Degree Of Chemical Modification Research Articles

Decomposition and Changes in InVivo Post-HA Filler Injection: A Review.

Hyaluronic acid (HA) fillers are widely used in aesthetic medicine, but their invivo behavior and long-term effects are not fully understood. To review the decomposition and changes occurring in the body following HA filler injections, focusing on crosslinking agents, degradation processes, and tissue responses. This review analyzed oxidative and enzymatic degradation processes of HA fillers, evaluated the impact of 1,4-Butanediol Diglycidyl Ether (BDDE) crosslinking, and examined histological changes post-injection. Uncrosslinked HA degrades rapidly due to endogenous hyaluronidase, while crosslinked HA undergoes slower degradation via free radicals and hyaluronidase. Complete cross-linking (C-MoD) showed better durability compared to partially cross-linked BDDE (P-MoD). The concept of modification efficiency (MoE) was proposed to optimize filler safety and viscoelastic properties. Histological analysis revealed collagen capsule formation and autologous tissue replacement, affecting long-term outcomes. The degree of chemical modification (MoD) influences filler durability and safety, with concerns raised about potential delayed immune reactions from accumulated pendent BDDE. Clinicians should consider injection site, tissue conditions, and filler properties for safe and effective HA filler use. Emphasizing thorough BDDE removal and optimal crosslinking can enhance treatment safety and efficacy. The balance between achieving desired viscoelastic properties and minimizing potential risks is crucial. Future studies should include diverse ethnic groups to validate findings and further explore long-term tissue responses to HA fillers.

Structural Analysis and Identity Confirmation of Anthocyanins in Brassica oleracea Extracts by Direct Injection Ion Mobility-Mass Spectrometry.

Anthocyanins are a subclass of plant-derived flavonoids that demonstrate immense structural heterogeneity which is challenging to capture in complex extracts by traditional liquid chromatography-mass spectrometry (MS)-based approaches. Here, we investigate direct injection ion mobility-MS as a rapid analytical tool to characterize anthocyanin structural features in red cabbage (Brassica oleracea) extracts. Within a 1.5 min sample run time, we observe localization of structurally similar anthocyanins and their isobars into discrete drift time regions based upon their degree of chemical modifications. Furthermore, drift time-aligned fragmentation enables simultaneous collection of MS, MS/MS, and collisional cross-section data for individual anthocyanin species down to a low picomole scale to generate structural identifiers for rapid identity confirmation. We finally identify anthocyanins in three other Brassica oleracea extracts based on red cabbage anthocyanin identifiers to demonstrate our high-throughput approach. Direct injection ion mobility-MS therefore provides wholistic structural information on structurally similar, and even isobaric, anthocyanins in complex plant extracts, which can inform the nutritional value of a plant and bolster drug discovery pipelines.

Research of Bioproof Materials at Superficial Modification of Wood

The mechanism and conditions of surface modification of wood by phosphorous-containing and siliceous organic compounds have been studied. Wood has the ability to absorb moisture from the air, and the moisture content of wood produces a significant effect on the physical and mechanical properties of wood. Traditional water-repellent agents of lignocellulosic materials are Organic Silicon Compounds (OSC). Our research is aimed at developing a “soft” silylation technology, in which the degree of chemical modification is negligible, and the content of chemically bound Si amounts to ~ 1%. As silylating agents, alkylhydride siloxanes, alkoxysilanes were used. From alkylhydride siloxanes, polyethylhydride siloxane (PEHS) and polymethylhydride siloxane (PMS) with different n-polymerization degrees were used. Activating hydrophilic additives were ammonium fluoride, potassium fluoride and titanates. The treatment of wood with salts, with the subsequent treatment with OSCs facilitated the penetration of OSCs into the wood while the processes of “soft” silylation proceeded. “Soft” silylation of wood with polyalkylhydride siloxanes proceeds in the presence of catalyst additives, the degree of silylation is low and depends on the nature of the additives. The dependence of distribution of OSCs in the wood on the nature of the additives is evidenced by the method of scanning electron microscopy. Phosphorous-containing organic compounds (FOC) have a high penetrating ability, while completely filling the intercellular structure of the wood. With the sequential impregnation of the wood with FOCs and OSCs, organic silicon compounds enter the intercellular space of the wood, with dense spongy OSC deposits, which in some places completely fill the internal cavities of cellular tubes of the wood. As FOC, for example, a 40% solution of trichloroethylphosphate (TCEP) was used. Decaying of wood over time starts from the surface, since there are no diffusive limitations in the sorption process. Surface modification of wood can increase its durability due to increased biological stability and hydrophobic behaviour, which will ensure a long-lasting protection. Long-lasting protection is due to the formation of covalent bonds of wood (cellulose) with a modifier. Wood samples after surface “soft” modification with FOCs and OSCs were tested for hydrophobic behaviour and biological stability. The samples were tested in the climate chamber with irrigation of the samples with water in a mode of -30°C to +40°C. To determine the hydrophobic behaviour, the limiting wetting angle was determined. The biological stability was determined by the growth of testing cultures of the fungi Aspergillus, Penicillium, Trihoderma and some others according to GOST 9.048-89. The amount of the data obtained allows to make a conclusion about the nondurable decrease in water absorption capacity during surface modification of wood with OSCs. Long-lasting biological and water resistance is achieved only in cases when surface application of OSCs is carried out on the pre-phosphorylated wood. Phosphorylation thus leads to the formation of covalent bonds. The compounds developed were successfully used for 10-15 years to preserve the monuments both of wooden architecture and the buildings and structures made of stone, bricks, and concrete.

Metamorphic evolution of sulphide-rich chromitites from the Chernichevo ultramafic massif, SE Bulgaria

The upper mantle rocks of the metamorphosed ophiolite of Chernichevo, Rhodope Metamorphic Complex in southern Bulgaria, host small chromite ores with unusual mineralization of base-metal sulphides rich in platinum-group elements. Mineralogical and chemical data indicate that after their formation in the mantle the Chernichevo’s chromite ores were modified by the intrusion of an alkaline mafic melt, which resulted in the precipitation of a suite of metasomatic minerals (sulphides, calcite, apatite and ilmenite), accompanied by an increase in FeO, TiO2, Ga, Zn, Vn, Mn, and especially Ti and Fe2O3 contents in the chromite. The degree of chemical modification and abundance of metasomatic minerals are positively correlated and mark the extent of reaction of the chromitite with the intruding melt. Sulphide segregation promoted the concentration of high amounts of PGEs (up to 3661 ppb), particularly Pt and Pd, yielding chromite ores with a typical flat to positive-sloped chondrite-normalized pattern. Subsequently, the chromite ores were deformed and metamorphosed together with their host rocks at ultra-high pressure (UHP) (>2.5 GPa, >1200 °C) to be later retrograded under eclogite and finally hydrous amphibolite-facies conditions, giving rise to three microstructural types. Metamorphism of the most metasomatized (i.e., sulphide-rich) chromitites at temperatures >700 °C within the conditions of UHP and eclogite-facies resulted in the formation of (1) non-porous recrystallized chromite, consisting of a granoblastic microstructure made-up of coarse-grained blasts and finer-grained chromite neoblasts. In contrast, hydrous metamorphism on the less metasomatized (i.e., sulphide-poor) chromitite under the conditions of amphibolite-facies (ca. 482–483 °C) resulted in the formation of (2) partly altered chromite, characterized by unaltered cores surrounded by Fe2+-rich and Al-depleted porous chromite containing abundant clinochlore, and (3) porous chromite corresponding to a chromite that was entirely transformed by the metamorphic alteration to Fe2+-rich and Al-depleted porous chromite. During metamorphism magmatic Ni-Fe-Cu sulphides originally formed during the metasomatic event in the mantle were altered, resulting in a major leaching of Cu-rich sulphides, leading to significant remobilization of Pt and Pd.

4D imaging of polymer electrolyte membrane fuel cell catalyst layers by soft X-ray spectro-tomography

4D imaging - the three-dimensional distributions of chemical species determined using multi-energy X-ray tomography - of cathode catalyst layers of polymer electrolyte membrane fuel cells (PEM-FC) has been measured by scanning transmission x-ray microscopy (STXM) spectro-tomography at the C 1s and F 1s edges. In order to monitor the effects of radiation damage on the composition and 3D structure of the perfluorosulfonic acid (PFSA) ionomer, the same volume was measured 3 times sequentially, with spectral characterization of that same volume at several time points during the measurements. The changes in the average F 1s spectrum of the ionomer in the cathode as the measurements progressed gave insights into the degree of chemical modification, fluorine mass loss, and changes in the 3D distributions of ionomer that accompanied the spectro-tomographic measurement. The PFSA ionomer-in-cathode is modified both chemically and physically by radiation damage. The 3D volume decreases anisotropically. By reducing the incident flux, partial defocusing (50 nm spot size), limiting the number of tilt angles to 14, and using compressed sensing reconstruction, we show it is possible to reproducibly measure the 3D structure of ionomer in PEM-FC cathodes at ambient temperature while causing minimal radiation damage.

Synthesis, freestanding membrane formation, and properties of novel sulfonated hyperbranched polyimides

A novel six-membered ring hyperbranched polyimide (HBPI) has been synthesized by condensation polymerization of a difunctional monomer, 9,9-fluorenylidenebis(4,1-phenylene)bis(oxy)-4,4′-bis(1,8-naphthalic anhydride) (FBPNA), and a trifunctional monomer, tris(4-aminophenyl)amine (TAPA), at the molar ratio of FBPNA/TAPA = 1:1 in m-cresol at 180°C for 20 h. The resultant HBPI is further modified via end-capping reaction with 4-phenoxy-1,8-anhydride naphthalene (PNA). Post-sulfonation is performed in concentrated sulfuric acid at different temperatures (50, 60, and 70°C) for the pristine HBPI and 50°C for the PNA-modified polyimides to give various sulfonated HBPIs. Freestanding and tough membranes have been successfully fabricated by casting the polymer solutions containing a cross-linker, bisphenol A epoxy resin, at 80°C. The ion exchange capacities of the resultant membranes are in the range of 1.35–2.21 meq g−1 depending on the degree of chemical modification and the sulfonation conditions. Membrane properties such as water uptake, swelling ratio, proton conductivity, and radical oxidative stability are investigated.

Positional Controlled Manipulation of the Carbon Nanotube Surface by Selective Screening

A scalable process has been demonstrated for the controlled functionalization and positional controlled buckling of multiwalled carbon nanotube (MWCNT) by selectively masking the nanotube surface with chemically inert and thermally stable ceramic material. A uniform thin layer of soluble ceramic precursor, polycarbosilane (PCS), was first coated on MWCNT by the modified solution-based coating technique. The discrete silicon carbide (SiC) islands were then produced on nanotube surface during annealing at high temperature. The size and distribution of SiC islands on the surface of nanotube could be topologically regulated by controlling the thickness of PCS layer on MWCNT. The modulated surface of MWCNTs was then exploited for the site specific functionalization by guiding the incoming functional groups to the exposed surface. By optimizing the openings of the exposed surface of MWCNTs, the degree of chemical modifications could be tailored make. The controlled screening of nanotube surface has also been utilized for the physical modifications like selective buckling of tube walls by impinging high-energy ions on MWCNTs where the position of bending under irradiation fluence could be customized by the degree of passivation of the nanotube surface.

Preparation and Characterization of Homopolymer Polyacrylonitrile-Based Fibrous Sorbents for Arsenic Removal

This research investigated the modification of homopolymer polyacrylonitrile (PAN) fibers for use as an adsorbent for removing arsenic from drinking water. Fibers were chemically modified and cross-linked using combinations of hydrazine hydrate and sodium hydroxide (NaOH) before being loaded with ferric hydroxide using two different iron loading procedures. Effects of reagent concentrations and reaction times on degree of chemical modification and fiber properties were investigated using Fourier transform infrared spectroscopy and ion-exchange measurements. Arsenate adsorption was a function of both the iron loading and the properties of the underlying fiber. For fibers treated with only a single reagent, both Fe3+ and arsenate adsorption could be understood in terms of ion-exchange properties of the fiber surfaces. However, for fibers treated with both hydrazine and NaOH, the ion-exchange properties of the surface could not explain the Fe3+ and arsenate adsorption behavior. The best arsenate removal performance was obtained using the simplest pretreatment procedure of soaking in 10% NaOH at 95°C for 90 min, followed by precipitation coating of ferric hydroxide. This simple preparation procedure involves only two commonly available and inexpensive reagents and can be carried out without any specialized equipment. This suggests that adsorbents based on inexpensive homopolymer PAN fabric may be produced in developing areas of the world where commercial products may not be available.

Dynamic Moisture Sorption Characteristics of Xerogels from Water-Swellable Oligo(oxyethylene) Lignin Derivatives

Highly swellable lignin derivatives were prepared by cross-linking of oxidatively preactivated spruce organosolv lignin (OSL) with poly(ethylene) glycol diglycidyl ether (PEGDGE). The lignin gels obtained are considered to be an environmentally friendly alternative to synthetic hydrogels and superabsorbents and represent a novel type of lignin based functional materials. For their application, it is not only the absorption of water in terms of hydrogel swelling that plays an important role, but also the adsorption and retention of moisture by the corresponding xerogels. To reveal the mechanisms involved in moistening and reswelling of the lignin gels, the interaction of water vapor with lyophilized xerogels was investigated and compared with sorption characteristics of parent lignin. The chemical structure of PEGDGE-modified lignin was investigated using attenuated total reflectance Fourier-transformed infrared spectroscopy and selective aminolysis and was related to its sorption and swelling characteristics. Bound and free water in hydrogels was determined by differential scanning calorimetry and by measuring the free swelling capacity of the gels. Moisture sorption of OSL and PEGDGE-modified lignin xerogels was determined using dynamic vapor sorption analysis. In order to determine monolayer and multilayer sorption parameters, sorption data were fitted to the Brunauer-Emmett-Teller and the Guggenheim-Anderson-de Boer model. Swelling properties of the hydrogels and moisture sorption of the corresponding xerogels were found to be strongly dependent on the degree of chemical modification with PEGDGE: Total and free water content of hydrogels decrease with increasing cross-linking density; on the other hand, water bound in hydrogels and moisture sorption of xerogels at high levels of water activity strongly increase, presumably because of the hydration of hydrophilic oligo(oxyethylene) and oligo(oxyethylene) glycol substituents, which lead to moisture diffusion into the xerogel matrix, plasticization, and swelling of the gels.

Effect of Organoclay’s characteristics during the preparation of complex ternary system PP-EP/EVA/Organoclay.

ABSTRACTIn this work, the effect of structural characteristics of organomodified clays on the dispersion degree, mechanical and rheological properties of the nanocomposites PP-EP/EVA/nanoclay has been studied. The studied effects were: degree of chemical modification of the clay, length of substitute groups on the surfactant, and the steric effect caused by surfactant structure. The characterization techniques used were Wide Angle X-ray Diffraction (WAXD), Scanning Transmission Electron Microscopy (STEM), Dynamic Mechanical Analysis (DMA), Tensile Test and Capillary Rheometry. Cloisite 6A, 15A and 20A were used to evaluate the first effect. Better intercalation-exfoliation and mechanical properties were obtained when the clay with lower content of surfactant was used (C20A), these results were attributed to a higher saturation of the system. In order to study the second effect, Cloisite 20A and Cloisite 25A were employed. It was found that the bigger initial intergallery space between these nanoclay’s caused by the longer chains in Cloisite 20A, allows the formation of a structure with better intercalated-exfoliated structure. This was confirmed with the observed increase in mechanical properties. Finally, the third effect was studied with Cloisite 10A and 15A. It was clearly seen that only with Cloisite 15A was possible to obtain an intercalated-exfoliated structure. This was attributed to a major steric effect when using C10A than with 15A.

Oxidative stabilisation of kraft lignin for carbon fibre production

Abstract With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules, as well as lignin fibres originating from birch with 5% poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (Tg) was investigated. The highest yield was achieved after stabilisation at 280°C during 2 h with a heating rate of 0.2°C min-1. The Tg of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.

Chemical Modification in Wear Tracks of Chemical Vapor-Deposited Diamond Surfaces Studied with X-ray Absorption Spectroscopy

We present high-quality X-ray absorption near edge structure spectra of chemical vapor-deposited diamond at the C K-edge recorded with high spatial resolution. We compare unworn surfaces with surfaces worn in Ar-atmosphere, in air, and in water, respectively. Strikingly, the degree of chemical modification in the wear tracks is strongest for wear in an inert Ar-atmosphere which we attribute to the massive creation of unsaturated bonds in the surface vicinity due to high friction forces. We discuss the nature of chemical modification, in particular, whether and to what degree graphitization, amorphization, and ex situ reactions take place.

Swelling properties of chemically modified oil palm empty fruit bunch based polyurethane composites

In this study, the diffusion of various types of solvent in oil palm empty fruit bunch/polyurethane composites, produced from chemically modified empty fruit bunches, was investigated. The solubility parameters and polymer–solvent interaction parameters of the produced composites were determined. The void contents of the composites were also determined before swelling tests to eliminate the free solvent present in the system. From the results obtained, we found that the diffusion of the solvents was dependent on the compatible group available and the voids present in the system. The solubility parameters of the empty fruit bunch/polyurethane composites with different degrees of chemical modification were 11.6 and 11.7 (cal/cm−3)1/2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

High Molecular Weight Melanoidins from Coffee Brew

The composition of high molecular weight (HMw) coffee melanoidin populations, obtained after ethanol precipitation, was studied. The specific extinction coefficient (K(mix)) at 280, 325, 405 nm, sugar composition, phenolic group content, nitrogen content, amino acid composition, and non-protein nitrogen (NPN) content were investigated. Results show that most HMw coffee melanoidins are soluble at high ethanol concentrations. The amino acid composition of the HMw fractions was similar, while 17% (w/w) of the nitrogen was NPN, probably originating from degraded amino acids/proteins and now part of melanoidins. A strong correlation between the melanoidin content, the NPN, and protein content was found. It was concluded that proteins are incorporated into the melanoidins and that the degree of chemical modification, for example, by phenolic groups, determines the solubility of melanoidins in ethanol. Although the existence of covalent interaction between melanoidins and polysaccharides were not proven in this study, the findings suggest that especially arabinogalactan is likely involved in melanoidin formation. Finally, phenolic groups were present in the HMw fraction of coffee, and a correlation was found with the melanoidin concentration.

Analytical Methods for Chitosan

SUMMARY Biopolymer chitosan is a prospective textile auxiliary agent prepared from chitin or from bioprocesses waste. Chitosan has a lot of important characteristicsespecially high sorption of basic ions and biodegradability. In this study we tested chitosan using the following analytical methodsviscosimetry, spectrophotometry (IR, VIS, UV), ninhydrin reaction and sorption methods. We discussed an influence of molecular weight and degree of chemical modification as well.

Synthesis and characterization of multi-walled carbon nanotubes reinforced polyamide 6 via in situ polymerization

Polyamide 6 (PA6)/carbon nanotubes (PA6/CNTs) composites have been prepared by in situ polymerization of ε-caprolactam in the presence of pristine and carboxylated multi-walled carbon nanotubes (MWNT and MWNTCOOH). Viscosity measurements show that adding 0.5 wt% of carbon nanotubes (CNTs) does not affect the molecular weight of PA6. Compared with pure PA6, the yield strength of PA6/CNTs composites loaded with 0.5 wt% CNTs is almost unchanged, and the tensile strength is increased slightly. Dynamic mechanical analysis (DMA) demonstrates that both the storage modulus ( E′) and glass transition temperature ( T g) of the PA6/CNTs composites increase, particularly for PA6/MWNTCOOH, indicating there is some chemical bonding between PA6 and MWNTCOOH. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra small-angle X-ray scattering (USAXS) show that MWNT and MWNTCOOH are well dispersed in PA6 matrix. Comparison of the USAXS data with a stiff-rod model and wormlike rod model reveals that the CNTs are quite flexible, regardless the degree of chemical modification. Due to the flexibility of CNTs, mechanical properties of the PA6/CNTs composites are marginally enhanced.

A study on the advanced oxidation of a cotton fabric by ozone

So‐called sdvanced oxidation involves the generation of free radical hydroxy species. Ozone, a highly unstable compound, liberates such radicals, which can be used for bleaching. In this work grey cotton fabric was bleached with an ozone/oxygen gas mixture, and the effects of ozone concentration and treatment time on the properties of the bleached fabric were studied. The properties evaluated were whiteness index, strength, elongation, extent of impurities (size and wax) removed, degree of chemical modification (carboxyl and aldehyde groups) and reactive dye take‐up. These properties were compared to those from conventionally bleached materials (acid desize‐scour‐peroxide/calcium hypochlorite bleach). The results show that an acceptable degree of whiteness (ready for dyeing) can be obtained by ozone bleaching in a very short time. This process is environmentally acceptable because it is does not use harmful chemicals, it requires a very low quantity of water, and bleaching is achieved in a very short time at room temperature.

Study of Thermoreversible Aggregates from Chemically-Modified PVCs

We report on a light scattering study performed on suspensions of aggregates of PVC and chemically-modified PVCs in diethyloxalate (DEO). The maximum in the scattering function reported by Mutin and Guenet is again observed. Its position, qm, depends upon the degree of chemical modification at constant polymer concentration: the larger the degree of modification, the lower the value of qm. The radius of gyration and the weight-averaged molecular weight of the aggregates are determined as a function of the preparation concentration from highly diluted suspensions. The radius of gyration is found to remain virtually unchanged when augmenting the degree of modification while a near 2-fold increase of the weight-averaged molecular weight is observed, the latter being consistent with the variation of qm. All these results point toward a cross-sectional growth of the fibrillar aggregates with chemical modification while the longitudinal fractal dimension does not vary significantly. Viscometry measurements provide further support to these conclusions.

The characterization of novel dispersants, fluorinated surfactants, and modified natural oils by laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD-FTICR-MS)

Laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD-FTICR-MS) with potassium cationization is a valuable technique for the characterization of a variety of industrial materials. Commercial products can be analyzed, with minimal sample preparation, in under twenty minutes. Poly(ethylene oxide) methyl ether styrene oligomers and tetrafluoroethylene-ethylene oxide copolymers are characterized by LD-FTICR-MS. Molecular weight and chemical composition distribution data are provided. Limitations of the technique are also explored. Virgin and modified natural oils are well characterized by LD-FTICR-MS. The degree of chemical modification is easily measured. Higher resolving powers allow identification of constituents of the oils.

Polyacrylamide sorbents. Synthesis and sorption properties

A series of hydrophilic sorbents having amino groups was prepared by aminolysis of acrylonitrile-divinylbenzene copolymers with ethylenediamine and diethylenetriamine. The degree of transformation of nitrile groups was up to ca. 0.35. Sorption properties of the sorbents towards p-nitrophenol and methyl orange were compared. In both cases, the overall sorption capacity was found to be higher than for the parent acrylonitrile sorbents. The degree of sorption depended on both chemical and supermolecular structure and increased with specific surface area. The sorption of methyl orange was found to be related to the ion-exchange capacity of the sorbents, i.e., to their degree of chemical modification. In fact, the degree of sorption of the dye per ionic group was similar for all sorbents. For sorbents derived from the same parent copolymers, the effect of amino group basicity on degree of sorption was insignificant. The sorption of methyl orange was found to be controlled by internal diffusion with a diffusion coefficient lower by two to three orders of magnitude than those for porous ion exchangers.