Ultrasonic-assisted synthesis of polyvinyl alcohol/phytic acid polymer film and its thermal stability, mechanical properties and surface resistivity

High water resistance starch based intelligent label for the freshness monitoring of beverages

The traditional starch-based intelligent freshness labels struggle to maintain long-term structural stability when exposed to moisture. To solve this problem, we prepared composite crosslinked labels using phytic acid for double crosslinking of corn starch and soybean isolate proteins, with anthocyanin serving as the chromogenic dye. The mechanical properties, hydrophobic characteristics, and pH responsivity of these crosslinked labels were assessed in this study. The prepared double-crosslinked labels showed reduced moisture content (15.96%), diminished swelling (147.21%), decreased solubility (28.55%), and minimized water permeability, which suggested that they have enhanced hydrophobicity and densification. The crosslinked labels demonstrated the ability to maintain morphological stability when immersed in water for 12 h. Additionally, the mechanical properties of the crosslinked labels were enhanced without compromising their pH-sensing capabilities, demonstrated a color response visible to the naked eye for milk and coconut water freshness monitoring, suggesting great potential for application in beverages freshness monitoring.

A nanocellulose-based flexible multilayer sensor with high sensitivity to humidity and strain response for detecting human motion and respiration

Biomass-based flexible sensors with excellent mechanical and sensing properties have attracted significant attention. In this study, based on the excellent dispersibility and degradability of nanocellulose crystals, we designed a polyvinyl alcohol/nanocellulose crystals/phytic acid (PCP) composite film with good flexibility and high sensitivity to humidity. A layer of multiwalled carbon nanotubes (MWCNT) and nanocellulose crystals (CNC) was further sandwiched between two PCP layers as a flexible multifunctional sensor (PCPW) to detect human movement and respiration. Phytic acid contains abundant phosphate groups that enhance proton conduction, allowing the PCPW composite film to change its electrical resistance in a sensitive and repeatable manner when the relative humidity was varied between 35 %-93 %. Meanwhile, CNC derived from sisal fibers enhanced the PCPW sensor's conductivity (3.3 S/m) and mechanical properties (elongation at break: 99 %) by improving the dispersion and connectivity of MWCNT. The PCPW sensor displayed a high sensitivity to strain (gauge factor: 49.5) and could monitor both facial expressions (smiling and winking) and the bending of joints. The sensor also generated stable electrical responses during breathing and blowing due to the change in humidity. Therefore, this biodegradable and multifunctional sensor has good application prospects.

A chitosan derivative/phytic acid polyelectrolyte complex endowing polyvinyl alcohol film with high barrier, flame-retardant, and antibacterial effects

Films with high barrier, flame-retardant, and antibacterial properties are beneficial in terms of food and logistics safety. Herein, a polyelectrolyte complex (PEC) of N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC, chitosan derivative) and phytic acid (PA) was successfully prepared and then incorporated into a polyvinyl alcohol (PVA) matrix to fabricate a composite film with satisfactory barrier, fire-retardant, and antibacterial properties. The influence of HTCC/PA (HTPA) on the structural, physical and functional properties of the PVA matrix was investigated. Compared with the PVA film, PVA-HTPA6 film exhibited 3.38 times of flexibility and 83.33 % and 80.64 % of water vapor permeability and oxygen permeability, respectively. Benefiting from HTPA, the PVA-HTPA6 film exhibited outstanding flame-retardant capacity, with a high LOI value (33.30 %) and immediate self-extinguishing behaviour. Furthermore, the HTPA endowed the films with excellent antibacterial properties. Compared with other films, the PVA-HTPA6 film effectively maintained the quality of pork during storage at 4 °C for 9 days. Our findings indicate that the films are promising for packaging and logistics safety with oil-containing foods.

The physical, mechanical, thermal and barrier properties of starch nanoparticle (SNP)/polyurethane (PU) nanocomposite films synthesised by an ultrasound-assisted process

This article reports on the ultrasound-assisted acid hydrolysis for the synthesis and evaluation of starch nanoparticles (SNP) as nanofillers to improve the physical, mechanical, thermal, and barrier properties of polyurethane (PU) films. During the ultrasonic irradiation, dropwise addition of 0.25 mol L^-1 H₂SO₄ was carried out to the starch dispersion for the preparation of SNPs. The synthesized SNPs were blended uniformly within the PU matrix using ultrasonic irradiation (20 kHz, 220 W pulse mode). The temperature was kept constant during the synthesis (4 °C). The nanocomposite coating films were made with a regulated thickness using the casting method. The effect of SNP content (wt%) in nanocomposite coating films on various properties such as morphology, water vapour permeability (WVP), glass transition temperature (Tg), microbial barrier, and mechanical properties was studied. The addition of SNP to the PU matrix increased the roughness of the surface, and Tg by 7 °C, lowering WVP by 60% compared to the PU film without the addition of SNP. As the SNP concentration was increased, the opacity of the film increased. The reinforcement of the SNP in the PU matrix enhanced the microbial barrier of the film by 99.9%, with the optimal content of SNP being 5%. Improvement in the toughness and barrier properties was observed with an increase in the SNP content of the film.

Alginate enriched with phytic acid for hydrogels preparation

Alginate hydrogels are extremely versatile and flexible biomaterials, with an enormous potential for bio-applications use. Their similarity with extracellular matrix is a key factor in their performance for cell and tissue regeneration. In this study superabsorbent high porous hydrogels based on sodium alginate physical crosslinked with a natural crosslinker compound namely phytic acid were prepared and evaluated from the viewpoint of their specific properties. The resulting hydrogels obtained with different ratios between alginate and phytic acid were characterized by Fourier transform infrared spectroscopy technique, scanning electron microscopy, XRD measurements, swelling tests in physiological environment, and thermal analysis by using a simultaneous TG/FT-IR/MS system. There are put into evidence the differences in physico-chemical properties of the hydrogels in relation with their composition, which endows them tunable properties and versatility.

High Frequency Sonoprocessing: A New Field of Cavitation-Free Acoustic Materials Synthesis, Processing, and Manipulation

Ultrasound constitutes a powerful means for materials processing. Similarly, a new field has emerged demonstrating the possibility for harnessing sound energy sources at considerably higher frequencies (10 MHz to 1 GHz) compared to conventional ultrasound (⩽3 MHz) for synthesizing and manipulating a variety of bulk, nanoscale, and biological materials. At these frequencies and the typical acoustic intensities employed, cavitation-which underpins most sonochemical or, more broadly, ultrasound-mediated processes-is largely absent, suggesting that altogether fundamentally different mechanisms are at play. Examples include the crystallization of novel morphologies or highly oriented structures; exfoliation of 2D quantum dots and nanosheets; polymer nanoparticle synthesis and encapsulation; and the possibility for manipulating the bandgap of 2D semiconducting materials or the lipid structure that makes up the cell membrane, the latter resulting in the ability to enhance intracellular molecular uptake. These fascinating examples reveal how the highly nonlinear electromechanical coupling associated with such high-frequency surface vibration gives rise to a variety of static and dynamic charge generation and transfer effects, in addition to molecular ordering, polarization, and assembly-remarkably, given the vast dimensional separation between the acoustic wavelength and characteristic molecular length scales, or between the MHz-order excitation frequencies and typical THz-order molecular vibration frequencies.

A facile and green strategy to simultaneously enhance the flame retardant and mechanical properties of poly(vinyl alcohol) by introduction of a bio-based polyelectrolyte complex formed by chitosan and phytic acid

There are still some key problems in the process of the flame retardant treatment of poly vinyl alcohol (PVA): poor compatibility, deteriorating mechanical properties and potential toxicity to human health and environment.

Synthesis of poly(acrylamide-co-itaconic acid)/MWCNTs superabsorbent hydrogel nanocomposite by ultrasound-assisted technique: Swelling behavior and Pb (II) adsorption capacity

In this research, the poly (acrylamide-co-itaconic acid)/multi-walled carbon nanotubes (P(AAm-co-IA)/MWCNTs) as a novel superabsorbent hydrogel nanocomposite was synthesized by graft copolymerization of acrylamide (AAm) and itaconic acid (IA) mixture in the presence of the MWCNTs using ammonium persulfate (APS) as a free radical initiator and methylenebisacrylamide (MBA) as a crosslinker under ultrasound-assisted condition. The blank P(AAm-co-IA) hydrogel and its composite with the MWCNTs were characterized by means of SEM, FTIR, XRD and TGA methods. The effects of different parameters such as pH, time, the MWCNTs content and salt solutions on swelling behavior were investigated. The stability of the hydrogel increased by any increase in the MWCNTs content, which might be attributed to the hydrophobic nature of the MWCNTs as well as the increase of the crosslinker density. The water retention capacity (WRC) of the P(AAm-co-IA) hydrogel increased in the presence of the MWCNT (10 wt%). The synthesized hydrogel nanocomposite was studied for Pb (II) adsorption from aqueous solution. The effects of different parameters such as contact time (5-90 min), Pb (II) initial concentration (25-175 mg/L) and initial pH (1.5-4.5) of solution on Pb (II) adsorption were investigated by batch method. In comparison to P(AAm-co-IA) hydrogel, the P(AAm-co-IA)/MWCNTs hydrogel nanocompoite showed better adsorption behavior toward Pb (II). One of the most important aspects of this research was to investigate the effects of ultrasonic waves on polymer matrix and its ability.

Nanopowder synthesis of novel Sn(II)-imprinted poly(dimethyl vinylphosphonate) by ultrasound-assisted technique: Adsorption and pre-concentration of Sn(II) from aqueous media and real samples

In this research, a novel Sn(II)-imprinted poly(dimethyl vinylphosphonate) nanopowder (Sn(II)-IPDMVPN) was prepared using Sn²⁺, dimethyl vinylphosphonate, azobis isobutyronitril and ethylene glycol dimethacrylate as the template, ligand, initiator and cross linker, respectively. The non-imprinted poly(dimethyl vinylphosphonate) nanopowder (NIPDMVPN) was also synthesized utilizing the same procedure without using SnCl₂·2H₂O in order to compare the results with the Sn(II)-IPDMVPN. The structure, morphology and composition of the products were characterized by XRD, SEM, EDX, XRF, BET, FT-IR and NMR techniques. Some experimental conditions including pH, eluent concentration and sample volume were optimized to maximize Sn(II) adsorption by the Sn(II)-IPDMVPN. It was found that the optimum conditions are pH = 5, 1.00 M of HNO₃ as eluent and sample volume up to 50 mL. The results obtained by ICP-MS indicated that the Sn(II)-IPDMVPN had much higher adsorption capacity for Sn(II) ions (about threefold) than the NIPDMVPN. The applicability of the Sn(II)-IPDMVPN was also investigated in three different real samples. Under the best experimental conditions, the calibration graphs were linear in the range of 0.19-90 μg L^-1 with a coefficient of determination (R²) of 0.990. The detection limit was calculated to be 0.06 μg L^-1. The relative standard deviation (RSD) for six replicate measurements of Sn(II) at 1.00 ng mL^-1 was determined to be 1.8%. The results showed that the Sn(II)-IPDMVPN-ICP-MS is a very simple, rapid, sensitive and efficient method for the determination of Sn(II) ions in water samples.

Using ultrasonic (US)-initiated template copolymerization for preparation of an enhanced cationic polyacrylamide (CPAM) and its application in sludge dewatering

In this study, the ultrasonic (US)-initiated template copolymerization was employed to synthesize a novel cationic polyacrylamide (CPAM) characterized by a microblock structure using dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomers, and sodium polyacrylate (NaPAA) as template. The polymers structure property was analyzed by Fourier transform infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR) and thermogravimetric analysis (TGA). The results showed that a novel cationic microblock structure was successfully synthesized in the template copolymer of DMDAAC and AM (TPADM). Meanwhile, the analysis result of association constant (M_K) provided powerful support for a I Zip-up (ZIP) template polymerization mechanism and the formation of the microblock structure. The factors affecting the polymerization were investigated, including ultrasonic power, ultrasonic time, monomer concentration, initiator concentration, m_AM:m_DMDAAC and n_NaPAA:n_DMDAAC. The sludge dewatering performance of the polymers was evaluated in terms of specific resistance to filtration (SRF), filter cake moisture content (FCMC), floc size (d₅₀) and fractal dimension (D_f). Flocculation mechanism was also analyzed and discussed. The sludge dewatering results revealed that the polymer with the novel microblock structure showed a more excellent flocculation performance than those with randomly distributed cationic units. A desirable flocculation performance with a SRF of 4.5 × 10¹² m kg^-1, FCMC of 73.1%, d₅₀ of 439.156 µm and D_f of 1.490 were obtained at pH of 7.0, dosage of 40 mg L^-1 and the molecular weight of 5.0 × 10⁶ Da. The cationic microblock extremely enhanced the polymer charge neutralization and bridging ability, thus obtaining the excellent sludge dewatering performance.

Ultrasonic-microwave assisted synthesis of three-dimensional polyvinyl alcohol carbonate/graphene oxide sponge and studies of surface resistivity and thermal stability

In the article, graphene oxide (GO) was prepared by flake graphite, nitric acid and peroxyacetic acid via the sonochemical method and characterized, and polyvinyl alcohol carbonate/GO composite (PVAC/GO composite) was synthesized by polyvinyl alcohol (PVA), dimethyl carbonate (DMC) and GO via the approach of transesterification in the case of ultrasonic-microwave synergistic effects and characterized, and three-dimensional PVAC/GO sponge (3D PVAC/GO sponge) was manufactured by PVAC/GO composite via the foaming approach and characterized, and the thermal stability and surface resistivity of 3D PVAC/GO sponge were investigated. Based on those, it had been attested that PVAC polymer was structured by DMC and PVA and had the six-membered lactone rings and the ether bonds, and PVAC/GO composite was constituted by 2D GO lattice and PVAC polymer, and 3D PVAC/GO sponge was constructed by PVAC/GO composite, and the surface resistivity of 3D PVAC/GO sponge with 0.00, 0.60, 1.20, 1.80 and 2.40 g of GO were 9.07  ×  10⁷, 6.02  ×  10⁷, 4.65  ×  10⁷, 2.47  ×  10⁷ and 1.06  ×  107 O/sq, and the thermal stability of 3D PVAC/GO sponge had improved.

The investigation of the specific behavior of a cationic block structure and its excellent flocculation performance in high-turbidity water treatment

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment. This study introduced an ultrasound (US)-initiated template polymerization (UTP) method to develop a novel cationic templated polyacrylamide (TPAA) with a microblock structure. TPAA was prepared using acrylamide (AM) and sodium (3-acrylamidopropyl)trimethylammonium chloride (ATAC) as the monomers and sodium polyacrylate (NaPAA) as the template. Factors that affected polymerization such as the ultrasound power, ultrasound time, initiator concentration, pH, and m_AM : m_ATAC and n_NaPAA : n_ATAC values were investigated. The properties of the polymers were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicated the successful formation of a cationic microblock structure in TPAA. In addition, TPAA displayed favorable thermal decomposition properties and a rough and coarse surface morphology, as shown by analyses using TGA and SEM, respectively. Moreover, a zip (type I) template polymerization mechanism was identified via analyses of the association constant (K_M), conversion (C_v) and polymerization rate (R_p). The flocculation performance of the templated copolymer TPAA was evaluated by treating high-turbidity water. According to the results for the zeta potentials and FTIR spectra of the generated flocs, it was indicated that the cationic microblocks in the templated copolymer could greatly enhance its charge neutralization, patching and bridging ability, and therefore excellent flocculation performance (residual turbidity: 5.8 NTU, D_f: 1.89, floc size d₅₀: 608.404 μm and floc kinetic: 15.86 × 10⁻⁴ s⁻¹) for treating high-turbidity water was achieved.

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment.