Grafting Efficiency Research Articles

Ammonium Persulphate Initiated Graft Copolymerization of Aniline onto Chitosan-A Comparative Kinetic Study

Ammonium persulphate (APS) has been used as efficient initiator for graft copolymerization of the aniline (ANI) onto chitosan at 25±0.1°C. Graft copolymerization of ANI onto chitosan has taken place through the cation radical initiation process. The grafting parameters have been evaluated by varying concentration of ANI, APS and chitosan. The effects of concentration of APS, ANI, chitosan and reaction time on graft copolymerization were studied by determining the grafting percentage (%G), grafting efficiency (%E) and percentage add-on. It was observed that bout rate of homopolymerization (Rh) and rate of graft coplymerization (Rg) increased with the increase in concentration of each component. On the basis of the experimental observations, initiating steps have been proposed and a suitable rate expression for graft copolymerization has been derived. Electrical conductivity of grafted polyaniline (PANI) onto chitosan (Chit-g-PANI, chitaline) was measured by the four probe method.

Constructing a Library of Doubly Grafted Polymers by a One-Shot Cu-Catalyzed Multicomponent Grafting Strategy

Doubly grafted polymers bearing two different macromolecular side groups in each repeat unit of the polymer backbone have received considerable attention because of their unique molecular structures and properties. However, the preparation of these polymers is challenging because of the synthetic difficulty arising from their steric crowding and structural complexity. Here, based on the diversity-oriented polymerization concept, we report the synthesis of well-defined doubly grafted polymers at 30 °C using a one-shot Cu-catalyzed multicomponent grafting strategy using readily accessible precursor polymers possessing sulfonyl azides and alkyne and amine macromonomers. Based on this strategy, we prepared 35 doubly grafted polymers. Detailed 1H NMR and SEC analyses revealed high grafting efficiency (79–99%) and narrow-to-moderate dispersities of the well-defined doubly grafted polymers.

Generation of Non-Small Cell Lung Cancer Patient-Derived Xenografts to Study Intratumor Heterogeneity.

Simple SummaryIt is widely thought that tumors are composed of different subpopulations of cancer cells carrying genetic alterations with some of them being common among all cells while others are unique for each subpopulation. This variable genetic profile of tumor cells is a component of what is collectively described as intratumor heterogeneity (ITH). Surviving the immune system and therapies, and establishing metastases are forces of natural selection that act upon ITH and drive tumor evolution and, eventually, the clinical presentation of patients. The aim of this prospective study was to investigate ITH in early-stage operable non-small cell lung cancer. We directly grafted human tumors in immunosuppressed mice and compared the genetic profile of the tumors grown in mice with that of the original human tumors. We identified clinical factors that affected the ability of human tumors to grow as mouse xenografts.Recent advances in sequencing technologies have allowed the in-depth molecular study of tumors, even at the single cell level. Sequencing efforts have uncovered a previously unappreciated heterogeneity among tumor cells, which has been postulated to be the driving force of tumor evolution and to facilitate recurrence, metastasis, and drug resistance. In the current study, focused on early-stage operable non-small cell lung cancer, we used tumor growth in patient-derived xenograft (PDX) models in mice as a fast-forward tumor evolution process to investigate the molecular characteristics of tumor cells that grow in mice, as well as the parameters that affect the grafting efficiency. We found that squamous cell carcinomas grafted significantly more efficiently compared with adenocarcinomas. Advanced stage, patient age and primary tumor size were positively correlated with grafting. Additionally, we isolated and characterized circulating tumor cells (CTC) from patients’ peripheral blood and found that the presence of CTCs expressing epithelial-to-mesenchymal (EMT) markers correlated with the grafting potential. Interestingly, exome sequencing of the PDX tumor identified genetic alterations in DNA repair and genome integrity genes that were under-represented in the human primary counterpart. In conclusion, through the generation of a PDX biobank of NSCLC, we identified the clinical and molecular properties of tumors that affected growth in mice.

ATRP-ARGET of a Styrene Monomer onto Modified Natural Rubber Latex as an Initiator.

Atom transfer radical polymerization with an activator regenerated by electron transfer (ATRP-ARGET) was performed for graft copolymerization of styrene onto natural rubber in the latex stage as a heterogeneous system. Deproteinized and subsequently brominated natural rubber particles in the latex stage were subjected to graft copolymerization of styrene on their surfaces in the presence of an activated ATRP catalyst. 1H NMR spectroscopy and size exclusion chromatography (SEC) characterized the particles. Ozonolysis was performed to deduct the polyisoprene contribution to SEC. Graft copolymerization in heterogeneous media by extraction with an acetone/2-butanone solution. Both the linear evolution of the molecular weight versus monomer conversion and the high grafting efficiency associated with a narrow molecular weight distribution of the resulting grafted polystyrene confirm a living radical behavior.

Synthesis and long‐term stability of acrylic acid and N, N‐methylene‐bis‐acrylamide radiation grafted polypropylene fibers

AbstractNew carboxyl ion‐exchange fibers prepared by acrylic acid (AA) and N, N‐methylene‐bis‐acrylamide (MBAA) monomer grafting to polypropylene (PP) fibers based on the method of γ‐rays pre‐irradiation in air followed by a Mohr's salt redox initiation of grafting reaction were studied. Grafting degree, homopolymer quantity, monomer conversion and grafting efficiency were determined. FTIR spectroscopy was used to establish the nature of the grafted fibers. The thermal stability of the materials was investigated based on DSC analysis in N2/O2 mixture. The long‐term stability during 6–8 years of storage was examined by the measurement of the tensile strength and the elongation at break of the fibers, and the chemical oxygen demand in water extracts as well as in the oxygen uptake experiments. The influence of some factors on the useful life of the grafted fibers was studied: a MBAA cross‐linking, exposure to day light, the Fe (III) residue presence, a grafting reaction temperature. It was found that small amounts of the adsorbed Fe (III) ions increase the deterioration rate of the grafted fibers, while small amounts of MBAA delay this negative process.

Synthesis of an Addition-Crosslinkable, Silicon-Modified Polyolefin via Reactive Extrusion Monitored by In-Line Raman Spectroscopy

We present the modification of ethylene-propylene rubber (EPM) with vinyltetra-methydisiloxane (VTMDS) via reactive extrusion to create a new silicone-based material with the potential for high-performance applications in the automotive, industrial and biomedical sectors. The radical-initiated modification is achieved with a peroxide catalyst starting the grafting reaction. The preparation process of the VTMDS-grafted EPM was systematically investigated using process analytical technology (in-line Raman spectroscopy) and the statistical design of experiments (DoE). By applying an orthogonal factorial array based on a face-centered central composite experimental design, the identification, quantification and mathematical modeling of the effects of the process factors on the grafting result were undertaken. Based on response surface models, process windows were defined that yield high grafting degrees and good grafting efficiency in terms of grafting agent utilization. To control the grafting process in terms of grafting degree and grafting efficiency, the chemical changes taking place during the modification procedure in the extruder were observed in real-time using a spectroscopic in-line Raman probe which was directly inserted into the extruder. Successful grafting of the EPM was validated in the final product by 1H-NMR and FTIR spectroscopy.

Research on the smart behavior of MCNT grafted CF/cement-based composites

To solve the disadvantages of weak bonding between the carbon fiber (CF) and the cement matrix, as well as the poor dispersion performance of multi-walled carbon nanotubes (MCNT) in cement paste, hydrothermal synthesis and chemical grafting methods were combined to graft MCNT on the surface of CF. Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were coupled used to evaluate the grafting efficiency. Four-electrode method and electrochemical impedance spectroscopy (EIS) were applied to assess the electrical property of MCNT grafted CF/cement-based composites. The smart behavior of MCNT grafted CF/cement-based composites were characterized under monotonic and cyclic loading. Results showed that the hydrothermal synthesis method can effectively graft MCNT on the surface of CF, and the grafting ratio as indicated by nitrogen element was 6.78%. The conductivity of MCNT grafted CF/cement-based composites was far superior to that of untreated CF/cement-based composites. Also, the composite with the addition of MCNT grafted CF was more sensitive to the cyclic stress. Therefore, the stress sensitive property of MCNT grafted CF/cement-based composites was significantly improved, compared to its untreated counterpart.

MASTIC-G-POLY (ACRYLAMIDE): MICROWAVE-ASSISTED SYNTHESIS AND CHARACTERISATION

Objective: The objective of the present investigation was the synthesis of grafted co-polymer gum mastic using acrylamide as the monomer.
 Methods: 3-factor 3-level response surface Box-Behnken design, which requires 15 runs including three replicates of the central run, was used for the synthesis of graft copolymers of mastic gum with acrylamide using ceric ammonium nitrate as the free radical initiator. The critical synthesis and process parameters; CSPP (A = concentration of monomer, B = concentration of initiator and C= Temperature) to generate design space and optimize formulation with an aim to obtain critical quality attributes (CQA, Y1 =% Yield, Y2 =% Grafting, Y3 =% grafting efficiency).
 Result: Formulation F14 having a maximum % yield of 75.89% with % grafting of 210% and % grafting efficiency 51.57% was selected as best.
 Conclusion: The microwave-assisted grafted mastic gum was prepared successfully and optimized by using Box Behnken design.

Preparation and solution properties of helical sulfonium-based polypeptides and their polyelectrolyte complexes

Polyelectrolyte complexes (PECs) are attractive soft materials with many promising applications, such as drug delivery and coatings. Study on the solution properties of α-helical polypeptide based PECs are still rare. Herein, new PECs composed of α-helical sulfonium-based polypeptides (PPBLG-DMS-I) and polysaccharides (i.e., carboxymethyldextran sodium salt, CMD) were prepared and investigated on their solution property. PPBLG-DMS-I were synthesized by an ultrafast ring-opening polymerization (ROP) and subsequent alkylation of methylthio groups with high grafting efficiency. The aggregation size of the polypeptide-polysaccharide based PECs was in the range of 450–600 nm at room temperature depending on the cationic/anionic weight ratios (RCAs) and polypeptide concentrations. It decreased by about 300 nm with increasing of the temperature by 40 °C. PEC solutions showed salt induced sharp phase transitions accompanied by the formation of coacervate droplets at low salt concentrations (e.g., 1.5 mg·mL−1). pH induced phase transitions of PEC solutions at both acidic (e.g., pH = 2.5) and basic conditions (e.g., pH = 11.5).

Free-Radical Photopolymerization of Acrylonitrile Grafted onto Epoxidized Natural Rubber.

The exploitation of epoxidized natural rubber (ENR) in electrochemical applications is approaching its limits because of its poor thermo-mechanical properties. These properties could be improved by chemical and/or physical modification, including grafting and/or crosslinking techniques. In this work, acrylonitrile (ACN) has been successfully grafted onto ENR- 25 by a radical photopolymerization technique. The effect of (ACN to ENR) mole ratios on chemical structure and interaction, thermo-mechanical behaviour and that related to the viscoelastic properties of the polymer was investigated. The existence of the –C≡N functional group at the end-product of ACN-g-ENR is confirmed by infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses. An enhanced grafting efficiency (~57%) was obtained after ACN was grafted onto the isoprene unit of ENR- 25 and showing a significant improvement in thermal stability and dielectric properties. The viscoelastic behaviour of the sample analysis showed an increase of storage modulus up to 150 × 103 MPa and the temperature of glass transition (Tg) was between −40 and 10 °C. The loss modulus, relaxation process, and tan delta were also described. Overall, the ACN-g-ENR shows a distinctive improvement in characteristics compared to ENR and can be widely used in many applications where natural rubber is used but improved thermal and mechanical properties are required. Likewise, it may also be used in electronic applications, for example, as a polymer electrolyte in batteries or supercapacitor.

Enhancement of Thermo-mechanical Properties of Okra Fiber by Photografting Technique

In this study, okra fibers were chemically modified with three different monomers such as ethylene glycol dimethacrylate (EGDMA), 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) solutions in the presence of methanol (MeOH) and photoinitiator (Irgacure-500) under ultraviolet (UV) radiation with a view to improve thermo-mechanical characteristics. Based on grafting efficiency and mechanical attributes the intensity of UV radiation and monomer concentration were maximized. A series of solutions by varying the concentrations (10–70%) of monomers in MeOH along with 2% photoinitiator were prepared. Experimental results revealed that fibers grafted with 30% EGDMA at 30th pass, 30% HEMA at 20th pass and 40% MMA at 30th pass of UV radiation achieved optimum mechanical properties over untreated fiber. The optimized solutions were further enhanced by adding various concentrations (1–2%) of urea, and the best properties were obtained with 1.5% urea-treated fiber. The chemical bonds formed due to photografting were inspected by Fourier transform infrared spectroscopy (FTIR). Degradation behavior under heat was performed through thermogravimetric analysis (TGA/DTG) and found that photografted fiber showed well-improved thermal stability than the untreated sample. Water uptake test exhibited that grafting reduced water retention capacity of treated fiber significantly. Furthermore, simulating weathering test also executed.

Functionalization of Chitosan Oligomers: From Aliphatic Epoxide to Cardanol-Grafted Oligomers for Oil-in-Water Emulsions.

Hydrophobically modified chitooligosaccharides (COSs) were tested for suitability as an emulsifier in cationic bituminous emulsions. COSs with polymerization degrees (DPs) of 5, 10, 15, and 20 were obtained by nitrous acid deamination. A complete study on depolymerization and precise product and side product characterization was undergone. Chemical modification of COSs was performed to achieve amphiphilic structures using three fatty epoxides with a growing chain length butyl (C4), octadecyl (C9), and hexadecyl glycidyl ether (C16)). The grafting efficiency according to reaction conditions was established. Different substitution degrees (DSs) were obtained by modulating the ratio of fatty epoxy to NH2. It was shown that after a certain DS, the oligomers thus formed were not water-soluble anymore. At the end, cardanol glycidyl ether was grafted on DP 5, 10, and 15 COSs, cardanol being a biobased compound extracted from cashew nut shell; this reaction led to a potentially fully biobased structure. Water-soluble candidates with a higher DS were used as surfactants to emulsify motor oil as a simulation of bitumen. Cardanol-chitosan-based surfactants led to direct oil-in-water emulsion (60/40 w/w) composed of particles of 15 μm average size that were stable at least for 24 h.

Efficient approach to produce functional polypropylene via solvent assisted solid-phase free radical grafting of multi-monomers

Herein an efficient approach to produce functional polypropylene via solvent assisted solid-phase grafting process is reported, in which acrylic acid, methyl methacrylate and maleic anhydride are used as multi-monomers, 2,2′-azobis(2-methylpropionitrile) as initiator and ether as swelling solvent and carrier. The effects of various factors such as the swelling solvent species and dosage, swelling time and temperature, monomer and initiator concentrations, reaction time and temperature, nitrogen flow rate and the stirring speed on the grafting percentage and grafting efficiency were investigated. To verify the polar species was grafted onto polypropylene, the resulted polymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction analysis, water contact angle measurement, tensile strength and melt flow rate measurement. All the results showed that using the ether assisted solid-phase free radical grafting process is an efficient and versatile approach to produce functional polypropylene.

Ghatti gum-base graft copolymer: a plausible platform for pH-controlled delivery of antidiabetic drugs.

In the present study, we aimed to develop a novel pH-sensitive polymeric delivery system (GG-g-PMMA) for antidiabetic therapy via grafting ghatti gum (GG) with methyl methacrylate (MMA) chains. The free radical polymerization technique was adopted to graft ghatti gum with methyl methacrylate, using ceric ammonium nitrate (CAN) as a redox initiator. The impact on grafting parameters such as grafting percentage (G%) and grafting efficiency (GE), of monomer and initiator concentrations was evaluated. The batch with higher grafting efficiency and percentage grafting was selected and characterized by elemental analysis (C, H and N), DSC, FT-IR spectroscopy, XRD, 1H-NMR and SEM morphology study. In addition, the efficacy of GG-g-PMMA-based pellets loaded with the hypoglycemic agent, metformin hydrochloride, to sustain drug release was investigated. In vitro release studies demonstrated a pH-dependent sustained release of the drug from GG-g-PMMA pellets. In addition, acute oral toxicity studies and histopathological analysis suggested the safety and biocompatibility of the grafted gum. Most importantly, in vivo efficacy studies underscored the efficient hypoglycemic potential of the prepared formulation, which was comparable to that of a sustained release marketed formulation. These results suggest that the developed pH-sensitive polymeric delivery system (GG-g-PMMA) might represent a promising delivery vehicle for facilitated antidiabetic therapy.

A modus operandi toward interfacial enhancement of ethylene propylene diene monomer rubber/ polybenzoxazine blends using EPDM‐grafted‐vinyltrimethoxysilane copolymer

AbstractCompatibilization of polymer blends is performed to obtain synergistic effects in physical and mechanical properties. The present work demonstrates the ability of vinyltrimethoxysilane‐grafted‐ethylene propylene diene monomer rubber (VTMS‐g‐EPDM) to improve the compatibility between EPDM and polybenzoxazine (PB). EPDM reacted with 5 phr of VTMS showed the highest grafting efficiency as well as a relatively low gel content, and was added to EPDM/PB blends. The addition of 8 phr of compatibilizer to 70/30 (w/w) EPDM/PB reduced the dispersed PB droplet size from 3.1 μm to 800 nm. Effects of various blend compositions at constant dosage of compatibilizer (8 phr) on the swelling behavior and tensile properties of the samples were also studied. The tensile strength increased from 12 to 14.5 MPa upon adding the compatibilizer at 50/50 blend ratio of EPDM/PB; however, the increase in the PB content had no significant impact on the tensile strength in both compatibilized and non‐compatibilized samples.

A New Device for Autologous Small Volume Fat Grafting

Many techniques and devices have been developed to improve small volume fat grafting efficiency and consistency for use in the operating room and outpatient procedure room. These methods require cumbersome or messy processing to remove excess oil and fluid from adipose graft. The aim of this study was to compare the fat processing efficiency of a novel handheld device, the Push-to-Spin (P2S) system, with that of other common processing techniques and validate tissue quality after lipoaspirate processing. Human lipoaspirate samples were processed by 1 of 3 methods: cotton gauze (Telfa) rolling, centrifugation (Coleman technique), or the P2S system. Efficiency of fat processing was evaluated in terms of total processing time, fat harvest ratio, and fat processed ratio. Histologic examination and immunohistochemical staining were used to compare tissue morphology and adipocyte viability, respectively. Experimental samples were compared with unprocessed lipoaspirate controls. Lipoaspirate processing was significantly faster with the P2S device than with other techniques. All 3 methods achieved similar fat harvest and fat processing ratios. Additionally, the P2S, Telfa, and Coleman techniques yielded grafts with similar cellularity and with similar perilipin and glycerol-3-phosphate dehydrogenase 1 expression. Measured differences between experimental and control samples were statistically significant. The P2S device is an easy-to-use, efficient, and potentially cost-effective handheld device that can be used for lipoaspirate harvest, processing, and grafting in any procedural setting. The resulting adipocytes have similar morphology, viability, and function to those yielded by other techniques. This handheld technology decreases procedure time, thereby improving surgeon efficiency and patient experience.

On the importance of the linking chemistry for the PEGylation of mesoporous silica nanoparticles

The typical method for minimizing serum protein adsorption in biological settings and prolonging blood circulation time of nanoparticles, is to anchor hydrophilic polymers (e.g., poly(ethylene glycol), PEG) on the particle surface, which is most often done by covalent attachment (PEGylation). Herein, different PEGylation methods were realised and compared to functionalize mesoporous silica nanoparticles (MSNs). First, reactive groups were installed using post-grafting procedures with different functional silanes. Further, PEGs carrying a functional group and having different chain lengths and termini, were used. The grafting efficacy as well as the structural and physicochemical characteristics of the resulting particles were determined. Finally, the serum protein adsorption behaviour of these functionalized particles was investigated using thermogravimetric analysis. The type of selected coupling method was shown to strongly influence the grafting efficiency as well as the resulting protein adsorption. The results highlight the importance of the right choice of the linking chemistry when aiming at surface functionalization of nanoparticles.

Optimizing the Process Efficiency of Reactive Extrusion in the Synthesis of Vinyltrimethoxysilane-Grafted Ethylene-Octene-Copolymer (EOC-g-VTMS) by Response Surface Methodology.

Thermoplastic polymers like ethylene-octene copolymer (EOC) may be grafted with silanes via reactive extrusion to enable subsequent crosslinking for advanced biomaterials manufacture. However, this reactive extrusion process is difficult to control and it is still challenging to reproducibly arrive at well-defined products. Moreover, high grafting degrees require a considerable excess of grafting reagent. A large proportion of the silane passes through the process without reacting and needs to be removed at great expense by subsequent purification. This results in unnecessarily high consumption of chemicals and a rather resource-inefficient process. It is thus desired to be able to define desired grafting degrees with optimum grafting efficiency by means of suitable process control. In this study, the continuous grafting of vinyltrimethoxysilane (VTMS) on ethylene-octene copolymer (EOC) via reactive extrusion was investigated. Successful grafting was verified and quantified by 1H-NMR spectroscopy. The effects of five process parameters and their synergistic interactions on grafting degree and grafting efficiency were determined using a face-centered experimental design (FCD). Response surface methodology (RSM) was applied to derive a causal process model and define process windows yielding arbitrary grafting degrees between <2 and >5% at a minimum waste of grafting agent. It was found that the reactive extrusion process was strongly influenced by several second-order interaction effects making this process difficult to control. Grafting efficiencies between 75 and 80% can be realized as long as grafting degrees <2% are admitted.

Improving cell survival and engraftment in vivo via layer-by-layer nanocoating of hESC-derived RPE cells

BackgroundHuman embryonic stem cell-derived retinal pigment epithelial (hESC-RPE) cell transplants have served as a cell therapy for treating retinal degenerative diseases. However, how to optimize the survival and engraftment of hESC-RPE cells is a great challenge.MethodsHere, we report hESC-RPE cells that are embedded with polyelectrolytes gelatin and alginate by layer-by-layer (LbL) self-assembly technique, based on the opposite charge of alternate layers. Cells were assessed for cell survival, immunogenicity, and function in vitro and in vivo.ResultsThis strategy obviously decreased the immunogenicity of hESC-RPE cells without affecting its activity. LbL-RPE cell transplants into the subretinal space of Royal College of Surgeons (RCS) rats optimized cell engraftment and decreased immunogenicity compared to untreated RPE cell transplants (immunosuppression was not used during the 21-week study). Visual-functional assay with electroretinogram recordings (ERGs) also showed higher B wave amplitudes in RCS rats with LbL-RPE cell transplants.ConclusionsWe demonstrate that transplanted LbL-RPE cells have better viability and grafting efficiency, optimized immunogenicity, and visual function. Therefore, LbL engineering is a promising method to increase the efficacy of hESC-RPE cell transplantation.

Thin wall injection‐overmoulding of polyamide 6/polypropylene multilayer parts: PA6/PP‐g‐ma interfacial adhesion investigations

AbstractThis work investigates the interfacial adhesion of PA6/PP‐g‐MA in a thin‐walled multilayer part obtained by injection overmoulding. This process is a good solution to the need of weight reduction for the sustainable and economic growth of food packaging. A rigid plastic food package is a complex multilayer structure obtained from the association of polymers with different properties to achieve good barrier, environment, or thermo‐mechanical performance. The present study aims to obtain a complete understanding of the interfacial adhesion of PA6/PP‐g‐MA interface in a three‐layer PA6/sealant/PP assembly through microscopy analysis, mechanical characterization, and inter‐diffusion models. Optical microscopy, XPS, and AFM analyses showed the presence of a copolymer interphase. This layer is greatly dependent on the holding pressure applied, which revealed to be the key parameter to obtain the best results in terms of failure strength. A better interface wettability improves the inter‐diffusion distance and thus chemical grafting efficiency. Other interface improvements were achieved by the addition of EVA in the PP‐g‐MA layer. The lowest viscosity of the EVA dispersed phase has led to a fully cohesive failure due to an interface diffusion efficiency. The presence of EVA increased more than 80% of the peeling performance of the assemblies.