High Degree Of Substitution Research Articles

Synthesis and characterization of carboxymethyl cellulose with high degree substitution from Vietnamese pineapple leaf waste

In this work, cellulose was successfully extracted from pineapple leaf waste by 0.75 M NaOH at 90oC and 5 M HNO3 at 70oC for 1.5 h and 5 h, respectively. The obtained cellulose fibres, with average diameters of 150-300 nm, were converted to carboxymethyl cellulose (CMC) by esterification. The pure cellulose was soaked in a solution mixture of isopropanol and NaOH for 2 h. It was then reacted with chloroacetic acid (MCA) at 60oC for 1.5 h. The optimum conditions for carboxymethylation were found to be 5 g cellulose, 1.5 g MCA, and 15 ml 16% w/v NaOH. The obtained CMC had a high degree of substitution (DS) of 2.3. The properties of CMC were determined.

Functionality-related characteristics of hydroxypropyl-β-cyclodextrin for the complexation

This research aimed to study the functionality-related characteristics (FRCs) of hydroxypropyl-β-cyclodextrin (HP-β-CD) for the complexation. Nine batches of HP-β-CD samples were collected for the characterizations and phase solubility studies. The correlation analysis revealed that the pH and the degree of substitution (DS), especially the DS, were critical in the complexation. Importantly, the DS-complexation correlation was dependent on the molecular weight (M.W.) of the model drugs, which was confirmed by literature databases and deeply understood by molecular modeling: with respect to the small M.W. drugs, the solubility was enhanced due to the increase in the DS in a lower range, whereas steric hindrance caused by a very high DS limited the solubilizing ability of HP-β-CD; complexations for high M.W. drugs were severely restricted by steric hindrance; thus, a lower DS was appreciated. This study provided guidance for the selection and application of HP-β-CD and contributed to coherent understanding of its FRCs.

Acetylation Modification, Characterization, and Anticomplementary Activity of Polysaccharides from Rhododendron dauricum Leaves.

This study focuses on the acetylation modification of polysaccharides from Rhododendron dauricum leaves (RDPs) with a high degree of substitution (DS) and then discusses their characterization and biological activity. The optimum acetylation conditions of RDPs were optimized by response surface methodology, which were reaction time 3 h, reaction temperature 50 °C, and the liquid-solid ratio 16 mL/g. Under the optima schemes, two eco-friendly acetylated polysaccharides from R. dauricum leaves (AcRDP-1 with DS of 0.439 ± 0.025 and AcRDP-2 with DS of 0.445 ± 0.022) were prepared. The results of structural characterization showed that the AcRDP-1 (9.3525 × 103 kDa) and AcRDP-2 (4.7016 × 103 kDa) were composed of mannose, glucose, galactose, and arabinose with molar ratios of 1.00:5.01:1.17:0.15 and 1.00:4.47:2.39:0.88, respectively. Compared with unmodified polysaccharides, the arabinose content and molecular weight of the two acetylated polysaccharides decreased, and their triple helix conformation disappeared, and further improved their anticomplementary activity. The two acetylated polysaccharides showed stronger a complement inhibition effect than the positive drug by blocking C2, C3, C4, C5, C9, and factor B targets in the classical and alternative pathways. This research indicated that acetylation modification could effectively enhance the anticomplementary activity of RDPs, which is beneficial for the development and utilization of R. dauricum leaves.

A novel approach in increasing carboxymethylation reaction of cellulose

Carboxymethyl cellulose (CMC) with a high degree of substitution (DS) was prepared from hardwood bleached pulp by a novel method. In this method, pulp was refined in PFI mill and/or enzymatically treated prior to carboxymethylation. The DS value of CMC increased from 0.5 to 2.4. The yield and molecular weight of CMC increased with increasing DS value. The correlation coefficient between DS and molecular weight was 0.9992. Spectroscopic, thermogravimetric, x-ray diffraction and scanning electron microscopic (SEM) and titrimetric analyses were performed to confirm the degree of substitution and surface modification of the cellulose. Micrograph and SEM image confirm surface modification of cellulose in prior treatment. A comparison of the FTIR spectra of the prepared CMC and standard CMC shows the presence of bands corresponding to ˗O˗, CH2˗ and ˗COO in the CMC, while these bands do not appear for cellulose. The crystallinity of untreated pulp was slightly decreased, while the crystallinity of the prepared CMCs was diminished.

The degree of substitution of OSA-modified starch affects the retention and release of encapsulated mint flavour

This study explored the effect of the degree of substitution (DS) of octenyl succinic anhydride (OSA)-modified starch on the retention and release properties of spray-dried mint flavour microcapsules. The results showed that a higher DS (0.0287, 0.0379) led to greater flavour retention (86.68 %, 90.10 %). The flavour release was negatively correlated with DS during simulated oral processing. A mechanism by which DS affects flavour release was proposed. The emulsifying capacity was improved with increasing DS, thus forming an effective interface. The effective interface increased the partition coefficient, thereby reducing the release. During oral processing, a lower friction coefficient and higher microstructural stability and carrier enzymatic resistance jointly promoted interface stabilization. Data obtained using the EPI suite, a gas chromatograph, a mini traction machine, a Mastersizer analyser and confocal scanning laser microscopy validated this mechanism. This study provides a strategy for designing flavour microcapsules with high retention and slow-release properties using OSA-modified starch.

Tailored sequencing of highly brominated Poly(ether ether ketone) as a means to preserve crystallizability and enhance Tg

In this report, the bromination of poly(ether ether ketone) (PEEK) using the mild reagent N-bromosuccinimide (NBS) is explored to generate controlled random and blocky microstructures. Bromination proceeded quantitatively in both the solution state and semicrystalline gel-state, and degrees of bromination between 25 and 175 mol% were obtained for both random and blocky BrPEEK. Spectroscopic evidence revealed a higher prevalence of unfunctionalized repeat units for blocky BrPEEK than random BrPEEK at similar degrees of functionality. Furthermore, at similar degrees of bromination, blocky BrPEEK exhibited enhanced glass transition temperatures, greater crystallizability, higher melting temperatures, and faster crystallization kinetics than random BrPEEK, suggesting longer segments of unfunctionalized PEEK in blocky BrPEEK. Overall, this work demonstrates that PEEK can be brominated to very high degrees of substitution in the semicrystalline gel-state while preserving crystallizability and effectively blocking up the functionality.

Cellulose allylcarbamate with high content of reactive double bonds for thiol-ene reaction

Polysaccharide phenylcarbonates react with amines to form carbamates with high efficiency and can be used to introduce reactive CC bonds into a biopolymer, which may be converted by thiol-ene click reactions. Thus, cellulose phenylcarbonates are allowed react with allylamine by nucleophilic reaction to yield cellulose allylcarbamate of very high degree of substitution (DS). The DS of allylcarbamate moieties could be controlled by the molar ratio of allylamine to phenylcarbonate groups. Pure products without remaining phenylcarbonate substituents were accessible. The allylcarbamate moieties are reactive regarding the radical thiol-ene reaction that was exemplified by the reaction of cellulose allylcarbamate with 2-(diethylamino)ethane-1-thiol hydrochloride (DEAET) in dimethyl sulfoxide using a photoinitiator under mild conditions. The phenylcarbonates- and allylcarbamates of cellulose as well as the DAEAET adduct were characterized by elemental analysis, NMR- and FTIR spectroscopy.

Guar gum propionate-kojic acid films for Escherichia coli biofilm disruption and simultaneous inhibition of planktonic growth

Nosocomial bacterial infections associated with biofilms inspire to explore newer bactericidal strategy with eco-friendly biomaterials as sustainable alternatives. In this research work, we successfully developed bio-safe films from kojic acid(KA) and guar gum propionate(GGP) for Escherichia coli biofilm disruption and planktonic cell killing. High DS(degree of substitution = 1.52) GGP was synthesized from guar gum (GG)assisted by chaotropic ions at room-temperature. Biopolymers were routinely characterized in CHN analyzer, FT-IR, TGA and XRD analysis. KA loaded GGP films were prepared by cross-linking the molecules in presence of epichlorhydrin and two different percentages of KA were employed. Film physical and tensile properties were systematically evaluated and optimized. Water vapour permeability (WVP) and tensile strength of final film GGPFK10 were recorded at 0.741 ± 0.09gmm−1kPa−1h−1 and 19.23 MPa. KA release from GGP matrix followed controlled diffusion process. MIC of GGP was 130 μg/mL and zone of inhibition of GGPFK10 was confirmed at 16.1 mm. SEM experiments disclosed the absence of pili-like structures with squeezed and elongated cellular morphology in dead planktonic cells. Disruption of biofilms was experimented in detail by CV assay, fluorescent, light microscopic and SEM studies. The film showed excellent cell-viability on human adult dermal fibroblast (HADF)cell-line. Overall, the biosafe film would be a potent antibacterial device for treating infections against E.coli biofilms and planktonic cells.

Green synthesis of carboxymethyl cellulose from agricultural waste its characterization

In the present study, corncob (an agricultural waste) has been explored as a source of cellulose. Cellulose was extracted from corncob through removal of hemicellulose and lignin. The carboxymethyl cellulose (CMC) was then synthesized from extracted cellulose by alkalization and etherification with 30% NaOH and 120% monochloro acetic acid (MCA) in ethanol medium respectively. Characterization of prepared CMC was carried out by various techniques like Fourier Transform Infra-Red (FTIR) spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscpoe (SEM). Back titration method was used to determine the Degree of Substitution (DS). The synthesized CMC obtained has a large DS value of 2.27. The purity of CMC was high at 91.65% and showed a yield of 1.20g/g, intrinsic viscosity of 1.02, water holding capacity 3.81g/g and oil holding capacity 1.66g/g. Higher degree of substitution is achieved in this work. The synthesized product is effective suitable additive for food and various pharmaceuticals industries.

Complexation behavior of carboxymethyl short-chain amylose and quaternized chitosan

The complexation of carboxymethyl short-chain amylose (CSA) and hydroxypropyl trimethyl ammonium chloride chitosan (HACC) and the stability of CSA/HACC nanocomplex were investigated. Resonance light scattering (RLS), turbidity, nanoparticle size and zeta potential analyses revealed that the complex coacervation occurred between CSA and HACC. The mass ratio and pH markedly influenced the complexation behavior; CSA with a higher degree of substitution (DS0.2) altered the complexation at a lower mass ratio and pH, increasing the turbidity and RLS intensity. The results of particle size and zeta potential analyses indicated that CSA/HACC complexes possessed the good pH and ionic strength stability. In addition to electrostatic interactions, hydrogen bonding and hydrophobic effects were also determined to be involved in the complexation process using thermal titration calorimetry (ITC). Additionally, the process was spontaneous, and CSA with a higher DS showed stronger complexation ability. These results may enable the understanding of polysaccharide complex behaviors.

Carboxymethylation modification, characterization, antioxidant activity and anti-UVC ability of Sargassum fusiforme polysaccharide

Taking the degree of substitution (DS) as the index, the carboxymethylation conditions of Sargassum fusiforme polysaccharide (SFP) were studied. According to the single factor experiment results, the optimum experimental conditions were obtained: sodium hydroxide concentration, 15% (20 mL); alkalization temperature, 50 °C; dosage of chloroacetic acid 1.5 g; etherification time, 2 h, and the Carboxymethyl Sargassum fusiforme polysaccharide (CSFP) with the highest DS (0.635) was obtained. And then, the physicochemical properties, structural information and bioactivity of SFP and CSFP were characterized. The SFP and CSFP were composed of four monosaccharides, with a small amount of protein, and their molecular weights to 780.2 kDa and 386.3 kDa respectively. The results of FTIR and NMR showed that the carboxymethyl was successfully grafted onto the C-4 and C-6 of sugar chain. The results of anti UVC experiment showed that SFP and CSFP had a certain negative effect on cell activity, and the degree of damage caused by UVC radiation was weakened, and the anti UVC performance of CSFP was better than that of SFP.

Encapsulation of indole-3-carbinol in Pickering emulsions stabilized by OSA-modified high amylose corn starch: Preparation, characterization and storage stability properties

The stability of hydrophobic bioactive compound indole-3-carbinol (I3C) is a challenge for application. In this work, Pickering emulsions were prepared to encapsulate I3C. As the emulsifier, high amylose corn starch was pretreated by acid hydrolysis, afterwards modified by different concentrations of octenyl succinic anhydride (OSA), and their emulsions were evaluated. The XRD, SEM and FTIR results indicated the successful modification. ζ-potential, mean droplet size and emulsification index (EI) of the emulsions confirmed that modified starch with a higher degree of substitution (DS) was more effective for enhancing the storage stability. The results of encapsulation efficiency (EE) and retention degree of I3C after 14 d also proved the assumption. Moreover, the Pickering emulsions protected I3C against ultraviolet light and achieved controlled release in vitro. The food-grade Pickering emulsion loading I3C is promising to be used as a nutrient or dietary supplement for food applications.

Preparation and Characterization of Thermoplastics Achira (Canna indica L.) Starch by Three Succination Methods

AbstractThermoplastic starches (TPS) from achira, succinated to 3% and 5% octenyl succinate anhydrous (OSA) using aqueous medium, reactive extrusion (REX), and in situ are developed (TPS 3A, TPS 5A, TPS 3R, TPS 5R, TPS 3I, and TPS I5). The physicochemical properties are studied to explore the effect of different methods applied to modified thermoplastic starches. Analysis of infrared spectroscopy and nuclear magnetic resonance of proton shows that the methods used in succination are effective in esterifying starches. REX and the in situ method make it possible to obtain materials with higher degree of substitution (DS), from 0.011 to 0.050, affecting thermoplasticization. The aqueous method promotes greater thermal stability, TPS 3A and TPS 5A are degraded at temperature ranges from 135 to 279 °C and shows a pattern similar to counterpart native TPS 0 (sample control), unlike the REX and the in situ method, both of them beginning degrading at lower temperature values than all starches. Mechanical properties and contact angle are influenced by the processing method and not by DS or glycerol content. All achira TPS developed are a feasible alternative for application in the industry dedicated to the processing of bioplastics.

In Situ Reduced Graphene Oxide and Polyvinyl Alcohol Nanocomposites With Enhanced Multiple Properties.

The nanocomposites formed by graphene oxide (GO) and carbazate-modified polyvinyl alcohol (PVA-N) were developed to investigate their multiple properties for wide applications. Their physicochemical characterizations confirmed that the in situ reduced GO (rGO) not only decreased the crystallization but also induced the porous structures inside the nanocomposites. Significantly, it revealed that the comprehensive performance of PVA-N2-2%GO consisted of PVA-N2 with the carbazate degree of substitution (DS) of 7% and the weight ratio (wt%) of 2% GO displayed 79% of tensile elongation and tensile strength of 5.96 N/mm2 (MPa) by tensile testing, glass transition temperature (Tg) of 60.8°C and decomposition temperature (Td) of 303.5°C by TGA and DSC, surface contact angle at 89.4 ± 2.1°, and electrical conductivity of 9.95 × 10−11 S/cm. The abovementioned comprehensive performance was enhanced with the increased amount of in situ rGO, contributed by the high DS of the carbazate group in PVA-N and high amount of GO. The rGO by in situ reduction was the main driving force for enhancing the multiple properties inside the nanocomposites.

Solubility of C-A-S-H phases with high degree of heavy metal ion substitution

Knowledge about interactions between cementitious materials and dissolved metal (Me) ions is key for environmental remediation and waste management, but thermodynamic data on this topic are still limited. We present solubility data for nanocrystalline C-A-S-H phases substituted by distinct Me ions with (Ca + Me)/(Si + Al) molar ratios from 0.86 to 1.04 and Ca2+ substitution of ∼ 48 mol% for Zn2+, ∼29 mol% for Co2+ and ∼ 27 mol% for Cu2+ in tobermorite-type Me-C-A-S-H. The solubility constants of the Me-C-A-S-H phases are significantly lower compared to pure C-A-S-H (logK = -8.3), ranging from logK = -8.6 to −11.3 for Co-C-A-S-H, logK = -9.1 to −11.6 for Cu-C-A-S-H and logK = -8.9 to −14.1 for Zn-C-A-S-H, as the Me content increases according to the expression:logKMe-C-A-S-H=0.11±0.03·%Mesubstitution-8.33±0.12;R2=0.89independent on the type of incorporated Me ion. Thus, newly-forming C-A-S-H phases have a high immobilization potential for aqueous Me ions. The novel solubility data open the door for thermodynamic modelling of Me ion mobility in aquatic media.

Degradation of Cellulose Acetate in Simulated Aqueous Environments: One‐Year Study

AbstractCellulose acetate (CA) is subjected to different aqueous environments (e.g., lake water, seawater, artificial seawater) under controlled laboratory conditions to investigate the degradation potential in natural water systems. The main changes in the CA films are detected during the first months of the 12‐month study. Approximately 5% and 10% weight losses are observed during the first month of aging at RT and at 60 °C, respectively. The temperature effect is rather negligible and the weight loss also does not significantly increase on prolonged aging. A quantitative high‐performance liquid chromatography analysis shows that this weight loss is mainly caused by deacetylation and depending on the aging conditions, 10–30% of the acetate groups are lost during the first 1–3 months of aging. Fourier transform infrared and nuclear magnetic resonance analyses further support this. It is well established that a high degree of substitution (DS) is the bottleneck for biodegradation of CA and a significantly higher biodegradation rate has been demonstrated for CA materials with degree of substitution, DS<2, compared to those with DS>2. The degree of deacetylation observed here is enough to decrease the DS to below 2, which can therefore have a significant effect on the subsequent biodegradation.

Preparation of pH-Responsive Poly(γ-glutamic acid) Hydrogels by Enzymatic Cross-Linking.

pH-responsive hydrogels are important for oral drug release applications, and they are increasingly demanded to reduce the adverse side effects of drug release and improve drug absorption. In this study, a new type of pH-responsive hydrogel comprised of poly(γ-glutamic acid) modified with tyramine (PGA-Tyr) was developed through enzymatic cross-linking in the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The gelation rate, stiffness, swelling behavior, and pore size of the resulting hydrogels were tuned by changing the concentrations of HRP and H2O2 or the degree of substitution (DS) of PGA-Tyr. The pH responsiveness of the hydrogels was evaluated by the swelling ratio in solutions with various pH values, and their pH responsiveness exhibited a good reversibility in pH 2.0 and 7.0 solutions. The degradation rate of the hydrogels in simulated intestinal fluid (SIF) was faster than that in simulated gastric fluid (SGF). Moreover, indomethacin (IM), a hydrophobic drug model, was encapsulated in the hydrogels by rapid in situ gelation, and the pH-dependent drug release of IM-loaded hydrogels was achieved in SGF and SIF. Importantly, when IM was entrapped in pluronic F-127 to form drug micelles, the burst release of the IM-micelle-loaded hydrogels with a high DS of PGA-Tyr was remarkably decreased in SGF, and sustained drug release was presented in SIF. Thus, pH-responsive PGA-based hydrogels have tremendous promise for biomedical applications, especially oral drug delivery.

Synthesis and characterization of sodium‐carboxymethylcellulose from cotton, powder, microcrystalline and nanocellulose

AbstractCotton cellulose, powder cellulose, microcrystalline cellulose and nanocellulose were carboxymethylated with monochloroacetic acid by the suspension method in an ethyl alcohol medium. The effects of reaction conditions such as cellulose materials, sodium hydroxide concentration, molar NaOH/anhydroglucose unit ratio, monochloroacetic acid consumption, reaction temperature and etherification time on product quality, especially the degree of substitution, degree of polymerization and water solubility of sodium‐carboxymethylcellulose, were studied. By controlling these parameters, completely water‐soluble sodium‐carboxymethylcellulose samples with a high degree of substitution within 0.75, 1.47, 0.88, and 1.23 were obtained from cotton cellulose, powder cellulose, microcrystalline and nanocellulose. The boundaries of complete solubility of the obtained sodium‐carboxymethylcellulose were at low degrees of substitution (0.6, 0.44, 0.43, 0.33) and degrees of polymerization (880, 490, 240, 150) obtained from cotton cellulose, powder cellulose, microcrystalline cellulose and nanocellulose, respectively.

Impact of the Incorporation of Nano-Sized Cellulose Formate on the End Quality of Polylactic Acid Composite Film.

Polylactic acid (PLA) films with good sustainable and biodegradable properties have been increasingly explored recently, while the poor mechanical property of PLA limits its further application. Herein, three kinds of nano-sized cellulose formate (NCF: cellulose nanofibril (CNF), cellulose nanocrystal (CNC), and regenerated cellulose formate (CF)) with different properties were fabricated via a one-step formic acid (FA) hydrolysis of tobacco stalk, and the influence of the properties of NCF with different morphologies, crystallinity index (CrI), and degree of substitution (DS) on the end quality of PLA composite film was systematically compared. Results showed that the PLA/CNC film showed the highest increase (106%) of tensile strength compared to the CNF- and CF-based films, which was induced by the rod-like CNC with higher CrI. PLA/CF film showed the largest increase (50%) of elongation at the break and more even surface, which was due to the stronger interfacial interaction between PLA and the CF with higher DS. Moreover, the degradation property of PLA/CNF film was better than that of other composite films. This fundamental study was very beneficial for the development of high-quality, sustainable packaging as an alternative to petroleum-based products.

Study on quantitative structure of oil from oily sludge by improved Brown-Ladner (B-L) method

Oily sludge is a mixture of crude oil, mud, and water contaminated by other organic matter. Oil from oily sludge was Soxhlet extracted using toluene solvent. Modern analytical techniques such as FT-IR, GPC, 1H-NMR were applied to characterize the structure of the extracted oil. The quantitative structure of the extracted oil was evaluated by improved B-L method. The average molecular weight and formula of the extracted oil were established. The extracted oil was found paraffin-based crude oil with aliphatic chain structure as main component, aromatic structure as a supplement, and aromatic rings were all the aliphatic side chain substituted unit rings with a high degree of substitution. This paper tried to apply the latest methods during the analysis of the sludge and extracted crude oil and provides theoretical basis of molecular structure for the recovery and utilization of oily sludge.