Graft Copolymerization Reaction Research Articles

Preparation of Consolidated Dust Suppression Materials Based on Pectin: Graft Modification Experiment and Reaction Mechanism.

The natural material pectin was used as the matrix to prepare a dust suppressant. The regression model in response to the grafting ratio was established, and the optimum modification scheme was determined. The amount of monomer, initiator, cross-linking agent, and reaction temperature was 3.20 g, 0.20 g, and 0.15 g and 92 °C, respectively. Through Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy tests, not only the formation of the product in graft copolymerization reaction was validated but also the wettability of pectin was significantly improved. The surface morphology of pectin before and after modification was observed by a scanning electron microscope. After graft copolymerization treatment, the surface of pectin presented a dense grid structure, which proved that the pectin-modified dust suppressant can play a crucial role in wetting and condensing coal dust. Contact angle tests were used to characterize the effect of pectin modification on the wettability of bituminous coal before and after modification. The results of contact angle tests showed that when the droplets just contacted the bituminous coal flakes, the contact angle of modified pectin droplets on the flakes was the smallest, and the value was 55.21°. Compared with pure water droplets and unmodified pectin droplets, it decreased by 21.66° and 18.50°. The modification reaction process and dust suppression mechanism were explained at the molecular level.

Creative synthesis of pH-dependent nanoporous pectic acid grafted with acrylamide and acrylic acid copolymer as an ultrasensitive and selective riboflavin electrochemical sensor in real samples

In current research, an innovative pectic acid was grafted with poly (acrylamide-co-acrylic acid) [PA-g-poly (AAm-co-AA)] nanoporous membrane using a free radical-mediated grafting copolymerization process. The optimized parameters for the grafting copolymerization reaction such as initiator concentration, monomer concentrations, polymerization reaction time, and temperature were studied. Additionally, the solid content, graft percentage, and conversion were calculated. The unique polymeric membrane was characterized using Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetry (TG), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) supported by energy dispersive X-ray spectroscopy (EDX). The formulated novel PA-g-poly (AAm-co-AA) had a nanoporous structure with a diameter of 113 nm. pH-dependent swelling and biodegradation measurements were also studied. The electrochemical characterizations of PA-g-poly (AAm-co-AA) were conducted through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Furthermore, the screen-printed electrode (SPE) was modified with pure PA and the new generation of its grafted polymeric nanoparticles to detect and quantify the concentration of riboflavin (RF) in real samples using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The modified electrode showed two linear concentration ranges from 0.01 - 2 nM and 2 – 90 nM with low detection limits (LODs) of 0.004 and 0.97 nM, respectively, demonstrating high sensitivity. Besides, the fabricated sensor exhibited more selectivity, simplicity, great reproducibility, repeatability, and good stability. Finally, the PA-g-poly (AAm-co-AA)-modified SPE based sensor was effectively used in real sample analysis of egg yolk, milk, and vitamin B2 drugs with good recovery rates.

Effect of different initiators on the properties of diacetone acrylamide grafted starch-based adhesive

Environmentally friendly and non-toxic bio-based adhesives are emerging as the most promising substitutes for petroleum-based adhesives, attracting increasing attention. This work involved the synthesis of a starch-based adhesive for particleboards by grafting diacetone acrylamide (DAAM) onto starch. The graft polymerization was initiated using three different initiators: ammonium persulfate (APS), hydrogen peroxide (H2O2)/ammonium ferrous sulfate system, and ceric ammonium nitrate (CAN). A comparative study was conducted to assess the varying effects of these initiators. The results showed that in the graft copolymerization of starch with DAAM, different initiators produced different types of free radicals, and CAN initiation produced alkyl radicals and long-chain alkyl radicals with a peak total spin value of 3.96 × 1015, and thus had the highest grafting efficiency and grafting rate of 72.59 % and 16.75 %, respectively. From the comparison of the total number of spins, it can be seen that CAN is more targeted for starch initiation. In addition, characterization results from Fourier transform infrared spectroscopy and confocal Raman spectroscopy showed that DAAM underwent a graft copolymerization reaction with starch. Notably, the adhesive initiated by CAN demonstrated the highest water resistance and mechanical strength, with an absorption thickness expansion and static bending strength of 8.52 % and 10.56 MPa, respectively.

Designing network structure hydrogels derived from carrageenan- phosphated polymers by covalent and supramolecular interactions for potential biomedical applications

Recently, various efforts have been made to explore the potential of natural polysaccharides derived from sea weeds to promote sustainable development. Herein, carrageenan (CG), a polysaccharide extracted from red sea algae, was utilized to design network structures as hydrogels, aimed at significant applications in drug delivery (DD) systems. Hydrogels were designed by graft copolymerization reaction of poly(bis [2-methacryloyloxy] ethyl phosphate [poly(BMEP)] and poly(acrylic acid) [poly(AAc)] onto CG in the presence of a crosslinking agent. Hydrogels were developed by covalent linkage by graft copolymerization and supramolecular interactions, existing in the copolymers. Copolymers were characterized by Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) instrumentations. The drug diffusion exhibited a sustained pattern due to polymer-drug interactions. The drug release followed non-Fickian diffusion mechanism and the release profile was most accurately depicted by first order kinetic model. The biocompatible nature of the copolymer was demonstrated from the hemolytic index value signifying minimal adverse interactions with blood component upon exposure. A protein adsorption test was performed using bovine serum albumin (BSA), exhibiting 8.15 ± 0.26 % albumin adsorption. Polymers exhibited mucoadhesive character, evidenced by their requirement of a detachment force measuring 195 ± 4.72 mN for separation from the membrane during interactions with the mucosal surface. The hydrogels exhibited antioxidant properties, evidenced by 2, 2′-Diphenylpicrylhydrazyl (DPPH) assay, revealing copolymer capable of scavenging 58.21 ± 2.26 % of free radical. The hydrogel revealed antimicrobial activity against P. aeruginosa and S. aureus bacteria, a property further enhanced in hydrogels with the drug doxycycline. These findings suggest suitability of these hydrogels for biomedical applications, with a significant emphasis on drug delivery.

Preparation and drug delivery of hydrogels based on grafting of methacrylamide (MAAm) / vinylsulphonic acid (VSA) co monomers onto psyllium

Recently, a plethora of advancements have been made in the area of polysaccharide research to improve their properties for human health care. The present research is an attempt to develop hydrogels from through grafting of methacrylamide (MAAm) and vinyl sulphonic acid (VSA) co monomers onto psyllium for use in drug delivery (DD) applications. Copolymer hydrogels were characterized by scanning electron micrographs (SEM), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 13C nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA) and differential thermal analysis (DTG). SEM, AFM and XRD revealed heterogeneous morphology of the copolymer hydrogels with surface roughness and amorphous state of polymer chains in copolymer hydrogels due to graft-copolymerization reactions. The appearance of the FTIR bands at 1636.87 (amide-I), 1618.11 cm−1 (amide- II), 1469.58 cm−1 (amide- III) indicated presence of amide and bands at 1167.12 cm−1, 1112.06 cm−1 band (symmetric vibrations of SO3H groups and anti-symmetric & symmetric stretching modes of C–S) presence of VSA. The appearance of bands at 181.801 ppm and 62.053 ppm indicated presence of CO carbon of functional groups poly (MAAm) and −CH2–SO3H of poly (VSA) in copolymer hydrogels. Diffusion of the antibiotic drug vancomycin occurred in sustained manner with a non-Fickian diffusion mechanism. The release profile was best described by Korsmeyar-Peppas kinetic model. The copolymers exhibited biocompatible nature and revealed haemolytic index less than 5 % during polymer-blood interactions. The hydrogel demonstrated mucoadhesive character and required 0.135 ± 0.01 N force to detach from mucous membrane. These properties demonstrated the suitability of copolymer hydrogels for drug delivery applications.

Smart mucoadhesive 3-D network hydrogels for use in localized impregnated anticancer drug delivery

Recently, bioactive dietary fibers (DFs) have been explored for various benefits to human health because of their therapeutic activities. Role of DF psyllium (arabinoxylan (Ax)) has been established for curing colon cancer. Herein, methotrexate (MXT), an anti-neoplastic agent, was impregnated into network hydrogels developed from DF psyllium, through graft copolymerization reactions for its sustained colon-specific drug delivery (DD). Copolymers were characterized through SEM, AFM, FTIR, C13-NMR and TGA analysis. Smart hydrogels demonstrated antioxidant (39.40 ± 0.78% free radical scavenging in the DPPH assay), biocompatible (1.16 ± 0.22% hemolysis value in blood-polymer interactions), and mucoadhesive (7.0 ± 0.1 mN detachment force from the mucous membrane) properties. Sustained diffusion of MXT in colonic conditions occurred with a Fickian mechanism, and release profile obeyed the Korsmeyer-Peppas kinetic model. Overall, findings suggested the suitability of DF psyllium-based DD carriers for colon with enhanced potential.

Designing aloe vera-sterculia gum based copolymeric hydrogel dressings for drug delivery

Herein the present work, aloe vera (AV) and sterculia gum (SG) based polymer network hydrogels have been designed for use in wound dressing and drug delivery (DD) applications. The hydrogels were prepared by graft copolymerization reaction of poly(2-(methacryloyloxy) ethyl trimethylammonium chloride) [poly (METAC)] onto AV and SG. Polymers were characterized by FESEM, SEM, EDS, AFM, C13 NMR, FTIR, XRD and TGA-DTG analysis. Swelling, drug delivery and biomedical properties of dressings have been evaluated. Sustained diffusion of moxifloxacin drug from dressings exhibited a non-Fickian diffusion mechanism and the release profile was best fitted in the Korsmeyer-Peppas kinetic model. Various interactions of polymers with blood and goat membranes revealed the biocompatible and mucoadhesive nature of the dressings. Hydrogel dressings were found permeable to O2 and water vapour and impermeable to microbes. Overall, these properties revealed that these hydrogels could act as suitable materials for design of wound dressings. Furthermore, antioxidant properties of AV, wound healing characteristic of SG, antibacterial properties of poly(METAC) and encapsulated moxifloxacin drug in hydrogel dressings may enhance the wound healing potential of hydrogel wound dressings (HWD).

Agar-gelatin-derived hydrogel-based controlled delivery devices for linuron herbicide to prevent environmental hazards

Innovation in agriculture chemicals and delivery systems is essential for the production of food for sustainable development. Herein, natural polymers and agar-gelatin-derived controlled delivery devices for linuron herbicide to prevent environmental and health hazards. These hydrogels were designed by the graft-copolymerization reaction of poly(methacrylamide) [poly(MAAm)] on agar-gelatin for use as controlled-release formulations (CRF). Copolymers were characterized by Copolymers were characterized scanning electron micrographs (SEM), Atomic force microscopy (AFM), X-ray diffraction (XRD) Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), and thermogravimetric analysis -differential thermogravimetry (TGA-DTG) techniques. SEM shows the uneven surface morphology, and AFM showed a rough surface with an average roughness value of 137.50 nm in the polymeric matrix. The amorphous nature of the polymer was confirmed with XRD techniques. Grafting of the poly(MAAm) on the agar and gelatin was confirmed by FTIR and 13C NMR spectra. Agar-gelatin-cl-poly(MAAm) hydrogels absorbed water at 4.05 ± 0.32 g per gram, which is useful for soil water retention. Release of the linuron herbicide occurred in a controlled manner during 72 h of observations and followed non-Fickian diffusion mechanism. The slow release of the linuron from the hydrogel is a useful observation for preventing leaching and evaporation loss of herbicide. In the soil column, the release of linuron occurred in a slow and sustained manner for 240 h. A soil adsorption study showed a decrease in ground water ubiquity score (GUS) for linuron-encapsulated hydrogel as compared to commercial formulations. It can reduce groundwater contamination risk due to the leaching of the linuron herbicide. Degradation of CRF may improve micronutrient and soil quality.

Functionalized magnetic chitosan-based adsorbent for efficient tetracycline removal: Deep investigation of adsorption behaviors and mechanisms

As removal performance of tetracyclines in traditional wastewater treatment plants cannot satisfy the increasingly strict discharge requirements, developing an efficient approach to overcome this problem is quite urgent. Herein, a novel functionalized magnetic chitosan-based adsorbent (Fe3O4@CAA) with core-shell structure and unique magnetic responsiveness was facilely prepared by ultrasound-initiated radical grafting copolymerization and cross-link reaction. The as-prepared Fe3O4@CAA was fully characterized with TEM, SEM, BET, FTIR, TGA, XRD, VSM, and served as an efficient adsorbent for tetracycline hydrochloride (TCH) removal. Adsorption behaviors of TCH by Fe3O4@CAA were deeply evaluated at different adsorption time, initial TCH concentration, reaction temperature, solution pH, and background pollutant concentration. Results showed that Fe3O4@CAA presented a more competitive adsorption capacity of 325.04 mg g−1 compared with Fe3O4@CS and other reported adsorbent, due to the introduction of more active adsorption sites by abundant functional groups, including amino groups, hydroxyl groups, and sulfonic acid groups. After saturated adsorption, TCH loaded Fe3O4@CAA was easily collected by magnetic separation, and recycled after acid pickling. Fe3O4@CAA was successfully reused in five adsorption-desorption cycles, without obvious adsorption capacity loss. In binary pollutant systems, inorganic cations and Pb(II) restrained TCH adsorption by competitive effect, while proper amount of Cu(II) promoted TCH adsorption by bridge effect. FTIR and XPS analyses revealed that the adsorption mechanism of TCH by Fe3O4@CAA mainly included electrostatic interaction and hydrogen bonding, and Cu(II) could play a “mediator” role to form a strong Cu(II)-TCH complex to enhance TCH removal performance. This study provides an effective strategy for the design of magnetic chitosan-based adsorbents and valuable guidance for the removal of tetracyclines from wastewater.

Functionalization of bioactive moringa gum for designing hydrogel wound dressings

In view of wound healing properties of moringa gum (MG) and the antibacterial activity of poly(METAC), in the present work, the antibiotic drug ofloxacin encapsulated MG-cl-poly(METAC) based hydrogel dressings were prepared by graft copolymerization reaction for better wound care. Network copolymeric structure was assessed by FESEM, AFM, EDX, 13C NMR, XRD, FTIR and DSC techniques. Swelling properties demonstrated that the network density of hydrogel dressings could be tailored as per the need of wound fluid sorption by controlling feed monomer and crosslinker content during synthesis. FESEM, AFM and XRD revealed a heterogeneous morphology of hydrogels with a rough surface and an amorphous patterns of polymeric materials. Diffusion of ofloxacin from dressing occurred by a non-Fickian diffusion mechanism in simulated wound fluid and was fitted best in First-order kinetic model. Wound dressings exhibited non-haemolytic (0.97% haemolytic potential), mucoadhesive (109.00 ± 4.00 mN peak detachment force) and antioxidant (92.94 ± 2.13% scavenging in DPPH assay) characteristics along with mechanical strength against external stress and strain. Hydrogel dressings were found to be permeable to H2O/O2 and impermeable to microbes. The synergic action of the drug and matrix with antibacterial activity can improve the wound-healing potential of the dressings. These physiological and biomedical properties pointed out the ideal character of moringa gum dressings for better wound healing.

Design of polysaccharide gum based network copolymeric hydrogels for drug delivery and wound dressing applications

This article deals with the exploration of the design of network crosslinked structure by covalent bonding for use as wound dressing materials keeping in view inherent therapeutic role of neem gum in wound healing. These copolymeric hydrogels were prepared by graft-copolymerization reaction of carbopol and poly (N-vinylpyrrolidone) (poly (NVP). Antibiotic drug levofloxacin was encapsulated in dressings for better wound healing. The scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal gravimetry (DTG), and differential scanning calorimetry (DSC) techniques were applied for characterization. NMR and FTIR demonstrated incorporation of carbapol and poly (NVP) in dressings. XRD indicated amorphous state in copolymeric dressings. Interactions of copolymers with drug, blood and bio membrane were studied to evaluate biomedical properties which revealed controlled release of drug from hydrogel dressings which were possessing blood-compatible (haemolytic value ​= ​2.45 ​± ​0.82) and mucoadhesive (detachment force ​= ​124 ​± ​41 ​mN) properties. Dressings were permeable to O2 and H2O vapour and absorbed 6.68 ​± ​0.62 ​g/g wound fluid which is ideal dressing characteristic. Diffusion mechanism type of drug levofloxacin was Fickian with kinetic model First order. These properties suggested use of hydrogel material for wound dressing and drug delivery applications for better wound care management.

Synthesis and antitumor activity of bagasse xylan derivatives modified by graft-esterification and cross-linking

A crucial aspect in achieving sustainable development of biomass materials is the modification of renewable polysaccharides to create various high-value functional materials. In this paper, bagasse xylan (BX) was used as a raw material to introduce benzyl methacrylate (BMA) through graft copolymerization reaction to generate the intermediate product BX-g-BMA. Subsequently, the target product (CA-BX-g-BMA) was synthesized by catalytic esterification of BX-g-BMA with citric acid (CA) in AmimCl ionic liquid. Meanwhile, the characterization and bioactivity studies of CA-BX-g-BMA were carried out. The graft copolymerization and esterification reactions induced significant changes in the morphological structure of BX and obviously improved its thermal stability and crystallinity. The application of density functional theory (DFT), molecular electrostatic potential (MEP) and molecular docking has revealed that CA-BX-g-BMA possesses multiple active sites, strong biological activity and a strong binding affinity to 6RCF tumor protein with a binding energy of −32.26 kJ/mol. The in vitro antitumor activity of this novel derivative was tested by MTT assay, and the results showed that CA-BX-g-BMA was non-toxic to normal cells and inhibited MDA-MB-231 (breast cancer cells) by up to 32.16 % ± 4.89 %, which is approximately 11 times higher than that of BX. The exploration of these properties is essential to promote future multidisciplinary applications of BX derivatives.

Preparation of cationic aggregates derived from sewage sludge for efficient capture of organic matter

Capturing the abundant organic matter residing in wastewater can not only reduce the emission of CO2 from the source, but the enriched organics can also be used for anaerobic fermentation to generate and offset energy consumption in wastewater treatment processes. The key is to find or develop low-cost materials that can capture organic matter. Herein, sewage sludge-derived cationic aggregates (SBC-g-DMC) were successfully prepared via a hydrothermal carbonization process coupled with a graft copolymerization reaction for recovering organic matter from wastewater. Based upon preliminary screening of synthesized SBC-g-DMC aggregates regarding grafting rate, cationic degree, and flocculation performance, SBC-g-DMC2.5 aggregate prepared with 60 mg of initiator, DMC-to-SBC mass ratio of 2.5:1, 70 °C, and 2 h of reaction time was selected for further characterization and evaluation. Results showed that SBC-g-DMC2.5 aggregate has a positively-charged surface over a wide pH range of 3–11 and a hierarchical micro-/nano-structure, endowing it with an excellent organic matter capture efficiency (97.2% of pCOD, 68.8% of cCOD, and 71.2% of tCOD). Meanwhile, SBC-g-DMC2.5 exhibits inappreciable trapping ability for the dissolved COD, NH3–N, and PO43−, guaranteeing the regular running of subsequent biological treatment units. Electronic neutralization, adsorption bridging, and sweep coagulation between cationic aggregates surface and organic matter were identified as the primary mechanisms for SBC-g-DMC2.5 to capture organics. This development is expected to provide a theoretical reference for sewage sludge disposal, carbon reduction, and energy recovery during municipal wastewater treatment.

Synthesis of cardanol grafted hydrophilic polymers and its mechanism of coal dust inhibition

A novel hygroscopic sodium cardanol polyoxyethylene ether sulfate (SCPES) dust suppressant was synthesized via graft copolymerization, sulfonation, and alkalization reactions of cardanol and polyoxyethylene. The critical micelle concentration, chemical synthesis and wetting mechanism of SCPES were investigated using pyrene fluorescence spectroscopy, Fourier transform infrared spectroscopy, quantum chemistry and molecular dynamics software. SCPES was synthesized in three steps: first, the phenolic –OH of cardanol was de-H and grafted with polyoxyethylene to form cardanol polyoxyethylene ether (CPE); second, the H atom of CPE was replaced by the –SO3H of H2SO4 to generate cardanol polyoxyethylene ether sulfate (CPES); finally, the H+ of CPES was alkalized with the OH− of NaOH to form SCPES. It was found that the active centers of the three reactions were all at the O–H bond, the activation energies were 233.66, 85.99, and − 66.91 KJ/mol, and the final composite had distinct aromatic ether (Ar–O, R–O), S–O, and S = O infrared absorption peaks, proving that SCPES had been successfully prepared. 0.10 g/L and 0.25 g/L were the critical association concentration and critical micelle concentration of SCPES, and the surface tension and contact angle at the critical micelle concentration were 33.12 mN/m and 39.5°. Compared with the H2O-lignite system, the H2O-SCPES-lignite system exhibited an increase in the total number of hydrogen bonds from 2082 to 2136, a decrease in the interaction energies from − 13863.35 kcal/mol to − 17817.77 kcal/mol, and an increase in the diffusion coefficients of H2O molecules from 0.12 to 0.73. The results indicated that the long hydrophobic tail chain in the molecular structure of SCPES was entangled with the hydrophobic sites on the coal surface, acting as intermediate carriers between water and coal to improve the wettability of coal dust, and providing a new technical means for coal dust inhibition.

Innovative hydrogels made from babassu mesocarp for technological application in agriculture

The controlled release of macronutrients via hydrogels using biopolymers is a solution for agricultural production. Two superabsorbent hydrogels (SAH) were synthesized by the graft copolymerization reaction of babassu mesocarp (MB) and polyacrylamide (PAM). Both were distinguished by the presence (HMBP) or absence (HMB) of potassium phosphate fertilizer, which can be used as nutrient carriers and soil’s conditions correctives as well. These materials were characterized by X-ray diffraction (XRD). The hydrogels presented crystallographic characteristics different from their precursors, which indicated interactions among the fertilizers and macromolecular chains. Through Fourier transform infrared spectroscopy (FTIR), a band at 1,121 cm−1 differentiates the HMBP and HMB hydrogels and was attributed to the incorporation of potassium phosphate. Thermogravimetric analyzes (TG and DTG) showed the thermal stability of the obtained materials. The swelling tests showed a superabsorbent capacity of the materials since they had swelling capacity ranging from 250 to 300 (g/g) at the expense of the pH of the medium. Regarding the toxicity of these materials, a study using Artemia showed that the developed products do not present risks. Furthermore, hydrogels containing potassium phosphate have great potential to control macronutrient delivery systems. Therefore, they are a promising input as soil conditioners and nutrient carriers for agricultural applications.

Exploration of the high energy radiation for the designing of psyllium-poly(MEDSAH) zwitterionic superabsorbent hydrogels for biomedical uses

The main objective of the present work is to develop the hydrogels as drug delivery carrier for the antibiotic drug ciprofloxacin by using graft copolymerization reaction of poly 2-(Methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide [poly(MEDSAH)] onto a bioactive dietary fiber psyllium. High energy gamma radiations were applied for the formation and sterilization of network hydrogels simultaneously. The release profile of the antibiotic drug ciprofloxacin was determined to evaluate the diffusion mechanism. Biomedical assay of polymers was also evaluated by determining the blood compatibility, antioxidant, mucoadhesive and degradation properties of the psyllium-poly(MEDSAH) network hydrogels prepared for drug delivery (DD) applications. The polymers were characterized by 13C NMR, FTIR, TGA/DTG, DSC, SEM, AFM and XRD. TGA confirmed thermal stability while SEM and AFM indicated porous and rough surface of the polymers. Both, zwitterionic monomer and radiation dose changed mesh size (from 87.94 to 529.33 nm) and crosslinking density (from 0.33 × 10−6 to 12.13 × 10−6 mol/cm3). The grafted polymers showed antioxidant nature of the material which exhibited 48.99 ± 1% free radical scavenging in DPPH assay. Polymer indicated biocompatible nature which showed 81.02 ± 5.91% thromboses percentage and less than 2% hemolytic index during blood-polymer interactions. Furthermore, detachment force required to detach the polymer from mucous membrane was Fmax=0.169 ± 0.035 N which required work of adhesion Wad=0.125 ± 0.014 N.sec showing the mucoadhesive nature of the polymeric hydrogels. The antibiotic drug ciprofloxacin diffusion occurred slowly with non-Fickian mechanism and Korsmeyer-Peppas model. Overall, results reflected their suitability of these DD carriers for colon in slow and sustained manner.

Effect of lignin source and initiation conditions on graft copolymerization of lignin with acrylamide and performance of graft copolymer as additive in water- based drilling fluid

In our previous study, as effective and eco-friendly polymer additive in the water-based drilling fluids (WBDFs), lignosulfonate-g-polyacrylamide (LS-g-PAAm) graft copolymers were successfully synthesized and characterized [J. Petroleum Science and Engineering, 171(2018) 484–494]. The aim of this study was to investigate effect of the functional groups (sources) of lignin as well as initiation condition on the chemical modification of lignin via graft copolymerization method. Kraft lignin (KL) extracted from black liquor (as a waste of paper mills) and sulfonated lignin (SL) were used as lignins with the different source and chemical structure. KL and SL were then modified by graft radical copolymerization of acrylamide initiated with thermal or redox initiator. The aliphatic hydroxyl groups were identified as the active sites in the graft copolymerization, where the number of these functional groups in the lignin chain had a significant effect on the progress of the graft copolymerization reaction. Structure of the copolymers was investigated qualitatively and quantitatively using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopies. The performance of lignin and lignin-based graft copolymers (with different grafting percentage) as an additive in the water-based drilling fluids (WBDFs) was studied. Before and after hot rolling, rheological properties including apparent viscosity, plastic viscosity, yield point as well as fluid loss were measured in the absence and presence of the salt contamination. In all fluids, except fluids containing unmodified lignin, an increase in apparent and plastic viscosities was observed. Also, thermal stability and resistance to the salt contamination were observed in fluids formulated with the graft copolymers. Best performance was observed for a fluid containing of kraft lignin graft copolymer 1 (KLGC1) where grafting percentage was as high as 452.9 wt%. Also, results showed that higher amounts of the aliphatic hydroxyl functional groups in the KL in comparison with the SL provides higher rate of the reaction progress, leading to a superior performance for use of corresponding graft copolymer as an additive in the WBDFs. The KL-based graft copolymers were able to maintain rheological and fluid loss properties during drilling operations under the hot rolling and salt contamination.

Thermo-responsive programmable shape memory polymer based on amidation cured natural rubber grafted with poly(methyl methacrylate)

This work proposes a facile and new approach that uses graft copolymerization and amidation reaction to prepare shape memory polymer (SMP) based on natural rubber (NR). The poly(methyl methacrylate) modified NR (MGNR) is cross-linked with diamine through an amidation reaction. In this kind of approach, a novel type of cross-linked MGNR with a three-dimensional network of amide linkage was prepared. The solvent resistance, mechanical properties, and phase morphology of MGNRs were significantly improved after being cross-linked by a diamine cross-linker. Additionally, the cross-linked MGNR40 also exhibited excellent shape fixation and shape recovery. This is a direct result of the vitrification of the grafted PMMA domains at low temperatures, preventing elastic recovery. Meanwhile, a cross-linked network from amide linkage facilitates recovery force upon heating. Hence, the shape memory performance of MGNRs can be tuned with both grafted PMMA content and the degree of diamine cross-link. The strategy in this research work offered an effective and convenient method to obtain cross-linked MGNR with unique molecular architecture. Consequently, this cross-linked MGNR delivered excellent mechanical strength and shape memory performance.

Synthesis and characterization of a cationic dextran-based flocculant and its application in bacterial sedimentation

As a promising material in the field of wastewater treatment, polysaccharide-modified flocculants have received increasing attention due to their environmental friendliness. In this study, an efficient and environmentally friendly flocculant was synthesized using a graft copolymerization reaction of dextran and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC). The reaction conditions were optimized at 3 mol/mol METAC/dextran, 60 g/L dextran concentration, 3 h reaction time, 60 ℃ and pH 7. The results of elemental analysis, Fourier transform infrared (FTIR) spectroscopy, NMR hydrogen spectroscopy (1H NMR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA) and viscosity measurement confirmed that the graft copolymerization reaction was successful. When flocculating a kaolin suspension used as synthetic wastewater, the flocculant showed effective flocculation performance at a low dosage. The results indicate that this cationic polysaccharide flocculant removed 98.2% of the kaolin solid suspended particles. Investigation of the flocculation mechanism showed that the flocculation process consisted of charge neutralization, charge patching and adsorption bridging mechanisms. When flocculating an E. coli culture medium, this flocculant showed high efficiency under acidic, neutral and alkaline conditions. In addition, this flocculant can be easily biodegraded by the enzymatic method. As a biomaterial, this cationic dextran derivative can contribute to future treatment of industrial wastewater and harvesting of microbial cells.

Improving the digestive stability and prebiotic effect of carboxymethyl chitosan by grafting with gallic acid: In vitro gastrointestinal digestion and colonic fermentation evaluation

Carboxymethyl chitosan (CMCS) is a useful polysaccharide with potential applications in food, cosmetic and biomedical industries. Nonetheless, CMCS is unfavorable for maintaining intestinal flora balance. In this study, gallic acid (GA) was grafted with CMCS through ascorbic acid/hydrogen peroxide initiated graft copolymerization reaction, producing GA grafted CMCS (GA-g-CMCS). The digestive and fermentative behavior of CMCS and GA-g-CMCS were investigated by using in vitro simulated gastrointestinal digestion and colonic fermentation models. Results showed that the average molecular weight (Mw) of CMCS gradually decreased during saliva-gastro-intestinal digestion, changing from original sheet-like morphology to porous and rod-like fragments. However, the Mw and morphology of GA-g-CMCS were almost unchanged under saliva-gastro-intestinal digestion. Meanwhile, the grafted GA moiety was not released from GA-g-CMCS during saliva-gastro-intestinal digestion. As compared with CMCS fermentation, GA-g-CMCS fermentation significantly suppressed the relative abundance of Escherichia-Shigella, Paeniclostridium, Parabacteroides, Lachnoclostridium, Clostridium_sensu_stricto_1, UBA1819 and Butyricimonas, while facilitated the relative abundance of Enterobacter, Enterococcus, Fusobacterium and Lachnospira. In addition, GA-g-CMCS fermentation significantly enhanced the production of short-chain fatty acids. These findings suggested that the digestive stability and prebiotic effect of CMCS were improved by grafting with GA.