Molecular Weight Determination Research Articles

Synthesis and Characterization of Novel Terpolymers as Viscosity Index Improvers Using Industrial Waste for Iraqi Lubricating Oil

The potential utilization of industrial waste, specifically polyethylene wax, to enhance the efficiency of alkyl acrylate polymers as viscosity index improver (VII) additives in lubricating compositions has been investigated. Four terpolymers (w1, w2, w3, and w4) were synthesized via free radical polymerization, incorporating hexyl acrylate, 1-tetradecene, and industrial waste-sourced polyethylene wax at varying molar ratios. These terpolymers were characterized through gel permeation chromatography (GPC) for molecular weight determination, Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR) spectroscopy for chemical structure analysis, and thermal gravimetric analysis (TGA) for thermal stability assessment. The study evaluated the efficiency of these terpolymers as viscosity index improvers (VII) in combination with free additives Iraqi lubricating oil (base oil 60). Our results demonstrate the feasibility of significantly enhancing the efficiency of viscosity improvers through the utilization of industrial waste, with improvements proportional to terpolymer concentration. The terpolymer w3, characterized by a balanced molar ratio of 1:1:1, exhibiting the highest degree of efficacy, which gave VI of 206 at 5 wt.% concentration compared with free additive lubricating oil, which gives VI of 98. This study offers promising insights into the sustainable use of industrial waste to improve lubricating compositions.

Fulvic acid transdermal patch: Its properties, optimization and release

There is a high demand for the design of fulvic acids (FA) transdermal patches being natural biologically active substances with a wide action. The difficulties in FA transdermal patches creating are due to the peculiarities of FA obtaining with high purity and solubility, the existence of many several polymorphic forms, as well as the problems of their insertion into dosage forms. In this work, we modified the FA isolation as water-soluble polymorph. This operation allowed us to reduce the impurities in the product, to optimize the formulation of the emulsion-based transdermal patches, to provide a quantitative assessment of FA release. Data of IR, 13C NMR, AAS, ICP-AES-spectra, direct and reverse titration of carboxyl groups and phenolic hydroxyls, potentiometry, molecular weight determination by cryoscopy (M.m=740 g/mol), fluorescent analysis, solubility (3.3 mL of water per gram) confirmed the receipt of the desired polymorph. Optimization of the transdermal patches formulations by Response Surface Methodology and release evaluation and kinetics mathematical modeling using a Franz cell showed the preferences of Pluronic Kolliphor p237 as a transcutant. The obtained water-soluble FA can be used as a potential component of transdermal patches with controlled release parameters.
 Keywords: fulvic acid, transdermal patches, pluronics, release

Study of Structural Elucidation, Degradation Kinetics and Antimicrobial Analysis of Copper (II) Sesame-Soap Complexes with Urea and Thiourea Ligand in Non-aqueous Solvents

Abstract: Surfactants have great importance in biological and drug industries and the complexes of metallic soaps with various ligands are used in approximately every region of national economy. Therefore, our keen interest to study of degradation kinetics and biological importance of Cu (II) surfactants in non-aqueous and non-polar solvent benzene. Present research work has been initiated with synthesis, systematic study of structural elucidation, thermal degradation, kinetics and biocidal activities of copper (II) sesame-soap complexes with macrocyclic nitrogen and sulphur containing donar ligands like urea and thiourea. The thermal degradation of copper (II) sesame-soap complexes were carried out for analysis of degradation kinetics and estimation of kinetic and thermodynamic parameters using different methods at heating rate 10oC min-1. Copper (II) sesame-soap complexes of such ligands have also been analysed against Staphylococus aureus. This research work consolidates the synthesis of copper (II) sesame soap-urea and thiourea complexes by conventional methods and the structure of these complexes were assigned according to elemental analysis and molecular weight determinations. IR, NMR and ESR spectral studies have also been done to understand structural aspects. The anti-microbial activities of copper (II) sesame-soap urea and thiourea complexes have been evaluated by testing against Staphylococus aureus. The present research work includes information of thermal analysis using TGA technique to find out their kinetic and thermodynamic parameters by using diverse equations such as Coats-Redfern equation, Horowitz-Metzger equation, Broido equation, Piloyan–Novikova equation. Moreover, the results obtained from anti-microbial screening have been used to analyze the anti-microbial activities of copper (II) sesame-soap urea and thiourea complexes against gram-positive bacteria Staphylococus aureus. These results show that complexes of copper ion co-ordinated with different nitrogen, oxygen and sulphur containing ligands, are very important in the field of pharmaceutical chemistry due to its significant role in the inhibition activity. The study of these complexes concludes that the synthesized complexes were found to possess appreciable bactericidal properties at different concentrations because chelation increases the anti-microbial potency.

Dynamic Non-Covalent Exchange Intrinsic Self-Healing at 20 °C Mechanism of Polyurethane Induced by Interactions among Polycarbonate Soft Segments.

Two polyurethanes (PUs) were similarly synthesized by reacting a cycloaliphatic isocyanate with 1,4-butanediol and two polyols of different nature (polyester, polycarbonate diol) with molecular weights of 1000 Da. Only the PU synthesized with polycarbonate diol polyol (YCD) showed intrinsic self-healing at 20 °C. For assessing the mechanism of intrinsic self-healing of YCD, a structural characterization by molecular weights determination, infrared and X-ray photoelectronic spectroscopies, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis, and dynamic mechanical thermal analysis was carried out. The experimental evidence concluded that the self-healing at 20 °C of YCD was due to dynamic non-covalent exchange interactions among the polycarbonate soft segments. Therefore, the chemical nature of the polyol played a key role in developing PUs with intrinsic self-healing at 20 °C.

An accessible technique for molecular weight determination by cryoscopy applicable for coordination compounds

An improved computerized method is proposed for determination of molecular weights by cryoscopy. The use of a precision digital platinum resistance thermometer greatly simplifies the measurement process in comparison with the classic Beckmann apparatus. All component parts of the device are factory-made (interchangeable) details, which are widely used in laboratory practice. A test report is formed with the aid of a computer using Microsoft Excel software. The use of molecular sieves for drying dimethyl sulfoxide (DMSO), as well as experimental procedures specific to organolithium compounds, make it possible to obtain reproducible measurement results for coordination compounds that are prone to oligomerization in solutions. The molecular structure of the bis(acetylacetonato)di(dimethyl sulfoxide)nickel(II) obtained from dimethyl sulfoxide solutions was determined by single crystal X-ray diffraction. P21/c, a = 8.7916(2), b = 12.3061(3), c = 8.7421(2) (Å), β = 99.4460(10)°, Z = 2. The complex [Ni(C5H7O2)2(C2H6OS)2] is mononuclear with a square-bipyramidal environment of the central atom. The coordination polyhedron of the Ni ion is formed by four oxygen atoms of two chelating acetylacetonate anions in the equatorial position and two atoms of dimethyl sulfoxide molecules in axial positions.

Joncryl chain extender reactivity with polylactide: Effect of d-lactide content, Joncryl type, and processing temperature

In this study, a highly crystallizable and an amorphous polylactide (i.e., cPLA and aPLA) with, respectively, low (0.5 mol. %) and high (12 mol. %) d-lactic acid contents and similar molecular weights were melt compounded with two different multifunctional epoxy-based Joncryl chain extenders (CEs, i.e., ADR 4400 and 4468) at 190 °C. Reactivity of Joncryl grades with aPLA was also explored at melt processing temperatures of 150, 170, and 210 °C. Small amplitude oscillatory shear rheological analysis was conducted to understand the extent of the Joncryl reaction with PLA molecules, and the results were confirmed with molecular weight determination using gel permeation chromatography. Extensional viscosity of the processed samples was also compared to control their strain hardening behavior. Results showed that the Joncryl reaction with cPLA and aPLA differs in terms of preference for chain extension or branching, indicating that molecular regularity affected the interactions with both Joncryl grades during reactive melt processing. Moreover, although the increase in processing temperature accelerated PLA degradation, it noticeably increased the reactivity of both Joncryl grades with aPLA. In all cases, ADR 4468 was more reactive in molecular chain extension/branching due to its higher functionality than ADR 4400. Differential scanning calorimetry results also revealed that the crystallization of cPLA was differently affected by the change in the Joncryl content and type.

Flash extraction of ulvan polysaccharides from marine green macroalga Ulva linza and evaluation of its antioxidant and gut microbiota modulation activities

In this study, flash extraction was used to rapidly extract water-soluble polysaccharides from Ulva linza. The optimal extraction process for the flash extraction was determined by Box–Behnken design with extraction temperature 80 °C, extraction time 117 s, liquid-solid ratio 46:1 (mL/g) and a corresponding yield of 18.5 %. The crude Ulva linza polysaccharides (CULP) were subsequently isolated by chromatography technology to obtain purified Ulva linza polysaccharide (ULP) and characterized by monosaccharide composition and molecular weight determination analysis. Furthermore, the antioxidant bioactivity of ULP was studied and the results revealed that it had a good scavenging effect on DPPH, ABTS and OH, with IC50 values of 149.2 μg/mL, 252.5 μg/mL and 1073 μg/mL, respectively. After in vitro fermentation by human fecal microbiota, the pH value of fermentation culture significantly decreased to 5.06, suggesting that ULP could be hydrolyzed and utilized by gut microbiota. The abundance of beneficial bacteria including Bacteroides, Parabacteroides and Faecalibacterium was improved. Meanwhile, the relative abundance of Prevotella, Blautia and Ruminococcus was decreased, and the low ratio of these organisms might reveal positive effects on maintaining the balance of gut microbial biodiversity. These results suggested that the composition of the human gut microbiota could be modulated by ULP, and ULP might possess the potential to maintain gut homeostasis and improve human intestinal health.

Advancing Molecular Weight Determination of Lignin by Multi-Angle Light Scattering.

Due to the complexity and recalcitrance of lignin, its chemical characterization is a key factor preventing the valorization of this abundant material. Multi-angle light scattering (MALS) is becoming a sought-after technique for absolute molecular weight (MW) determination of polymers and proteins. Lignin is a suitable candidate for MW determination via MALS, yet further investigation is required to confirm its absolute MW values and molecular size. Studies aiming to break down lignin into a variety of renewable products will benefit greatly from a simple and reliable determination method like MALS. Recent pioneering studies, discussed in this review, addressed several key challenges in lignin's MW characterization. Nevertheless, some lignin-specific issues still need to be considered for in-depth characterization. This study explores how MALS instrumentation manages the complexities of determining lignin's MW, e.g., with simultaneous fractionation and fluorescence interference mitigation. Additionally, we rationalize the importance of a more detailed light scattering analysis for lignin characterization, including aspects like the second virial coefficient and radius of gyration.

Characterization by Gel Permeation Chromatography of the Molecular Weight of Supramolecular Polymers Generated by Forming Polyrotaxanes through the Introduction of External Stoppers.

Supramolecular polymers find wide applications across diverse domains, and the molecular weight exerts a critical influence on their applicability. Consequently, the measurement of molecular weight for supramolecular polymers assumes paramount significance. Gel Permeation Chromatography (GPC) requiring low-concentration condition is a common characterization employed for molecular weight determination, which is not suitable for supramolecular polymers possessing concentration-independence property. Here, to break this threshold, we synthesized M1 embodying dibenzo-24-crown-8 (DB24C8) moiety as well as dibenzylammonium salt (DBA) group, which was capable of self-assembling into supramolecular polymers terminated with aldehyde groups at its end. Upon the addition of (4- (1,2,2-Triphenylvinyl) phenyl) methylamine (TPE-NH2), supramolecular polymers underwent a transition into polyrotaxanes, for which it was led by the generation of imine bonds. By virtue of GPC, the molecular weight of polyrotaxanes was obtained, then it was available to gain the molecular weight of supramolecular polymers with the help of transformation efficiency.

Quantitation of Active Pharmaceutical Ingredients in Polymeric Drug Products Using Elemental Analysis.

Polymeric prodrugs have gained significant popularity as a strategy to enhance the bioavailability and improve the pharmacokinetic properties of active pharmaceutical ingredients (API). Since the amount of the API in a polymeric prodrug product directly impacts both safety and efficacy, there is a pressing need for robust and accurate analytical methods to quantify the API in these formulations. Presently, drug quantification methods include reversed-phase high-performance liquid chromatography (RP-HPLC) and size exclusion chromatography (SEC)-based molecular weight determination. Even though these methods are highly precise and reproducible, a deep understanding of chromatography is required for complex method development, including optimization of the elution profile and selecting the appropriate column and mobile phase. In this chapter, we introduce the automated elemental analyzer for drug quantification, which is simple to use and does not require special method development.

Evaluation of multi-solvent size exclusion chromatography columns packed with sub-2 μm particles for the characterization of synthetic polymers

With the recent development of small particle stationary-phases and dedicated instrumentation, the combination of size-exclusion chromatography (SEC) with ultra-high performance liquid chromatography (UHPLC) technology has been realized. It opened up a new polymer analysis technique called UHP-SEC. Although high resolution and fast analysis can be achieved, the multi-solvent suitability for a given column was limited to either organic or aqueous eluents. In this work, the capability of novel SEC columns (AdvanceBio SEC columns) packed with 1.9 μm particles for the characterization of synthetic polymers in organic solvents as well as the multi-solvent compatibility for organic and aqueous eluents have been demonstrated. About six times faster separation for both polystyrene (PS) and polyethylene glycol (PEG) with good peak shape and repeatability were achieved in comparison with standard SEC columns at comparable resolution. Especially for PEG, in contrast to other SEC columns, this column could provide close-to-accurate determination of molecular weights with tetrahydrofuran (THF) as mobile phase. Good reproducibility was obtained after switching several times from water to THF and vice versa with RSD% in retention times less than 0.5 %. Different samples such as polyols, isocyanates and additives can also be analyzed for molecular weight and distribution or composition determination. Volume overload, especially with injection volumes higher than 10 µL needs to be considered. This new column offers a powerful choice for oligomer and polymer analysis with both aqueous and organic mobile phase. Ultimately, hyphenating SEC columns to various detectors can enable more information regarding chemical composition, molecular weight, concentration, and structure.

High molecular weight bimodal polyethylene elastomers using N,N'-nickel catalysts appended with methoxy and trifluoromethoxy functionality

Polyolefinic materials displaying bimodal molecular weight distributions are of interest since they can potentially provide mechanical toughness from the high molecular weight component without losing processability on account of the low molecular weight component. With this in mind, a series of nickel(II) complexes, [1-[2,6-{(4-MeOC6H4)2CH}2–4-(F3CO)C6H2N]-2-(ArN)C2C10H6]NiBr2 (Ar = 2,4-Me2C6H3Ni1, 2,6-Et2C6H3Ni2, 2,6-iPr2C6H3Ni3, 2,4,6-Me3C6H2, Ni4, 2,6-Et2-4-MeC6H2Ni5, 2,6-Me2C6H3Ni6) have been synthesized and have shown, following treatment with MMAO or Et2AlCl, excellent activity for the polymerization of ethylene (up to 19.87 × 106 g (PE) mol−1 for Ni4/Et2AlCl) generating high molecular weight branched polyethylene. More importantly, the elastomeric material produced using Et2AlCl as activator displays bimodal characteristics as well as low crystallinity and a medium to high branching density. By contrast, the material prepared using MMAO was more unimodal and showed higher crystallinity and lower branching density. Stress–strain and stress–strain recovery tests performed on the bimodal PE’s revealed a range of tensile properties with a sample prepared using Ni5/Et2AlCl combining both high tensile strength and high fracture strength (σ = 20.3 MPa, ε = 892.0 %). Conversely, a PE sample prepared using Ni4/Et2AlCl showed the highest elastic recovery with a stress relaxation (SR) value of 67.6 %. Besides branching analysis, molecular weight determinations and mechanical tests on the polymers, all nickel complexes and precursor 1,2-bis(arylimino)acenaphthenes, have been characterized by a combination of spectroscopic techniques, elemental analysis and in the cases of Ni1(OH2) and Ni4 by single crystal X-ray diffraction. A theory is also proposed to explain the observed bimodality.

Fed-batch cultivation of Euglena gracilis for the high-yield production and GPC-assisted molecular weight determination of paramylon.

Paramylon, a starch-like carbohydrate accumulated in Euglena gracilis cells, could be a potential source as a raw material for chemical products; its high-yield production would thus be highly desired. Although the molecular weight and polymerization degree of paramylon are important properties for its use as a raw material for chemical products, the available information about paramylon molecular weight remains insufficient. Therefore, in this study, we investigated a high-density E. gracilis culture approach and how culture conditions affect paramylon molecular weight. The nitrogen source, cultivation temperature, and nutrient feeding were optimized for maximum biomass and paramylon productivity. The maximum dry cell weight and paramylon content yields reached 108.9g/L and 87.2%, respectively. Paramylon molecular weight was in the range of 220000-320000Da. Our gel permeation chromatography analysis showed that the cells with a higher paramylon content tended to contain paramylon of a higher molecular weight.

Unfolding of Lignin Structure Using Size-Exclusion Fractionation.

The heterogeneous and recalcitrant structure of lignin hinders its practical application. Here, we describe how new approaches to lignin characterization can reveal structural details that could ultimately lead to its more efficient utilization. A suite of methods, which enabled mass balance closure, the evaluation of structural features, and an accurate molecular weight (MW) determination, were employed and revealed unexpected structural features of the five alkali lignin fractions obtained with preparative size-exclusion chromatography (SEC). A thermal carbon analysis (TCA) provided quantitative temperature profiles based on sequential carbon evolution, including the final oxidation of char. The TCA results, supported with thermal desorption/pyrolysis gas chromatography-mass spectrometry (TD-Py-GC-MS) and 31P NMR spectroscopy, revealed the unfolding of the lignin structure as a result of the SEC fractionation, due to the disruption of the interactions between the high- and low-MW components. The "unraveled" lignin revealed poorly accessible hydroxyl groups and showed an altered thermal behavior. The fractionated lignin produced significantly less char upon pyrolysis, 2 vs. 47%. It also featured a higher occurrence of low-MW thermal evolution products, particularly guaiacol carbonyls, and more than double the number of OH groups accessible for phosphitylation. These observations indicate pronounced alterations in the lignin intermolecular association following size-exclusion fractionation, which may be used for more efficient lignin processing in biorefineries.

Molecular Weight Determination of Relevant Organometallic Catalysts in Solution by DOSY-NMR to Monitor Reactivity

Molecular Weight Determination of Relevant Organometallic Catalysts in Solution by DOSY-NMR to Monitor Reactivity

Poly(propylene glycol)‐Based Non‐Isocyanate Polyurethane Ionenes: Thermal, Morphological and Conductive Properties

AbstractThe synthesis and characterization of a series of polyurethane ionenes using a non‐isocyanate approach is disclosed. Imidazole‐capped, urethane‐containing prepolymers are prepared by first reacting carbonyl diimidazole (CDI) with several poly(propylene glycol) (PPG) diols with variable molecular weight, followed by subsequent reaction with 3‐aminopropylimidazole (API). Polymerization with 1,4‐dibromomethylbenzene followed by anion exchange resulted in the desired polyurethane ionenes bearing the [NTf2] counteranion as a series of viscous liquids. NMR and FTIR spectroscopy are used to characterize the intermediates and final ionenes, including molecular weight determination by end‐group analysis. A single glass transition temperature (Tg), as determined by differential scanning calorimetry (DSC), is observed for each ionene (−38 to −64 °C) with the Tg decreasing with increasing PPG molecular weight. Thermogravimetric analysis (TGA) indicated a two‐step decomposition for each ionene, with the first being degradation of the PPG segment, followed by the urethane/ionic segment. Microphase separation is observed from x‐ray scattering profiles with Bragg distances that increased with increasing PPG molecular weight. Ionic conductivity is found to be inversely dependent upon DSC Tg at lower temperatures (RT and below); however, at higher temperatures, conductivity appears to be more dependent upon the ability of ionic aggregates caused by phase separation to interact.

Synthesis, spectral characterization, and biological activities of novel palladium(II) and platinum(II) complexes of active Schiff base ligands

ABSTRACT. A new series of palladium(II) and platinum(II) Schiff base complexes have been synthesized by the interaction of ligands N-(2-fluoro benzylidene)isonicotinohydrazone (L1H) and N-(2-fluorophenylethanone) isonicotinohydrazone (L2H) with PdCl2 and PtCl2. Elemental investigations, melting point determinations, molecular weight determinations, IR, 1H NMR, and UV-Visible spectral studies were used to describe the structure and bonding pattern of ligands and their metal complexes. These analyses revealed that the ligands coordinate with the metal ions in a monobasic bidentate manner and that the complexes have a square planar geometry. The antimicrobial activities of both the ligands and their palladium(II) and platinum(II) complexes have been tested against various bacterial and fungal strains and showed considerable antifungal and antibacterial characteristics. The in vitro cytotoxic activity of [Pt(L2H)]Cl2 complex was assessed by examining its potential to inhibit cell proliferation against the human HeLa cell line(cervical cancer cell line) using MTT assay and the antioxidant activity of [Pt(L1H)2]Cl2 compound was performed against DPPH. The results showed a dose-dependent cytotoxic and radical scavenging activity thus pointing towards the biological significance of Pt(II) complexes.
 KEY WORDS: Schiff base ligands, Antimicrobial activity, Scavenging activity, Cytotoxic
 Bull. Chem. Soc. Ethiop. 2023, 37(6), 1383-1396. DOI: https://dx.doi.org/10.4314/bcse.v37i6.7

Evaluation of Lacc134 Oxidoreductase of Ganoderma multistipitatum in Detoxification of Dye Wastewater under Different Nutritional Conditions

In the present study, we investigated the effects of different carbon sources (glucose, sucrose, and maltose) on laccase production from mycelium of Ganoderma multistipitatum grown on malt extract agar plates. The preliminary screening test was performed on the guaiacol plate, where a maroon brown zone formed after laccase oxidation. A few pure mycelial discs of Ganoderma species were transferred into submerged fermentation nutrient broth. The nutrient medium of submerged fermentation at 20 g of glucose revealed the highest laccase activities (2300 U/L) than other carbon sources. The interesting results also shown by inorganic NaNO3 in the production of maximum laccase (7800 ± 1.1 U/L). The organic nitrogen inducer, namely yeast extract, exhibited 5834 U/L laccase activity and a potential source of laccase secretion. The results concluded that C and N inducers enhanced the laccase production. This production process is eco-friendly and effective in the removal of dye from water. Laccase from the cultural broth was partially purified by SDS-PAGE for molecular weight determination, while Native-PAGE confirmed the laccase band after staining with guaiacol. The Km and Vmax values of Lacc134 were 1.658 mm and 2.452 mM min−1, respectively. The Lacc134 of this study effectively removed the Remazol Brilliant Blue R (RBBR) dye (extensively used in textile industries and wastewater). For dye removal capacity, 2.0 mg, 4.0 mg, 5.0 mg, and 6.0 mg were used, from which 6.0 mg was most effective in removal (85% and 88%) dye concentration in 1st and 2nd h interval treatment, respectively. Total organic carbon (TOC) quantity after dye removal percentage in the first- and second-hour time interval was 62% and 89%, respectively, at 30 g glucose. According to the experimental finding of this study, the breakdown products catalyzed by Lacc134 are less hazardous due to lower molecular weight than the dye itself.

Comparative analysis of molecular weight determination techniques for cellulose oligomers

Comparative analysis of molecular weight determination techniques for cellulose oligomers

Characterisation of locust bean gum with asymmetric flow field-flow fractionation (AF4) and light scattering

We present a detailed characterisation of locust bean gum (LBG), an industrially significant galactomannan, utilising asymmetric flow field-flow fractionation (AF4) and light scattering. Molecular weight and size determination of galactomannans is complicated by their tendency to aggregate, even in dilute solutions; AF4 allows us to confirm the presence of aggregates, separate these from well-dispersed polymer, and characterise both fractions. For the dispersed polymer, we find Mw=9.2×105 g mol−1 and Rg,z=82.1 nm; the distribution follows Flory scaling (Rg∼Mν) with ν∼ 0.63, indicating good solvent conditions. The aggregate fraction exhibited radii of up to 1000 nm and masses of up to 3×1010 g mol−1. Furthermore, we demonstrate how both fractions are influenced by changes to filtration procedure and solvent conditions. Notably, a 200 nm nylon membrane effectively removes the aggregated fraction; we present a concentration-dependent investigation of solutions following this protocol, using static and dynamic light scattering, which reveals additional weak aggregation in these unfractionated samples. Overall, we demonstrate that AF4 is highly suited to LBG characterisation, providing structural information for both well-dispersed and aggregated fractions, and expect the methods employed to apply similarly to other galactomannans and associating polymer systems.