Gel Permeation Chromatography Research Articles

Polymer-type flame retardants based on a DOPO derivative for improving the flame retardancy of polyamide 6: Preparation, properties and flame retardancy mode of action

A polymer-type flame retardant (PFR) based on a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative was synthesised here to improve the flame retardancy of polyamide 6 (PA6). The chemical structure and thermal property of the PFR were characterised by Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PFR and PA6 were melt-blended to obtain a flame-retardant polyamide 6 (FRPA6). Its thermal property, mechanical property and flame retardancy were characterised via TGA, DSC and tensile, impact, vertical burning and limiting oxygen index (LOI) tests. Its flame-retardant mode of action was analysed by scanning electron microscopy, FTIR spectroscopy, cone calorimetry and pyrolysis-gas chromatography-mass spectrometry. The FRPA6 with a phosphorus content of 3000 ppm passed the UL-94 V-0 rating, and the LOI of the FRPA6 with a phosphorous content of 5000 ppm reached 28.8 %. Compared with pure PA6, the peak heat release rate, total heat release and effective heat of FRPA6–5000 were reduced by 35.4 %, 21.9 % and 26.5 %, respectively. These results indicate that the flame-retardant mode of action of PFR mainly involved the quenching effect of phosphorus-containing radicals in the gas phase.

Evaluation of the polycaprolactone hydrolytic degradation in acid solvent and its influence on the electrospinning process

AbstractPolycaprolactone (PCL) is a pivotal biopolymer in biomedicine, especially in tissue engineering for scaffolds and biomaterials. Recognized for its effectiveness as a drug carrier with superior controlled release properties, PCL is commonly processed via electrospinning, typically employing chlorinated or fluorinated solvents known for cellular toxicity. As an environmentally conscious alternative, this study explores glacial acetic acid (AA) as a solvent for electrospinning solutions. Investigating PCL's molecular degradation through acid hydrolysis in acidic solvents (AA/formic acid) (FA), the study assesses the impact of storage time on resulting structures. Solutions containing 30% PCL in AA/FA (9:1) were stored at 35°C for up to 14 days, revealing a 50% molar mass reduction during solubilization through gel permeation chromatography, x‐ray diffraction, and Fourier‐transform infrared analyses. This reduction influenced chain packing, raising crystallinity indices from approximately 37% to 49% with prolonged storage. The reduced molar mass resulted in unstable Taylor cones, generating diverse mat morphologies. Intriguingly, this degradation enhanced water adsorption capacity, indicating exposed hydrogen bonds from acid hydrolysis as an advantageous trait for regenerative medicine. This underscores the hydrolyzed materials' potential for cell anchoring in tissue engineering.

Low molar mass polycarbonate diols from degradation of terpolymers obtained by epoxide/o-phthalaldehyde/CO2 copolymerization

In this manuscript, we describe the synthesis of low molar mass polycarbonate diols by acid cleavage of labile acetal linkages included in high molar mass poly(ether-co-carbonate-co-acetal) terpolymers. These copolymers were prepared by terpolymerization of propylene oxide (PO) with o-phthalaldehyde (OPA) and carbon dioxide (CO2), using triethyl borane (TEB) as activator and an onium salt as initiator. The advantage of this strategy of synthesis of poly(propylene carbonate) diols (PPC-diols) lies in the minute amounts of TEB and initiator required. Moreover, OPA could be isolated through post-hydrolysis of the terpolymers and recycled for subsequent use. We also demonstrated that this strategy works for the synthesis of low molar mass poly(ethylene carbonate) diols (PEC-diols). The structural integrity of the terpolymers before and after acid treatment, the characterization of low molar mass PPC-diols, and recycling process of OPA were carried out by 1H NMR spectroscopy, gel permeation chromatography, and matrix-assisted laser desorption ionization time of flight (MALDI-TOF) MS.

Variation pattern in the macromolecular (cellulose, hemicelluloses, lignin) composition of cell walls in Pinus tabulaeformis tree trunks at different ages as revealed using multiple techniques

The plant cell wall is a complex, heterogeneous structure primarily composed of cellulose, hemicelluloses, and lignin. Exploring the variations in these three macromolecules over time is crucial for understanding wood formation to enhance chemical processing and utilization. Here, we comprehensively analyzed the chemical composition of cell walls in the trunks of Pinus tabulaeformis using multiple techniques. In situ analysis showed that macromolecules accumulated gradually in the cell wall as the plant aged, and the distribution pattern of lignin was opposite that of polysaccharides, and both showed heterogenous distribution patterns. In addition, gel permeation chromatography (GPC) results revealed that the molecular weights of hemicelluloses decreased while that of lignin increased with age. Two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) analysis indicated that hemicelluloses mainly comprised galactoglucomannan and arabinoglucuronoxylan, and the lignin types were mainly comprised guaiacyl (G) and p-hydroxyphenyl (H) units with three main linkage types: β-O-4, β-β, and β-5. Furthermore, the C-O bond (β-O-4) signals of lignin decreased while the C-C bonds (β-β and β-5) signals increased over time. Taken together, these findings shed light on wood formation in P. tabulaeformis and lay the foundation for enhancing the processing and use of wood and timber products.

Evaluation of Modified Asphalt Binders with Soybean Oil-Based Polymers: Preparation Temperature and Rheological Characterization

To investigate the feasibility of bio-based polymers in the modification of base asphalt binder, two soybean oil-based polymers (PAESO) were synthesized from bio-monomers with different functionalities via free radical polymerization. The characterization of both PAESOs was conducted using Hydrogen nuclear magnetic resonance and Gel Permeation Chromatography analyses, the results showed that the bio-monomer with a higher functionality exhibited a stronger tendency towards self-polymerization, resulting in the polymer with a high conversion rate (44.44 %) and a slightly lower molecular weight (14.76 kDa). The optimal mixing temperature for preparing PAESO-modified asphalt binders was determined through Molecular Dynamics (MD) simulation and Laser Scanning Confocal Microscopy. The MD simulation results indicated that PAESO-modified asphalt models had reached the most stable configurations at a mixing temperature of 160 °C, as evidenced by fewer and more homogeneous distributed small bright spots observed in fluorescence images. This suggested that the outstanding compatibility between PAESO and asphalt binders could be obtained at the optimal mixing temperature of 160 °C. Furthermore, the rheological characteristics of asphalt binders modified with PAESO were examined through Dynamic Shear Rheometer and Bending Beam Rheometer tests. The results revealed that PAESO mainly exhibited a softening effect by significantly enhancing the flexibility, stress relaxation, fatigue, and thermal cracking resistance of the base asphalt binders at intermediate and low temperatures. PAESO-L modified asphalt manifested elastic properties akin to those observed in polymer-modified asphalt within the low-frequency and high-temperature domain. Additionally, PAESO derived from monomers with a higher functionality presented notable benefits in enhancing thermal and fatigue cracking resistance than that of PAESO with a lower functionality. These findings provide valuable insights for the preparation and development of bio-polymer additives for use in asphalt materials.

Antioxidant activities of sea buckthorn polysaccharides and their potential application in cosmetic industry

BackgroundMany natural polysaccharides have been reported to protect against skin aging through antioxidant pathways, but sea buckthorn polysaccharides have been less well studied in terms of antioxidant activity, and the related studies are not well developed. ObjectiveBy examining the chemical structure of sea buckthorn polysaccharides, this research aimed to offer a scientific foundation for their use in cosmetics and explore the in vitro antioxidant potential of these polysaccharides. Materialsand Methods: We made SP (sea buckthorn crude polysaccharide) using both hot water extraction and ultrasonic extraction. Then, we used the anion exchange method to separate and purify it to get three different polysaccharides: SPA (polysaccharide eluted from deionized water), which is a neutral polysaccharide, and SPB (polysaccharides eluted from 0.1M NaCl) and SPC (polysaccharide eluted from 0.2M NaCl), which are acidic polysaccharides. The characteristics of the four polysaccharides (SP, SPA, SPB and SPC) were determined using high-performance gel permeation chromatography (HPGPC), high-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and x-ray diffractometry (XRD). In vitro antioxidant assays were used to test their antioxidant activities. ResultsThe in vitro antioxidant assay showed that the four sea buckthorn polysaccharides (SP, SPA, SPB, and SPC) were good at getting rid of superoxide anion and DPPH radicals, especially ABTS radicals. They were also better at getting rid of free radicals than VC at low concentrations, and they were also good at reducing other molecules. ConclusionThese results showed that sea buckthorn polysaccharide has certain antioxidant activity; therefore, sea buckthorn polysaccharide has a strong potential to be applied in antioxidant and anti-aging functional cosmetics.

Synthesis of Dendrimer-Like Molecules with Partial Carbon Chain via Iterative Single Unit Monomer Insertions.

Carbon-chain dendritic polymers hold unique properties and promising applications. However, synthesizing carbon-chain dendrimers, beyond conjugated ones, remains a challenge. Here, the use of the iterative single unit monomer insertion technique for synthesizing 2.5 generation partial-carbon-chain dendrimers (G2.5) is described, utilizing bismaleimide as the core, a maleimide-trithiocarbonate conjugate as the branching unit, and indene as the spacer unit, following a divergent growth strategy. The optimized conditions for synthesizing the maleimide-trithiocarbonate branching unit are a bismaleimide to trithiocarbonate ratio of 5:1 and a reaction time of 30 min. The structures are verified using 1H nuclear magnetic resonance, gel permeation chromatography, and matrix-assisted laser desorption/ionization-time of flight mass spectra. A four-arm star polymer is then synthesized using the G2.5 as the core. This synthesis of a partial-carbon-chain dendrimer establishes a foundational step toward creating all-carbon-chain ones and may open new application avenues in material science.

Analytical data of Acacia nilotica var. Nilotica gum

This study aimed to characterize the exudate gum from Acacia nilotica var. nilotica in Sudan and compare its physicochemical properties to Acacia seyal var. seyal and Acacia senegal var. senegal (gum Arabic). Samples were collected from six different states in Sudan over three seasons. The gum had a moisture content of 10.50%, ash content of 1.86%, pH value of 5.19, specific optical rotation of +94.70, intrinsic viscosity of 10.44 cm3 g-1, nitrogen content of 0.024%, protein content of 0.16%, acid equivalent weight of 1907.82, and total uronic acid content of 10.18%. Sugar content analysis revealed arabinose (41.20%), galactose (17.43%), and rhamnose (10.68%). Potassium was the predominant cation, followed by calcium, magnesium, sodium, lead, and iron. Acacia nilotica was classified as part of the Gummeferae series and exhibited a positive specific optical rotation. The Number average molecular weight (Mn) was estimated using osmometric measurements and gel permeation chromatography. The gum had a higher molecular weight and lower intrinsic viscosity compared to gum Arabic, suggesting a spheroidal shape of molecule. Amino acid analysis showed similarities with gum Arabic, with hydroxyproline and serine as principal amino acids. Variations in cationic composition were attributed to differences in soil type among collection locations. KEY WORDS: Physicochemical characterization, Acacia senegal var. senegal gum, Acacia seyal var. seyal gum, Acacia nilotica var. nilotica gum, gammiferae Bull. Chem. Soc. Ethiop. 2024, 38(4), 839-852. DOI: https://dx.doi.org/10.4314/bcse.v38i4.2

Controlled Magnetite Grafted Poly(glycidyl methacrylates) for Heavy Metal Absorption and Recovery via SET-LRP

A versatile magnetite based stringent polymer for effective metal capture was prepared by reacting iron oxide based initiator with glycidyl methacrylate monomer via single-electron transfer living radical polymerization (SET-LRP) technique. The versatile grafted polymer was successfully synthesized by metal catalyzed living radical polymerization using the catalyst system Cu/N,N,N',N'',N'''-pentamethyldiethylenetriamine as the ligand. The structural confirmation of the initiator and the grafted polymer was analyzed by using instrumentation methods such as proton nuclear magnetic resonance spectroscopy, UV-visible, TGA, SEM and gel permeation chromatography for molecular weight measurements. As the polymerization time increased, both the conversion and the molecular weight were observed to increase linearly with time. Narrow dispersed lower polydispersity index (PDI) and dispensable magnetite-g-PGMA was utilized for the extract of toxic lead from the wastewater. Sustained binding was observed due to the presence of epoxide ring in the repeating units of the polymer and recovered by magnetic effect. The material shows good stability as evident by TGA curves and better affinity to toxic lead as observed by UV-visible and SEM techniques.

Cascadic degradation of selected polyolefin grades in a simulated closed-loop recycling process

AbstractReintroducing recycled plastics into production processes can lead to irreversible degradation and changes in their properties, thereby limiting their recycling potential to a finite number of loops. This study investigates the impact of process-induced degradation resulting from multiple reprocessing cycles on specific material properties and aims to establish structure–property relationships. Four different polyolefins, including two polypropylenes, high-density polyethylene, and low-density polyethylene, were selected for the study. The materials underwent extrusion, pelletizing, injection molding, and milling before being reintroduced into the reprocessing cycle. This sequence of processing steps was repeated six times on each material. Various characterization techniques, including high-temperature gel permeation chromatography, melt mass flow rate, parallel-plate rheology, differential scanning calorimetry, gas chromatography–mass spectrometry, and optical defect control system, were performed to evaluate the molecular structure, rheological behavior, thermal stability, and the resulting contaminants and defects after each reprocessing step. The reprocessing of polypropylene resulted in a gradual decrease in the average molecular weights accompanied by a shift to lower viscosities and higher melt mass flow rates, whereas the polyethylene grades showed the opposite trend with a less pronounced effect in high-density polyethylene. The volatile organic compounds rose in polypropylene and sank in polyethylene after reprocessing. Additionally, all four materials exhibited an increase in degradation-related defects based on optical defect analysis. Graphical abstract

Argon nonthermal plasma etching of poly(L-lactic acid) films: Tunning the local surface degradation and hydrolytic degradation rate

Plasma technology is widely used in the industry for the surface modification of polymeric materials, improving the adhesion of paints in polymeric packaging and cellular adhesion on polymers' surfaces without using hazardous chemicals. Plasma etching is a fast way to modify polymers, creating new nanostructure surfaces and adding chemical groups for new applications like antimicrobial surfaces. Poly(L-lactic acid) (PLLA) is a biodegradable polymer with exciting properties for biomedical, tissue engineering, food packaging, and other applications. In many cases, these products must undergo plasma surface treatments to meet the technical requirements of their function. Herein, we evaluated the effects of surface modification of PLLA using Argon nonthermal plasma etching. The results from Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray Excited Photoelectron Spectroscopy (XPS), and Matrix-assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-ToF-MS) show that increasing the plasma exposure time causes an enhancement in bulk and local surface degradation, crystallization kinetics and susceptibility to hydrolytic degradation for PLLA. Atomic Force Microscopy (AFM) show that the PLLA films present the highest surface roughness after 60 s of plasma etching times. Our findings suggest that plasma etching can be a suitable tool to adjust the polymer degradation rate to design intracorporeal devices with controlled degradation kinetics.

Fructosyl Amino Oxidase as a Therapeutic Enzyme in Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is an age-related disorder that is a global public health problem. The non-enzymatic Maillard reaction results in the formation of advanced glycation end products (AGEs). Accumulation of AGEs in drusen plays a key role in AMD. AGE-reducing drugs may contribute to the prevention and treatment of AGE-related disease. Fructosamine oxidase (FAOD) acts on fructosyl lysine and fructosyl valine. Based upon the published results of fructosamine 3-kinase (FN3K) and FAOD obtained in cataract and presbyopia, we studied ex vivo FAOD treatment as a non-invasive AMD therapy. On glycolaldehyde-treated porcine retinas, FAOD significantly reduced AGE autofluorescence (p = 0.001). FAOD treatment results in a breakdown of AGEs, as evidenced using UV fluorescence, near-infrared microspectroscopy on stained tissue sections of human retina, and gel permeation chromatography. Drusen are accumulations of AGEs that build up between Bruch's membrane and the retinal pigment epithelium. On microscopy slides of human retina affected by AMD, a significant reduction in drusen surface to 45 ± 21% was observed following FAOD treatment. Enzymatic digestion followed by mass spectrometry of fructose- and glucose-based AGEs (produced in vitro) revealed a broader spectrum of substrates for FAOD, as compared to FN3K, including the following: fructosyllysine, carboxymethyllysine, carboxyethyllysine, and imidazolone. In contrast to FN3K digestion, agmatine (4-aminobutyl-guanidine) was formed following FAOD treatment in vitro. The present study highlights the therapeutic potential of FAOD in AMD by repairing glycation-induced damage.

Identification of plastic-degrading bacteria in the human gut

Environmental pollution caused by the excessive use of plastics has resulted in the inflow of microplastics into the human body. However, the effects of microplastics on the human gut microbiota still need to be better understood. To determine whether plastic-degrading bacteria exist in the human gut, we collected the feces of six human individuals, did enrichment cultures and screened for bacterial species with a low-density polyethylene (LDPE) or polypropylene (PP)-degrading activity using a micro-spray method. We successfully isolated four bacterial species with an LDPE-degrading activity and three with a PP-degrading activity. Notably, all bacterial species identified with an LDPE or PP-degrading activity were opportunistic pathogens. We analyzed the microbial degradation of the LDPE or PP surface using scanning electron microscopy and confirmed that each bacterial species caused the physical changes. Chemical structural changes were further investigated using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy, confirming the oxidation of the LDPE or PP surface with the formation of carbonyl groups (C=O), ester groups (CO), and hydroxyl groups (-OH) by each bacterial species. Finally, high temperature gel permeation chromatography (HT-GPC) analysis showed that these bacterial species performed to a limited extent depolymerization. These results indicate that, as a single species, these opportunistic pathogens in the human gut have a complete set of enzymes and other components required to initiate the oxidation of the carbon chains of LDPE or PP and to degrade them. Furthermore, these findings suggest that these bacterial species can potentially biodegrade and metabolize microplastics in the human gut.

Meniscal repair with additive manufacture of bioresorbable polymer: From physicochemical characterization to implantation of 3D printed poly (L-co-D, L lactide-co-trimethylene carbonate) with autologous stem cells in rabbits.

Three-dimensional (3D) structures are actually the state-of-the-art technique to create porous scaffolds for tissue engineering. Since regeneration in cartilage tissue is limited due to intrinsic cellular properties this study aims to develop and characterize three-dimensional porous scaffolds of poly (L-co-D, L lactide-co-trimethylene carbonate), PLDLA-TMC, obtained by 3D fiber deposition technique. The PLDLA-TMC terpolymer scaffolds (70:30), were obtained and characterized by scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, thermal gravimetric analysis, compression mechanical testing and study on in vitro degradation, which showed its amorphous characteristics, cylindrical geometry, and interconnected pores. The in vitro degradation study showed significant loss of mechanical properties compatible with a decrease in molar mass, accompanied by changes in morphology. The histocompatibility association of mesenchymal stem cells from rabbit's bone marrow, and PLDLA-TMC scaffolds, were evaluated in the meniscus regeneration, proving the potential of cell culture at in vivo tissue regeneration. Nine New Zealand rabbits underwent total medial meniscectomy, yielding three treatments: implantation of the seeded PLDLA-TMC scaffold, implantation of the unseeded PLDLA-TMC and negative control (defect without any implant). After 24weeks, the results revealed the presence of fibrocartilage in the animals treated with polymer. However, the regeneration obtained with the seeded PLDLA-TMC scaffolds with mesenchymal stem cells had become intimal to mature fibrocartilaginous tissue of normal meniscus both macroscopically and histologically. This study demonstrated the effectiveness of the PLDLA-TMC scaffold in meniscus regeneration and the potential of mesenchymal stem cells in tissue engineering, without the use of growth factors. It is concluded that bioresorbable polymers represent a promising alternative for tissue regeneration.

Effect of comonomer loading on the thermal and mechanical properties of biobased copolyamides PA6/PA56

With bio-renewable and environmentally friendly nature, biobased polyamides have emerged as attractive alternatives to traditional petroleum-derived polymers. However, poor thermal and mechanical performance, high costs, and limited scalability significantly hinder their practical applications. Herein, a series of biobased copolyamides PA6/PA56 (CoPAs) were successfully synthesized from caprolactam, adipic acid, and the lysine-derived biobased monomers 1,5-pentanediamine. The copolyamides were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (1H NMR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), rheological analysis, mechanical testing, and scanning electron microscopy (SEM). The result shows the α to γ transition in the crystalline form of the copolyamides with comonomer loading. The melting temperature, crystallization temperature, and crystallinity gradually decrease due to the introduction of the odd-even structure, causing deviation in amide positions and reducing hydrogen bond formation between molecular chains. Furthermore, variable-temperature infrared (VTIR) analysis and density functional theory (DFT) calculations further confirm a decrease in intermolecular forces. Importantly, the mobility of the molecular chains in the amorphous region is significantly improved, endowing the copolyamides with sufficient degrees of freedom to cope with externally applied strains. Moreover, significant entanglement facilitates effective stress transfer during stretching. As a result, the synthesized copolyamides achieve a high strength of 51 MPa and a remarkable toughness of 199 MJ/m3, without sacrificing thermal stability and processing properties. These biobased CoPAs show great potential and prospects in the field of high-performance thermoplastic materials, films, and textiles.

Physicochemical Characterization, Antioxidant and Anticancer Activity Evaluation of an Acidic Polysaccharide from Alpinia officinarum Hance.

AHP-3a, a triple-helix acidic polysaccharide isolated from Alpinia officinarum Hance, was evaluated for its anticancer and antioxidant activities. The physicochemical properties and structure of AHP-3a were investigated through gel permeation chromatography, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. The weight-average molecular weight of AHP-3a was 484 kDa, with the molar percentages of GalA, Gal, Ara, Xyl, Rha, Glc, GlcA, and Fuc being 35.4%, 21.4%, 16.9%, 11.8%, 8.9%, 3.1%, 2.0%, and 0.5%, respectively. Based on the results of the monosaccharide composition analysis, methylation analysis, and NMR spectroscopy, the main chain of AHP-3a was presumed to consist of (1→4)-α-D-GalpA and (1→2)-α-L-Rhap residues, which is a pectic polysaccharide with homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) structural domains containing side chains. In addition, the results of the antioxidant activity assay revealed that the ability of AHP-3a to scavenge DPPH, ABTS, and OH free radicals increased with an increase in its concentration. Moreover, according to the results from the EdU, wound healing, and Transwell assays, AHP-3a can control the proliferation, migration, and invasion of HepG2 and Huh7 hepatocellular carcinoma cells without causing any damage to healthy cells. Thus, AHP-3a may be a natural antioxidant and anticancer component.

Sustainable production of heavy metal-binding levan by a subarctic permafrost thaw lake Pseudomonas strain 2ASCA

Pseudomonas strain 2ASCA isolated in subarctic Québec, Canada, produced a cell membrane bound levan-type exopolymer (yield 1.17 g/L), after incubation in growth media containing 6 % sucrose (w/v) at temperature of 15 °C for 96 h. The objective of this study was to optimize levan production by varying the growth parameters. Moreover, the polymer's chemical characterization has been studied with the aim of increasing knowledge and leading to future applications in many fields, including heavy metal remediation. Higher levan yields (7.37 g/L) were reached by setting up microbial fermentation conditions based on the re-use of the molasses obtained from sugar beet processing. Spectroscopy analyses confirmed the levan-type nature of the exopolymer released by strain 2ASCA, consisting of a β-(2,6)-linked fructose repeating unit. Gel permeation chromatography revealed that the polymer has a molecular weight of 13 MDa. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) showed that the levan sequestered with a strong affinity Cr(III), which has never been previously reported, highlighting an interesting biosorption potential. In addition, SEM analysis revealed the formation of nanoparticles in acidified water solution.

Development of a facile one-pot synthesized fluorescent green polyesters as cooling water antiscalants for industrial application

Currently, antiscalants used in cooling water are expected to be environmental-friendly, good scale inhibitive, fluorescence tracing, and industrial-friendly. Aliphatic biodegradable photoluminescent polymers (BPLPs) synthesized from citric acid, aliphatic diols, and various amino acids are fluorescent polymers containing heteroatom six-membered conjugated ring chromophores. Their cross-linked BPLPs have potential for use as implant or device materials, and vivo bioimaging probes. However, so far, no one has found that BPLPs can be used as efficient antiscalants for cooling water. In this work, we demonstrate a facile one-pot microwave-assisted synthesis of BPLPs from cost-effective materials. The products were characterized by Fourier transforms infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy, gel permeation chromatography, and fluorescence spectroscopy. Thus prepared BPLPs can be directly used as a novel type green fluorescent antiscalant without further purification. They have an excellent calcium phosphate inhibition efficiency that can reach 98.6 % with a dosage of 25 mg·L−1 in the static scale inhibition test at 80 °C.

Terahertz time-domain spectroscopy as a novel tool for crystallographic analysis in cellulose: tracking lattice changes following physical treatments

The authors’ series of studies aimed to explore the potential of terahertz time-domain spectroscopy (THz-TDS) in cellulose crystallographic studies, since THz radiation can detect most intermolecular vibrations and respond to lattice phonons. In this study, we tracked changes in four types of cellulose after ball milling. As the planetary ball milling time increases, it is observed through electron microscopy that the four types of cellulose particles are gradually destroyed into finer particles, while gel permeation chromatography can prove that the molecular weight gradually decreases after ball milling and the dispersity gradually approaches one, which indicates that the dispersion of the material was reduced. The most fascinating observation was made by THz-TDS, that is we have confirmed that after ball milling, the absorption characteristics of cellulose I and II in cellulose I treated with 10% NaOH (crystalline partial transition from cellulose I to II) exhibited an opposite trend. Specifically, the absorption of cellulose II at 2.40THz and 2.77THz increased, while the absorption of cellulose I at 2.11THz and 3.04THz decreased after ball milling, which suggests an increased conversion rate of cellulose I to cellulose II post-milling. Cellulose with different crystalline allomorphs shows different characteristic absorption in the THz region, and the peak position will not change even after the ball milling, only the absorption intensity changes. Although it can be observed through the most traditional X-ray diffraction method that the crystallinity index of all cellulose samples gradually decreases after ball milling. However, different from the THz results, the change after ball milling of cellulose I treated with 10% NaOH is only reflected in very subtle pattern changes, that is, the peak close to the 200 crystalline plane position is slightly shifted after ball milling.

The impact of mechanical recycling on the degradation of polyamide

There is currently no agreement on the degradation mechanisms for PA6 as a result of mechanical recycling. In this study, PA6 was extruded five times to simulate mechanical melt recycling process. Both virgin PA6 and the extruded PA6 were characterised to determine the predominant degradation mechanism. Melt flow rate (MFR) increases with increasing number of extrusion passes suggesting a reduction in melt viscosity due to mechanical processing. Gel permeation chromatography (GPC) results confirmed a reduction in molecular weight from 18,600 g/mol to 13,100 g/mol. Chain ends titration showed a decrease in the concentration of both the amine and carboxyl chain ends after the fifth extrusion. There were no changes to the chemical structure of the virgin PA6 and extruded PA6 observed from the Fourier transform infra-red (FTIR) and Nuclear magnetic resonance (NMR) spectra. X-ray photoelectron spectroscopy (XPS) showed a reduction in the C–N peak area supporting the scission of the N-alkylamide bond. The increase in the O=C–N peak area suggests that chain recombination via branching is possible. The shorter chains have higher mobility, and this gives rise to an increase in the crystallisation rate as seen from the differential scanning calorimeter (DSC) thermograms. The appearance of the γ phase after the fifth extrusion was identified in the DSC melting endotherms. The understanding of the degradation process of recycled PA6 will enable targeted modifications involving the incorporation of additives in the recycling process to ensure good mechanical properties in the recycled polymer.