Increase In Degree Of Grafting Research Articles

Soluble hemp protein-xylose conjugates fabricated by high-pressure homogenization and pH-shifting treatments.

The process of Maillard conjugation occurs with plant proteins and sugars and can be influenced by several factors, such as processing time, pH, and shear force. By utilizing cavitation processes such as high-pressure homogenization (HPH) and pH-shifting, it is possible to regulate the degree of grafting, functional characteristics, and structural changes in the formation of conjugates. The present study aimed to improve the hemp protein concentrate (HPC) through two different conjugation techniques: HPH and pH-shifting-assisted processes. The best conjugation conditions for the conventional method were identified as a 1:2 HPC to xylose ratio, a pH of 10, and 3 h of treatment at 70 °C. The use of HPH and pH 12-shifting methods resulted in a remarkable 2.5-fold increase in grafting degree, requiring less processing time. Fourier transform infrared spectra confirmed the formation of conjugates. Conjugates produced through HPH with pH 12-shifting (MPHX) transformed into soluble glycoproteins with a particle size of 74 nm. MPHX solubility increased by 5.7-fold than HPC, reaching 85.7%, with a more negatively charged surface at -32.4 mV. Microimages showed cracked and sharp forms for conjugated proteins compared to untreated HPC. Additionally, MPHX conjugates demonstrated superior properties in emulsion stability, foaming capacity, and antioxidant activity compared to HPC and classical conjugates. The use of HPH and pH-shifting-assisted Maillard conjugation was highly effective in enhancing the functional attributes of hemp protein conjugates. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Positron annihilation lifetime study of subnano level free volume features of grafted polymer electrolyte membranes for hydrogen fuel cell applications

AbstractThe subnano level free‐volume hole features of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) are investigated using positron annihilation lifetime spectroscopy (PALS). The hole sizes are formed mainly at the graft‐polymerization step and are not altered dramatically at the sulfonation. With increasing grafting degree, τ4, standing for the annihilation of ortho‐positronium (o‐Ps) in the larger free‐volume holes of the mobile amorphous layers and the PSSA grafts outside of the lamellae, decreases monotonously, whereas τ3, representing for that in the smaller free‐volume holes of the lamellar amorphous regions, the PSSA grafts, and the interface zones inside the lamellae, only shows a slight decrease. From the viewpoint of free‐volume hole sizes, gas molecules are predicted to pass dominantly through the mobile amorphous phases and the PSSA grafts outside of the lamellae. Specifically, the limited hole concentration induced by confining lamellae at the interfacial zones is observed. Thus, the obtained results are associated with a significant reduction of gas passing and the moderate or higher tensile strength for the ETFE‐PEMs in comparison to Nafion‐212.

Structural characteristics and emulsifying properties of lotus seed protein isolate-dextran glycoconjugates induced by a dynamic high pressure microfluidization Maillard reaction

Lotus seed protein isolate (LSPI) is nutritious but with poor solubility and emulsifying properties. Therefore, to improve utilization of LSPI in the food industry, glycoconjugates with LSPI and Dextran under dynamic high pressure microfluidization (DHPM) assisted glycosylation reaction method were produced, which dramatically accelerated the glycosylation reaction and contributed to grafting more dextran on LSPI compared with traditional treatment. The formation of new peaks in a Fourier transform infrared spectrum and the increase of grafting degree were verified by the successful generation of LSPI-Dextran glycoconjugates. Secondary and tertiary structural results suggested that DHPM-induced glycosylation reaction promoted the unfolding of LSPI molecules with more flexible conformation. The solubility and emulsifying properties of LSPI-Dextran glycoconjugates were dramatically improved with an increase in treatment pressure. Moreover, confocal laser scanning analysis confirmed LSPI-Dextran glycoconjugate with the assistance of 120 MPa DHPM could produce the smallest and most homogeneous oil droplets. LUMiSizer centrifugal analysis observed the slowest transmission profiles, further confirming that 120 MPa DHPM optimal treatment for glycation reaction between LSPI and Dextran, which showed the greatest improvements in emulsifying ability and stability. These findings provided a foundation for the development of LSPI-based products with desirable characteristics.

A novel anion exchange membrane based on poly (2,6-dimethyl-1,4-phenylene oxide) with excellent alkaline stability for AEMFC

We report a novel comb-shaped anion exchange membrane based on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and 4-(dimethylamino)butyraldehyde diethyl acetal (DABDA). The Menshutkin reaction successfully introduced DABDA into the brominated PPO backbone, which was proved through FT-IR and 1H NMR. The distinct hydrophilic/hydrophobic microphase separation structure observed by transmission electron microscope (TEM). As the increase of grafting degree, so does the water uptake, swelling ratio, hydroxide conductivity and alkaline stability. The membranes also possess good mechanical property with tensile strength from 14.2 to 38.11 MPa. This is due to the increasing number of hydroxide and unique steric hindrance effect caused the higher water uptake and higher dimensional stability. Simultaneously, especially PPO/DABDA-60 in comb-shaped membranes demonstrate an excellent long-term alkali resistance stability. In a 576-h alkali resistance stability test, the retained ionic conductivity of the PPO/DABDA-60 membrane is 96% of the initial value. The PPO/DABDA-60 is a potential candidate material for AEM.

Whey protein isolate-dextran conjugates: Decisive role of glycation time dependent conjugation degree in size control and stability improvement of colloidal nanoparticles

Whey protein isolate-dextran (WPI-dextran) conjugates were acquired via Maillard reaction for different durations (1–7 days) and their potential to govern the size and stability of colloidal nanoparticles formed from heating electrostatic complexes of WPI-dextran conjugates and chondroitin sulfates was assessed. The grafting degree and browning index gradually increased with the reaction time. The intensity of amide bands increased in the first 2 days and then declined. As the duration increased, the content of α-helix increased from 23.9% to 29.6%, while β-sheet and random coil decreased from 23.8% and 38.1% to 19.6% and 32.7%, respectively. Moreover, the surface hydrophobicity was reduced as the conjugation progressed, while surface and total sulfhydryl content gradually increased from 5.3 and 15.4 μmol/g to 11.0 and 17.9 μmol/g, respectively. Meanwhile, fluorescence intensity of conjugates decreased with prolonged durations. These changes with increasing grafting degree prompted greater steric hindrance, weakened hydrophobic interaction, and improved stability of protein during heating, thus facilitating the decreasing diameter of the corresponding heat-induced nanoparticles. In comparison with the nanoparticles derived from non-conjugated mixture of WPI and dextran, those from WPI-dextran conjugates showed an excellent stability to aggregation and dissociation upon synergistic influence of pH variation (1–10) and enhancing ionic strength (0–4 mol/L).

Characterization of maleic anhydride/styrene melt-grafted random copolypropylene and its impact on crystallization and mechanical properties of isotactic polypropylene

Maleic anhydride/styrene-grafted random copolypropylene (MPP) was prepared by multi-monomer melt grafting. Fourier transform infrared spectroscopy verified that maleic anhydride and styrene were successfully grafted onto the polypropylene random copolymer (PPR) backbones. Dynamic rheological tests indicated the existence of long branched chains on MPP. The influence of grafting degree of maleic anhydride on the crystallization behavior of MPP was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. The results showed that the crystallization rate of MPP was higher than that of PPR, and it increased with the increase in grafting degree. The long-chain branched structure could promote heterogeneous nucleation formation of MPP, resulting in the increase in crystallization rate and the decrease in spherulite size. Moreover, the effect of MPP content on crystallization and mechanical properties of isotactic polypropylene (PP)/MPP blends was further investigated. It was found that the interfacial interaction in the blends with 1–10 wt% of MPP was higher than PP/MPP-15% blend. Introducing MPP into PP could induce the formation of β-crystal. Consequently, the incorporation of MPP into PP increased the tensile strength and impact strength and maximum values were obtained for PP/MPP-10% blend.

Real-time monitoring of radical grafting of poly(lactic acid) with itaconic anhydride in melt

Poly(lactic acid) (PLA) was functionalized with itaconic anhydride (IAH) via radical grafting in melt initiated by 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101). The main interest was the real-time monitoring of grafting reaction using oscillatory rheology which was considered as an effective tool for monitoring radical grafting. It was found that low concentration of IAH and high concentration of L101 leads to the high grafting efficiency while further increase of IAH concentration does not lead to the proportional increase of grafting degree due to predomination of β-scission. Nevertheless, high grafting efficiency is accompanied by PLA crosslinking as evidenced from both rheology data. Therefore,2,6-di-tert-butyl-4-methylphenol (BHT) was applied at different L101/BHT molar ratio with potential to reduce the extent of crosslinking. The effect of BHT was real-time evidenced during the reaction performed by internal mixer and rotational rheometer. The kinetics of the PLA grafting/crosslinking was studied using differential scanning calorimetry (DSC) which confirmed both rheological data and the difference in kinetics parameters for radical reaction with/without BHT. Both techniques proved desired effect of BHT at L101/BHT molar ratio greater than 1/0.5 which makes BHT promising agent for better control of grafting process and suppression of undesired collateral reactions.

Thermal degradation kinetics and estimation of lifetime of radiation grafted polypropylene films

In this research work, thermal stability and degradation behavior of acrylic acid grafted polypropylene (PP-g-PAAc) films were investigated by using thermogravimetric (TGA) analysis at four different heating rates 5, 10, 15 and 20°C/min over a temperature range of 40–550°C in nitrogen atmosphere. The kinetic parameters namely activation energy (Ea), reaction order (n) and frequency factor (Z) were calculated by three multiple heating rate methods. The thermal stability of PP-g-PAAc films is found to decrease with increase in degree of grafting. The TGA data and thermal kinetic parameters were also used to predict the lifetime of grafted PP films. The estimated lifetime of neat PP as well as grafted PP decreased with increase in temperature by all the three methods. Studies also indicated that Ea and lifetime of PP-g-PAAc films decreased with increase in degree of grafting, which may also be helpful in biodegradation of grafted PP films.

Study on Crystal Form Transition and Non-Isothermal Crystallization of Glycidyl Methacrylate Grafted Isotactic Polybutene-1

Abstract We report the impact of grafting glycidyl methacrylate (GMA) at different degrees onto isotactic polybutene-1 (iPB-1) on the crystallization process. The study of the crystal form transition using FTIR and X-ray Diffraction (XRD) revealed that the conversion degree from form II to form I of the grafted iPB-1 (iPB-g-GMA) was higher than that of iPB-1 under the same experimental conditions and increased with increasing grafting degree. The spherulitic size of iPB-g-GMA was smaller compared to iPB-1 at the same amplification factor in Polarized Optical Microscopy (POM). The kinetic parameters of the non-isothermal crystallization process have been determined based on Differential Scanning Calorimetry (DSC) experiments and the Ozawa and Mo equation. The results showed that the crystallization rate of iPB-g-GMA was higher than that of iPB-1. The activation energy for the non-isothermal crystallization process of iPB-g-GMA (with a grafting degree of 1.54%) was lower than that of iPB-1, which further illustrated that grafting GMA on iPB-1 accelerated the crystallization rate.

Optimization of acrylic acid grafting onto polypropylene using response surface methodology and its biodegradability

Simultaneous radiation grafting was optimized to graft acrylic acid monomer on the polypropylene (PP) films to make them hydrophilic and enhance their biodegradability. Experiments were designed based on full factorial central composite design (response surface methodology) and influence of monomer concentration, radiation dose, inhibitor concentration, solvent concentration on degree of grafting was investigated. The extent of grafting was found to increase with increasing monomer concentration, inhibitor concentration and radiation dose. The targeted 35% grafting could be achieved at optimum condition viz. monomer concentration 12.09wt%, radiation dose 12.40 kGy, inhibitor concentration 0.07M and solvent concentration 0.12M. The grafted PP films at different degrees of grafting were tested for tensile properties and characterized by swelling studies, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Successful grafting of acrylic acid onto polypropylene films was indicated by FTIR and confirmed quantitatively by determination of carboxylic groups on the film surface. Tensile strength of grafted PP films decreased with increase in degree of grafting. The crystallinity of the grafted PP films was lower than that of PP film as indicated by DSC studies. Grafting of acrylic acid increased the roughness on the surface of PP films indicated by SEM studies. The maximum biodegradability of the 34.55% grafted film was 5.5%.

Enhancing hydrophilicity performance of polysulfone hollow fiber membrane by surface modification via UV-induced graft polymerization of HEA

In order to enhance hydrophilicity performances, polysulfone (PSF) hollow fiber membrane was modified through graft polymerization with 2-Hydroxyethylacrylate initiated by ultraviolet radiation. The effects of irradiation time and monomer concentration on the grafting degree of the membranes were examined. Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectra, scanning electron microscopy, thermal gravimetric analysis, and different thermo analysis were used to characterize the chemical and morphological changes of the PSF membrane matrix surface. Static contact angle measurements showed that the hydrophilicity of PSF matrix was enhanced after grafting modification. Water flux and bovine serum albumin filtration experiments also show that the hydrophilicity and fouling resistance of the grafted membranes were obviously increased with increasing grafting degree.

ETFE-g-pentafluorostyrene: Functionalization and proton conductivity

In this study we propose a relatively simple and versatile method for the preparation of a polyelectrolyte membrane based on poly(pentafluorostyrene) (PFS) owing proton exchange functionalities for proton conducting applications. The method includes two steps: grafting of the PFS from an irradiated ETFE film, followed by post-functionalization. The advantage of our approach lies in grafting a polymer with highly reactive functional groups suitable for efficient post-sulfonation/phosphonation. The grafting step is optimized both in terms of the system (bulk, non-/solvent and gas-phase grafting) and the conditions (radiation doses, time and temperature) used. The kinetics of the grafting shows a linear increase of grafting degree with both time and temperature suggesting a lower diffusion control and a reduced termination reaction rate for the optimized grafting process. Both phosphonation and sulfonation of the PFS grafted ETFE result in a corresponding high functionalization degree of 50% and 70% with IEC values of 1 and 1.5mequivg−1 and conductivities of 170 and 90mScm−1 at 120°C, 90% RH for the sulfonated and phosphonated ETFE-g-PFS respectively. The high conductivity is attributed to the homogeneous distribution of the PFS within the ETFE matrix (EDX-SEM micrographs) and relatively high acidities of the sulfonic and the phosphonic acids.

Ion exchange bipolar membrane: poly(ether ether ketone) grafting poly(2-(N,N-dimethylaminoethyl) methacrylate) synthesized via ATRP

Poly(ether ether ketone) (PEEK) containing methyl groups was synthesized by the aromatic nucleophilic polycondensation reaction of 4, 4′-difluorobenzophenone, bisphenol-A and 2, 3,5-trimethylhydroquinone. Side-chain-type ion exchange membranes based on PEEK-g- P(DMAEMA) (poly(2-dimethylamino ethyl methacrylate)) were successfully synthesized via atom transfer radical polymerization (ATRP), using bromethylated poly(ether ether ketone) (BMPEEK) as the macroinitiator. These copolymers contain tertiary amino groups on their side chains with high molecular weight. The copolymer membranes exhibit excellent mechanical properties due to their aromatic backbone structure and flexible DMAEMA aliphatic chains. With the increase of grafting degree of DMAEMA, the ion exchange capacity (IEC) and water content of the membranes increase from 2.17 to 2.49 mmol · g−1 and 67.22 to 90.97 %, respectively. The bipolar membranes originated from PEEK-g-P(DMAEMA) display reasonably high OH− permeability and low AC impedance with high IEC.

Physicochemical Properties and Surface Activities of Collagen Hydrolysate-Based Surfactants with Varied Oleoyl Group Grafting Degree

A series of collagen hydrolysate-based surfactants (CHBS) were prepared by grafting different amount of oleoyl group onto collagen hydrolysate (CH). Their physicochemical properties and surface activities were investigated, and their emulsifying ability on rapeseed oil–water emulsion was evaluated. The results showed that, as increasing grafting degree of oleoyl group, the free amino content and isoelectric point of CHBSs and the size of CHBS particles formed in aqueous solution declined, while their molecular weight and surface hydrophobicity increased. The CHBSs with high grafting degree, such as CHBS-30, CHBS-40, and CHBS-50 (postfix datum represents mmol amount of oleic acid chloride to react with 10 g collagen hydrolysate), exhibited satisfactory wetting capacity and foaming capacity, and the CHBSs with low grafting degree, such as CHBS-10 and CHBS-20, presented good emulsifying capacity. The surface activity of CHBSs was closely correlated with the hydrophobicity of their molecules, as well as their capacity to reduce the surface tension of air–water interface. In addition, CHBS-20 showed good emulsifying ability on rapeseed oil–water emulsion in neutral and alkaline pH, even in the condition of low salt concentration.

Enhanced antitumor efficacy of folate modified amphiphilic nanoparticles through co-delivery of chemotherapeutic drugs and genes

Folate (FA) modified amphiphilic linoleic acid (LA) and poly (β-malic acid) (PMLA) double grafted chitosan (LMC) nanoparticles (NPs) with optimum grafting degrees of hydrophobic LA and hydrophilic PMLA were developed for the co-delivery of paclitaxel (PTX) and survivin shRNA-expressing plasmid (iSur-pDNA). The resultant NPs exhibited particle size of 161 nm and zeta potential of 43 mV. FA modification and the increasing grafting degrees of LA and PMLA were correlated with the suppressed protein adsorption, the inhibited release of PTX, and the accelerated dissociation of pDNA. PTX loading, cellular uptake, nuclear accumulation of pDNA, in vitro gene silencing efficiency, and cell growth inhibition were promoted by FA modification and higher grafting degree of LA, but impeded by increasing grafting degree of PMLA. In tumor-bearing mice, co-delivery of PTX and iSur-pDNA exhibited enhanced antitumor efficacy and prolonged survival period as compared with single delivery of PTX or iSur-pDNA. These results indicated that amphiphilic LMC NPs could serve as a promising platform for the co-delivery of antitumor drugs and genes, and highlighted the importance of adjusting the hydrophobic and hydrophilic grafting degrees.

Graft copolymerization of glycidyl methacrylate onto delignified kenaf fibers through pre-irradiation technique

Glycidyl methacrylate grafted kenaf (GMA-g-Kenaf) was prepared by pre-irradiation grafting technique. Kenaf fibers were treated with different concentration of sodium chlorite solution before used as trunk polymer. Treated kenaf fibers were irradiated by electron beam followed by grafting reaction in GMA/water emulsion system. The degree of grafting was determined as a function of absorbed dose, reaction time, reaction temperature and concentration of monomer. The results showed that the lignin content was decreased from 14.3% to as low as 3.3% with the increased of sodium chlorite concentration. This was evidenced by SEM pictures which show the surface of treated kenaf fibers was cleaner and smoother compared to that of untreated one. The degree of grafting increased with the increase of absorbed dose, reaction temperature, reaction time and monomer concentration as well as with decreasing lignin content. Formation of graft copolymer was confirmed with SEM, FTIR analysis. The structural investigation by XRD showed that degree of crystallinity of graft copolymers decreased with the increase in degree of grafting.

Bioinert membranes prepared from amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) graft copolymers

Poly(vinyl chloride) (PVC) membrane was hydrophilically modified by grafting with poly(oxyethylene methacrylate) (POEM) using atom transfer radical polymerization (ATRP). The successful grafting of PVC main chain by POEM was characterized by Fourier transform infrared spectroscopy (FT-IR). The molecular weight and hydrophilicity of membranes increased with the amount of POEM grafting, as characterized by gel permeation chromatography (GPC) and contact angle measurement, respectively. Transmission electron microscope (TEM) and small angle X-ray scattering (SAXS) analysis revealed the microphase-separated structure of PVC-g-POEM and the domain spacing increased from 59.3 to 86.1nm with increasing grafting degree. Scanning electron microscopy (SEM) was used for the direct visualization of the mouse embryonic fibroblast (MEF) cell and bacteria adhesion on the membrane surface. Protein adsorption and eukaryotic and prokaryotic cell adhesion tests showed that the bioinert properties of membranes were significantly increased with POEM content.

Insight into the role of N,N-dimethylaminoethyl methacrylate (DMAEMA) conjugation onto poly(ethylenimine): cell viability and gene transfection studies

In the present study, the effect of N,N-dimethylaminoethyl methacrylate (DMAEMA) conjugation onto branched poly(ethylenimine) (PEI) with different grafting degree was examined for gene delivery applications. The DMAEMA-grafted-PEI conjugates were characterized and complexed with plasmid DNA (pDNA) at various concentrations, and the physicochemical properties, cell viability, and in vitro transfection efficiency of the complexes were evaluated in HEK 293T cells. Computational techniques were used to analyze the interaction energies and possible binding modes between DNA and conjugates at different grafting degrees. The cytotoxicity analysis and in vitro transfection efficiency of the conjugate/pDNA complexes exhibited a beneficial effect of DMAEMA conjugation when compared to PEI alone. The computational results revealed that the DNA/vector interaction energy decreases with increasing grafting degree, which can be associated to an enhanced release of the pDNA from the carrier once inside cells. The results indicate the significance of DMAEMA conjugation onto PEI as a promising approach for gene delivery applications.

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.

Facile Synthesis of Size-Controlled Silver Nanoparticles Using Plant Tannin Grafted Collagen Fiber As Reductant and Stabilizer for Microwave Absorption Application in the Whole Ku Band

Size-controlled silver nanoparticles (AgNPs) were facilely synthesized on collagen fiber (CF), in which bayberry tannin (BT), a natural plant polyphenol, was grafted on CF to act as a reductant and stabilizer without any additional reagent (surfactant, template, and capping agent) or treatment (heat and photoirradiation) needed. The as-synthetic AgNPs-BT@CF was well characterized via combined techniques including SEM, HTEM, XRD, XPS, and FT-IR. The particle diameter and size distribution of AgNPs in BT@CF matrix are feasible to adjust by varying the grafting degree of BT on the CF surface. When the grafting degree of BT was 0.4, the particle size of AgNPs is as small as 5.2 ± 1.9 nm. Furthermore, the complex permittivity, and complex permeability of the AgNPs-BT@CF were also investigated in detail. It was found that with the increase of grafting degree of BT on CF the imaginary part (ε″) of complex permittivity was dramatically increased, whereas the real part (μ′) and imaginary part (μ″) of complex permittivity were not obviously changed. The reflection loss (RL) of AgNPs-BT@CF exceeding −10 dB was achieved in the whole Ku band (12.5–18 GHz).