Retention Of Functional Group Research Articles

Using 1,8-cineole plasma with both pulsed and continuous depositions to modify commercially available wound dressing materials.

The current clinical standards for infected chronic wounds are oral and topical antibiotics. These strategies are problematic because antibiotic resistance can occur with prolonged use. As an alternative to clinical methods, essential oils show promise in preventing bacterial growth. Specifically, 1,8-cineole-an active component in eucalyptus oil-exhibits antifungal, anti-inflammatory, and antibacterial properties. Applying 1,8-cineole directly onto a wound is challenging, however, due to its volatile nature. To combat this issue, plasma-enhanced chemical vapor deposition (PECVD) has been established as a method to deposit a stable 1,8-cineole-derived film on model surfaces (e.g., glass and electrospun polystyrene nanofibers). The current study represents an extension of previous work, where both pulsed and continuous 1,8-cineole plasmas were used to deposit a 1,8-cineole-derived film on two commercially available wound dressings. Three surface analyses were conducted to characterize the plasma-modified dressings. First, water contact angle goniometry data demonstrated a decrease in hydrofiber wettability after treatment. Through scanning electron spectroscopy, the surface morphology of both materials did not change upon treatment. When comparing pulsed and continuous treatments, deconvolution of high-resolution C1s x-ray photoelectron spectra showed no differences in functional group retention. Importantly, the chemical compositions of treated wound dressings were different compared to untreated materials. Overall, this work seeks to elucidate how different PECVD parameters affect the surface properties of wound dressings. Understanding these parameters represents a key step toward developing alternative chronic wound therapies.

Allenyl Carbonate as a Butadiene Surrogate in Cobalt-Catalyzed Crotylation of Aldehydes

Allenyl carbonate was used as a 1,3-butadiene surrogate to develop a photocatalytically sustainable protocol for cobalt-catalyzed crotylation of aldehydes. The developed method tolerated a wide range of aromatic and aliphatic aldehydes with retention of functional groups under mild conditions and produced good-to-excellent yields of crotylated secondary alcohols. Based on preliminary mechanistic studies and literature precedents, a plausible mechanism is proposed.

Thermally stable proton conductivity from nanodiamond oxide.

Herein, we report nanodiamond oxide (NDOx), obtained from modified Hummers' oxidation of nanodiamond (ND), showing excellent proton conductivity and thermal stability. NDOx possesses hydrophilicity resulting in higher water adsorption and the retention of functional groups at elevated temperatures can be attributed to the high proton conductivity and thermal stability, respectively.

Encapsulation of soy isoflavone extract by freeze drying, its stability during storage and development of isoflavone enriched yoghurt.

Soybean is a natural source of isoflavone. Its extract has a bitter and astringent taste and undergoes through oxidative deterioration. The study aimed at encapsulation of isoflavone extract using different carrier material through freeze drying. Maltodextrin, β-cyclodextrin, and tapioca starch were employed in 1:3 while sodium alginate and carboxymethyl cellulose in 1:1.25 as extract to carrier material ratio for encapsulation. Carrier material reflected significant (< 0.05) effect on encapsulation efficiency, isoflavone content and morphology of encapsulated extract. Maltodextrin was selected as the best material for encapsulation of isoflavone extract reflecting significantly higher encapsulation efficiency along with homogenous coating on the particle surface as examined through SEM. The band stretching in FTIR analysis also indicates the retention of functional groups after encapsulation. The encapsulated extract packed in ambered glass vials can be stored safely for a period of 6 months with a higher withholding of isoflavones under refrigerated conditions. Furthermore, encapsulated isoflavone extract was incorporated in yoghurt @ 50mg isoflavone which improved its functional and sensory properties. About 96.83% of isoflavone was retention in yoghurt containing encapsulated extract compared to yoghurt having extract without encapsulation.

The future of green energy and chemicals: Rational design of catalysis routes

<h2>Summary</h2> Over the past 100 years, technological reforms in energy and chemicals have promoted the economic and social development. Due to the depletion of natural resources and the environment and climate changes, the future development of society will inevitably show the trend of green, low-carbon, and circular economy, offering an opportunity for catalysis technology to continue to play a leading role. This Perspective focuses on the novel processes of efficient thermal catalysis and electrocatalysis, as well as the disruptive innovation of photocatalysis, the key to which lies in creating functional catalysis routes to maximize the retention of functional groups. Furthermore, rational design of catalysis routes and systems for energy molecules, alkenes, and aromatics should lead to 11 revolutionary breakthroughs in catalytic science and technology from resource driven to ecology driven.

Parametric optimization by Taguchi L9 approach towards biodiesel production from restaurant waste oil using Fe-supported anthill catalyst

Restaurant waste oil is easily obtainable from local restaurants, while anthills grow widely in Oro, Nigeria. The anthills were first carbonized, then steam activated to prepare an inert, porous support capable of functional group adsorption. The support was then doped with Fe (II) using FeSO4 and the Fe/A catalyst was used in biodiesel synthesis from the RWO. L9 Taguchi OA was chosen to optimize the transesterification proves parameters comprising of catalyst concentration, methanol to oil ratio, reaction temperature and reaction time. The optimization revealed that methanol concentration does not affect the biodiesel yield significantly, while reaction time has the highest contribution. A biodiesel yield of 99.73 % was attained at 60 °C for 1.5 h with 1.2 % catalyst and 6:1 methanol:oil ratio. GC analysis showed the product to be rich in methyl esters. Fuel characterization tests show that the product has properties exceeding the standards set by ASTM. Kinetic studies show the process adheres to pseudo 1st order kinetics and has high reaction rate and frequency factor (A) with low EA, while the catalyst shows very efficient retention of functional groups, as evident from its reusability up to 7 times. Thus the process is energy and cost efficient, with a potential for commercialization.

Using sewage sludge with high ash content for biochar production and Cu(II) sorption

The ash content of municipal sewage sludge is generally high. However, the manner in which the composition of ash affects biochar properties and sorption remains unclear. Sewage sludge from two cities, Chongqing and Kunming, were pyrolyzed at different temperatures to produce biochar in this work. The physicochemical properties of biochar were investigated by bulk chemical characteristics (such as FTIR, XPS, Raman analysis, and elemental analysis) and benzene polycarboxylic acid (BPCA) molecular biomarkers, after which they were correlated with sorption characteristics. In comparison with biochar from Chongqing sewage sludge (CSS), biochar from Kunming sewage sludge (KSS) showed stronger polarity, a larger specific surface area (SSA) and more functional groups, but a lower degree of graphitization and aromatization. These differences may result from the higher aluminum (Al) content of KSS. The single-point sorption coefficient Kd values of biochar derived from CSS and KSS were analyzed together. Kd was positively correlated with the SSA and pore volume of sewage sludge and biochar produced at 200–300 °C. For biochar produced at 300–700 °C, the Kd value was positively correlated with the O content, O/C and (O + N)/C. The pyrolysis temperature of 300 °C was a threshold temperature for Cu(II) sorption onto biochar, at which there was a balance between decreased oxygen-containing functional groups and increased SSA. The findings of this study show that higher Al content in sewage sludge was beneficial to pore volume enlargement and functional group retention during the pyrolysis process.

Synthesis of surface-anchored stable zwitterionic films for inhibition of biofouling

The article reports a two-step method for the synthesis of antifouling films; wherein we first deposited the copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p-4VP-co-EGDA) onto the surface of different substrates (e.g., delicate substrate such as reverse osmosis (RO) membranes, Si wafers and gold sensors) via an all-dry and substrate-independent technique known as initiated chemical vapor deposition (iCVD). The iCVD technique is based upon free radical polymerization where vapors of initiator and monomers are transported to the surface to be modified to initiate simultaneous polymerization and thin film formation. In a subsequent step, th as-deposited copolymer films were converted to zwitterions by a diffusion limited gas-phase reaction with vapors of 1,3-propane sultone to form polysulfobetaine (pSB) type of zwitterionic surface moieties. Bare and the surface modified substrates were characterized by AFM, FTIR and XPS for their topographical and compositional analysis. The presence of zwitterionic moieties considerably discourages the irreversible attachment/adhesion of proteins and bacterial cells as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) and SEM analysis respectively. The results of bacterial adhesion studies showed 99.6% lower attachment of Pseudomonas aeruginosa cells onto the surface of modified RO membranes as compared to bare membranes. The authors wish to mention that a new pyridine-based pSB type of antifouling zwitterionic films has been added to the library of iCVD films. We believe that the demonstrated attempt of membrane surface modification strategy holds promise for potentially controlling the biofouling of other polymeric membranes such as ultrafiltration, nanofiltration and RO membranes. Furthermore, salient features such as solvent less nature, the easy tunablity of film and the capability of retention of functional group make iCVD a unique method to modify the surface of virtually any substrate including, metals, polymeric membranes, Si and gold sensors etc. Thus, it is expected that the developed coating technique could possibly lead to prepare a wide spectrum of environmentally benign antifouling films for other applications such as biomedical devices, medical implants and ship hulls where inhibition of microbial adhesion and subsequent biofilm growth is a severe challenge.

Weathering, salt spray corrosion and mar resistance mechanism of clay (nano-platelet) reinforced polyurethane nanocomposite coatings

Performance properties like weathering and corrosion resistance are critical for automotive top coats. Using two types of clays Cloisite 30B(C30B) and Cloisite 20 A(C20 A), a 2 K polyurethane (PU) pack coating formulation was modified at nanoscale. These coatings show better resistance to salt spray (500 h) and accelerated weathering conditions (1000 h). When observed under atomic force microscopy (AFM) nanoscale morphology of these nanocomposite coatings show globular (C30B) and rod-like (C20 A) hard segment formation of size˜200 nm, which compared to pristine PU coatings are more uniformly formed and evenly distributed across the microscale surface (surface texturing). Visual, spectroscopic & chemical analysis confirmed better performance of nanocomposite coatings under ultraviolet/humidity and salt cycles. Dry film thickness & gloss; dft1000 (G[1000]) was reduced by 25% (32%) for pure PU, 14.03% (16.7%) for PU-3C30B and 20% (22.7%) for PU-3C20 A respectively. The overall colour difference in CIELab values ΔE* was 9.794, 7.623 and 8.450 for PU, PU-3C30B and PU-3C20 A. Salt spray (500 h) rusted about 35% area of mild steel (ms panels) for PU, while for PU-3C30B and PU-3C20 A it was only 5% and 10% respectively. Fourier transform infrared (FTIR) shows better retention of functional groups in aged and corroded nanocomposite coatings versus pristine coatings. This proves that two dimensional clay particles when duly exfoliated interact with hard segments and play a significant role in resisting weathering forces, salt spray corrosion and even mar.

Synthesis of highly functionalised plasma polymer films from protonated precursor ions via the plasma α-γ transition.

Chemically functionalized surfaces may be produced via plasma polymerization, however a high degree of functional group retention is often difficult to achieve. Here, the plasma polymerization of three structurally related ester precursors, ethyl isobutyrate (EIB), methyl isobutyrate (MIB) and ethyl trimethylacetate (ETMA) is compared at low and high pressure. In moving from a low pressure to higher pressure regime, significant changes in the plasma chemistry and resulting plasma polymer deposit were observed with much higher retention of chemical functionality at the higher pressure observed. Until now these changes would have been attributed to a decrease in the energy/molecule, however we show by direct measurement of the chemistry and physics of the plasma that there is fundamental shift in the properties of the plasma and surface interactions which explain the results. At low pressure (α regime) precursor fragmentation and neutral deposition dominate resulting in poor functional group retention. Increasing the pressure such that the sheath region close to surfaces becomes collisional (γ regime) favours production of protonated precursor ions which retain functionality and dominate the deposition process rather than radical species.

Adhesion improvement at the PMMA bone cement-titanium implant interface using methyl methacrylate atmospheric pressure plasma polymerization

Abstract In this work, methyl methacrylate based coatings are deposited on Ti, using an atmospheric pressure DBD plasma to improve the Ti–PMMA bone cement interfacial adhesion. Surface analysis (XPS, AFM, optical reflectance spectroscopy) indicates a well-controlled deposition process of long-term water-stable coatings with good tunability towards thickness and functional group retention. Different sample series, both plasma activated and plasma coated, immobilized in bone cement, are submitted to pull-out tests. Results show a maximum increase of 50% in adhesive force. Ageing tests show that plasma-treated samples return to their original adhesive properties within 14 days, while plasma-coated samples maintain stability.

Chemical and physical processes in the retention of functional groups in plasma polymers studied by plasma phase mass spectroscopy.

Surface engineering of functionalised polymer films is a rapidly expanding field of research with cross disciplinary implications and numerous applications. One method of generating functionalised polymer films is radio frequency induced plasma polymerisation which provides a substrate independent coating. However, there is currently limited understanding surrounding chemical interactions in the plasma phase and physical interactions at the plasma-surface interface, and their effect on functional group retention in the thin film. Here we investigate functionalised plasma polymer films generated from four precursors containing primary amines. Using XPS and fluorine tagging with 4-(trifluoromethyl)benzaldehyde, the primary amine content of plasma polymer films was measured as a function of applied power at constant precursor pressure. The results were then correlated with analysis of the plasma phase by mass spectrometry which showed loss of amine functionality for both neutral and ionic species. Surface interactions are also shown to decrease primary amine retention due to abstraction of hydrogen by high energy ion impacts. The stability of the plasma polymers in aqueous solution was also assessed and is shown to be precursor dependent. Increased understanding of the chemical and physical processes in the plasma phase and at the surface are therefore critical in designing improved plasma polymerisation processes.

Ultra-Thin Plasma Polymer Films as a Novel Class of Adhesion Promoters: A Critical Review

Several reaction mechanisms have been proposed for formation of plasma polymers, such as monomer fragmentation followed by poly-recombination into randomly structured and crosslinked films; fragmentation, accompanied by the formation of acetylene or other film-forming intermediates and deposition of polystyrene-like material; plasma-initiation of radical chain-growth polymerization; and ion-molecule reactions, as well as ionic chain-growth polymerization. The bulk structure of plasma polymers was found to be more or less randomly formed, far from that of classic polymers. Nevertheless, the retention of functional groups in the plasma polymer is higher than the retention of monomer structure in repeat units of polymer backbones. Such functional groups bearing plasma polymers were found to be suitable as adhesion promoting layers in polymer composites. These functional groups are essential for covalent bonding to substrate and coating. Additional introduction of aliphatic spacers could flexibilize the interface between plasma polymer covered substrate and coating. Thus, maximum adhesion in composites and laminates was produced. Several examples are given where plasma polymers alone or linked with spacers have been shown to be effective as adhesion promoter.

Atmospheric Pressure Non-Equilibrium Plasma Deposition with Retention of Functional Group

A non-equilibrium atmospheric pressure plasma was applied for the polymerization of the methacrylic monomers such as (2-hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA) and butyl methacrylate (BMA)). These monomers were successfully polymerized with retaining the functional groups of ester or acid. The polymerization mechanism was discussed on the basis of the optical emission spectroscopy (OES) of the plasma. It was strongly suggested that the functional groups could be retained in the polymerization proceeds when the HOMO-LUMO gap of the monomer is close to the energy of Ar metastable atom, which initiates the polymerization.

The link between mechanisms of deposition and the physico-chemical properties of plasma polymer films

Film thickness and functional group retention are routinely measured parameters for plasma polymers. It is known that other parameters such as density, solubility and mechanical properties can affect the performance of the plasma polymer film, however such parameters are not often measured; nor is there any understanding of the link between the mechanisms of film growth and these properties. In this investigation we produced thin films from three classes of commonly used plasma polymers (hydrocarbons, glymes and carboxylic acids). By choosing the monomer structure and applied RF power, the dominant mechanism of film growth was varied between ionic deposition and neutral grafting. The density, solubility and modulus of the resulting films were then measured by atomic force microscopy. Films grown from saturated monomers had higher moduli, were less soluble, and surprisingly had lower density compared to their unsaturated analogues. The results demonstrate that cognizance of the mechanism of film growth allows the physical properties of the film to be tailored for specific applications.

Preparation of antibacterial surfaces by hyperthermal hydrogen induced cross-linking of polymer thin films

The covalent immobilization of polymers on surfaces has the potential to impart new properties and functions to surfaces for a wide range of applications. However, most current methods for the production of these surfaces involve multiple chemical steps or do not impart a high degree of control over the chemical functionalities at the surface. Described here is the preparation of surfaces covalently functionalized with quaternized poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), a known antibacterial polymer. PDMAEMA was coated onto octadecyltrimethoxysilane modified silicon wafers and was then cross-linked by the selective cleavage of C–H bonds using a hyperthermal hydrogen treatment. The surfaces were then quaternized with ethyl bromide. At each step the surfaces were characterized extensively using techniques including atomic force microscopy, contact angle measurements and X-ray photoelectron spectroscopy. These results demonstrated a high degree of functional group retention throughout the process. The antibacterial properties of the surfaces against Gram-positive S. aureus and Gram-negative E. coli were investigated using a “drop test” assay. Furthermore, the process was successfully applied to produce antibacterial butyl rubber surfaces, demonstrating the versatility of the method for grafting onto unfunctionalized hydrocarbon surfaces.

Mechanisms of Plasma Polymerization – Reviewed from a Chemical Point of View

AbstractSeveral reaction mechanisms have been proposed for the formation of plasma polymers, such as monomer fragmentation followed by poly‐recombination into randomly structured and crosslinked films; fragmentation, accompanied by the formation of acetylene or other film‐forming intermediates and deposition of polystyrene‐like material; plasma‐initiation of a radical chain‐growth polymerization; and ion‐molecule reactions, as well as ionic chain‐growth polymerization. The bulk structure of plasma polymers is completely irregular, far from that of conventional polymers. The retention of functional groups during plasma polymerization tends to be greater than that of the entire monomer structure found again as an intact repeat unit in the resulting plasma polymer. An alternative method for depositing ultra‐thin, pin‐hole free coatings, ones that possess regular structures, is by electrospray ionization (ESI) of pre‐fabricated polymers.magnified image

Immobilization of Biomolecules to Plasma Polymerized Pentafluorophenyl Methacrylate

Thin films of plasma polymerized pentafluorophenyl methacrylate (pp-PFM) offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with different aminated reagents and biological molecules. The present paper follows on from previous work on the plasma deposition of pentafluorophenyl methacrylate (PFM) for optimum functional group retention (Francesch, L.; Borros, S.; Knoll, W.; Foerch, R. Langmuir 2007, 23, 3927) and reactivity in aqueous solution (Duque, L.; Queralto, N.; Francesch, L.; Bumbu, G. G.; Borros, S.; Berger, R.; Förch, R. Plasma Process. Polym. 2010, accepted for publication) to investigate the binding of a biologically active peptide known to induce cellular adhesion (IKVAV) and of biochemically active proteins such as BSA and fibrinogen. Analyses of the films and of the immobilization of the biomolecules were carried out using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The attachment of the biomolecules on pulsed plasma polymerized pentafluorophenyl methacrylate was monitored using surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the presence of immobilized biomolecules on the plasma polymer and was used to determine the mass coverage of the peptide and proteins adsorbed onto the films. The combined analysis of the surfaces suggests the covalent binding of the peptide and proteins to the surface of the pp-PFM.

Combined Continuous Wave and Pulsed Plasma Modes: For More Stable Interfaces with Higher Functionality on Metal and Semiconductor Surfaces

AbstractA novel approach to producing improved bio‐interfaces by combining continuous wave (CW) and pulsed plasma polymerization (PP) modes is reported. This approach has enabled the generation of stable interfaces with a higher density of primary amine functionality on metal, ceramic and semiconductor surfaces. Heptylamine (HA) was used as the amine‐precursor. In this new design, a thin CW PPHA layer is introduced to provide strong cross‐linking and attachment to the metal or semiconductor surfaces and to provide a good foundation for better bonding a pulsed PPHA layer with high retention of functional groups. The combined mode provides the pulsed mode advantage of a 3‐fold higher density of primary amines, while retaining much of the markedly higher stability in aqueous solutions of the continuous mode.magnified image

Solvent-Induced Porosity in Ultrathin Amine Plasma Polymer Coatings

Plasma polymers deposited from n-heptylamine onto silicon wafers have been found to form a porous microstructure when immersed in water and other solvents, with pores of dimensions and densities that vary considerably between coatings deposited under different plasma conditions. This solvent-induced pore formation was found to correlate with the observed percentage of extractable material. With low radio frequency (rf) power inputs, the resultant softer coatings possess considerably more extractable material than coatings deposited at higher applied power levels. The porosity is thus proposed to result from the formation of voids created by the extraction of soluble low-molecular-weight polymeric material, which produces shrinkage stress that the coating, firmly attached to the substrate, cannot relieve by macroscopic contraction. The microscopic contraction of plasma polymer volume creates voids that appear to span the entire film thickness. The effect of aging plasma polymers in air was also investigated. For films deposited at low power it led to reduced extraction of soluble material and different pore morphology, whereas for films deposited at higher rf power levels, the extracted amounts and pore formation were the same for aged coatings. It was also found that the density of surface amine groups was lower for films deposited under the two lowest power settings, in contrast to the commonly held belief that the use of minimal applied rf power aids retention of functional groups. These porous plasma polymer coatings with surface groups suitable for further interfacial chemical immobilization reactions may be useful for various membrane and biotechnology applications.