Grafting Ratio Research Articles

Rational modification of xanthan gum based on assistance of molecular dynamics simulation

Graft copolymerization is an effective approach to improve performance of polysaccharide. However, selecting the most suitable modification strategy can be challenging due to the intricate molecular structure. Rational design through computer aided molecular dynamics (MD) simulations requires substantial computational resources. This study designed a simplified MD simulation strategy and suggested that grafting acrylamide (AM) could effectively adjust the molecular conformation of xanthan gum (XG) and its derivatives, thus regulating its viscosity and gelation properties. To rationally modify XG, a uniform experimental design was applied to tune the grafting ratios ranging from 72 % to 360 %, resulting in XG-AM solutions with viscosity ranging from 9 to 104 mPa•s at a concentration of 0.3 %. XG-AM was crosslinked by acid phenolic resin to generate gel with the viscosity of 7890 mPa·s in 3 days, which was 13 times the viscosity of unmodified XG. The controllable gelation will enhance the efficacy of XG-AM in oil recovery. By integrating rational selection of grafting strategies based on simplified MD simulation of polysaccharide derivatives and controllable grafting modification with specified grafting rates, customized production of polysaccharide derivatives can meet the requirements of a diverse range of applications.

Porous Morphology of High Grafting Density Mixed Polyelectrolyte Brushes Grown from a Y-Inimer Coating.

Mixed A/B polyelectrolyte (PE) brushes of opposite charges are grown from a Y-shaped initiator-bearing coating to facilitate intimate mixing of the A and B polyelectrolytes in a 1:1 grafting ratio. The design of the Y-shaped inimer includes both ATRP and NMP initiators attached to a common Y-junction. A copolymer of a Y-shaped inimer with glycidyl methacrylate is cross-linked to the substrate resulting in a stable ultrathin coating decorated with Y-shaped initiators. Weak PE A/B mixed brushes based on poly(methacrylic acid)/poly(2-vinylpyridine) (PMAA/P2VP) with a high grafting density of ∼1 chain/nm2 are grown by surface-initiated ATRP and NMP, respectively. Detailed morphological characterization of the PMAA/P2VP brushes in response to pH changes reveals a nanoporous morphology under conditions that maximize complex coacervate formation between oppositely charged brushes. The charge ratio between the A and B brushes is varied via the composition of the brushes to further study the morphology evolution. The effect of intimate contact between the A and B brushes on the morphology is probed by comparing with a mixed A/B PE system with random fluctuations in grafting composition. A quantitative and qualitative study of the pore evolution with pH as well as charge composition is presented using a combination of atomic force microscopy, water contact angle measurement, and image analysis using Gwyddion software. These studies demonstrate that the porous morphology is enhanced and most uniform when the brushes are grown from the Y-inimer, indicating that a 1:1 grafting ratio and intimate contact between A and B brushes are essential.

Radiation-induced grafting of polyethyleneimine onto cellulose triacetate membrane for separation of cesium ions from aqueous solution

Radiation grafting of polyethyleneimine (PEI) onto the surface of cellulose triacetate (CTA) membrane was successfully performed. Pre-radiation and co-radiation were applied by gamma rays at the dose of 12 kGy. FT-IR, SEM, XPS, contact angle, zeta-potential, grafting ratio, etc. Were used to characterize the PEI-CTA membranes before and after grafting. The FT-IR spectrum showed that a notable discernible shoulder peak of N–H appeared for amide at co-radiation and pre-radiation, and XPS analysis indicated that co-radiation achieved the highest N percent of 9.75%, suggesting that PEI was introduced into the membrane surface. In a forward osmosis (FO) process, the PEI-CTA membrane obtained higher cesium, Cs(I), retention (95–97%) than the CTA membrane with Cs(I) retention of 92%. Cs(I) fluxes significantly decreased from 0.09 to 0.02–0.03 mmol m−2h−1 after PEI modification. Effective Cs(I) retention was attributed to increase of the positive charges on CTA membrane when PEI was added, which exerted a repulsive effect on Cs(I), preventing them from moving towards the membrane direction. In the FO process, the PEI-CTA membrane featured the water flux of 23 L m−2 h−1 a little lower than that of CTA membrane (24 L m−2 h−1). Although modified PEI increased the hydrophilicity, the increase of water flux did not occur with the co-irradiated membrane, which was related to the high graft, higher thickness and resistance of the membrane.

Modification of poly(styrene‐b‐isobutylene‐b‐styrene) using hyaluronic acid via surface graft polymerization and cytotoxicity investigation

AbstractPoly(styrene‐b‐isobutylene‐b‐styrene) (SIBS) is a biomedical elastomer with excellent overall properties. However, the low surface energy and the surface hydrophobicity of SIBS have limited its application as a human implantable material. To improve its biocompatibility, in this work, hyaluronic acid (HA) was introduced onto the surface of SIBS. Firstly, glycidyl methacrylate (GMA) and HA were employed to prepare GMA‐modified HA (GMHA) via grafting reaction. Due to the introduction of carbon–carbon double bonds on the side chain of HA, the GMHA could be used for free radical polymerization between SIBS. The effects of UV illumination time, GMHA concentration, and initiator concentration on the grafting ratio were investigated. FTIR, 1H NMR, and XPS confirmed the successful grafting of HA onto SIBS. The experimental results showed that the surface modification method not only ensured that the excellent properties of the SIBS would not be destroyed but also improved its surface properties successfully. Besides, the MTT assay indicated that the GMHA‐modified SIBS was not bio‐toxic, so it could meet the need to expand its use in the biomedical fields.

Study on interfacial compatibilizing effect of PB grafts on PB/GNP thermally conductive composites

AbstractUsing polymer‐grafts to improve the interfacial compatibilization of composites is by far the most common and effective strategy. However, although polybutene‐1 (PB) resin enjoys the reputation of “gold plastic” in the field of industry, there are few studies on its grafting and functional modification. In this work, PB‐grafts were prepared by melt grafting method with maleic anhydride (MAH) and styrene (St) as the functional monomers. The effect of two PB‐grafts (PB‐g‐MAH and PB‐g‐MAH‐co‐St) on the interfacial compatibilization of PB/GNP (Graphene nanosheet) thermally conductive composites was compared and the corresponding compatibilizing mechanism is discussed. Results indicate that PB‐g‐MAH‐co‐St has better compatibizing effect than that of PB‐g‐MAH because the cooperation of St with MAH enhanced the grafting degree of functional monomers on PB, and increased the surface energy of PB‐g‐MAH‐co‐St, which reduced the interface energy between PB and GNP and improved its interfacial adhesion. A better compatibilization effect has achieved when the compatibilizer and filler at the mass ratio of 1:4. Under this ratio, when the content of GNP is 30 wt%, the thermal conductivity and electrical conductivity of PB/GNP/ PB‐g‐MAH‐co‐St composite achieved 1.82 W·m−1·K−1 and 8.44 × 10−8 S·cm−1, which are 857.89% and 9 orders of magnitude higher than that of neat PB, respectively. Moreover, the composite has good mechanical properties and processability, which is beneficial to industrialization.Highlights PB‐g‐MAH‐co‐St has higher grafting ratio than that of PB‐g‐MAH. The surface energy of PB/GNP composites is reduced by use of PB‐g‐MAH‐co‐St. There is a suitable mass ratio between compatibilizer and filler. The composite of PB/GNP/PB‐g‐MAH‐co‐St achieved high thermal conductivity. The PB/GNP/PB‐g‐MAH‐co‐St composites have good melting processability.

Preparation of caffeic acid grafted poly(D,L-lactide)-b-poly(2-hydroxyethyl methacrylate)/polylactide films with bioactive properties

Derived from renewable sources like corn starch or sugarcane, poly(lactic acid) (PLA) presents an eco-friendly alternative to traditional petroleum-based plastics. PLA lacks inherent functional groups, posing a challenge for certain applications. The modification and functionalization of PLA contribute to the facilitation of innovative applications across diverse fields. To address this limitation, in this study a bioactive compound, caffeic acid, strategically grafted the onto poly(D,L-lactide)-b-poly(2-hydroxyethyl methacrylate) block copolymer (PLA-b-PHEMA). The resulting caffeic acid grafted copolymer (PLA-b-PHEMA-g-CA) was characterized by size exclusion chromatography, NMR, UV–Vis and FT-IR spectroscopies, and then blended with commercial PLA to produce films. The synthesis involves polymerizing 2-hydroxyethyl methacrylate with a poly(D,L-lactide) macroinitiator via ATRP method, yielding PLA-b-PHEMA. Subsequent functionalization via Steglich esterification yields PLA-b-PHEMA-g-CA. Characterization indicated a grafting ratio of 60.7%. Both grafted copolymer and films exhibited antioxidant property and antimicrobial effect against S. aureus and E. coli, showcasing potential applications in sustainable materials.

Dual-responsive nanocarriers for efficient cytosolic protein delivery and CRISPR-Cas9 gene therapy of inflammatory skin disorders.

Developing protein drugs that can target intracellular sites remains a challenge due to their inadequate membrane permeability. Efficient carriers for cytosolic protein delivery are required for protein-based drugs, cancer vaccines, and CRISPR-Cas9 gene therapies. Here, we report a screening process to identify highly efficient materials for cytosolic protein delivery from a library of dual-functionalized polymers bearing both boronate and lipoic acid moieties. Both ligands were found to be crucial for protein binding, endosomal escape, and intracellular protein release. Polymers with higher grafting ratios exhibit remarkable efficacies in cytosolic protein delivery including enzymes, monoclonal antibodies, and Cas9 ribonucleoprotein while preserving their activity. Optimal polymer successfully delivered Cas9 ribonucleoprotein targeting NLRP3 to disrupt NLRP3 inflammasomes in vivo and ameliorate inflammation in a mouse model of psoriasis. Our study presents a promising option for the discovery of highly efficient materials tailored for cytosolic delivery of specific proteins and complexes such as Cas9 ribonucleoprotein.

Synthesis of grafted bromoisobutyryl esterified starch using electron transfer atom transfer radical polymerization method with high-performance adhesion and film properties

Nowadays, few investigations on the process parameters of grafted starch synthesized using electron transfer atom transfer radical polymerization (ARGET ATRP) and its applications in warp sizing and paper-making are presented. Therefore, this study aimed to survey the appropriate process parameters of bromoisobutyryl esterified starch-g-poly(acrylic acid) (BBES-g-PAA) synthesized by the ARGET ATRP, and also aimed to provide a new biobased BBES-g-PAA adhesive. The appropriate synthesis process parameters were 1.2, 0.32, and 0.6 in the molar ratios of vitamin C, CuBr2, and pentamethyldivinyltriamine to BBES, respectively, at 40 °C for 5 h. The BBES-g-PAA samples with a grafting ratio range of 4.63–14.14 % exhibited bonding forces of 57.8–64.6 N to wool fibers [55.5 N (BBES) and 53.8 N (ATS)], and their films showed breaking elongations of 3.29–3.80 % [2.74 % (BBES) and 2.49 % (ATS)] and tensile strengths of 29.1–25.4 MPa [30.4 MPa (BBES) and 34.7 MPa (ATS)]. Compared with BBES, significantly increased bonding forces and film elongations, and decreased film strengths for the BBES-g-PAA samples with grafting ratios ≥10.54 % were displayed (p < 0.05). The time (100–42 s) taken for the BBES-g-PAA films was significantly shorter than that of ATS (246 s) and BBES (196 s) films (p < 0.05), corresponding to better desizability.

Effects of catechol grafting on chitosan-based coacervation and adhesion

In this study, we investigated detailedly the contribution of catechol in tuning the formation and adhesive properties of coacervates. We have constructed a series of catechol-grafted Chitosan (Chitosan-C), and investigated their coacervation with gum arabic (GA) and the corresponding adhesion. We demonstrate that, increasing catechol grafting ratio from 0 %–44 % impacted the coacervation moderately, while enhanced the adhesion of the coacervate up to 438 % when the catechol faction was 37 %. Further increasing the grafting ratio to 55 % led to precipitated coacervates associated with a declined adhesion. Our findings identify the optimal grafting threshold for coacervation and adhesion, providing insights into the underlying mechanism of coacervate binding. Moreover, the catechol enhancement on adhesion of coacervates tolerates different substrates and diverse polyelectrolyte pairs. The revealed principles shall be helpful for designing adhesive coacervates and boosting their applications in various industrial and biomedical areas.

Importance of cohesive failure mode in fracture toughness enhancement of polymer nanocomposites with covalent grafting: A multiscale study

The covalent grafting between the nanoparticles and polymer matrix is considered a useful design factor to control the mechanical properties (e.g., fracture toughness). Meanwhile, in the theoretical viewpoint, the toughening mechanisms of the epoxy nanocomposites with covalent grafting are still unclear. In this study, a new multiscale fracture model is proposed to quantify the toughness enhancement of epoxy nanocomposites induced by the covalent grafting. Especially, it was concentrated on the investigation of the influences of the cohesive failure mode on the fracture toughness and revealed that the failure mode transition (from the adhesive failure mode to cohesive failure mode) near the nanoparticles with increasing grafting ratio is critical factor for the toughening mechanisms of the epoxy nanocomposites with covalent grafting. The theoretically derived multiscale model demonstrated that the cohesive failure mode significantly enhanced the fracture toughness of polymer nanocomposites by dissipating more energy compared to the adhesive failure mode. This study underscores the critical importance of rationally designing nanocomposites with an optimal grafting ratio that properly reflects the cohesive failure mode. It is anticipated that the multiscale analysis approach outlined in this study will provide valuable design guidelines and insights for polymer nanocomposites incorporating covalent grafting.

Enhanced gut microbiota delivery of a model probiotic (Faecalibacterium prausnitzii): Layer-by-layer encapsulation using riboflavin-conjugated sodium alginate and glycol chitosan

Faecalibacterium prausnitzii (F. prausnitzii) exhibits a variety of biological functions that make it suitable for use as a next-generation probiotic. However, its high sensitivity to oxygen and digestive fluids currently limits its application. Riboflavin is known to support the growth of F. prausnitzii in oxygen environments, but it is important that it is in close proximity to the probiotics. Layer-by-layer assembly can be used to form protective coatings around probiotics, which can protect them from adverse environmental conditions. Moreover, riboflavin can be conjugated to these coatings, thereby increasing its efficacy by bringing it close to probiotic surfaces. In this study, we therefore evaluated the potential of electrostatic layer-by-layer assembly to protect F. prausnitzii by coating them with riboflavin-alginate and glycol-chitosan layers. Initially, we showed that riboflavin could be successfully conjugated to alginate, with a grafting ratio of around 4.35%. Then, the layer-by-layer method was used to coat F. prausnitzii using cationic glycol chitosan and anionic riboflavin-alginate. The coating formed was found to have a thickness of approximately 18.5 nm. Encapsulation did not adversely affect the growth of F. prausnitzii, but it significantly enhanced its resistance to oxygen and digestive fluids. The encapsulated probiotic was shown to have enhanced mucoadhesive properties using an in vitro intestinal monolayer model. Furthermore, the encapsulated probiotics colonized the colons of rats for longer than nonencapsulated ones. These results show that coating F. prausnitzii with riboflavin-rich biopolymer layers improves its resistance to oxygen and digestive fluids, and enhances its mucoadhesion and colonization properties, which should enhance its potential as an orally administered probiotic.

Redox-sensitive self-assembling polymer micelles based on oleanolic modified hydroxyethyl starch: Synthesis, characterisation, and oleanolic release

Our study aimed at developing polymer micelles that possess redox sensitivity and excellent controlled release properties. 3,3′-dithiodipropionic acid (DTDPA, Abbreviation in synthetic polymers: SS) was introduced as ROS (Reactive oxygen species)response bond and connecting arm to couple hydroxyethyl starch (HES) with oleanolic acid (OA), resulting in the synthesis of four distinct grafting ratios of HES-SS-OA. FTIR (Fourier Transform infrared spectroscopy) and 1H NMR (1H Nuclear magnetic resonance spectra) were used to verify the triumphant combination of HES-SS-OA. Polymer micelles were found to encapsulate OA in an amorphous form, as indicated by the results of XRD (X-ray diffraction) and DSC (Differential scanning calorimetry). When the OA grafting rate on HES increased from 7.72 % to 11.75 %, the particle size decreased from 297.79 nm to 201.39 nm as the polymer micelles became compact due to enhanced hydrophobicity. In addition, the zeta potential changed from −16.42 mv to −25.78 mv, the PDI (polydispersity index) decreased from 0.3649 to 0.2435, and the critical micelle concentration (CMC) decreased from 0.0955 mg/mL to 0.0123 mg/mL. Results of erythrocyte hemolysis, cytotoxicity and cellular uptake illustrated that HES-SS-OA had excellent biocompatibility and minimal cytotoxicity for AML-12 cells. Disulfide bond breakage of HES-SS-OA in the presence of H2O2 and GSH confirmed the redox sensitivity of the HES-SS-OA micelles and their excellent controlled release properties for OA. These findings suggest that HES-SS-OA can be potentially used in the future as a healthcare drug and medicine for the prevention or adjuvant treatment of inflammation.

Preparation of shape memory polyurethane composite materials by grafting PCL onto CNFs with different carboxyl content

This study describes the preparation of cellulose nanofibers (CNFs) with varying amounts of carboxyl groups from rice straw pulp using the TEMPO/NaBr/NaClO oxidation system. The resulting CNFs were found to be in the form of nanofibers with an average diameter of 6 nm and an average length of 160 nm. To further enhance their properties, the CNFs were grafted with polycaprolactone (PCL) to create CNFs-g-PCL, which was then blended with shape memory polyurethane (SMPU) to produce CNFs-g-PCL/SMPU composites. It was observed that as the carboxyl content in CNFs increased from 0.35 to 1.14 mmol/g, the graft ratio of PCL on CNFs decreased from 24.6 to 10.7%. Consequently, the hydrophobicity of the grafted product (CNFs-g-PCL) also decreased. When 10% CNFs-g-PCL was added to the SMPU matrix, the elastic modulus and tensile stress of the resulting composite were both higher than those of the pure SMPU, increasing by up to 54.4% and 67.3%, respectively. Additionally, the shape retention and shape recovery rates of the composite remained stable after addition of CNFs-g-PCL. In conclusion, incorporating CNFs-g-PCL into SMPU can improve its mechanical properties while maintaining its shape memory properties.Graphical abstract

Exploring the emulsification potential of chitosan modified with phenolic acids: Emulsifying properties, functional activities, and application in curcumin encapsulation

This study successfully grafted caffeic acid and 3,4-dihydroxybenzoic acid into chitosan through a coupling reaction, yielding grafting ratio of 8.93 % for caffeic acid grafted chitosan (CA-GC) and 9.15 % for 3,4-dihydroxybenzoic acid grafted chitosan (DHB-GC) at an optimal concentration of 4 mmol phenolic acids. The characterization of modified chitosans through ultraviolet visible spectrometer (UV–vis), Fourier transform infrared spectrometer (FTIR), proton nuclear magnetic resonance (1H NMR), and x-ray photoelectron spectrometer (XPS) confirmed the successful grafting of phenolic acids. In the subsequent step of emulsion preparation, confocal laser scanning microscope images confirmed the formation of O/W (oil-in-water) emulsions. The phenolic acid-grafted chitosans exhibited better emulsification properties compared to native chitosan, such as reduced droplet size, more uniform emulsion droplet distribution, increased ζ-potential, and enhanced emulsifying activity and stability. Moreover, the modified chitosans demonstrated increased antioxidant activities (evidenced by DPPH and β-carotene assays) and displayed greater antimicrobial effects against E. coli and S. aureus. Its efficacy in curcumin encapsulation was also notable, with improved encapsulation efficiency, sustained release rates, and enhanced storage and photostability. These findings hint at the potential of modified chitosans as an effective emulsifier.

Regulation of Cell Adhesion on Physically Crosslinked Hydrogels Composed of Amino Acid‐Based Polymers by Changing Elastic Modulus Using Shape Fix/Memory Properties

AbstractThe elastic modulus of hydrogels is one of the most important factors for controlling cell fate. In this study, hydrogels composed of poly(N‐acryloylglycinamide) (PNAGAm) grafted with arginine (R)–glycine (G)–aspartic acid (D)–serine (S) peptide is designed without a chemical crosslinker. The hydrogels are prepared by the conventional radical copolymerization of N‐acryloylglycinamide with a polymerizable RGDS peptide. The peptide grafting ratio is easily controlled by adjusting the feed composition for polymerization. The hydrogels exhibit thermo‐responsiveness of the upper critical solution temperature type based on the PNAGAm moiety. This characteristic reflects the shape fix/memory properties of hydrogels because of the reversible formation of multiple hydrogen bonds. The cell adhesiveness of the hydrogels drastically improves in the presence of a small amount of the peptide graft. The hydrogels exhibit good biocompatibility; the adhered cells proliferate on the hydrogels, and macrophages do not show activation or inflammation. Surfaces with different elastic modulus regions are successfully constructed on the same hydrogel by using shape fix/memory properties, allowing the regulation of cell adhesion. This hydrogel system offers promising opportunities for the design and application of functional cell scaffolds.

Temperature-Responsive Separation Membrane with High Antifouling Performance for Efficient Separation.

Temperature-responsive separation membranes can significantly change their permeability and separation properties in response to changes in their surrounding temperature, improving efficiency and reducing membrane costs. This study focuses on the modification of polyvinylidene fluoride (PVDF) membranes with amphiphilic temperature-responsive copolymer and inorganic nanoparticles. We prepared an amphiphilic temperature-responsive copolymer in which the hydrophilic poly(N-isopropyl acrylamide) (PNIPAAm) was side-linked to a hydrophobic polyvinylidene fluoride (PVDF) skeleton. Subsequently, PVDF-g-PNIPAAm polymer and graphene oxide (GO) were blended with PVDF to prepare temperature-responsive separation membranes. The results showed that temperature-responsive polymers with different NIPAAm grafting ratios were successfully prepared by adjusting the material ratio of NIPAAm to PVDF. PVDF-g-PNIPAAm was blended with PVDF with different grafting ratios to obtain separate membranes with different temperature responses. GO and PVDF-g-PNIPAAm formed a relatively stable hydrogen bond network, which improved the internal structure and antifouling performance of the membrane without affecting the temperature response, thus extending the service life of the membrane.

A new starch-based adhesive material containing diblock branches for sizing cotton and cotton/polyester

A new starch macroinitiator (dibromopropyl etherified starch, DPES) with two active sites per dibromopropyl substituent, was successfully prepared and then conducted a two-step graft polymerization with EMA and AA, respectively, to prepare new grafted starch (DPES-g-poly(ethyl methacrylate)-b-poly(acrylic acid), DPES-g-PEMA-b-PAA) samples using the electron transfer atom transfer radical polymerization (ARGET ATRP) technique in an aqueous medium. The DPES-g-PEMA-b-PAA had excellent adhesion to cotton and cotton/polyester roving. As the grafting ratios increased from 0 to 9.346%, gradually promoted adhesion forces from 61.3 N to 76.8 N for cotton roving and from 91.2 N to 123.0 N for cotton/polyester roving were presented. In addition, the DPES-g-PEMA-b-PAA possessed lower film crystallinity and brittleness as well as higher viscosity compared with ATS. Based on these results, the DPES-g-PEMA-b-PAA with a total grafting ratio of 9.346% was concluded as a new adhesive material in the application of sizing cotton and cotton/polyester warps.

Molecular design of switchable nanochannels modified by zwitterion polymer chains with dissipative particle dynamics simulation

Conventional artificial nanochannels have obvious shortcomings in permeability regulation and environmental friendliness, which challenge their practical applications. Polymer-modified switchable nanochannels are considered as a potential solution owing to their high chemoselectivity and controllability. Herein, systematic dissipative particle dynamics (DPD) simulations are performed to investigate the conformational transition and stretching behavior of polysulfobetaine in the presence of an explicit solvent. Polysulfobetaine is one kind of zwitterion polymer with a responsive property to the change of salt ion concentration, which is grafted onto the internal surface of the nanochannel to achieve the "open-close-open" switch. The simulation results indicate that the grafting ratio of 1.52 chains/rc2 (rc is a reduced unit of length, 1 rc = 0.857 nm) and salt ion concentration of 5 wt% NaCl are optimal parameters to achieve the "open-close-open" functionality. Specifically, salt ions promote the closure of nanochannels via regulating the electrostatic attraction of the polymer chain in z-direction and the excluded volume effect caused by conservative forces. On the other hand, the competition mechanism between electrostatic force and conservative force is revealed, i.e. at low salt concentration, electrostatic force dominates and close the nanochannel; With salt ions concentration increasing, conservative force gradually exceeds electrostatic force, and becomes the dominant force and reopens the nanochannel. This study provides some molecular insights for the design of stimulus-responsive artificial nanochannels, which may find application in the exploitation of natural gas hydrates, such as temporary plugging agents in well drilling for gas hydrate reservoirs.

Bio-based active packaging: Gallic acid modified agarose coatings in grass carp (Ctenopharyngodon idellus) preservation

Antioxidant and antimicrobial agarose coatings were developed by grafting gallic acid through the carbodiimide coupling method. Structural characterization revealed that the carboxyl group of gallic acid was successfully grafted onto the C6-OH of D-galactose in agarose, with the highest observed grafting ratio being 13.73 %. The grafting of gallic acid significantly increased the antioxidant and bacteriostatic activities of the agarose. As the grafting ratio of gallic acid-modified agarose (GaAg) increased from 0 to 13.73 %, the scavenging ratio of DPPH and the inhibition ratio of β-carotene bleaching were observed to increase from 0 % to 65.92 % and 6.89 % to 73.46 %, respectively. GaAg exhibited up to 100 % inhibition of Escherichia coli and Staphylococcus aureus. The physicochemical properties of gel strength, viscosity, gelling temperature and melting temperature decreased to 971.3 g/cm2, 17.9 mPa·s, 31.7 °C and 84.1 °C, respectively. The gel contact angle was increased from 22.1° to 73.6°. Fish preservation tests have demonstrated that it effectively inhibited bacterial growth, prevented fat oxidation, blocked light, reduced moisture loss, and enhanced the overall quality of grass carp (Ctenopharyngodon idellus) fillets during refrigeration, which was more effective than native agarose in extending the shelf life of fish. Therefore, GaAg holds promise as an aquatic product preservative.

Fluorine-free and hot water repellent superhydrophobic palygorskite: A combined experimental and molecular dynamics study

The present work investigates the wettability of dodecyltrimethoxysilane (DTMS) functionalized palygorskite (PAL) using both experimental and molecular dynamics approaches. The best superhydrophobicity was achieved at a PAL/DTMS ratio of 0.60 g/mL. Changes in wettability were simulated by varying the DTMS grafting ratio from perspectives of contact angle, interaction energy, the water molecule’s distribution characteristics, and hydrogen bonds. The results show that DTMS grafting promotes hydrophobicity, whereas excess grafting ratio declines hydrophobicity due to roughness decrease. The hot water resistance was analyzed from interaction energy, diffusion behavior, and cohesion energy, and the findings are consistent with the experimental results.