Improve the physical and chemical properties of biocompatible polymer material by MeV He ion beam

There is a high interest in improving the hydrophilicity of polymer surfaces due to their wide use for technological purposes. In this study Ultra High Molecular Weight Polyethylene (UHMWPE) as a biocompatible material was bombarded with 1 MeV He ions to the fluences ranging from 1×10¹³ to 5×10¹⁴ cm^?2. The pristine and ion beam modified samples were investigated by photoluminescence (PL), ultraviolet–visible (UV–vis) spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The changes of wettability and surface free energy were determined by the contact angle measurements. The obtained results showed that the ion bombardment induced decrease in integrated luminescence intensity and decrease in the transmittance with increase of ion fluence as well. This is might be attributed to degradation of polymer surface and/or creation of new electronic levels in the forbidden gap. The FTIR spectral studies indicate that the ion beam induces chemical modifications within the bombarded UHMWPE. Formation of carbonyl groups (C=O) on the polymer surface was studied. Direct relationship of the wettability and surface free energy of the bombarded polymer with the ion fluences was observed.     

Influence of montmorillonite nano-dispersion on polystyrene photo-oxidation

UV photo-oxidative degradation of polystyrene/montmorillonite nanocomposites (PS/o-MMTs) and microcomposite (PS/Na/MMT), obtained via in situ bulk polymerization, has been studied in accelerated conditions. Imidazolium or standard alkylammonium surfactants were used to modify MMT. The chemical modification resulting from photo-oxidation has been followed using infrared spectroscopy (FT-IR). The rate of photo-oxidation of PS/o-MMT and PS/Na/MMT was faster than that of pristine PS. The results suggest that the photo-oxidative instability could be related to the degree of exfoliation and then to the presence of catalytic active sites on the MMT layer surface.     

Understanding and improving direct UV detection of monosaccharides and disaccharides in free solution capillary electrophoresis

Direct UV detection of carbohydrates in free solution capillary electrophoresis at 270 nm is made possible by a photo-oxidation reaction. Glucose, rhamnose and xylose were shown to have unique UV absorption spectra hypothesizing different UV absorbing intermediates for their respective photo-oxidation. NMR spectroscopy of the photo-oxidation end products proved they consisted of carboxylates and not malondialdehyde as previously theorized and that oxygen thus plays a key role in the photo-oxidation pathway. Adding the photo-initiator Irgacure^® 2959 in the background electrolyte increased sensitivity by 40% at an optimum concentration of 1 × 10⁻⁴ mM and 1 × 10⁻⁸ mM for conventional 50 μm i.d. capillaries and for the corresponding extended light path capillaries, respectively.     

微波固相剥离法制备功能化石墨烯及其电化学电容性能研究(英文)

通过微波固相剥离氧化石墨制备了功能化石墨烯材料。石墨烯的剥离,是由于微波加热过程中氧化石墨烯片上的官能团分解为CO2和H2O,产生的压力超过了片层间的范德华力。形貌表征显示了石墨烯的有效剥离和纳米孔结构的形成。红外光谱分析结果表明微波剥离的功能化石墨烯仍然有少量的官能团残留。N2等温吸附-脱附测试结果表明样品具有高比表面积(412.9m2·g-1)和大孔容(1.91cm3·g-1)。电化学测试结果表明功能化石墨烯具有良好的电化学电容行为和207.5F·g-1的比电容。     

A comparison of modifications induced by Li<Superscript>3+</Superscript> and Ag<Superscript>8+</Superscript> ion beams irradiation in poly(lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) films

Poly(lactide-co-glycolide) (PLGA) films were irradiated by 180 MeV/amu Ag⁸⁺ ions and 50 MeV/amu Li³⁺ ions at different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 1 × 10¹² ions/cm². Modifications of polymer films induced by the swift heavy ions (SHI) irradiation were studied by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The dominant effect of the SHI beam irradiation is proposed to be chain scission which leads to breakage of polymer chains, followed by hydrogen abstraction. The results from FTIR spectroscopy showed that the intensity of all peaks of the irradiated samples decreased at high fluence of SHI, suggesting PLGA samples significantly degraded at high SHI fluence. The variation in optical band gap energy and Urbach energy with increasing fluence was calculated from UV–Vis spectroscopy and explained in terms of changes occurring in the polymer matrix. X-ray diffraction patterns also show appreciable changes in PLGA at high fluence. FESEM results revealed that the hydrophilicity of the PLGA surface increased with an increase in ion fluence. In this paper the optical, chemical and structural changes with different fluence rates are discussed.     

Patterned Hydrophilization of Nanoporous 1,2‐PB by Thiol‐ene Photochemistry

We present an efficient method for functionalizing the large polymer–air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross‐linked 1,2‐polybutadiene is tuned by thiol‐ene photo‐grafting of mercaptosuccinic acid or sodium 2‐mercaptoethanesulfonate. The reaction is monitored by FT‐IR, UV–Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol‐ene “click” reactions in nano‐confinement, neatly revealing their chain‐like nature. Top–down photolithographic patterning is demonstrated, realizing hydrophilic nanoporous “corridors” exclusively hosting water. The presented approach can be relevant for many applications where, e.g., high control and contrast in hydrophilicity, chemical functionality or refractive index are needed.

     

Acid-Containing Tyrosine-Derived Polycarbonates: Wettability and Surface Reactivity

Tyrosine-derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4-6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (-COOH) to carboxylate ion (-COO⁻). The surface compositions of imidazole-labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N-hydroxysuccinimide.     

A novel biocompatible drug carrier for oral delivery and controlled release of antibiotic drug: loading and release of clarithromycin as an antibiotic drug model

In this work, a novel biocompatible carrier was designed by modification of nanoporous carbon material and synthesized by hydrothermal condensation of d-Fructose, as the carbon source, in the presence of Pluronic^® F127, as the surfactant. The prepared material is completely biocompatible and suitable for oral drug delivery. As this nanoporous carbon has surface decorated hydroxyl groups, they are able to react with 3-aminopropyltriethoxysilane agent and produce amino-functionalized nanoporous carbon. The synthesis of amine-modified carbon nanoporous material was confirmed by X-ray powder diffraction, IR spectroscopy, elemental analysis, thermal analysis and nitrogen adsorption analysis. Clarithromycin as an active drug molecule with carbonyl and hydroxyl functional groups in chemical structure was chosen as the drug model and stored in pores of the amine-modified nanoporous carbon. Release of clarithromycin from modified nanoporous carbon was investigated in mouth and stomach pH values. The results showed that this drug carrier can transfer the drug up to stomach without any leak or release. The release time was investigated, and the results showed that the carrier is also successful for the controlled-release delivery.     

Sequential injection system for on-line analysis of total nitrogen with UV-mineralization

An automatic method for the determination of total nitrogen in wastewater by sequential injection analysis and mineralization with UV radiation has been developed. The method is based on the mineralization of the samples with sodium persulphate in basic medium under UV radiation. Small volumes of sample and reagents are firstly aspirated into a single channel and then propelled by flow reversal to the UV reactor and then to the detector. The organic and inorganic nitrogen compounds are oxidized to nitrate that is then measured at 226 nm. The sequential injection procedure has been optimized and the factors affecting the efficiency of the oxidation have been studied with a number of test substances with different chemical structures and properties. Solutions in the concentration range 1-56 g l⁻¹ of nitrogen can be analyzed with the described procedure. The sample rate is of 30-40 samples h⁻¹. The LOD is 0.6 mg l⁻¹ N and the reproducibility is 1.8% (28 mg l⁻¹ N). Organic carbon in the form of glucose was added to a number of test solutions to study the potential interference of organic matter.The method was compared with the Kjeldahl digestion method by analyzing 15 wastewater samples with both methods. The nitrate and nitrite content of the non-oxidized samples were subtracted from the corresponding nitrogen content determined after photo-oxidation and the value compared with the Kjeldahl nitrogen content.     

Photooxidation of polymers: Relating material properties to chemical changes

This paper is devoted to a comprehensive study of the photo-oxidation of polymeric materials with the goal of correlating modifications of the polymer properties at the molecular and macroscopic levels. Several techniques were used to characterise the modifications of the chemical properties and mechanical behaviour over time under UV light. The methodology was developed on materials used as organic coatings; initially, a well-characterised phenoxy resin (PKHJ^®) was chosen as a model and then the approach was applied to an acrylate-melamine thermoset currently used as a topcoat in the automotive industry. Analysis of degraded samples by IR spectroscopy allowed us to propose a photo-oxidation mechanism. This mechanism suggested that chain scission occurred under photo-oxidation. To entirely understand the degradation of the polymers, gel fraction, thermoporosimetry, DMA, AFM nanoindentation and micro-hardness determinations were performed. The results showed that crosslinking reactions occurred in competition with chain scission and explained for the first time why crosslinking reactions were quite prevalent. Based on the obtained results, quantitative correlations were made between the various criteria of degradation, thus relating the chemical structure changes to the mechanical property modifications.     

Activated carbon prepared from polyaniline base by K2CO3 activation for application in supercapacitor electrodes

An activated carbon was prepared from a polyaniline base using K₂CO₃ as an activating agent. The morphology, surface chemical composition, and surface area of the as-prepared carbon materials were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, and Brunauer?CEmmett?CTeller measurement, respectively. Electrochemical properties of the as-prepared sample were studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6?mol?L^?1 KOH aqueous solution. Compared with the non-activated carbon, activated carbon showed superior capacitive performance. The activation carbon presented a high specific gravimetric capacitance of 210?F?g^?1. The good electrochemical performance of the activated carbon was ascribed to well-developed micropores, high surface area, the presence of nitrogen and oxygen functional groups, and larger pore volume.     

Interfacial Properties of Poly(Caprolactone) and Derivatives

Abstract

Monolayers of biodegradable polymers, poly(caprolactone) (PCL), poly(caprolactone) diol (PCL‐diol), and poly(caprolactone) triol (PCL‐triol) in the air/water interface were studied and characterized. The Langmuir–Blodgett technique was used for the monolayer transfer onto hydrophilic and hydrophobic solid substrates. The results obtained in both cases are dependent on the functional groups incorporated in the respective polymers. The surface energy (SE), and the polar and dispersion contributions, γ^p and γ^d, respectively, were obtained by wettability measurements. For polymeric spin‐casted thin films deposited over glass, the results also indicate an increment in the polymer hydrophilicity by hydroxyl groups insertion.     

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L^?1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.     

Pore structure and adsorption properties of stone active carbons prepared by physicochemical and chemical activation methods

Active carbons (ACs) with diverse microporous and developed mesoporous structures were prepared by chemical and phisochemical activation methods from walnut shells, fruit stones, and grape seeds. The surface chemistry was studied by chemical titration and spectroscopy in the IR, UV, visible, and near IR regions. The ACs prepared by chemical activation contain carboxyl and phosphate groups, which impart acidic properties to the surface. Basic functional groups are mainly formed on the ACs prepared by physicochemical activation. The AC surface has a complicated chemical composition, which results in high adsorpion activity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 744–748, May, 2006.     

Study of the photodegradation of epoxy polymers with slow positron annihilation spectroscopy

The photodegradation of an amine‐cured epoxy coating after exposure to accelerated UV‐340 and UV‐313 irradiation was investigated with an atomic‐level technique, positron annihilation spectroscopy (PAS), which detected and characterized the free volumes and defects as a function of the depth. Significant changes in the subnanometer defect parameters S and W were observed as a function of the exposure time near the surface. This was interpreted as due to a loss of the free volume and hole fraction resulting from photodegradation. A dead layer near the surface, resulting from UV irradiation from the surface up to a thickness of 0.4 μm, at which there was nearly no positronium formation, was observed. Correlations between physical defects from PAS in terms of the free volumes and chemical defects from electron spin resonance spectroscopy in terms of free radicals and chemical structural changes measured by ultraviolet–visible and Fourier transform infrared spectroscopy were established. A high sensitivity of PAS for detecting the early stage of degradation, on the order of hours for UV‐313 and on the order of days for UV‐340 irradiation, was observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2441–2459, 2004     

EFFECTS OF ORGANIC COLORANTS ON PHOTO-INITIATED CROSSLINKING AND PHOTO-OXIDATION DEGRADATION OF POLYETHYLENE AND RELATED MECHANISM

The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations,X-ray photoelectron spectroscopy (XPS),mechanical property tests,UV spectroscopy,and light microscope.The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) sam...     

Some surface aspects of the photo-oxidation of polystyrene films as revealed by ESCA: Part II—Irradiations in air

The changes in surface chemistry during the photo-oxidation (λ > 290 nm) of polystyrene films in air have been monitored by means of ESCA. The data reveal that the reactions involve the ring opening of the pendent phenyl groups and that the rate and extent of oxygen uptake are strongly dependent on the partial pressure of oxygen at the gas/solid interface. Comparison of cyclic and continuous irradiations indicates that photo-oxidation in the surface is influenced by the presence and extent of dark periods.     

Plasma surface modification of poly (l-lactic acid) and poly (lactic-co-glycolic acid) films for improvement of nerve cells adhesion

Radio frequency (RF) plasma treatment in O₂ was applied to modify the surface of poly (l-lactic acid) (PLLA) and poly (d,l-lactic acid-coglycolic acid) (PLGA) as biodegradable polymers. The surface structure, morphology, wettability and surface chemistry of treated films were characterized by water drop contact angle measurement, scanning electron microscope (SEM), optical invert microscope, differential scanning calorimetry (DSC) and ATIR–FTIR spectroscopy. The cell affinity of the oxygen plasma treated film was evaluated by nervous tissue B65 cell culture in stationary conditions. The results showed that the hydrophilicity increased greatly after O₂ plasma treatment. The results showed that improved cell adhesion was attributed to the combination of surface chemistry and surface wettability during plasma treatment. Cell culture results showed that B65 nervous cell attachment and growth on the plasma treated PLLA was much higher than an unmodified sample and PLGA. Surface hydrophilicity and chemical functional groups with high polar component play an important role in enhancing cell attachment and growth.     

Photochemical behavior of inorganic and organic selenium compounds in various aqueous solutions

Selenium possesses interesting chemical, biochemical and geochemical behaviors. However, studies of its photochemical properties in aqueous systems are scarce. A better understanding of these phenomena is of great importance for further application of such properties to selenium speciation. In this work, the photochemical behavior of selenium and some of its organic compounds have been systematically studied in various aqueous matrices under UV irradiation at 300 nm. It was observed that the photochemical oxidation rate of Se(IV) to Se(VI) was greatly enhanced in the presence of HN0₃ at ≥1 × 10⁻³ M, but not by NaNO₃. However this photo-oxidation could be inhibited by the presence of Cl⁻. Under UV irradiation, organoselenium compounds went through two successive photochemical reactions in pure water: a direct photolysis (photo-cleavage) followed by a photo-oxidation to form Se(VI). These two steps could also be greatly accelerated in presence of NO₃⁻ although the second step required an acidic condition. The photo cleavage rates varied from one organic compound to another and 10-fold differences were observed. Similarly to Se(IV), the further oxidation to Se(VI) could be prevented by Cl⁻ for all studied organoselenium compounds. Detailed reaction mechanisms involving OH radicals are proposed to explain Se photochemical behaviors in different matrices.     

Electrofluorochromic Detection of Cyanide Anions Using a Nanoporous Polymer Electrode and the Detection Mechanism

An electrofluorochromic (EFC) conjugated copolymer ( P_EFC ) containing carbazole and benzothiadiazole (BTD) moieties is synthesized through Suzuki coupling followed by electrochemical polymerization, resulting in a nanoporous EFC polymer electrode. The electrode exhibits high sensitivity and selectivity in the EFC detection of cyanide anions (CN^?) in largely aqueous electrolyte (67 vol % water) because electrochemical oxidation of P_EFC leads to significant fluorescence quenching, and the presence of different concentrations (1 to 100 μM ) of CN^? in the electrolyte can weaken the oxidative quenching to substantially different extents. Although P_EFC is hydrophobic in the neutral state, it is converted to radical cation/dication states upon oxidation, rendering the P_EFC some hydrophilicity. Moreover, its nanoporous morphology provides a large surface area and short diffusion distance, facilitating the movement of CN^? in the electrolyte into the P_EFC film to interact with receptors. Density functional theory calculations show that the noncovalent interaction between electron‐deficient BTD and nucleophilic CN^? is energy favorable in the oxidized states in both aqueous and organic media, suggesting that the specific π^?–π⁺ interaction plays the main role in the CN^? detection.