Surface Of Polymeric Materials Research Articles

Detection and speciation of brominated flame retardants in high‐impact polystyrene (HIPS) polymers

Polymeric materials have been suggested as possible environmental sources of persistent organic pollutants such as flame retardants. In situ, micrometre-scale characterization techniques for polymer matrix containing flame retardants may provide some insight into the dominant environmental transfer mechanism(s) of these brominated compounds. In this work, we demonstrate that micro X-ray fluorescence spectroscopy (μXRF), focused ion beam scanning electron microscopy (FIB-SEM) combined with energy dispersive X-ray spectroscopy (EDS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are promising techniques for the elemental and chemical identification of brominated fire retardant compounds (such as the deca-congener of polybrominated diphenyl ether, BDE-209) within polymeric materials (e.g. high-impact polystyrene or HIPS). Data from μXRF demonstrated that bromine (Br) inclusions were evenly distributed throughout the HIPS samples, whereas FIB SEM-EDS analysis revealed that small antimony (Sb) and Br inclusions are present, and regionally higher concentrations of Br surround the Sb inclusions (compared to the bulk material). Four prominent mass-to-charge ratio peaks (m/z 485, 487, 489 and 491) that correspond to BDE-209 were identified by ToF-SIMS and can be used to chemically distinguish this molecule on the surface of polymeric materials with respect to other brominated organic molecules. These techniques can be important in any study that investigates the route of entry to the environmental surroundings of BDE-containing materials.

Pathway of programmed cell death in HeLa cells induced by polymeric anti-cancer drugs

Synthesis of anticancer polymeric materials plus their biological applications is one of the most charming and active research areas in biological functional materials. However, the predominant mechanisms for controlling cancer cell viability are not yet clear. In this work, cell culture polymeric materials co-immobilized with death signal proteins interferon-γ (IFN-γ)/tumor necrosis factor-α (TNF-α) on the surface were prepared by photochemical method to develop an anticancer polymeric drug model. Various characterizations on the microstructures and compositions, including the Fourier transform infrared spectroscopy, UV absorption spectroscopy, fluorescence measurement, atomic force microscopy, and electron spectroscopy for chemical analysis, were performed. For addressing the biological applications, we investigated systematically the death pathways of HeLa cells attached onto the drug model by means of a series of cell-biology techniques. It was demonstrated that the IFN-γ plus TNF-α co-immobilized on the polymeric material surface exhibited more notable inhibitive effects than the free IFN-γ plus TNF-α, and the induced HeLa cells were mainly along apoptosis-like PCD with the translocation of EndoG from the cytoplasm to the nucleus. These findings indicate that the polymeric drugs with the co-immobilized IFN-γ plus TNF-α may offer significant potentials for therapeutic manipulation of human cervical cancer.

Preliminary in vivo study of apatite and laminin‐apatite composite layers on polymeric percutaneous implants

A polymeric material coated with a hydroxyapatite (HA) layer would be useful as a flexible percutaneous device with good biocompatibility and resistance to bacterial infection. We have recently developed a simple, safe, and mild coating process to form an HA layer on the surfaces of polymeric materials. In this study, our coating process was applied to an ethylene-vinyl alcohol copolymer film. The resulting HA-coated film was percutaneously implanted in the scalp of a rat to examine the stability and biocompatibility of the HA layer. From the results of histological analysis, the HA layer remained undissolved on the film surface under the skin tissue even 3 days after implantation. Owing to the good biocompatibility of HA, the HA-coated film suppressed a host's foreign-body response and integrated with the surrounding skin tissue for as long as 14 days, in a similar fashion to a conventional percutaneous device composed of ceramic HA. Immobilization of a cell adhesion protein, laminin, into the HA layer was found to improve the adhesion strength between the film and the surrounding skin tissue without compromising good biocompatibility of HA. Our coating process to form HA and laminin-HA composite layers would be useful in fabricating polymeric percutaneous devices with a reduced risk of bacterial infection, although further in vivo studies are required.

A New Method of Making Grating - Etched by SPM

The original grating is etched by using the nanometer etching function of Scanning Probe Microscopy (SPM). There are five grooves etched on the surface of polymer material. The grating constant is 796.87 nm, so the fringe density is 1254 lp/mm. Diffraction pattern of the original grating is obtained on Michelson interferometer. A new method of making original grating is found. Since the Nominal Tip Radius of Curvature (NTRC) of Etched Silicon Probe (ESP) of used Veeco SPM is 5-10 nm, the etching grating should have fringe density of 50 000 -100 000 lp/mm.

Topographical and chemical characterization of polymer surfaces modified by physical and chemical processes

AbstractNanoscale changes to the surface of polymeric materials enables changes in materials' adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is therefore used in applications such as antimicrobial or non‐fouling materials, biosensors, and active packaging. The range of available modification and analytical techniques used across laboratories prevents accurate comparison of techniques in terms of their effects on surface chemistry and topography. It was therefore our goal to evaluate the effects of four surface modification techniques (chromic acid, piranha solution, ultraviolet irradiation, and oxygen plasma) on polyethylene films. Changes in surface chemistry and topography were quantified using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), contact angle measurement, and direct measurement of available surface carboxylic acids. Roughness increased in the order: piranha (57.7 nm); oxygen plasma (76.3 nm); UV irradiation (76.4 nm); chromic acid (120 nm). Hydrophobicity decreased in the order: piranha (77.20), chromic acid (73.50), oxygen plasma (61.70), UV irradiation (58.70). Functionalization (by IR absorbance intensity between 1680–1780 cm−1) increased in the order: oxygen plasma (0.06), piranha (0.09), chromic acid (0.34), UV irradiation (0.50). By analyzing these methods using consistent analytical techniques, side‐by‐side comparisons have been accurately made. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Devices for measuring electrostatic generation and dissipation on the surfaces of polymeric materials

Dynamic electrostatic generation and dissipation on polymer surfaces are of great importance for materials such as yarns and films. To support fundamental research in this area, innovative devices and experimental techniques that can lead to a better understanding of these phenomena are of obvious academic and industrial interest. This paper reports the development of devices for testing the electrostatic generation/dissipation properties of polymer surfaces. These devices include a tester for assessing moving yarns, a high-resistance system to measure the yarn's linear resistance, a tester for evaluating stationary fabrics or films while rubbing against a moving surface and a contact charge tester for investigating charge generated by contacting of two surfaces. These devices enable the study of the influences of relative moving speed, yarn tension, electrostatic charge properties of yarns, as well as contact pressure, rubbing speed, number of rubbings or contacts on the static charge properties of films.

Preparation and Characterization of Oil-Dosed Phases Created by Supercritical Fluid on Polymer Materials

Ultra-high molecular weight polyethylene (UHMWPE) and polyamide 66 (PA66) were used as model polymers in order to conduct research on the preparation and characterization of oil-dosed phases created by supercritical fluid on polymer materials. Dioctyl adipate (DOA, Mw = 370) and alkyldiphenylether (ADE, Mw = 440) were the lubrication oils used to impregnate the polymer. Oil impregnation conditions were controlled to between 40 and 150°C and 10 and 20 MPa in a supercritical carbon dioxide (scCO2) environment. Experimental results showed that the total amount of oil impregnation correlated with processing temperature and duration. After impregnation, phases with a crystal structure different from the inside were observed on the polymer surface areas. The depth profile and chemical distribution of oil-dosed phases by scCO2 impregnation were analyzed using Fourier-transform infrared (FTIR) spectroscopy. FTIR spectroscopy results have shown that it is possible to create phases having high concentrations of lubrication oil at a depth of about 25–30 μm from the surface of polymer materials.

Wyladowania koronowe w powietrzu jako metoda modyfikowania warstwy wierzchniej materialow polimerowych

The physical and chemical principles of the process of polymeric material surface layer (WW) modification using corona discharge (WK) in an air were discussed. The phenomenon of low temperature plasma formation and the way of its interaction with polymer surface were described. Basic aims of the process of modification with WK were presented as well as the results obtained this way for particular polymers, among others PE, PP, PVC, PET. In case of PE and PP also the composite materials with polyolefine matrix or fiber filler were considered. The possibilities of corona discharge use in graft polymerization were noticed. Also numerous directions of practical use of the changes of polymers' surface layers caused by corona discharge were marked.

Hybrid coating of hydroxyapatite and collagen within poly(D,L‐lactic‐co‐glycolic acid) scaffold

To improve the cell-affinity of biodegradable polymer scaffold, coating hydroxyapatite (HA) or collagen on the surface of polymer materials seemed to be a strategy to combine both advantages of them. The objective of this study was to develop a novel method to introduce HA and collagen inside polymer scaffold uniformly. HA and collagen suspension was mixed with paraffin microspheres, and molded to form a composite sample. After the sample was dried, HA/collagen composite was left among and on the surface of paraffin microspheres. Poly(D,L-lactic-co-glycolic acid) (PLGA) (50/50) solution was cast into the inter-space of the paraffin microspheres and dried. Afterwards, the paraffin was dissolved and removed, HA/collagen was transferred to the surface and even inside of the pore wall of PLGA scaffolds. Collagen fibers and HA particles which were inlaid inside the PLGA pore wall could help to enhance the coating strength between HA/Col coating and the pore wall surface of the PLGA scaffold. The scaffolds with HA/Col coating were expected to exhibit desirable properties in bone tissue engineering.

The formation of convex microstructures on the surface of polymeric materials under laser irradiation

The formation of convex structures on the surface of colored samples of polymethylmethacrylate (PMMA) when they are irradiated by the second-harmonic radiation of a neodymium laser has been experimentally investigated. The dependences of the height and the diameter of the resulting convex microstructures on the energy density of the laser pulse have been investigated. The formation threshold of structures has been determined for various samples, and the optimum structuring regimes have been found. The possibility of obtaining arrays of convex structures (microlenses) and structures in the form of convex fillets has been demonstrated.

Surface morphology study of fluorocarbon macromolecule deposited on polyimide substrates

Plasma treatment and polymerization have been widely applied to modify the surface of polymer materials in the last decades. In this paper, fluorocarbon macromolecules were deposited on polyimide (PI) substrates by R.F. magnetron sputtering with argon gas as plasma, and PTFE as targets. The surface morphology of the deposited substance was observed by Scanning Electron Microscopy (SEM). It was found that some segregated grains deposited on the PI substrates tended to be finer, more uniformly dispersed and more round with increasing energy. At certain conditions (1 Pa, 400 W, 60 min), quite uniform nanometer sized particles 40–50 nm have been obtained. Fluorocarbon macromolecules were also observed by Atom Force Microscopy (AFM). They have form of round particles with tendency to grow in vertical direction. They are packed closely to each other. The growth mode of fluorocarbon macromolecule is to be one-dimensional island. The experimental results obtained by Transmission Electron Microscopy (TEM) show that in the range of 60 min, the speed of nanometer sized fluorocarbon macromolecule deposition was constant of approximately 10 nm/min.

Development of a highly sensitive analytical technique for surfactants by time-of-flight secondary ion mass spectrometry

We have developed a highly sensitive analytical technique for detecting the distribution of surfactants existing on a polymer surface. We studied the chemical modification of surfactants with the hydroxyl group by using amine-containing compounds in the gaseous phase at 23 °C; then, we performed measurements by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). We found that 4-(dimethylamino) phenyl isocyanate as a modification reagent is capable of modifying the hydroxyl group when 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) is used as a catalytic agent. We demonstrated this modification with stearyl alcohol on a polymer material surface. The signal sensitivity of stearyl alcohol after the modification increased considerably in comparison with that of the unmodified stearyl alcohol. Moreover, we confirmed that this modification method can be used for the distribution analysis of surfactants. The distribution conditions of traces of surfactants with the hydroxyl group can be observed clearly by using this modification method.

Change in surface of polymer materials upon irradiation of accelerated micro-particles

As a new method of use of a particle accelerator (ionizing radiation generator), we irradiated accelerated micro-particles of silver (Ag) onto polymer materials such as polyimides, glass, ceramics and semi-conductors. The particles can be generated at a Van de Graaff electrostatic accelerator operating at 1–3MV. The velocity was around 1–10km/s, size of diameter was about 1–10μm and charge was about 1–2μC. We investigated the change in surface of materials upon irradiation, by using laser microscope, atomic force microscope and scanning electron microscope. Crater-shaped irradiation spots having limb structure were found, and their diameter and depth were evaluated, ranging in a few micrometers. The planar distribution of the projectile around the irradiation spot was examined with energy dispersive X-ray spectroscopy. Correlation between size of the irradiation spots and kinetic energy of the accelerated micro-particles was investigated, and compared with an empirical formula and molecular dynamics study. Numerical simulation dealing with dynamic behaviour of elastic structure was carried out based on SPH (Smoothed Particle Hydrodynamics) method, a kind of (virtual) particle method. The simulation also found that a crater-shaped spot having limb structure is formed upon collision of the accelerated projectile with the target-materials. The results of simulation were compared with the experimental observations. These experiment and simulation are important for the evaluation of damages and resistance of polymer materials used in the space, such as the thermal control material, and cover glass of solar cells etc., towards space debris and dusts. It would be complement the on-ground radiation resistant tests on the materials conducted by using electron and ion beam accelerators.

Plasma functionalization of polypropylene with acrylic acid

Tailor-made surfaces of polymer materials are required, e.g. for the improvement of their printability or adhesion and for many applications concerning medical equipment or life science products. Polypropylene (PP) is one of the few common polymers widely used in technical applications. But often the surface chemistry has to be modified by introducing special chemical functionalities like carboxylic groups or by coating the PP with thin films, e.g. with poly(acrylic acid). The radio frequency plasma technique was used for functionalization and coating of PP by using acrylic acid as monomer gas. After optimization of the plasma parameters, high concentration of carboxylic groups as well as solvent-stable thin films with good adhesion to the PP substrates could be obtained. Characterization of the plasma-modified PP substrates was performed by using the captive bubble method, ESCA (Electron Spectroscopy for Chemical Analysis) and fluorescence spectroscopy in combination with derivatization techniques and FTIR (Fourier Transformation Infrared Spectroscopy). The thickness of the polymer films was analyzed by AFM (Atomic Force Microscopy).

Studies of polymer surfaces by sum frequency generation vibrational spectroscopy.

Recently, sum frequency generation (SFG) vibrational spectroscopy has been developed into a powerful technique to study surfaces of polymer materials. This review summarizes the significant achievements in understanding surface molecular chemical structures of polymer materials obtained by SFG. It reviews in situ detection at the molecular level of surface structures of some common polymers in air, surface segregation of small end groups, polymer surface restructuring in water, and step-wise changed polymer blend surfaces. Studies of surface glass transition and surface structures modified by rubbing, plasma deposition, UV light irradiation, oxygen ion and radical irradiation, and wet etching are also discussed. SFG probing of polymer surfaces provides valuable insights into the relations between polymer surface structures and surface properties, which will assist in the design of polymer materials with desired surface properties.

The Evaluation of AFM Roughness of the Surface of Polymeric Materials Used in Surgery

The Evaluation of AFM Roughness of the Surface of Polymeric Materials Used in Surgery

The Evaluation of AFM Roughness of the Surface of Polymeric Materials Used in Surgery

Polypropylene (PP) meshes of different kinds are widely used in medical surgery. Polylactide (PL) belongs to the class of biopolymers of various applications in medicine. It was proposed to cover PP meshes by PL layer to improve the biocompatibility of surgery meshes [1]. Atomic Force Microscopy was used for the preliminary studies of topography of the following polymeric materials: -the surface of polypropylene mesh [Fig. 1, 1′], -the surface of polylactide layer deposited on mica [Fig. 2, 2′], -the surface of polylactide layer deposited on polypropylene mesh [Fig 3, 3′]. The roughness of the samples was determined as the root mean square (RMS) parameters, which were as follows (in nm): -PP mesh RMS = 3.1 - 3.4 -PL film on mica RMS = 1.5 - 0.8 -PP mesh covered with PL film RMS = 3.3 It can be concluded that the presence of polylactide layer on polypropylene leads to the increase of external surface; this can result in the better affinity of tissues to the mesh.

Mucin coating on polymeric material surfaces to suppress bacterial adhesion

Mucin, a group of large glycoproteins, constitutes one of the major components of mucous which covers the lumenal surfaces of epithelial organs and serves as a physical barrier between the extracellular milieu and the plasma membrane. The molecules have a generic structure consisting of a thread-like peptide backbone with densely packed carbohydrate side chains. Protein and carbohydrate contents are about 30 and 50%, respectively. On hydrophobic materials in aqueous environments the naked parts of mucin’s protein backbone will adhere due to their hydrophobicity, while the carbohydrate side chains are thought to orient themselves away from the surface. This gives the mucin molecules their unique properties as surfactants, i.e. they tend to adsorb to hydrophobic surfaces via protein-surface interactions while they hold water molecules via their hydrophilic oligosaccharide clusters. In the present work, bovine submaxillary gland mucin (BSM) is purified by SEC and subsequently characterized with PAGE. Four polymeric materials, PMMA, silicone, Tecoflex® polyurethane and polystyrene, are selected as coating targets. Contact angle measurements show significant changes in these materials after coating with BSM. Surface concentrations of adsorbed BSM are determined by amino acid analysis and found to correlate well with observed reductions in contact angle. Both Staphylococcus aureus and CNS S. epidermidis are used to contaminate uncoated and BSM coated surfaces of all four materials, demonstrating a correlation between suppression of bacterial adhesion and surface concentration of BSM. Thus, bacterial counts on the coated PMMA, PS, PU and silicone specimens amount to ≈3, 10, 8 and 30% of the counts found on their uncoated counterparts. These results suggest that mucin coatings could profitably be employed to reduce the risk of microbial infections on polymeric biomaterials.

The effect of fluorinated surface modifying macromolecules on the surface morphology of polyethersulfone membranes

Polyethersulfone (PES) has been recently adopted for membrane materials in applications such as ultrafiltration and haemodialysis. As a biomaterial, the factors which affect the blood compatibility of PES membranes include surface energetics, hydrophobicity, and surface morphology. Surface fluorination of materials has been found to create surfaces with improved blood compatibility and chemical stability. One novel approach to generating fluorinated polymer surfaces has included the use of fluorinated surface modifying macromolecules (SMMs). These macromolecules have been reported to establish fluorinated functional groups at surfaces of polymeric materials without significantly affecting the physical properties of the base polymer. However, to date there has been relatively little information published on the nature of the surface structure for PES materials containing these SMMs. In this study, synthesized SMMs with varying chemical compositions were characterized and blended with PES, and fabricated into flat sheet membranes. The bulk thermal transitions of PES materials were not significantly altered by the addition of 4 wt% SMMs. Contact angle data showed that the addition of SMMs in PES created more hydrophobic surfaces, accompanied by an increase in surface heterogeneity. X-ray photoelectron spectroscopy studies confirmed the presence of elemental fluorine at the surface. Through microscopy studies, it was shown that surface modification was achieved by the migration of SMM concentrated microdomains to the air-membrane interface. The generated microdomains (approximately 1-2 μm in diameter) are dispersed within the top 8 μm of the surface. The concentration of microdomains was gradually depleted from the surface to the bulk of the membrane. A schematic of the morphology for SMMs within the PES membrane surface was proposed.

Self-Affine Measurements on the Fracture Surface of Plastic Materials by AFM

AbstractThe self-aff'me behavior of fracture surfaces of polymeric materials was qualitatively and quantitatively studied. SEM images of fracture surfaces of both polypropylene and polystyrene show Chevron marks at several magnifications. In addition, for polystyrene the mirror and Hackle zones were also observed. For quantitative analysis, the average roughness exponent, ζ, of height profiles generated by AFM images, was estimated by applying the variable bandwidth method. Values of ζ=0.788 and ζ=0.810 were obtained for polypropylene and polystyrene, respectively. These results are in very good agreement with the claimed universal exponent of 0.8 reported in the literature for other non-polymeric materials. By choosing the AFM appropriate operating conditions, measurements of roughness on plastic material surfaces could be performed.