mesophase pitches has received widespread attention. Coal tar pitch and Tetrahydronaphthalene (THN) were selected as raw material and hydrogen supply solvent to synthesize mesophase pitches through hydrogenation and vacuum polycondensation. The compositions and structure of resultant hydrogenated and mesophase pitches were characterized and analyzed by various methods. The results revealed that the introduction of THN could effectively increase the H content in hydrogenated pitches, and the transformation of HN to Har was observed with the extension of the reaction time. The softening point of the resultant mesophase pitches was 230–245 °C, the Mn ranged from 1400 to 2000 Da, the anisotropic content was up to 96 %, and the contents of the four subfractions were THFI > HI-TS > HS > TI-THFS in descending order. This work provided an efficient and convenient approach for the synthesis of mesophase pitches, with a view to providing a theoretical and practical foundation for spinning-grade mesophase pitch preparation.

Fluorescent zinc acrylate resins containing coumarin structures with enhanced antifouling performance

The demand for non-toxic antifouling coatings has led to the development of multifunctional antifouling coatings. In this work, a series of coumarin acids with fluorescence were first prepared via the Knoevenagel condensation reaction. Then, multifunctional zinc acrylate resins were produced successfully by employing an acrylic acid monomer, ZnO, and coumarin acids by free radical polymerization and polycondensation processes. The self-polishing and antifouling properties of the resins were investigated by dynamic simulation experiments, E. coli growth inhibition experiments, algae adhesion inhibition experiments, and marine environment antifouling experiments. The results show that the zinc acrylate resins containing the coumarin structures not only have good self-polishing performance but also have better antifouling performances than the zinc acrylate resin containing benzoic acid. This work not only reveals the antifouling mechanism of the multifunctional resins, but also provides a new strategy for the development of environmentally friendly antifouling coatings.

Rational design of a novel siloxane-branched waterborne polyurethane coating with waterproof and antifouling performance

Inferior water resistance remains a bottleneck in the development of the waterborne polyurethane (WPU) coatings industry. Herein, a novel strategy for the facile preparation of hydrophobic antifouling WPU coatings is presented in this work. Specifically, a series of siloxane-branched modified polyurethanes (BSi-WPU) was prepared by synergistically introducing diol-hydroxyl single-ended silicone oil (DSSiO) as the branched modified monomer and hydroxylated fluorinated siloxane (HTFSi) as the functional soft-chain segment into the WPU system via a simple polycondensation process. The effects of the introduction of DSSiO on the water resistance and mechanical properties of the BSi-WPU were investigated, and the antifouling and chemical resistance of the modified coatings were also examined. The results demonstrated that the branched DSSiO possessed excellent surface migration efficiency, which effectively improved the water repellence (contact angle up to 109.3°), waterproofness (absorption reduced to 7.5 %), and hydrolysis resistance (minimum 1.6 % loss of strength after water immersion) of the coatings. In addition, owing to thermodynamic immiscibility, the incorporation of HTFSi and appropriate DSSiO amounts enlarged the microphase separation of the polyurethane, whereby the material exhibited improved mechanical properties over ordinary polyurethanes. More importantly, based on the surface enrichment of low-surface-energy silicon and fluorine units, the coatings exhibit excellent repellency to contaminated liquids and corrosive chemical solutions. This approach provided a more applicable alternative idea to the industrial fabrication of hydrophobic and antifouling WPU coatings.

Facile Green Synthesis of Zingerone Based Tissue‐Like Biodegradable Polyester with Shape‐Memory Features for Regenerative Medicine

AbstractThe abundance of plants as a renewable bioresource has captured the significant attention of researchers, driving them to explore new biodegradable polymeric materials. However, there are still many biobased materials with untapped potential, offering opportunities to synthesize novel biodegradable polymers with multifunctional properties. This work provides a unique solvent and catalyst‐free melt polycondensation process to prepare a series of polyesters using zingerol (Zing‐OH), a reduced form of zingerone, as a primary component for the first time. Briefly, Zing‐OH (a ginger‐based component) is employed in conjunction with a variety of renewable resources, such as citric acid (CA), sebacic acid (SA), and xylitol (Xy), to synthesize multifunctional soft tissue‐like ZCSX polyesters. Fourier‐transform infrared (FTIR) and 1H‐nuclear magnetic resonance (NMR) spectroscopy are used to validate the synthesis of the polyesters, while thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and universal testing machine (UTM) are employed to investigate their physicochemical properties. Moreover, the synthesized polyester's thermal, mechanical, and biodegradation properties can be fine‐tuned by simply varying the Zing‐OH feed ratio. The mechanical properties of the synthesized polymer resemble various human tissues, including the liver, uterus, bladder, breast, and temporal and nasal cartilage. This suggests that the synthesized polyesters can potentially be useful in tissue engineering applications. Furthermore, the polyester demonstrated exceptional recovery responses and good shape memory behavior at ambient body temperature. Additionally, as observed from Alamar blue, live/dead assays, and time‐dependent in vitro wound images, the synthesized polyester demonstrated antibacterial activity, good in vitro cytocompatibility, cell proliferation, and wound healing capabilities against mouse fibroblast cells (NIH/3T3). The developed biocompatible polyester also exhibits excellent hemocompatibility for human blood, indicating its potential use in the field of regenerative medicine.

Effect mechanism of phosphorous-containing additives on carbon structure evolution and biochar stability enhancement

The regulation of the pyrolysis process is a key step in increasing the carbon sequestration capacity of biochar. The effect of K3PO4 addition on the yield, chemical composition, characteristic functional groups, macromolecular skeleton, graphite crystallites, and stability of biochar was studied in this paper using two-dimensional infrared correlation spectroscopy (2D-PCIS), X-ray photoelectron spectroscopy, Raman spectrum, and other characterization methods combined with thermal/chemical oxidation analysis. It is discovered that adding K3PO4 may effectively minimize the graphitization temperature range and increase biochar's yield, aromaticity, H/C ratio, and proportion of refractory/recalcitrant organic carbon. The 2D-PCIS and Raman analysis revealed that K3PO4 mostly promoted the dehydrogenation and polycondensation process of the aromatic rings in the char precursor, transforming the amorphous carbon structure of biochar into an ordered turbostratic microcrystalline structure. K3PO4 enhanced biochar stability mostly at medium-high temperatures (350 ~ 750℃) by stimulating the transformation of unstable structures of biochar to stable carbon-containing structures or by inhibiting the interaction of its active sites with oxidants through the mineralization process. A 20% phosphorus addition increased biochar's refractory index (R50) by roughly 11%, and it also boosted biochar's oxidation resistance (H2O2 or K2CrO4) efficiency, reducing carbon oxidation loss by up to 7.31%. However, at higher temperatures (> 750 ℃), the doping of phosphorus atoms into the carbon skeleton degraded the biochar structure's stability. The results of this study suggest that using exogenous phosphorus-containing additives is an efficient way to improve the stability of biochar.Graphical abstract

Application of ultrasound-assisted compression and 3D-printing semi-solid extrusion techniques to the development of sustained-release drug delivery systems based on a novel biodegradable aliphatic copolyester

The purpose of this study was to investigate the ability of two advanced hot-processing technologies, Ultrasound-Assisted Compression (USAC) and 3D-printing Semi-solid Extrusion (SSE), to manufacture sustained-release drug delivery systems based on a novel biodegradable aliphatic copolyester. The copolymer was synthesized from ω-pentadecalactone (PDL), 1,4-cyclohexanedimethanol (CHDM) and dimethyl succinate (DMS) (monomer ratio PDL/CHDM/DMS 70/30/30) by enzymatic ring opening polymerization and two-step melt polycondensation processes and has a random microstructure, a high molecular weight (107,100 g mol−1) and a relatively low melting point (∼65 °C). The antibacterial agent metronidazole (MTZ) was chosen as model drug and binary physical mixtures copolymer:drug were prepared at 90:10 and 70:30 w/w ratios. Thermal analysis studies evidenced that the formulations could be processed below their degradation temperatures. Drug delivery devices with dense and meshed structures were manufactured using USAC and SSE techniques, respectively, with USAC devices exhibiting more reproducible physical properties than the SSE systems. Powder X-ray diffraction and scanning electron microscopy studies showed a partial sintering of the copolyester during USAC processing while MTZ remained mostly crystalline. In contrast, the copolymer melted and the drug underwent some amorphization when processed using SSE. In vitro drug release studies in phosphate buffer (pH 6.8) showed that, after an initial burst release of metronidazole, USAC and SSE devices exhibited a prolonged and/or sustained drug release over 20 days. The initial burst release was dependent on the manufacturing technique and the drug/polymer ratio, being minimized for SSE devices containing 10 wt% MTZ. The whole drug release profiles fitted well to the Peppas-Sahlin model, being drug diffusion the predominant release mechanism. After the burst release, the sustained release period of USAC and SSE devices containing 10 wt% MTZ showed a good fit to the zero-order kinetic model, with faster drug release from the SSE devices due to the larger surface area of their meshed structure. In conclusion, this work demonstrates that processing the aliphatic copolyester by both USAC and SSE technologies provides an attractive strategy to manufacture biodegradable drug delivery systems for long-term release of metronidazole.

Process Cascade for the Production of Green Polymers from CO2 and Electric Energy

AbstractProduction processes based on CO2 as raw material offer high scalability and sustainability. Here, a novel process cascade is introduced, combining the advantages of electrochemical CO2 conversion with the synthetic potential of industrial biotechnology: CO2 is electrocatalytically reduced to formic acid as substrate for the metabolically engineered bacterium Methylorubrum extorquens that produces l‐lysine as precursor of the polymer building block 1,5‐diaminopentane (cadaverine). Cadaverine is purified through targeted downstream processing and finally used in a polycondensation process to produce polyamide materials.

Synthesis and Characterization of an Alicyclic Acid Anhydride Containing four Stereoisomers and the Derived Polyamideimides using Diisocyanates

AbstractAn alicyclic acid anhydride BOTA, containing four stereoisomers, racemic (1S,2R,3R,4R,5R)‐bicyclo[2.2.2]octane‐2,3,5‐tricarboxylic acid‐2,3‐anhydride (7a+7a’) and racemic (1S,2S,3S,4R,5R)‐bicyclo[2.2.2]octane‐2,3,5‐tricarboxylic acid‐2,3‐anhydride (7b+7b’), was synthesized using phthalic anhydride as the starting material. The chemical structures of the products in each step were fully characterized by NMR spectroscopy, GC‐MS, elemental analysis, and single‐crystal X‐ray diffraction. The polycondensation process involving BOTA and several diisocyanates was applied to prepare PAIs. Furthermore, PAI‐Xs were prepared using methylene diphenyl diisocyanate (MDI) and various mole ratios of BOTA and 4,4'‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). PAI‐Xs exhibited good solubility in organic solvents such as DMSO, NMP, DMAc, GBL, DMF, and m‐cresol at room temperature. They can form flexible films with low coefficients of thermal expansion (CTE) (51‐70 ppm/°C) and high glass transition temperatures (Tg) (222‐272 °C). They also demonstrated high transparency with transmittance at 500 nm (T500nm) ranging from 77.2‐82.5%. BOTA can be a significant building block in PAI synthesis, offering an alternative to trimellitic anhydride (TMA).This article is protected by copyright. All rights reserved

Enhancing the flame retardancy of polylactic acid nonwoven fabric through solvent-free transparent coating

Polylactic acid (PLA) nonwovens, recognized as eco-friendly substitutes for petroleum-based synthetic fibers, face a significant challenge due to their inherent flammability. This work addresses this concern by synthesizing a hyperbranched polyphosphoramide flame retardant (TPDT) through a one-step polycondensation process without using solvent and catalyst. TPDT is subsequently applied to PLA nonwovens using a dip-pad finishing technique. Notably, with a mere 7 wt% weight gain of TPDT, the PLA nonwovens exhibit a substantial increase in the limited oxygen index (LOI) value, reaching 32.3 %. Furthermore, the damaged area in the vertical burning test is reduced by approximately 69.2 %. In the cone calorimeter test, 17 wt% weight gain of TPDT results in a 51.4 % decrease in peak heat release rate and a 56.0 % reduction in total heat release compared to the control PLA. Additionally, char residue increases from 1.5 wt% to 31.1 wt% after combustion. The strong affinity between TPDT and PLA molecules persists even after repeated abrasion, ensuring sustained flame retardancy. Importantly, the introduction of TPDT also imparts increased softness to the PLA nonwovens. This work addresses this concern by synthesizing a hyperbranched polyphosphoramide flame retardant (TPDT) through a solvent-free, catalyst-free, and one-step polycondensation process.