Degree Of Surface Modification Research Articles

Efficient Approach for Direct Robust Surface Grafting of Polyethyleneimine onto a Polyester Surface during Moulding.

This paper uses a very effective way for surface modification of thermoplastic polymers during moulding. It is based on a grafting reaction between a thin layer of a functional polymer, deposited on a substrate in advance, and a polymer melt. In this paper, a glycol-modified polyethylene terephthalate (PETG) that was brought in contact with a polyethyleneimine layer during fused filament fabrication is investigated. The focus of this paper is the investigation of the reaction product. Grafting was realised by the formation of stable amide bonds by amidation of ester groups in the main chain of a PETG. XPS investigations revealed that the conversion of amino groups was very high, the distribution was even, and the quantity of amino groups per polyester surface area was still very high. The surface properties of the produced polyester part were mainly characterised by polyethyleneimine. The grafting was able to resist several cycles of extraction in alkaline solutions. The stability was only limited by saponification of the polyester. The degree of surface modification was dependent on the molar mass of polyethyleneimine. This could be rationalised, because grafting only occurred with the one polyethyleneimine molecule that is in close vicinity to the polyester surface when both components come in contact. Fused deposition modelling was chosen as the model process with control over each processing step. However, any other moulding process may be applied, particularly injection moulding for mass production.

Reduction of mesoporous poly(ether ether ketone) materials, preserving pore size

AbstractPoly(ether ether ketone) (PEEK) is an important high‐performance engineering polymer that is used extensively in numerous engineering applications that require chemical, solvent and thermal resistance. These attributes make PEEK attractive for the preparation of porous materials and membranes. Chemical modifications of preformed porous PEEK materials can expand the utilization of PEEK in a range of applications. It is desirable to carry out chemical functionalization without affecting the preformed porous structure or the degree of polymer crystallinity responsible for the sought‐after properties. We report here on the heterogeneous functionalization of preformed mesoporous PEEK materials with hydroxyl groups using sodium borohydride as a reducing agent in a poly(ethylene glycol)/tetrahydrofuran solvent mixture. The pore structure of functionalized materials was characterized, and the degree of modification with functional groups was measured as a function of reaction protocol. The methodology was applied to the preparation of porous PEEK materials in the form of beads and hollow fibers that differed in semicrystalline morphology and pore structure. The degree of surface modification by –OH groups in reduced PEEK (PEEK‐OH) porous materials was determined quantitatively by measuring the carbocation adduct concentration formed upon the dissolution of PEEK‐OH in sulfuric acid using UV–visible spectroscopy. Bis(4‐(4‐methoxyphenoxy)phenyl)methanone was used to optimize the reaction condition protocol. The degree of crystallinity and pore structure of the functionalized articles were largely preserved following modification. © 2024 Society of Industrial Chemistry.

Study of a Conical Plasma Jet with a Cloth-Covered Nozzle for Polymer Treatment.

Although atmospheric pressure plasma jets (APPJs) have been widely employed for materials modification, they have some drawbacks, such as the small treatment area (couple of cm2). To overcome this limitation, a funnel-like APPJ with a wide exit has been proposed. In this work, a gas-permeable cotton cloth covered the nozzle of the device to improve the gas flow dynamics and increase its range of operation. The funnel jet was flushed with Ar, and the plasma was ignited in a wide range of gas flow rates and the gap distances between the exit nozzle and the sample holder. The device characterization included electric measurements and optical emission spectroscopy (OES). To evaluate the size of the treatment and the degree of surface modification, large samples of high-density polyethylene (PE) were exposed to plasma for 5 min. Afterward, the samples were analyzed via water contact angle WCA measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It was found that surface modification occurs simultaneously on the top and bottom faces of the samples. However, the treatment incorporated different functional groups on each side.

An Overview of Dendrimers as Novel Carriers in Drug Delivery

Dendrimers and dendrimer based nanocarriers are gaining much attention in the field of therapeutic drug delivery owing to their advantages such as ease of multifunctionalization, well-defined chemical structure, near-to-monodispersity, as well as multivalency. Dendrimers are used as vectors in gene therapy, solubility enhancers and blood substitutes. Dendrimers have also been investigated as genetic material carriers with potential diagnostic and therapeutic applications. In the current review, an overview of the different types, synthesis methods, unique structural properties, factors affecting properties and applications of dendrimers. Further, the major concerns and future perspectives of the dendrimers have been discussed. The surface-modified dendrimers have been succeeded in their clinical translation and making remarkable progress in the phase of clinical trials. Extensive research is required in order to foster a robust large-scale synthetic method with adequate reproducibility. Significant studies necessarily be carriedout to find the correlation between the degree of surface modification (product quality) and their biological behavior, like pharmacokinetic profiles, therapeutic efficiency, safety and toxicity. In conclusion, dendrimers and dendritic nanoparticles have prospective insight in the arena of health sector in the forthcoming years.

Surface Modification of PHBV Fibrous Scaffold via Lithium Borohydride Reduction.

In this study, lithium borohydride (LiBH4) reduction was used to modify the surface chemistry of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibers. Although the most common reaction employed in the surface treatment of polyester materials is hydrolysis, it is not suitable for fiber modification of bacterial polyesters, which are highly resistant to this type of reaction. The use of LiBH4 allowed the formation of surface hydroxyl groups under very mild conditions, which was crucial for maintaining the fibers' integrity. The presence of these groups resulted in a noticeable improvement in the surface hydrophilicity of PHBV, as revealed by contact angle measurements. After the treatment with a LiBH4 solution, the electrospun PHBV fibrous mat had a significantly greater number of viable osteoblast-like cells (SaOS-2 cell line) than the untreated mat. Moreover, the results of the cell proliferation measurements correlated well with the observed cell morphology. The most flattened SaOS-2 cells were found on the surface that supported the best cell attachment. Most importantly, the results of our study indicated that the degree of surface modification could be controlled by changing the degradation time and concentration of the borohydride solution. This was of great importance since it allowed optimization of the surface properties to achieve the highest cell-proliferation capacity.

Enhanced Defluoridation of Water Using Zirconium-Coated Pumice in Fixed-Bed Adsorption Columns.

Millions of people across the globe suffer from health issues related to high fluoride levels in drinking water. The purpose of this study was to test modified pumice as an adsorbent for the purification of fluoride-containing waters. The adsorption of fluoride onto zirconium-coated pumice (Zr–Pu) adsorbent was examined in fixed-bed adsorption columns. The coating of zirconium on the surface of VPum was revealed by X-ray diffractometer (XRD), Inductively coupled plasma-optical emission spectroscopy (ICP-EOS), and X-ray fluorescence (XRF) techniques. The degree of surface modification with the enhanced porosity of Zr–Pu was evident from the recorded scanning electron microscope (SEM) micrographs. The Brunauer-Emmett-Teller (BET) analysis confirmed the enhancement of the specific surface area of VPum after modification. The Fourier transform infrared (FTIR) examinations of VPum and Zr–Pu before and after adsorption did not reveal any significant spectrum changes. The pH drift method showed that VPum and Zr–Pu have positive charges at pHPZC lower than 7.3 and 6.5, respectively. Zr–Pu yielded a higher adsorption capacity of 225 mg/kg (2.05 times the adsorption capacity of VPum: 110 mg/kg), at pH = 2 and volumetric flow rate (QO) of 1.25 mL/min. Breakthrough time increases with decreasing pH and flow rate. The experimental adsorption data was well-matched by the Thomas and Adams-Bohart models with correlation coefficients (R2) of ≥ 0.980 (Zr–Pu) and ≥ 0.897 (VPum), confirming that both models are suitable tools to design fixed-bed column systems using volcanic rock materials. Overall, coating pumice with zirconium improved the defluoridation capacity of pumice; hence, a Zr–Pu-packed fixed-bed can be applied for defluoridation of excess fluoride from groundwater. However, additional investigations on, for instance, the influences of competing ions are advisable to draw explicit conclusions.

Aluminium trihydrate-filled poly(methyl methacrylate) (PMMA/ATH) waste powder utilization in wood-plastic composite boards bonded by MUF resin

An alternative approach to producing a wood-plastic composite (WPC) from wood particles, aluminium trihydrate-filled poly(methyl methacrylate) (PMMA/ATH) waste powder, and melamine-urea-formaldehyde (MUF) resin is described. The surface of PMMA/ATH powder was modified with ureido- and amino-functional silane coupling agents at four different degrees of modification: 0.3%, 0.5%, 1.0%, and 2.0%. An X-ray photoelectron spectroscopy (XPS) analysis was executed on a silane-modified PMMA/ATH material, and the results revealed the presence of chemically bonded silanes on the PMMA/ATH surface. Contact angle measurements were also performed to calculate the surface free energies of the modified powders. Water contact angles of modified powders slightly decreased as surface free energy increased with the degree of surface modification. Mechanical tests of the composites showed that different degrees of surface modification had a significant influence on modulus of elasticity (MOE) and modulus of rupture (MOR) of the composite boards. However, there were no significant differences between the silanes used.

Detection of the trace level of heavy metal ions by pH-regulated conical nanochannels

The exceeding of the heavy metal ions concentration in human body to a certain critical level can lead to serious diseases. Since this critical level is usually of trace value, developing an efficient yet economic method to estimate that value is both desirable and necessary. Based on the ion current rectification behavior of a conical, polyethylene terephthalate nanochannel surface modified by 18-crown-6, we propose a method to estimate the concentration of Pb2+ in an aqueous medium. Numerical simulation is conducted to examine the performance of this nanochannel under various conditions by varying the background LiCl concentration, the concentration of Pb2+, and the degree of surface modification. Regression analysis is also conducted to obtain the range of Pb2+ concentration suitable for detection and its lower limit. We show that the performance of the nanochannel proposed is satisfactory. The possibility of detecting the concentration of Cu2+ by the nanochannel proposed is also examined.

Characterization of zwitterion-modified poly(amidoamine) dendrimers in aqueous solution via a thorough NMR investigation

.Zwitterions are a class of unique molecules that can be modified onto nanomaterials to render them with antifouling properties. Here we report a thorough NMR investigation of dendrimers modified with zwitterions in terms of their structure, hydrodynamic size, and diffusion time in aqueous solution. In this present work, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) were partially decorated with carboxybetaine acrylamide (CBAA), 2-methacryloyloxyethyl phosphorylcholine (MPC), and 1,3-propane sultone (1,3-PS), respectively with different modification degrees. The formed zwitterion-modified G5 dendrimers were characterized using NMR techniques. We show that the zwitterion modification leads to increased G5 dendrimer size in aqueous solution, suggesting that the modified zwitterions can form a hydration layer on the surface of G5 dendrimers. In addition, the hydrodynamic sizes of G5 dendrimers modified with different zwitterions but with the same degree of surface modification are discrepant depending on the type of zwitterions. The present study provides a new physical insight into the structure of zwitterion-modified G5 dendrimers by NMR techniques, which is beneficial for further design of different biomedical applications.Graphical abstract

Ligand-Binding Cooperativity Effects in Polymer-Protein Conjugation.

We present an electron paramagnetic resonance (EPR) spectroscopic characterization of structural and dynamic effects that stem from post-translational modifications of bovine serum albumin (BSA), an established model system for polymer-protein conjugation. Beyond the typical drug delivery and biocompatibility aspect of such systems, we illustrate the causes that alter internal dynamics and therefore functionality in terms of ligand-binding to the BSA protein core. Uptake of the paramagnetic fatty acid derivative 16-doxyl stearic acid by several BSA-based squaric acid macroinitiators and polymer-protein conjugates was studied by EPR spectroscopy, aided by dynamic light scattering (DLS) and zeta potential measurements. The conjugates were grafted from oligo(ethylene glycol) methyl ether methacrylate (OEGMA), forming an overall core-shell-like structure. It is found that ligand-binding and associated parameters such as binding affinity, cooperativity, and the number of binding sites of BSA change drastically with the extent of surface modification. In the course of processing BSA, the ligands also change their preference for individual binding sites, as observed from a comparative view of their spatial alignments in double electron electron resonance (DEER) experiments. The protein-attached polymers constitute a diffusion barrier that significantly hamper ligand uptake. Moreover, zeta potentials (ζ) decrease linearly with the degree of surface modification in protein macroinitiators and an effective dielectric constant can be estimated for the polymer layer in the conjugates. All this suggests that ligand uptake characteristics in BSA can be fine-tuned by the extent and nature of such post-translational modifications (PTMs). We show that EPR spectroscopy is suitable for quantifying these subtle PTM-based functional effects from self-assembly of substrate and ligand.

Studies on the Development of Electrochemical Immunosensor for Detection of Diphtheria Toxoid

In the recent years, the growing number of diphtheria cases (also lethal) has been observed. As the diphtheria disease characterizes with rapid development and highly nonspecific initial symptoms, the fast detection method of pathogenic Corynebacterium strains, especially by the diphtheria toxin, is of particular importance. Herein, we present the studies on the development of an electrochemical immunosensor toward diphtheria toxoid (part of the vaccines inducing an immune response). The monoclonal (from rat ascites) and polyclonal (guinea pigs) antibodies were compared as receptor elements. The influence of different immobilization methods, electrode surface blocking agents or metallic nanoparticles on the biosensor response was examined. The degree of surface modification and further interaction with diphtheria toxoid was verified using cyclic and square – wave voltammetry as well as impedance spectroscopy. The calculated dissociation constant (6.892·10−5 Lf/mL) for the developed sensing layer confirmed high affinity toward the toxoid. The linear dependence of redox current change versus diphtheria toxoid was recorded within 10−4 to 10−1 Lf/mL. Moreover, the selectivity studies indicated a distinctly lower biosensor response for thrombin, lysozyme, IgG and Phe-Ala peptide what allowed for detection of diphtheria toxoid in real sample.

Effect of Surface Modification to Photoanodes in Alkoxysilyl Dye-Sensitized Solar Cells on the Photovoltaic Performance

The effect of surface modification to dye-adsorbed TiO2 electrodes in alkoxysilyl dye-sensitized solar cells on the photovoltaic performance was investigated with using alkylcarboxylic acids with different alkyl-chain lengths as surface modifiers. More effective suppression of a back-electron-transfer reaction was observed with the increment of the amount of the adsorbed modifier on the dye-adsorbed TiO2 electrode and with lengthening the alkyl chain of the alkylcarboxylic acid. The photovoltaic performance of the cells was confirmed to be improved by the surface modifications of the dye-adsorbed TiO2 electrodes using alkylcarboxylic acids, and the necessities of tuning the surface-modification degree and the selection of the alkyl-chain length with regarding the molecular size of the sensitizing dye were exhibited for the efficient improvement of the photovoltaic performance of the cell.

Green surface modification and nano-multifunctionalization of denim fabric

Eco-friendly multifunctional denim products using environmentally sound technologies are still a challenge. In current study, enzymatic pretreatments of denim fabric using acid pectinases, laccases, and acid cellulases individually and in admixtures were carried out followed by post-nanocoating of bio-treated fabric samples with ZnO- and TiO2-NPs along with citric acid/sodium hypophosphite as ester-crosslinking/binding system using the pad-dry-microwave fixation technique. The impacts of enzymatic and subsequent nano-treatments on some physico-chemical, color change, anti-microbial and UV-blocking properties were assessed. Also, surface modification and nano-metal oxides immobilization were observed and confirmed using scan electron microscope and energy dispersive X-ray spectroscopy analysis. The experimental results revealed that the degree of surface modification and subsequent multifunctionalization are governed by type of enzyme or hybrid enzyme as well as kind of nano-metal oxide and its extent of fixation onto the modified/ester-crosslinked denim fabric structure. The synergistic effect and positive impacts of enzymatic treatment followed by nanofinishing especially in case of using ZnO-NPs on imparting better and durable performance and multifunctional properties without adversely affecting the coloration properties of denim fabric samples are confirmed and discussed. Mode of interactions was also suggested.

Study on the Effect of Modified Walnut Shell Filter on Oil Removal from Oilfield

Walnut shell filter materials has strong adsorption and contaminants interception ability, anti-oil immersion, high hardness, good wear resistance and stable chemical properties, its surface was easily polluted by the absorbed crude oil in oily sewage to reduce its filtering and backwashing effect. The surface modification of the walnut shell was the introduction of hydrophilic groups to enhance its hydrophilic oleophobic property; Used different ratio of sulfite to boil the walnut shell at a certain temperature to make a modification on the hydrophilicity of walnut shell surface, the modified filter materials with varying degree of surface modification was obtained. Measured the contact angle between walnut shell and water, the wetting performance was significantly improved, the contact angle was decreased from 95° to 36.75°, the surface properties were changed from lipophilicity to hydrophily. the micropores of surface become smaller, and it was conducive to the accumulation of emulsified oil beads; After filtration treatment of oily wastewater containing polymer, filter oil removal rate was over 78%, the oil removal rate of the modified filter materials was increased by 25% than that of the unmodified filter materials, and oil content in the filtered sewage was below 45 mg/L, the backwashing oil removal effect of modified filter materials increased from 17% to 87%, intercepted oil in the before process of filtration was more easier removed in the after process of backwashing to make the filtering performance regeneration of walnut shell filter materials. In the case of filtration treatment on the same amount of oily sewage its lifetime could be extended more than twice.

Nanostructured micro-raspberries from superparamagnetic iron oxide nanoparticles: Studying agglomeration degree and redispersibility of nanoparticulate powders via magnetisation measurements

Surface modified superparamagnetic iron oxide nanoparticles are assembled into nanostructured micro-raspberry particles via spray drying. The micro-raspberry powder is readily redispersed to individual nanoparticles or nanostructured sub-units, depending on the initially adjusted nanoparticle modification. In this work, it is demonstrated how the technique of magnetic zero-field-cooled/field-cooled (ZFC/FC) measurements can be used to judge the degree of agglomeration, i.e. the extent of hard-agglomerates and soft-agglomerates in a system and predict the redispersibility of the powder particles. Furthermore, the uniformity of surface modification of the individual nanoparticles can be judged via this method. In addition, the technique can be applied to characterise complex nanostructured particle systems composed of iron oxide nanoparticles mixed with another type of nanoparticulate building-block. Thus, this work shows that magnetic measurement techniques are a promising approach to characterise agglomeration states of nanoparticles, their degree of surface modification and their distribution in complex particle and composite systems.

Effects of the degree of surface modification on the rheological responses of precipitated silica suspensions in benzyl alcohol

ABSTRACTTwo types of precipitated silica powders modified by poly (dimethylsiloxane) (PDMS) were suspended in benzyl alcohol and their rheological properties were investigated as a function of silica volume fraction, φ. The suspensions were classified into sol, pre-gel, and gel states based on the increase in φ. An increase in the degree of surface modification by PDMS caused gelation at higher φ. Plots of apparent shear viscosity against shear rate in the sol and pre-gel states of highly modified silica suspensions showed weak shear thickening behavior, while the same plots for silica suspensions with a low modification level exhibited shear thinning behavior. The dynamic moduli of hydrophobic suspensions in the pre-gel and gel states were dependent on the surface modification: the storage modulus G′ was larger than the loss modulus G″ in the linear region and these moduli increased with increasing φ, irrespective of the silica powder. The linear region of the φ range for the precipitated silica suspensions was wider than that for the fumed silica powders modified by PDMS suspended in benzyl alcohol, while the G′ value in the linear region for the precipitated silica suspensions was less than those for the fumed silica suspensions.

Surface modification of silica nanoparticles using phenyl trimethoxy silane and their dispersion stability in N-methyl-2-pyrrolidone

Abstract Surface modified silica nanoparticles were prepared through two-step sol-gel process. The introduction of phenyl group onto the surface of silica nanoparticles could be processed by varying the amounts of NH4OH and phenyl trimethoxysilane (PTMS) and molar ratio of H2O/Si during the second step. Under the optimized condition, the surface properties of silica nanoparticles were completely different before and after surface modification, since silanol groups were substituted by phenyl groups. The qualitative analysis of modified silica nanoparticles was conducted with Fourier transform infrared spectroscopy (FTIR). The degree of surface modification at the silica nanoparticles was examined based on the surface hydrophilic/hydrophobic moiety, surface charge and morphology. The mechanism of surface modification was inferred from a surface roughness. Finally when the silica was dispersed in N-methyl-2-pyrrolidone (NMP) as organic solvent, the modified silica was better in dispersion ability at high concentration (20 wt.%).

Effects of multiwalled carbon nanotube morphology on the synthesis and electrocatalytic performance of Pt supported by multiwalled carbon nanotubes

The effect of the diameter of multiwalled carbon nanotubes (CNTs) during the synthesis of CNT-supported Pt (Pt/CNT) has been studied. Three different CNTs with mean diameters of 10, 20 and 60nm were chemically treated in acidic media and used as supports for Pt nanoparticles. Features such as specific surface area and the degree of surface modification during the chemical treatment are strongly influenced by the diameter of the CNT. Those features are key aspects that determine the size and loading of the Pt particles immobilized onto the nanotubes. Therefore, the catalysts prepared using nanotubes with smaller diameters exhibit both higher Pt loading and dispersion. Consequently, the performance of the catalysts during the electrooxidation of CO and oxygen reduction reaction in acidic media varies with the diameter of the CNTs. Remarkably, the catalyst prepared on 60-nm diameter CNTs is the most stable during long-term use. This higher stability arises from both the superior stability of the larger Pt particles and the stronger anchorage of the Pt onto the CNTs with higher amounts of surface oxygen groups. The groups increase in number with increased CNT diameters.

Nafion-type membranes doped with silica nanoparticles with modified surface

Silica with surface modified with hydrophobic perfluorododecyl groups was used as the additive for perfluorosulfonic acid MF‐4SC membranes (Russian analogue of Nafion). The hybrid materials were prepared by membranes casting from alcohol polymer solutions contained precursors for the particles formation followed by the hydrolysis of precursors. Membranes with silica concentration ranging from 0 to 10wt.% and contained silica with various degree of surface modification were investigated. It was found that incorporation of silica with hydrophobic surface results in the decrease of water uptake in comparison with membrane doped with pure SiO2 and initial membrane while conductivity of this membranes is noticeably higher in comparison with membranes doped with pure silica. The maximal conductivity value was observed for MF-4SC membrane doped with 3wt.% of SiO2 contained 5mol% of 1H,1H,2H,2H-perfluorododecyl groups and reaches 0.25S/sm at 90°C. Explanation of the phenomenon of conductivity increase in membrane doped with silica nanoparticles with hydrophobic surface has been proposed.

Formation of coatings with tailored properties on polyperoxide-modified polymeric surfaces

Modification (peroxidation) of polymer surfaces, polypropylene, polyethylene, polyethylene terephthalate, nylon 6-6, poly(phenylene oxide), and ethylene–propylene copolymer were affected by the surface grafting of functional polyperoxides (FPPs) such as poly(5-tert-butylperoxy-5-methyl-1-hexene-3-yne-co-octylmethacrylate) (VEP-co-OMA), poly{N-[(tert-butylperoxy)-methyl]acrylamide-co-octyl methacrylate} (PO-co-OMA), and poly(tert-butylperoxy-methacrylate-co-octyl methacrylate) (PEst-co-OMA). The degree of surface modification was shown to be determined primarily by the structure of the polymer substrate. Using a peroxidized surface as an initiator of grafted copolymerization enabled the grafting of functional monomers (acrylic acid, acrylamide, 4-vinylpyridine, and hydroxyethyl methacrylate) and polysaccharides (heparin, dextran, etc.) and thereby imparted adhesive, antibacterial, haemocompatible properties to the polymer surface.