Synthesis and Characterization of a New Copolymer Consisting of Polyamide 1210 and Reactive Phosphorus-Nitrogen Flame-Retardant.

The thermal stability and reactivity of organophosphorus flame-retardants play a critical role in synthesizing copolymerized flame-retardant polyamides. Herein, this work successfully synthesizes a flame-retardant CEPPA-DDA salt (CDS) with both good thermal stability and high reactivity by reacting 2-carboxyethyl phenyl phosphonic acid (CEPPA) with 1,12-dodecanediamine (DDA). Flame-retardant polyamide 1210 (FRPA) is further prepared by copolymerizing the CDS, DDA, and sebacic acid (SEA). The test results show that the introduction of CDS can significantly improve the flame-retardant properties of FRPA. Specifically, the flame-retardant polyamide 1210 (FRPA-7) with 7 wt% CDS addition can reach V-0 grade according to UL-94 standard, accompanying limiting oxygen index value of 30.2% and tensile strength of 38.62 MPa. Compared with pure polyamide 1210, the peak heat release rate and total heat release rate of FRPA-7 reduce by 24.11% and 9.40%, respectively. This study provides a simple strategy to prepare flame-retardant polyamides with high flame retardancy and good mechanical properties, which are expected to show great potentials in future industrial applications.

Mechanism Study of the Polymerization of Polyamide 56: Reaction Kinetics and Process Parameters.

Polyamide 56 (PA56) has gained significant attention in the academic field due to its remarkable mechanical and thermal properties as a highly efficient and versatile biobased material. Its superior moisture absorption property also makes it a unique advantage in the realm of fiber textiles. However, despite extensive investigations on PA56's molecular and aggregate state structure, as well as processing modifications, little attention has been paid to its polymerization mechanism. Herein, the influence of temperature and time on PA56's polycondensation reaction is detailed studied by end-group titration and carbon nuclear magnetic resonance (NMR) techniques. The reaction kinetics equations for the pre-polymerization and vacuum melt-polymerization stages of PA56 are established, and possible side reactions during the polycondensation process are analyzed. By optimizing the reaction process based on kinetic characteristics, PA56 resin with superior comprehensive properties (melting temperature of 252.6 °C, degradation temperature of 371.6 °C, and tensile strength of 75 MPa) is obtained. The findings provide theoretical support for the industrial production of high-quality biobased PA56.

Janus-Structural AIE Nanofiber with White Light Emission and Stimuli-Response.

White-light emitting elastomers (WLEEs) based on stimuli-responsive aggregation-induced emission (AIE) and regulated Förster resonance energy transfer (FRET) have aroused increasing attention due to the demands for wearable optoelectronic devices. Herein, the blue and orange AIEgens with different environmental sensitivities are synthesized and then encapsulated on both sides of nanofibers via side-by-side electrospinning aiming to achieve the Janus WLEEs. After regulating the blue-orange AIEgens ratio, efficient and stable white light emission with a CIE coordinate of about (0.33, 0.31) is achieved at a blue-orange AIEgens mass ratio of 3:1. Besides, the Janus nanofibers (Janus-NFs) also present super stretchability with elongation at the break over 150% and tensile strength close to 7 MPa. The sensitivity of fluorescence for Janus-NFs to its stretching deformation is used to visualize the evolution of the microstructure of nanofibers during stretching. Moreover, the Janus-NFs are also sensitive to HCl and NH3 , of which the fluorescence color would change under HCl and NH3 fuming above 2 and 57 ppm in air, respectively. The promising applications of the white light Janus-NFs in smart fabrics, warning sensors, and anti-counterfeiting packaging are demonstrated. This finding provides an efficient strategy for achieving wearable WLEEs with multiple functionalities, promoting the development of wearable devices.

An efficient method for CTCs screening with excellent operability by integrating Parsortix™-like cell separation chip and selective size amplification.

In this article, an attempt for efficient screening of circulating tumor cells (CTCs) with excellent operability on microfluidic chips was reported. A Parsortix™-like cell separation chip was manufactured in our lab. This chip allowed lateral flow of fluid which increased the flow rate of blood. And, an air valve controlled injection pump was manufactured which allowed eight chips working simultaneously. This greatly facilitated the blood treatment process and saved time. As for the mechanism of screening circulating tumor cells, selective size amplification was utilized. By size amplification of cancer cells, both the hardness and the size of CTCs increased which differentiated them from blood cells. And the modification procedure of beads used for size amplification of cancer cells was optimized. Finally, by integrating the commercialized Parsortix™-like cell separation chip and selective size amplification, a practical method for screening circulating tumor cells was established.

Key Process Control for Synthesizing High-Performance Inherently Flame-Retardant Long-Chain Bio-Based Polyamide.

Long-chain bio-based polyamide has shown promising development prospects due to its excellent properties and green renewable characteristics; however, synthesizing inherently flame-retardant long-chain bio-based polyamide remains a big challenge due to the lack of effective knowledge of the key polymerization process. Herein, intrinsicly flame-retardant long-chain bio-based polyamide 512 (PA512) was synthesized in the presence of a reactive flame retardant with high thermal stability and good water solubility. The reaction conditions and existing problems in each stage of the copolymerization system have been clarified and optimized. By utilizing a two-step pre-polymerization approach, a series of intrinsicly flame-retardant PA512 (FRPA512) with large molecular weight, high phosphorus element content and good mechanical properties were obtained. More importantly, the prepared FRPA512 with 5wt% flame retardant loading exhibited good flame retardancy, showing a limiting oxygen index (LOI) of 28.1% and a vertical burning rating of V-0. This study provides a feasible solution to the common problem in the synthesis of flame-retardant polyamides, while also offering new insights for future modification of polyamide copolymerization.

In Situ Polymerization of Antibacterial Modification Polyamide 66 with Au@Cu2O-ZnO Ternary Heterojunction.

In situ polymerization has proven to be an effective route through which to introduce function materials into polyamide materials. In this work, a nano-heterojunction material was evenly dispersed in PA66 via in situ polymerization methods to yield the antimicrobial PA66. The composites showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli, with strong mechanical properties. Fourier transform infrared spectroscopy (FTIR) showed that metal ions reacted with oxygen-containing functional groups. In addition, the shift of oxygen peaks in XPS spectra confirmed the occurrence of a complexation reaction. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) confirmed the effect of nano-heterojunction, which induced crystallization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed uniform dispersion of heterojunctions in PA66. Tensile testing revealed decreased toughness with higher loadings. The nanocomposite polyamide material has good processing properties which can be processed into thin films, molds, and wires without changing the morphology, and can be widely used in a variety of fields.

Effect of Nano Silica Particles on Impact Resistance and Durability of Concrete Containing Coal Fly Ash.

In this study, the effect of adding nano-silica (NS) particles on the properties of concrete containing coal fly ash were explored, including the mechanical properties, impact resistance, chloride penetration resistance, and freezing-thawing resistance. The NS particles were added into the concrete at 1%, 2%, 3%, 4%, and 5% of the binder weight. The behavior under an impact load was measured using a drop weight impact method, and the number of blows and impact energy difference was used to assess the impact resistance of the specimens. The durability of the concrete includes its chloride penetration and freezing-thawing resistance; these were calculated based on the chloride diffusion coefficient and relative dynamic elastic modulus (RDEM) of the samples after the freezing-thawing cycles, respectively. The experimental results showed that the addition of NS can considerably improve the mechanical properties of concrete, along with its freezing-thawing resistance and chloride penetration resistance. When NS particles were added at different replacement levels, the compressive, flexural, and splitting tensile strengths of the specimens were increased by 15.5%, 27.3%, and 19%, respectively, as compared with a control concrete. The addition of NS enhanced the impact resistance of the concrete, although the brittleness characteristics of the concrete did not change. When the content of the NS particles was 2%, the number of first crack impacts reached a maximum of 37, 23.3% higher compared with the control concrete. Simultaneously, the chloride penetration resistance and freezing-thawing resistance of the samples increased dramatically. The optimal level of cement replacement by NS in concrete for achieving the best impact resistance and durability was 2-3 wt%. It was found that when the percentage of the NS in the cement paste was excessively high, the improvement from adding NS to the properties of the concrete were reduced, and could even lead to negative impacts on the impact resistance and durability of the concrete.

A novel wide-range microfluidic dilution device for drug screening.

Microfluidic dilution chip is a crucial approach to perform gradient dilution of experimental samples in many biological investigations. In this study, we developed two serial wide-range dilution chips with dilution rates of 1:1 and 1:4 on the basis of the microfluidic oscillator by designing a series chamber, which was similar to a series circuit. The size of this chamber was adjusted and mixed with the neighboring air chamber to form dilution rates by oscillatory methods. We applied this microfluidic oscillator to estimate cellular kinetics and perform an acute oxidative stress test on Caenorhabditis elegans (C. elegans) in order to further validate their effectiveness. We estimated the kinetic parameters of ß-galactosidase, the biocatalyst responsible for the hydrolysis of lactose, and found out that K m was 602 ± 73 µM and k cat was 72 ± 12/s. In addition, our result of the study on acute oxidative stress of C. elegans using this novel chip was consistent with the result using 96-well plates. Overall, we believe that this novel chip can be applied to enzymatic reaction kinetics to evaluate accurately drug screening in bio-nematode models such as C. elegans. In summary, we have provided a novel microfluidic dilution chip that can form a wide range of sample concentration gradients. Our chip may facilitate drug screening, drug toxicology, and environmental toxicology.