Integrating multifunctional highly efficient flame-retardant coatings with superhydrophobicity, antibacterial property on cotton fabric.

There has been a growing interest in bio-based flame-retardant coating layer with good antibacterial activity for cotton fabric owing to the arising environmental pollution and viral and bacterial infectious risks. In this study, multifunctional flame-retardant coatings with superhydrophobicity and antibacterial property were integrated on cotton fabric through two-step method. The first layer of phosphorylated chitosan (PCS) biobased coating (C4) endowed the fabric highly efficient flame retardancy and antibacterial activity, and the second layer of modified poly(2-hydroxyethyl methacrylate phosphate ester) (PHEMAP) coating by perfluorooctyltriethoxysilane (P/F) provided the fabric excellent superhydrophobicity and self-cleaning ability. The C4-P/F fabric exhibited a shorter damage length of only 6.2 cm and achieved a higher char yield of 22.3 % than the C4 fabric in the vertical combustion test, and the limited oxygen index of the C4-P/F fabric increased to 32.5 %. The water contact angle (WCA) of the C4-P/F fabric reached above 150 o. Moreover, the C4-P/F fabric exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus. The highly efficient flame-retardant, superhydrophobic, antibacterial fabric is promising in home and public decoration, fire protection fields.

The miR166d/TaCPK7-D Signaling Module Is a Critical Mediator of Wheat (Triticum aestivum L.) Tolerance to K+ Deficiency.

It is well established that potassium (K+) is an essential nutrient for wheat (Triticum aestivum L.) growth and development. Several microRNAs (miRNAs), including miR166, are reportedly vital roles related to plant growth and stress responses. In this study, a K+ starvation-responsive miRNA (miR166d) was identified, which showed increased expression in the roots of wheat seedlings exposed to low-K+ stress. The overexpression of miR166d considerably increased the tolerance of transgenic Arabidopsis plants to K+ deprivation treatment. Furthermore, disrupting miR166d expression via virus-induced gene silencing (VIGS) adversely affected wheat adaptation to low-K+ stress. Additionally, miR166d directly targeted the calcium-dependent protein kinase 7-D gene (TaCPK7-D) in wheat. The TaCPK7-D gene expression was decreased in wheat seedling roots following K+ starvation treatment. Silencing TaCPK7-D in wheat increased K+ uptake under K+ starvation. Moreover, we observed that the miR166d/TaCPK7-D module could affect wheat tolerance to K+ starvation stress by regulating TaAKT1 and TaHAK1 expression. Taken together, our results indicate that miR166d is vital for K+ uptake and K+ starvation tolerance of wheat via regulation of TaCPK7-D.

Highly Efficient Flame-Retardant and Enhanced PVA-Based Composite Aerogels through Interpenetrating Cross-Linking Networks.

Poly(vinyl alcohol) (P)/alginate (A)/MMT (M) (PAM) composite aerogels was modified through interpenetrating cross-linking of methyltriethoxysilane (Ms) or γ-aminopropyltriethoxysilane (K) and calcium ion (Ca2+) as a cross-linking agent, respectively. The compressive moduli of the cross-linked PAM/MsCa and PAM/KCa aerogels greatly increased to 17.4 and 22.1 MPa, approximately 10.5- and 8.2-fold of that of PAM aerogel, respectively. The limited oxygen index (LOI) values for PAM/MsCa and PAM/KCa composite aerogels increased from 27.0% of PAM aerogel to 40.5% and 56.8%. Compared with non-cross-linked PAM aerogel, the peak heat release rate (PHRR) of PAM/MsCa and PAM/KCa composite aerogels dramatically decreased by 34% and 74%, respectively, whereas the PAM/KCa aerogel presented better flame retardancy and lower smoke toxicity than the PAM/MsCa aerogel because of the release of more inert gases and the barrier action of more compact char layer during the combustion. The highly efficient flame-retardant PAM-based composite aerogels with excellent mechanical properties are promising as a sustainable alternative to traditional petroleum-based foams.

Enzyme-free and isothermal discrimination of microRNA point mutations using a DNA split proximity circuit with turn-on fluorescence readout.

MicroRNAs (miRNAs) hold immense potential as disease biomarkers, yet their short lengths and high sequence homology pose unique challenges in detection. Conventional methods such as the gold standard qRT-PCR and other isothermal amplification methods require sophisticated primer designs and use of enzymes which add uncertainties to the assay robustness. In this work, we demonstrate the use of a plug-and-play molecular detection platform, termed split proximity circuit (SPC), to achieve a selectivity comparable to qRT-PCR in differentiating point mutations using several miRNAs as proof-of-concept models. The analytical sensitivity of SPC has been improved by a hundred-fold over our previous work and matches/outperforms the enzyme-free assays reported in the literature by evolving the core signal-generating domains. Key design changes include improved hybridization chain reaction (HCR) hairpin sequences and the incorporation of a turn-on fluorescence signal based on fluorophore-quencher format. The core domains were then kept constant while redesigning the target recognition region to be complementary to various target sequences, all of which yield similar analytical performance. Notably, SPC maintained robust signal recovery with low variance even in complex biological matrices. With its enzyme-free and single room temperature operation, SPC presents a promising platform for quick and easy miRNA quantification.

Fabrication of highly efficient phenylphosphorylated chitosan bio-based flame retardants for flammable PLA biomaterial.

Modified chitosan (CS)-based flame retardants exhibit promising prospects owing to their sustainability, biodegradability, and good charring properties. A series of novel modified-CS bio-based flame retardants (phenylphosphorylated CS (PhPCS) and phenylphosphoramidated CS (PhPNCS)) were prepared by the phosphorylation and phosphoramidation reactions of CS with phenylphosphoryl dichloride and tetraethylenepentamine, respectively. Bio-based PhPCS and PhPNCS exhibited excellent flame retardancy efficiency for poly(lactic acid) (PLA). The limited oxygen index (LOI) values of the PLA/3 wt% PhPCS and PLA/3 wt% PhPNCS biocomposites increased to 29% and 27%, respectively, and they both achieved a V-0 rating during the UL-94 vertical combustion test. However, the mechanical properties of the PLA/PhPCS biocomposites decreased with increasing PhPCS content. The mechanical strengths of the PLA/PhPNCS biocomposites were better than those of the PLA/PhPCS biocomposites owing to the reactive compatibilization of the interface between the amino and carboxyl end groups of the PhPNCS nanoparticles and PLA matrix, respectively.

Gelation, flame retardancy, and physical properties of phosphorylated microcrystalline cellulose aerogels.

Flame-retardant bio-based cellulose aerogels, with abundant renewable sources, are considered as promising sustainable heat-insulation alternatives to conventional petroleum-based foams. An environmentally friendly method was employed to fabricate phosphorylated microcrystalline cellulose (PMCC) aerogel through the gelation of PMCC/H2O dispersion and freeze-drying of PMCC hydrogel. The dispersion stability of PMCC and its readiness to undergo gelation in the aqueous phase were enhanced by increasing the phosphorous content via phosphorylation, thereby effectively weakening the strong intra- and intermolecular hydrogen-bond interactions of the cellulose chains. The morphology of the PMCC aerogel changed from a short rod-shaped and sheet-like aggregation of a three-dimensional skeleton structure to a mostly sheet-like aggregation of a three-dimensional structure with increased phosphate esterification. Remarkably, PMCC aerogels exhibited improved flame retardancy and superior suppression of toxic gas, compared to MCC. This is attributable to the synergic effect of phosphate dehydration, catalytic carbonization, and protection of the aerogel network structure.

Flame Retardancy and Toughness of Poly(Lactic Acid)/GNR/SiAHP Composites.

A novel flame-retardant and toughened bio-based poly(lactic acid) (PLA)/glycidyl methacrylate-grafted natural rubber (GNR) composite was fabricated by sequentially dynamical vulcanizing and reactive melt-blending. The surface modification of aluminum hypophosphite (AHP) enhanced the interfacial compatibility between the modified aluminum hypophosphite by silane (SiAHP) and PLA/GNR matrix and the charring ability of the PLA/GNR/SiAHP composites to a certain extent, and the toughness and flame retardancy of the PLA/GNR/SiAHP composites were slightly higher than those of PLA/GNR/AHP composites, respectively. The notched impact strength and elongation of the PLA composite with 20 wt. %GNR and 18 wt.% SiAHP were 13.1 kJ/m2 and 72%, approximately 385% and 17 fold higher than those of PLA, respectively, and its limiting oxygen index increased to 26.5% and a UL-94 V-0 rating was achieved. Notedly, the very serious melt-dripping characteristics of PLA during combustion was completely suppressed. The peak heat release rate and total heat release values of the PLA/GNR/SiAHP composites dramatically reduced, and the char yield obviously increased with an increasing SiAHP content in the cone calorimeter test. The good flame retardancy of the PLA/GNR/SiAHP composites was suggested to be the result of a synergistic effect involving gaseous and condensed phase flame-retardant mechanisms. The high-performance flame-retardant PLA/GNR/SiAHP composites have great potential application as replacements for petroleum-based polymers in the automotive interior and building fields.

Highly efficient flame-retardant and low-smoke-toxicity poly(vinyl alcohol)/alginate/ montmorillonite composite aerogels by two-step crosslinking strategy.

A highly efficient flame-retardant and ultra-low-smoke-toxicity biodegradable material, poly(vinyl alcohol) (PVA)/alginate/montmorillonite (MMT) composite aerogel, was fabricated by a new environment-friendly two-step crosslinking strategy using borate and calcium ions. Compressive and specific moduli of the crosslinked PVA/alginate/MMT (P4A4M4/BA/Ca) aerogel increased to 7.2- and 1.9-folds those of the non-crosslinked aerogel, respectively, and the limited oxygen index value increased to 40.0%. Cone calorimeter tests revealed that the total heat release and peak heat release rate values of the P4A4M4/BA/Ca composite aerogel distinctly decreased. Remarkably, the total smoke release value of the P4A4M4/BA/Ca aerogel was considerably lower than those of non-crosslinked PVA composite aerogels, indicating its superior smoke suppression ability and high fire hazardous safety. The flame-retardancy mechanism of the crosslinked P4A4M4/BA/Ca composite aerogels involved a combination of the gaseous phase and condensed phase flame retardancy. The high-performance PVA/alginate/MMT biodegradable composite aerogels with good sustainability is a promising alternative to conventional flame-retardant foams.

The Microstructure of GNR and the Mechanical Properties of Biobased PLA/GNR Thermoplastic Vulcanizates with Excellent Toughness.

A series of different contents of glycidyl methacrylate (GMA)-grafted natural rubber (GNR) copolymers were fabricated via green bulk melt-grafting reactions, and super-tough bio-based poly (lactic acid) (PLA)/GNR thermoplastic vulcanizates (TPVs) were achieved by in-situ dynamic vulcanization. Increasing the graft yield, gel fraction, and crosslinking density of GNR vulcanizates effectively improved the ductility of the PLA/GNR TPVs, while prolonging the dynamic vulcanization time and increasing the GMA graft yield led to a notable enhancement in the impact toughness of the PLA/GNR TPVs. PLA/30 wt % GNR TPVs exhibited a significantly increased elongation (410%) and notched impact strength (73.2 kJ/m²), which were 40 and 15 times higher than those of the PLA/30 wt % NR TPVs, respectively. The new bio-based PLA/GNR TPVs offer promise as replacements for petroleum-based polymers in the automotive, 3D printing, and packaging fields.

Fire safety enhancement of a highly efficient flame retardant poly(phenylphosphoryl phenylenediamine) in biodegradable poly(lactic acid).

Flame-retarded poly(lactic acid) (PLA) biodegradable materials are viewed as promising as sustainable alternatives to petroleum-based commodity polymers. A new highly efficient flame retardant, poly(phenylphosphoryl phenylenediamine) (PPDA), was synthesized by the condensation of phenylphosphoryl dichloride with p-phenylenediamine and its structure was confirmed by 1H nulear magnetic resonance and Fourier-transform infrared spectroscopy. When 3 wt% PPDA was incorporated into PLA, the limited oxygen index increased from 20.0% of neat PLA to 25.5% and its UL-94 vertical burning testing achieved V-0 rating. Moreover, the total heat release and peak heat release rate values of PLA/3 wt% PPDA material were decreased from 109.1 MJ/m2 and 643.7 kW/m2 of PLA to 98.3 MJ/m2 and 570.0 kW/m2, respectively, and the fire performance index increased from 0.081 of PLA to 0.132 m2 s/kW. The high fire safety of PPDA in PLA is mainly attributed to the combined effects of the phosphorous-containing radical inhibition and inert gases and the barrier action of the formed char layer. The addition of less than 3 wt% PPDA has little influence on the tensile and impact properties of PLA. The flame retardant PLA blends have great application potential in electrical casing, automobile interiors and three-dimensional printing materials.

Solvent-induced crystallization behaviors of PLLA ultrathin films investigated by RAIR spectroscopy and AFM measurements.

The crystallization of poly(L-lactide acid) (PLLA) ultrathin films induced by different solvents was investigated using reflection-absorption infrared (RAIR) spectroscopy and atomic force microscopy (AFM). Irregular PLLA dendrite lamellae grew in the flat-on orientation with dichloromethane solvent before being redissolved after longer induction times owing to the strong interaction between the PLLA segments and solvent molecules. Faster formation of PLLA spherulites was induced with acetone than with dichloromethane, and these remained unchanged with increasing induction time because of the polarity difference between the PLLA segments and acetone molecules. PLLA ultrathin films could not be induced to crystallize using chloroform because of the very strong interactions between the chloroform (CHCl3) molecules and PLLA amorphous chains, which caused the CHCl3 solvent molecules to rapidly permeate the PLLA random coils and dissolve the amorphous chains. These phenomena are attributed to solvent-specific competition between solvent-induced crystallization and dissolution effects in PLLA ultrathin films, which ultimately leads to the higher degree of crystallinity obtained with acetone than with dichloromethane.

Hydroxyapatite induces spontaneous polymerization of model self-etch dental adhesives.

The objective of this study is to report for the first time the spontaneous polymerization phenomenon of self-etch dental adhesives induced by hydroxylapatite (HAp). Model self-etch adhesives were prepared by using a monomer mixture of bis[2-(methacryloyloxy)ethyl] phosphate (2MP) with 2-hydroxyethyl methacrylate (HEMA). The initiator system consisted of camphorquinone (CQ, 0.022 mmol/g) and ethyl 4-dimethylaminobenzoate (4E, 0.022-0.088 mmol/g). HAp (2-8 wt.%) was added to the neat model adhesive. In a dark environment, the polymerization was monitored in-situ using ATR/FT-IR, and the mechanical properties of the polymerized adhesives were evaluated using nanoindentation technique. Results indicated that spontaneous polymerization was not observed in the absence of HAp. However, as different amounts of HAp were incorporated into the adhesives, spontaneous polymerization was induced. Higher HAp content led to higher degree of conversion (DC), higher rate of polymerization (RP) and shorter induction period (IP). In addition, higher 4E content also elevated DC and RP and reduced IP of the adhesives. Nanoindentation result suggested that the Young's modulus of the polymerized adhesives showed similar dependence on HAp and 4E contents. In summary, interaction with HAp could induce spontaneous polymerization of the model self-etch adhesives. This result provides important information for understanding the initiation mechanism of the self-etch adhesives, and may be of clinical significance to strengthen the adhesive/dentin interface based on the finding.

Lamellar orientation and crystallization dynamics of poly (L-lactic acid) thin films investigated by in-situ reflection absorption infrared spectroscopy.

In situ reflection-absorption infrared (RAIR) spectroscopy was used to investigate the molecular orientation and crystallization dynamics of PLLA thin films crystallized at various temperatures. The results show that the annealing temperature has significant effect on the lamellar orientation of PLLA thin films, which is confirmed by atomic force microscopy (AFM) data. It is found that edge-on lamellar crystals of PLLA thin films are mainly formed by cold crystallization at low temperatures (70-90 °C), whereas the flat-on crystals occur when the crystallization temperature reaches to 100 °C. Of particular note, our in situ RAIR data collected during the whole isothermal crystallization process suggests that the orientation of PLLA chain takes place in the early stage of the crystallization process. Moreover, the analysis on the crystallization dynamics of PLLA thin film indicates that the crystal growth dimensional and nucleation modes are also strongly affected by the crystallization temperature.