Barbara Trzebicka

Approaches to mitigate polymer-core loss in plastic optical fibers: a review

Within fiber optics, plastic optical fibers (POFs) have always had to take a back seat due to their relatively high loss. This kept them as a specialty fiber for illumination, sensing and low speed short data links. However, continued research and development on the core materials used in POFs are improving their performance significantly as we are now able to manufacture POFs with low transmission loss, high temperature resistance and stable bandwidth over distance. The improved performance, the ease of installation and the low cost of POFs has led to a renewed interest in these fibers. This review looks at the material developments that have and continue to improve the optical loss factors in POFs. Both intrinsic and extrinsic loss mechanisms are discussed. In particular the intrinsic loss mechanisms are reviewed in greater detail. Intrinsic losses are associated with the chemical and physical structure of the fiber materials, while extrinsic losses are related to losses due to contaminants and various production imperfections.

Graphene oxide-based drug delivery vehicles: functionalization, characterization, and cytotoxicity evaluation

Abstract As a consequence of graphene oxides (GOs) high chemical versatility, there is great interest in functionalized as a nanocarrier for in vitro and in vivo drug delivery. Within this review, the structure and properties of GO that allow covalent and non-covalent functionalization are discussed. In short, toxicity investigations show functionalized GO is biocompatible. Various works demonstrate the potential of GO derivatives as exciting nanocarriers for the loading and delivery of therapeutic drugs.

Polyglycidol-block-poly(ethylene oxide)-block-polyglycidol: synthesis and swelling properties

Triblock copolymers containing central poly(ethylene oxide) blocks and polyglycidol side chains were synthesized using cesium polyoxyethylene glycolates as macroinitiators. Water soluble copolymers containing central blocks of 40 to 230 structural poly(ethylene oxide) units and side chains of 30 to 70 polyglycidol units and relatively narrow molecular weight distribution were obtained. The copolymers were crosslinked with glutar aldehyde and their swelling in water and methanol was investigated.

Poly[tri(ethylene glycol) ethyl ether methacrylate]-coated surfaces for controlled fibroblasts culturing.

Well-defined thermosensitive poly[tri(ethylene glycol) monoethyl ether methacrylate] (P(TEGMA-EE)) brushes were synthesized on a solid substrate by the surface-initiated atom transfer radical polymerization of TEGMA-EE. The polymerization reaction was initiated by 2-bromo-2-methylpropionate groups immobilized on the surface of the wafers. The changes in the surface composition, morphology, philicity, and thickness that occurred at each step of wafer functionalization confirmed that all surface modification procedures were successful. Both the successful modification of the surface and bonding of the P(TEGMA-EE) layer were confirmed by X-ray photoelectron spectroscopy (XPS) measurements. The thickness of the obtained P(TEGMA-EE) layers increased with increasing polymerization time. The increase of environmental temperature above the cloud point temperature of P(TEGMA-EE) caused the changes of surface philicity. A simultaneous decrease in the polymer layer thickness confirmed the thermosensitive properties of these P(TEGMA-EE) layers. The thermosensitive polymer surfaces obtained were evaluated for the growth and harvesting of human fibroblasts (basic skin cells). At 37 °C, seeded cells adhered to and spread well onto the P(TEGMA-EE)-coated surfaces. A confluent cell sheet was formed within 24 h of cell culture. Lowering the temperature to an optimal value of 17.5 °C (below the cloud point temperature of the polymer, TCP, in cell culture medium) led to the separation of the fibroblast sheet from the polymer layer. These promising results indicate that the surfaces produced may successfully be used as substrate for engineering of skin tissue, especially for delivering cell sheets in the treatment of burns and slow-healing wounds.

Numerical analysis of EPR spectra of coal, macerals and extraction products

Abstract The multi-component structure of the EPR spectra of Polish medium metamorphosed coal, its macerals and their pyridine extractrion products were analyzed. The bes numerical approximation of the EPR spectra for exinite, vitrinite and their extraction residues was obtained when two Lorentz and one Gauss curve were chosen for calculation. The EPR spectra of inertinite and its residue are superposition of two Lorentz lines. The EPR spectra of the extracts are fitted by single Lorentz lines. Four groups of paramagnetic centres which give the EPR signals with different ranges of linewidths are present in the macerals and the extraction products. Paramagnetic centres with the narrow EPR lines are present not only in inertinites, but also in exinites and vitrinites. Each of the four types of paramagnetic centres is present in macromolecular and molecular part of the macerals. As was expected, four component lines were detected for the EPR spectra of the coal and its residue. Paramagnetic centres responsible for the broad lines are located on structures consisting of a few aromatic rings. Paramagnetic centres of large aromatic structures are responsible for the narrow lines.

Polymeric nanoparticle engineering: from temperature-responsive polymer mesoglobules to gene delivery systems.

A novel approach for the preparation of nano- and microcapsules in aqueous solutions by using thermoresponsive polymer (TRP) templates (mesoglobules) is described. The method comprised three steps: formation of mesoglobules, coating the templates by seeded radical copolymerization, followed by core dissolution and core removal upon cooling. When mesoglobule entraps biomacromolecules during the process of their formation, it makes it possible to load a controlled amount of bioactive compounds without covalent attachment. Special attention is paid to the mesoglobule dissolution upon cooling, as well as their loading efficiency. Details on the outer shell formation and the possibilities for targeting ligands incorporation and control of the shell porosity are discussed. Finally, the seeded radical copolymerization was used for covering DNA complexes with cationic copolymers bearing TRP blocks. This Review is an attempt to convince researchers of the promising perspectives for using mesoglobules as potential reservoirs, carriers, and transferring agents for biologically active substances.

Polyether nanoparticles from covalently crosslinked copolymer micelles.

Double hydrophilic block copolymers poly(ethylene oxide)-b-polyglycidol were synthesized using living anionic polymerization. The polyglycidol blocks were made hydrophobic by the esterification of a part of hydroxyl groups with cinnamic acid, thus simultaneously attaching UV-sensitive double bonds to the polymer backbone. The block copolymers were found to spontaneously associate in aqueous solution forming well-defined micelles, where the corona of the micelles was formed of EO units and the cores consisted of hydrophobic glycidyl cinnanamate units. The critical micelle concentration was determined by light-scattering measurements and fluorescence spectroscopy. Stabilization of micelles was obtained by covalently crosslinking the cores of polyether micelles formed from amphiphilic block copolymers of the type poly(ethylene oxide)-b-poly(glycidol-co-glycidyl cinnamate) (denoted EO(113)-b-(Gl(33)-co-GlCA(33-x))). To obtain stable nanoparticles double bonds of cinnamate units contained in core were crosslinked under UV irradiation. The kinetics of the stabilization process was investigated using SEC-MALLS and UV spectroscopy. The parameters of the micelles and nanogels were calculated from the light-scattering data.

CVD growth of 1D and 2D sp 2 carbon nanomaterials

The discovery of graphene and carbon nanotubes (rolled-up graphene) has excited the world because their extraordinary properties promise tremendous developments in many areas. Like any materials with application potential, it needs to be fabricated in an economically viable manner and at the same time provides the necessary quality for relevant applications. Graphene and carbon nanotubes are no exception to this. In both cases, chemical vapor deposition (CVD) has emerged as the dominant synthesis route since it is already a well-established process both in industry and laboratories. In this work, we review the CVD fabrication of graphene and carbon nanotubes. Initially, we briefly introduce the materials and the CVD process. We then discuss pretreatment steps prior to the CVD reaction. The discussion then switches to the CVD process, provides comparative data for thermal CVD and plasma-enhanced CVD, and includes coverage of kinetics, thermodynamics, catalyst choice, and other aspects of growth as well as post production treatments. Finally, conclusions are drawn and presented.

Review: tailoring the properties of macroporous carbon foams

Carbon foams are non-toxic, highly porous, light materials which demonstrate a wide range of properties. That fact allows carbon foams to be applied in many areas of life, ranging from electronics industry, through machinery, car and construction industry, to environmental protection. The properties of carbon foams are closely connected with their density, and its value is especially influenced by their internal structure, i.e. mainly size and number of pores, pore wall thickness and structural order of solid matrix. That is why it is possible to design the properties of carbon foams by controlling their growth. The main control factors are selecting the suitable raw material, the process parameters (temperature and pressure) and the suitable production method. Additionally, the properties of carbon foams may be modified by doping them with carbon or mineral fillers. The second method is the enrichment of carbon matrix with heteroatoms, mainly of boron and nitrogen. This paper presents the review of the possibilities of tailoring the structure and properties of carbon foams, based on the current level of knowledge available in the literature.

Microwave saturation of e.p.r. spectra of vitrinite and products of its pyridine extraction

Abstract The influence of microwave saturation on e.p.r. lines of vitrinite and products of its pyridine extraction was investigated. E.p.r. spectra taken at higher microwave power have clearly revealed the complex structure of resonance absorption lines both for vitrinite and the residue. The best numerical approximation of e.p.r. spectra for both samples was obtained when two Lorentz and one Gauss curve were chosen for calculation. The values of the g -factor, the widths of the components and their fraction in the total spectrum were determined. The e.p.r. spectrum of the pyridine extract of vitrinite was fitted with a single line of Lorentz shape.