Degree Of Substitution Research Articles

On the determination of charge and nitrogen content in cellulose fibres modified to contain quaternary amine functionality

Research interest in quaternization of cellulose fibres has increased considerably over the past decades. However, there is little or no consensus regarding how to characterize the material in terms of degree of substitution (DS), and the literature suggests a range of different methods focusing on charge determination as well as nitrogen content quantification. This work aims to fill the knowledge gap regarding how the different methods perform in relation to each other, and for what cellulosic systems each method has advantages, disadvantages and even potential pitfalls. FT-IR and NMR measurements are used to establish successful modification and determine the relative number of substituent groups. Another six methods are compared for the determination of the DS of cellulosic fibres and nanofibrils. The methods include Kjeldahl measurements, nitrogen determination by chemiluminescence, determination of molecular nitrogen by the Dumas method, colloidal titration, conductometric titration and polyelectrolyte adsorption. It can be concluded that most techniques investigated are reliable within certain ranges of DS and/or when using appropriate post-treatment of the quaternized material and suitable sample preparation techniques. The results from the present work hence provide recommendations to make an educated choice of method, and experimental protocol, based on the technique at hand.

Synthesis and characterization of etherified cationic starch flocculant derived from Manihot esculenta peel with varying degrees of substitution

Cationic Manihot esculenta (ME) peel starch was synthesized through etherification method using 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC) as cationizing monomer. The optimization of the main factors influencing the degree of substitution (DS) was conducted using central composite design (CCD) and response surface methodology (RSM). The factors assessed include CHPTAC concentration, catalyst sodium hydroxide (NaOH) concentration, and reaction time. The DS values of the cationic starches were obtained between 0.39 and 0.99. The maximum DS value was up to 0.99 at 0.615 mol/L of CHPTAC, 30 % (w/v) NaOH, and a reaction time of 5 h. The finding based on the optimization using RSM reflected that CHPTAC and NaOH concentrations are the key variables determining the DS value, while reaction time has a negligible impact on the etherification process. Furthermore, the chemical composition, morphology, and structure of the cationic ME peel starch were characterized by scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and nuclear magnetic resonance spectroscopy (1H NMR). It was confirmed that the modifying monomers penetrated the surface layer of the starch granules and attached to the starch backbone.

OSA modified porous starch acts as an efficient carrier for loading and sustainedly releasing naringin

To select an efficient carrier for loading and sustainedly releasing naringin (NAR), complexes of porous starch (PS) and NAR (PS-NAR) as well as those of octenyl succinic anhydride (OSA) esterified PS and NAR (OSAPS-NAR) with different degree of substitution (DS) were prepared by an ultrasonic method with an ethanol solution. The micro-morphological features, structural and thermal properties of complexes and their constituents were characterized, and in vitro release rate and kinetic of NAR from complexes were investigated. The findings revealed that NAR was successfully loaded in PS/OSAPS in an amorphous form, and the NAR's loading efficiency improved as DS increased, reaching 86.85 % at DS 0.0427. NAR cumulative release rate from the complexes in simulated digestion fluids was much higher than that of free (unloaded) NAR, but decreased as DS increased. NAR's in vitro release from complexes mainly depended on the carrier rather than NAR itself, and OSAPS with higher DS had stronger protection and slower release effect on NAR. The results would provide a new means for starch-based carrier construction to develop an efficient delivery and sustainedly releasing system for NAR, thus broadening the application ranges both for modified starch and citrus flavonoids such as NAR.

Soy glycinin-carboxymethyl cellulose “chain bead-like” nanocomplexes: Focus on formation mechanism, functional characteristics and stability properties

In this study, the aim was to solve the problem of poor functional characteristics and stability of soy glycinin (11S). 11S and carboxymethyl cellulose (CMC) nanocomplexes (SCs) were prepared by pH-driven method. They were further analyzed for the effects on the SCs formation mechanism, function and stability properties of CMC concentration (0.05%, 0.1%, 0.5%, 1%, w/v) and degree of substitution (DS, 0.7, 0.9, 1.2). The particle size and zeta potential indicated that the SCs were small in size, uniformly distributed, and high in potential. Classical DLVO theory calculation, FTIR, 3D fluorescence spectroscopy, and UV spectroscopy revealed that 11S and CMC interact mainly through electrostatic forces and hydrogen bonding, and the secondary and tertiary structures of the protein were altered. SEM, AFM and TEM showed that 11S formed “protein nanobeads” and engulfed the “chain” of CMC, generating “chain bead-like” SCs. With the increase in CMC concentration and DS, the hydrophobicity decreased and the molecular flexibility increased of SCs. The solubility, turbidity, emulsifying and foaming properties showed the tendency to enhance and then decrease as the CMC concentration increased; these properties improved better when the DS was stronger. The optimum functional characteristics of the formed SCs were obtained when the concentration and DS of CMC were 0.5% and 1.2, respectively. Furthermore, the addition of CMC significantly improved the pH, ionic stability and thermal stability of the nanocomplexes. This study will provide a theoretical basis for deeper understanding of the mechanism of pH-driven protein-polysaccharide interactions and applications in functional foods.

Photo-responsive decellularized small intestine submucosa hydrogels.

Decellularized small intestine submucosa (dSIS) is a promising biomaterial for promoting tissue regeneration. Isolated from the submucosal layer of animal jejunum, SIS is rich in extracellular matrix (ECM) proteins, including collagen, laminin, and fibronectin. Following mild decellularization, dSIS becomes an acellular matrix that supports cell adhesion, proliferation, and differentiation. Conventional dSIS matrix is usually obtained by thermal crosslinking, which yields a soft scaffold with low stability. To address these challenges, dSIS has been modified with methacrylate groups for photocrosslinking into stable hydrogels. However, dSIS has not been modified with clickable handles for orthogonal crosslinking. Here, we report the development of norbornene-modified dSIS, named dSIS-NB, via reacting amine groups of dSIS with carbic anhydride in acidic aqueous reaction conditions. Using triethylamine (TEA) as a mild base catalyst, we obtained high degrees of NB substitution on dSIS. In addition to describing the synthesis of dSIS-NB, we explored its adaptability in orthogonal hydrogel crosslinking and used dSIS-NB hydrogels for cancer and vascular tissue engineering. Impressively, compared with physically crosslinked dSIS and collagen matrices, orthogonally crosslinked dSIS-NB hydrogels supported rapid dissemination of cancer cells and superior vasculogenic and angiogenic properties. dSIS-NB was also exploited as a versatile bioink for 3D bioprinting applications.

Micellar structure of decenyl succinic anhydride modified pullulan with degree of substitution dependence in aqueous solution

A broad distribution pullulan (PUL) sample was hydrophobically modified by a relative longer decenyl succinic anhydride (DCSA) side chains with seven different degree of substitution (DS) to obtain the PUL-DCSA. The micellar structure of PUL-DCSA with DS dependence was investigated by pyrene-probe fluorescence and small-angle X-ray scattering (SAXS) in 0.05 M aqueous NaCl. While PUL-DCSA with DS > 0.26, both the SAXS and fluorescence results can be explained by the flower necklace model, when DS < 0.26, PUL-DCSA forms the loose flower necklace model. Moreover, the micellar structure of PUL-DCSA characterized by SAXS and fluorescence was different from that of the PUL-bearing shorter alkyl (octenyl or nonenyl) chains. The smaller chain stiffness qFN and larger number of monomer (glucose residues) per unit flower micelle N0u of PUL-DCSA, mainly due to the difference in the different hydrophobic alkyl side chains. This research will provide a theoretical guidance for designing biomedical materials with appropriate scale and characteristic functions in drug delivery system.

Properties of hydrogel for adsorbent textile dye waste based cellulose-carboxymethyl sago starch

Abstract The use of a single natural polymer in hydrogel preparations is considered insufficient to produce hydrogels that are more durable, more stable, and stronger. Blends of various natural polymers can improve each sago other’s lack of physicochemical characteristics and produce new properties. This research combines two natural polymers, cellulose and starch. Cellulose isolation from Gracilaria verrucosa seaweed using acid hydrolysis and alkaline autoclaving method produced 14.01% cellulose. This study combined the results of cellulose isolation with carboxymethyl sago starch at 0.09; 0.14 and 0.24 mol/mol AGU. The isolated cellulose-carboxymethyl sago starch has the potential as a hydrogel material with the addition of crosslinkers such as epichlorohydrin (ECH). This study aims to synthesize hydrogels from cellulose-carboxymethyl sago starch with application as a textile dye waste absorbent with a concentration of epichlorohydrin (ECH) at 7.5%. Analysis of carboxymethyl sago starch is degrees of substitution, water-soluble index (WSI), and swelling power (SP). The hydrogel properties are characterized by the degree of swelling, degree of polymerization, FTIR, and SEM, and the hydrogel adsorption ability is characterized by adsorption efficiency using a microplate reader. The research results show that hydrogel can be synthesized optimally by adding carboxymethyl sago starch (CMSS) at 0.24 mol/mol AGU. The results of FTIR analysis are also by chemical measurements (swelling and gel fraction). In contrast, for maximum colour absorption, the addition of carboxymethyl sago starch is 0.09 mol/mol AGU for purple, yellow, and black and 0.14 mol/mol AGU for green color absorption. In conclusion, the adsorption ability of hydrogel in commercial textile dyes is maximum when the carboxymethyl sago starch (CMSS) is added at 0.09 mol/mol AGU with the best adsorption efficiency at purple 86.22%, yellow 77.40%, black 73.70% and at the addition of CMSS 0.14 mol/mol AGU the best adsorption efficiency in green is 73.46%.

Effect of Mg modification on the catalytic performance of zinc malachite for methanol synthesis

The complex conditions of methanol production from coke-oven gas have brought challenges to the copper-based methanol synthesis catalyst. In this work, a series of zinc-malachite samples with different Mg contents were prepared. The zinc-malachite and calcined samples were characterized by in-situ X-ray diffraction (XRD), thermogravimetry-mass spectrometry (TG-MS), N2 physical adsorption, H2 programmed temperature reduction (H2-TPR), CO2 programmed temperature desorption (CO2-TPD) and other methods. The effects of Mg addition on the structure of zinc-malachite and its catalytic performance of methanol synthesis were investigated. The results showed that the addition of Mg increased the degree of Cu substitution inside the zinc-malachite structure and promoted the formation of high temperature carbonates in the catalyst after roasting. With the increase of Mg content, the specific surface area of the calcined catalyst increased gradually, and the Cu grain size decreased simultaneously. In-situ XRD results showed that a small amount of Mg could effectively inhibit the growth of copper grain size during the heat treatment. The evaluation showed that the initial activity of the catalyst increased first and then decreased with Mg addition, and the activity of the Mg-doped catalyst remained at a relatively high level after heat treatment. The appropriate Mg addition is beneficial to the initial activity and thermal stability of Cu-based methanol synthesis catalyst.

Assessing the substitutability of mobile and fixed internet: The impact of 5G services on consumer valuation and price elasticity

In this study, we explore the dynamics of consumer choices in the Polish telecommunications market, focusing on preferences and valuations for home fixed, home mobile, and purely mobile Internet connections. Key attributes such as speed, latency, data limits, and cost are examined. Central to our research is the investigation of how the integration of 5G technology might influence demand elasticity. Using a detailed discrete choice experiment, we apply a mixed logit model with random parameters to analyze stated choice data, enabling us to unravel the complexities of demand elasticity, especially in terms of own and cross-price elasticities. This approach facilitates an assessment of the degree of substitutability between fixed and mobile Internet services.Our findings indicate a moderate substitution effect between fixed and mobile Internet services. Results from a Small but Significant and Non-transitory Increase in Price (SSNIP) test suggest that these markets should continue to be regulated separately, mirroring the distinct regulation observed in fixed and mobile telephony. Furthermore, simulations provide insights into potential future market shifts with the advent of 5G services. This paper contributes significantly to the discourse on fixed-mobile Internet substitution and offers vital insights for defining markets in antitrust discussions, competitive agreements, and potential mergers within the telecom sector.

Highly phosphorylated cellulose toward efficient removal of cationic dyes from aqueous solutions

Highly phosphorylated cellulose was produced under different processing parameters and used as an effective adsorbent for methylene blue (MB) dye removal from aqueous systems. The characteristics of the designed adsorbent were analyzed using different technics. The zeta potential measurement of the developed adsorbents was negative (−11.3 to −49.4 mV) in the pH range of 4 to 11. Batch removal tests were performed under different processing parameters of contact time, initial concentration, phosphorylation degree and pH. The developed adsorbent with a high substitution degree of 1.07 (13.22 % of P), revealed an outstanding retention capacity for MB dye (up to 3153.5 mg/g) during an extremely low equilibrium adsorption time (∼30 min), which is 130-fold higher than pure MCC (15.3 mg/g). Interestingly, this capacity raised up to 3236.6 mg/g when raising the pH of the solution (from 7 to 11). The experimental adsorption data in the examined conditions were well fitted by the Langmuir type isotherm and pseudo-second-order kinetic models, highlighting the significance of the reaction medium and phosphate content in determining the adsorbent's retention capacity. This investigation has demonstrated the potential of converting pure MCC into high value-added adsorbent for the efficient purification of organic dye from aqueous solutions.

Colourful 3-amino-1,8-naphthalimide alkyl-substituted fluorescent derivatives

The optical properties of four 3-amino-1,8-naphthalimide derivatives differing in the degree of substitution at the amino functionality were synthesised and studied by UV–visible absorbance and fluorescence spectroscopy in 1:1 (v/v) methanol/water and methanol. The compounds were structurally characterized by NMR, IR and HRMS. The charge transfer absorbance band was observed to shift to longer wavelength with increasing ethyl substitution. The emission band was also observed to shift to longer wavelengths with a decrease in the emission intensity with increasing ethyl substitution due to the peri effect. Irradiation of dye methanol solutions and in the solid state with a 365 nm UV lamp reveals distinct emission colours for each compound. Significantly larger Stokes shifts are observed in methanol than in mixed aqueous methanol. Quantum chemical calculations at the B3LYP/TZVP level of theory provided insight into the optimized ground state geometry, frontier molecular orbitals levels and solute-solvent dynamics revealing a stronger hydrogen bond between the 3-amino-1,8-naphthalimides and methanol in the lowest S1 excited state. The dyes were tested as fluorescent stains in MCF-7 cancer cells and observed to emit green emission in various organelles.

Conjugation of CRAMP18-35 Peptide to Chitosan and Hydroxypropyl Chitosan via Copper-Catalyzed Azide-Alkyne Cycloaddition and Investigation of Antibacterial Activity.

We developed a synthesis strategy involving a diazo transfer reaction and subsequent click reaction to conjugate a murine cathelicidin-related antimicrobial peptide (CRAMP18-35) to chitosan and hydroxypropyl chitosan (HPC), confirmed the structure, and investigated the antimicrobial activity. Chitosan azide and HPC-azide were prepared with a low degree of azidation by reacting the parent chitosan and HPC with imidazole sulfonyl azide hydrochloride. CRAMP18-35 carrying an N-terminal pentynoyl group was successfully grafted onto chitosan and HPC via copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The chitosan-peptide conjugates were characterized by IR spectroscopy and proton NMR to confirm the conversion of the azide to 1,2,3-triazole and to determine the degree of substitution (DS). The DS of the chitosan and HPC CRAMP18-35 conjugates was 0.20 and 0.13, respectively. The antibacterial activity of chitosan-peptide conjugates was evaluated for activity against two species of Gram-positive bacteria, Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), and two species of Gram-negative bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa). The antimicrobial peptide conjugates were selectively active against the Gram-negative bacteria and lacking activity against Gram-positive bacteria.

Effect of chromium Cr3+ substitution in BaFe12-xCrxO19 barium ferrites on the temperature dependences of the initial magnetic permeability

In this paper we studied the possibility of synthesizing solid solutions based on barium hexaferrite, iron atoms Fe3+ in which are partially substituted by Cr3+ atoms, and their magnetic properties.Thirteen solid solutions of BaFe12-xCrxO19 compositions with varying degrees of chromium substitution x (Cr) = 0–6 with a step of x (Cr) = 0.5 were obtained using the solid-phase synthesis method. X-ray phase analysis showed that at a temperature of T = 1400 °C, solid solutions with a single crystalline phase corresponding to the structure of magnetoplumbite were formed within 5 h. As a result of chromium Cr3+substitution for iron Fe3+, a monotonous decrease in the parameters of the crystal lattice occurred.We studied the temperature and frequency dependences of the initial magnetic permeability of the resulting ferrites. It was revealed that substitution of iron by chromium led to a decrease in the Curie temperature. All the studied compositions had a feature in the form of a narrow peak near the Curie temperature. We suggested that this feature appeared as a result of a change in the domain structure. Analysis of the temperature dependences allowed us to conclude that Cr3+ substituted for iron in all crystallographic positions with equal probability. It was shown that the initial permeability of ferrites decreased with increasing frequency.

The Effects of Substitution Degree in the Carboxymethylation of Jackfruit Seed Starch on Starch Digestibility

The Effects of Substitution Degree in the Carboxymethylation of Jackfruit Seed Starch on Starch Digestibility

Chitosan based hydrogel for iron (III) chelation in biological conditions

In this study, a chitosan derivative with strong iron (III) chelating capabilities was developed by grafting the Deferoxamine (DFO) chelator to achieve a substitution degree of 3.8 ± 0.2 %. Through blending with ungrafted chitosan of low degree of acetylation (DA), a formulation able to form a physical hydrogels was formed in aqueous media, without the requirement of a cross-linking agent. The functionalization of chitosan with DFO led to xerogels exhibiting superior iron (III) chelation capacity and higher swelling when exposed to aqueous solutions, in comparison with to an unmodified chitosan xerogel. Notably, this material extracts iron (III) even against the strong iron chelator deferiprone. Furthermore, the material demonstrates selectivity for iron (III) chelation even in the presence of competing cations like copper (II) and zinc (II).

Continuous-Flow Synthesis of Zn1-xMnxS Nanoparticles at Ambient Conditions.

With its large direct band gap and good chemical stability, ZnS is suitable for many applications, including light-emitting diodes, panel displays, and photodetection. Here, nanoparticles of ZnS are synthesized phase pure under ambient conditions by precipitation in a simple and scalable continuous-flow reactor. Furthermore, different degrees of Zn substitution with Mn have been investigated, Zn1-xMnxS, with x = 0.05, 0.19, and 0.25 according to X-ray fluorescence measurements. The products are analyzed with multitemperature synchrotron powder X-ray diffraction (PXRD) and X-ray total scattering. The analysis reveals phase-pure synthesis products with the sphalerite structure and crystallite sizes in the range of 3.8-4.7 nm in agreement with scanning transmission electron microscopy. Only Zn0.75Mn0.25S shows traces of Mn3O4, indicating that x = 0.25 is above the substitution limit as the impurity appears. Substitution of Zn with Mn in the nanoparticles is confirmed by energy-dispersive X-ray spectroscopy, as well as an observed decrease in the band gap, decrease in the sphalerite-to-wurtzite phase transition temperature, and increase in the unit cell dimensions with increasing Mn content. Based on the modeling of the PXRD Rietveld refined atomic displacement parameters, the Debye temperature for ZnS and Zn0.95Mn0.05S is determined to be 322 ± 13 and 394 ± 22 K, respectively.

Facile and convenient electrochemical syntheses of novel multifunctional (catalytic, antioxidant and in vivo antimicrobial) phosphorylated chitosan derivatives

The electrochemical coupling of N-protected chitosan with diphenylphosphine oxide was recognized as new facile, fast, and convenient route to phosphorylated chitosans. The reaction affords low substituted (capable of self-assembling into nanoparticles), moderately substituted (water soluble) or highly substituted (soluble in both water and toluene) polymeric chitosan phosphonates. The degree of substitution can be adjusted by simply increasing the triphenylphosphine oxide/chitosan ratio. Highly substituted polymers (CH-P0.70) are efficient homogeneous catalysts towards the model reaction of monoglyceride synthesis (ca. 100% yield in 3 h). The phosphorylated chitosans are also efficient antioxidants. Their antioxidant effect increases with an increase in their degree of substitution. CH-P0.70 exhibits an antioxidant activity comparable to that of the natural antioxidant ascorbic acid. Remarkably, the highly substituted species is characterized by a strong in vivo antibacterial effect which is even more pronounced than that of the commercial antibiotics ampicillin and gentamicin. Moreover, the obtained phosphorylated chitosan CH-P0.70 demonstrates neither acute nor subacute in vivo toxicity.

Production of resistant starches via citric acid modification: Effects of reaction conditions on chemical structure and final properties

Aiming to contribute to the current knowledge on the impact of reaction conditions on the chemical structure and target properties of starch citrates, in the current contribution different corn starch citrates were prepared by manipulation of reaction time, temperature and citric acid concentration. Modified starches were characterized in terms of chemical structure, morphology, crystallinity, swelling power and resistant starch content. For the first time, total substitution, crosslinking and monosubstitution degrees were quantitatively determined; and the relationship among final chemical structure, reaction conditions and target starch citrates properties was comprehensively analyzed. Products with total substitution values in the range of 0.075–0.24, crosslinking degrees in the 0.005–0.11 interval, and monosubstitution extents within the 0.05–0.12 range, were produced. By proper selection of reaction conditions products with almost 100 % of resistant starch were obtained. Results evidenced that starch citrates properties (mainly swelling power and RS content) depend on both chemical structure and the reaction conditions employed. Actually, the reaction temperature set (120 °C or 150 °C) proved to play a determinant role in the final products properties as evidenced from starch citrates with similar chemical structure and substantially different swelling and digestibility properties.

Single-Component Cellulose Acetate Sulfate Hydrogels for Direct Ink Writing 3D Printing.

Hydrogels, typically favored for 3D printing due to their viscoelasticity, are now trending toward ecofriendly alternatives amid growing environmental concerns. In this study, we crafted cellulose-based hydrogels, specifically employing cellulose acetate sulfate (CAS). By keeping the acetyl group substitution degree (DSacetyl = 1.8) and CAS molecular weight constant, we varied rheological properties by adjusting sulfate group substitution (DSsulfate = 0.4, 0.7, and 1.0) and CAS concentration (2-5 wt %). Rheological characterizations, including shear-thinning, yield stress, and thixotropy, were performed to identify optimal conditions for formulating CAS hydrogel ink in direct ink writing for 3D printing under selected experimental conditions. Based on rheological findings, CAS hydrogels with DSsulfate 0.7 and concentration of 4 wt % was used for 3D printing, with subsequent evaluation of printing metrics. Additionally, the effect of ionic cross-linking using Ca2+ ions on the structural integrity of 3D-printed structures was evaluated, demonstrating effective preservation through reinforced polymer networks. The shrinking and swelling behaviors of the 3D-printed structures were also significantly affected by this ionic cross-linking. Building on these findings, this work could broaden the range of cellulose derivatives available for the preparation of cellulose-based hydrogels for 3D printing.

Molecular and Crystal Structures of Some Bromocymantrenes

Crystals of mono- and dibromo as well as two isomeric tribromocymantrenes [Mn(C5H5-nBrn)(CO)2(PPh3)] (n = 1–3) were obtained and examined by X-ray diffraction. The degree of substitution has only minor influence on bond lengths and angles. However, the relative orientations of bromo substituents and PPh3 ligand as well as relative orientation of the cyclopentadienyl ring and the MnC2P tripod are sensitive to the number and position of bromines. All compounds show weak Br…O interactions, mostly combined with hydrogen bonds, while Br…Br interactions are unimportant. These interactions lead to sometimes complicated chain structures.Graphical In the crystal structures of the bromocymantrenes [Mn(C5H5-nBrn)(CO)2(PPh3)] (n = 1–3) a combination of H bonds and Br…O/Br…Br interactions leads to one-dimensional molecular chains or double-chains, which are not further connected in the other dimensions.