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.

Strategies for High Grafting Efficiency of Functional Ligands to Lipid Nanoemulsions for RGD-Mediated Targeting of Tumor Cells In Vitro.

Lipid nanoemulsions (LNEs) are promising nanocarriers for delivering high payloads of lipophilic molecules. Nonetheless, the dynamic nature at their aqueous interfaces results in poor surface chemistry and thus ligand functionalization can be challenging. Herein, two independent strategies, postconjugation and preconjugation, were explored to prepare LNEs grafted covalently with model ligands, fluorescein dye and RGD peptide, respectively. Fluorescein was successfully conjugated with high grafting efficiency to an amine-functionalized lipid nanoemulsion (NH2-LNE) as determined by spectrophotometric analysis. First, we formulated NH2-LNEs by a low-energy spontaneous emulsification technique in the presence of oleylamine (OA) within the oily core of the nanodroplets, thus creating primary amine-reactive sites at the oil/water interface. These amines were used to incorporate fluorescein, yielding fluorescent LNEs with grafting efficiencies of 33, 69, and 69% at NH2-LNEs with [OA]oil = 0.18, 0.34, and 0.49 M, respectively. We also developed RGD-labeled LNEs (RGD-LNEs) and evaluated the nanomaterial with model cell lines that overexpress αVß3 integrins on their surfaces. To this end, we initially synthesized an RGD-Oleate fatty acid-peptide conjugate by solid-phase synthesis. The lipophilic segment of this conjugate readily embedded into the oily core of the LNE, and the hydrophilic head (RGD moiety) was oriented toward the LNE interface. In vitro cytotoxicity and cellular uptake studies were undertaken on different cancer cell lines including HaCaT human umbilical vein endothelial cells (HUVECs), MCF-7, and U-87 MG and compared to uptake experiments with RAW 264.7 macrophages. Confocal imaging and flow cytometry showed that RGD-LNEs were preferentially taken up by all of the tumor cell lines but showed very slight accumulation in RAW macrophages. Unmodified LNE controls did not show any appreciable cellular uptake. This work provides a simple and reliable methodology for the incorporation of multiple ligands on a single surface to facilitate active tumor targeting with LNE-based drug/imaging carriers for theranostic applications.

Study of suspension grafting process of polypropylene.

Grafting efficiency is an important indicator of polypropylene grafting reaction. A series of studies have been accomplished, including the conditions of free radical presence on PP backbone during peroxide initiation, the effect of preheat treatment and reaction time on PP suspension grafting results, and the effect of peroxide residue on properties of modified PP. An optimized grafting process was proposed by mixing and preheating polypropylene (PP) and the initiator benzoyl peroxide (BPO) before adding the grafting monomer glycidyl methacrylate (GMA),resulting in an increase in grafting efficiency from 50.0% to 78.2%. With initiator residue removed by alternating temperature treatment, the suspension grafting reaction time could be substantially reduced.

Leaf-disc grafting for the transmission of Candidatus Liberibacter asiaticus in citrus (Citrus sinensis; Rutaceae) seedlings.

PREMISE OF THE STUDY: The search for resistance/tolerance to the devastating citrus huanglongbing disease (syn. HLB or citrus greening) is generating an increasing number of new plants of diverse genetic makeup. As the increasing number of new plants require more space, resources, and time, the need for faster and more efficient HLB screening tests becomes crucial. METHODS AND RESULTS: The leaf-disc grafting system described here consists in replacing a disc of leaf tissue with a similar disc from an infected plant. This can be performed in young seedlings not yet big enough to endure other types of grafting. Graft success and infection rates average approximately 80%. CONCLUSIONS: We describe the successful adaptation of leaf-disc grafting as a powerful screening tool for HLB. The system requires minimal plant material and can be performed in seedlings at a very young age with increased efficiency in terms of time, space, and resources.

Surface modification of Fe2TiO5 nanoparticles by silane coupling agent: Synthesis and application in proton exchange composite membranes.

Modifying surfaces of nanoparticles with silane coupling agent provides a simple method to alter their surface properties and improve their dispersibility in organic solvents and polymer matrix. Fe2TiO5 nanoparticles (IT) were modified with 3-aminopropyltriethoxysilane (APTES) as novel reinforcing filler for proton exchange membranes. The main operating parameters such as reaction time (R.T), APTES/IT and triethylamine (TEA)/IT ratios have been optimized for maximum grafting efficiency. The optimum conditions for R.T, APTES/IT and TEA/IT ratios were 6h, 4 and 0.3 respectively. It was observed that the APTES/IT and TEA/IT ratios were the most significant parameters affecting the grafting percentage. Modified nanoparticles were characterized using FT-IR, TGA, SEM, TEM and XRD techniques. Effects of modified nanoparticles in proton exchange membrane fuel cells (PEMFC) were evaluated. The resulting nanocomposite membranes exhibited higher proton conductivity in comparison with pristine SPPEK and SPPEK/IT membranes. This increase is attributed to connectivity of the water channels which creates more direct pathways for proton transport. Composite membrane with 3% AIT (6.46% grafting amount) showed 0.024 S cm(-1) proton conductivity at 25 °C and 149 mW cm(-2) power density (at 0.5V) at 80 °C which were about 243% and 51%, respectively higher than that of pure SPPEK.

The graft polymers from different species of lignin and acrylic acid: synthesis and mechanism study.

The influence of lignin species on the grafting mechanism of lignosulfonate (from eucalyptus and pine, recorded as HLS and SLS, respectively) with acrylic acid (AA) was investigated. The graft polymers were confirmed by the absorption of carbonyl groups in the FTIR spectra. The decreasing phenolic group's content (Ph-OH) is not only due to its participation as grafting site but also to the negative effect of initiator. In the initial period (0-60 min), HLS and SLS both accelerate the polymerization of AA. Additionally, Ph-OH group's content is proportional to product yield (Y%), monomer conversion (C%) and grafting efficiency (GE%), strongly indicating that it acts as active center. Nevertheless, compared with HLS, Y% and C% in SLS grafting system are lower though it has higher Ph-OH group's content, which is due to the quinonoid structure formed by the self-conjugated of phenoxy radical in Guaiacyl unit. Finally, the lignosulfonate grafting mechanism was proposed.

Synthesis and characterisation of starch grafted superabsorbent via 10 MeV electron-beam irradiation.

A starch-graft-polyacrylamide (St-g-PAM) superabsorbent crosslinked by N,N'-methyl bisacrylamide (MBA) was prepared using 10 MeV simultaneous electron beam irradiation at room temperature and subsequent alkaline hydrolysis. The effects of the irradiation dose, acryliamide-to-anhydroglucose unit (AM-to-AGU) ratio and crosslinker amount on the properties of the obtained polymers were evaluated. The structure of the graft copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Optimisation treatments were carried out and found for a total dose of 8 kGy, an AM-to-AGU ratio of 4.5 mol mol(-1) and a crosslinker-to-AM ratio of 0.4%mol mol(-1). The obtained superabsorbent polymer showed the maximum absorptions of 1,452 gg(-1) and 83 gg(-1) for distilled water and saline solution, respectively (relative to its own dry weight). The results suggest 10 MeV electron beam irradiation is more efficient than γ-ray irradiation due to its higher energy and dose rate.