Fabrication of a planar polymeric deformation Bragg sensor component by excimer laser radiation

Polymethylmethacrylate is irradiated by a UV-laser in order to modify its optical properties photochemically. Thus, by a lithographic method, the refractive index can be locally increased in a controllable way permitting the manufacturing of integrated-optical waveguiding and dispersive structures at the surface of a planar polymer chip. By this method, a polymeric Bragg sensor in integrated-optical form was fabricated by the UV-light of an excimer laser. The surface topography and the functional properties of the planar polymeric deformation Bragg sensor have been examined. Experiments concerning the evanescent field of the sensor have also been carried out in order to clarify the Bragg reflection mechanism.     

The Influence of High Pressure Treatment and Thermal Pasteurization on the Surface of Polymeric Packaging Films

Several common single layer films (PE‐HD, PE‐LD, PP‐BO, PA6‐BO and PET‐BO) and multilayer (PS/PE, PP‐BO/PEpeel and PET‐BO/PE) films were treated by either high pressure (600 MPa) or temperature (80 °C/90 °C) to simulate a high pressure or thermal pasteurization process. The samples were tested by atomic force microscopy (AFM), profile method and surface energy measurements to obtain information about the influence of the treatments on the surface topography and surface energy of the samples and by differential scanning calorimetry and by tensile testing concerning material properties. As key figures arithmetic surface roughness (by AFM at Pulsed Force Mode and profile method), surface energy by surface energy measurement and adhesion between tip and surface by AFM were extracted. Results indicate an influence of both high‐pressure processing and thermal‐processing on the surface roughness of biaxial oriented polymer films as single layer films. Laminated biaxially oriented polymer films showed no changes regardless of which processing was performed. The surface energy was hardly affected by both of the treatments for any stretched, non‐stretched, single or laminated films.     

Biokompatible und bioaktive polymere Beschichtungen

Biocompatible and bioactive polymer surface for most biomedical applications of polymers biocompatible surface properties are highly needed. here we present various methods to immobilize biocompatible and also bioactive hydrogels on polymer surfaces. In one approach, macroinitiator‐based reactive layers are attached to polycondensates which are able to allow the grafting‐from of various hydrogels. on the other hand, it is possible to immobilize hydrophilic polymers on various substrates by plasma and e‐beam treatment. Stability, swelling and biocompatibility of the polymer films could be verified. by incorporating ph and thermo‐responsive groups, it is possible additionally to control the swelling behaviour by external triggers.     

Fabrication of 3-D gelatin-patterned glass substrates with layer-by-layer and lift-off (LbL-LO) technology

The assembly of multilayer films of gelatin onto glass substrates using layer-by-layer and lift-off (LbL-LO) technology to modify the surface topography and chemistry properties of in vitro cell culture scaffolds is described. The ability to generate such nanoscale systems containing cell-adhesive materials on optically transparent substrates with microscale lateral dimensions, nanoscale vertical dimensions, molecular vertical precision, and flexibility in material selection has important implications for tissue engineering, drug discovery, and basic research in cell biology. Toward this goal, a systematic study on the electrostatic adsorption properties of fluorescein 5-isothiocyanate-gelatin B (FITC-gelatin) was completed. In addition, the integration of protein nanoassembly with microlithographic feature definition was used to pattern three-dimensional FITC-gelatin nanofilms on planar glass substrates. The experimental results indicate that FITC-gelatin is negatively charged at pH 9 and can be alternately assembled with a positively charged polyion, poly(diallyldimethylammonium chloride) (PDDA), to form multilayer films on solid templates with thickness of 5-10 nm per bilayer. Furthermore, images of protein/polymer nanocomposites indicate that LbL-LO is an efficient way to realize the designed substrates. These findings will benefit future research on cell culture and tissue engineering that require methods of generating protein patterns to fabricate novel in vitro cell culture systems.     

Optical properties of planar polymer waveguides doped with organo-lanthanide complexes

Lanthanide complexes, Eu(dbm)₃(Phen), [Et₄N][Eu(nta)₄] and Er(dbm)₃(Phen), are employed as luminescent dopants within planar waveguides based on a UV-processable fluorinated polymer material. Thin films doped with each of the complexes are fabricated and their spectroscopic properties investigated in detail. The films act as low loss multi-mode planar waveguides capable of guiding visible and near infrared light emitted following optical excitation of the lanthanide dopants. Judd–Ofelt parameters are calculated for the europium complex dopants and effects of the polymer host environment on the photophysical properties of the chelates are identified. The radiative properties of the europium complexes are also determined viz. their potential for use in optical amplification applications.     

Characterisation of Mechanical Properties of Magnetite‐Polymer Composite Films

Abstract: Time dependent mechanical properties of magnetic polymer films were investigated. These polymer films, synthesised by using solution polymerisation followed by the inverse emulsion process, consist of poly (MMA‐co‐MAA‐co‐BA) and different weight ratios of magnetite nano‐particles. This study deals with the influence of weight ratios of magnetite nano‐particles on the time dependent mechanical properties of hybrid copolymer films. The viscoelastic properties of aforementioned polymer films with 0, 20 and 40% of magnetite nano particles were studied. Ramp‐hold experiments were performed by using a custom‐made tension testing apparatus to evaluate the time dependent stress‐strain behaviour of magnetic polymer films under uniaxial tensile load at different loading strain rates. It can be seen that the magnetite nano‐particles weight percentage of polymer has a strong effect on the stress‐strain relations of polymer films. The polymer with a higher weight ratio of magnetite nano‐particles can sustain higher stress under the same test condition. Experimental data were fitted into 3, 5 and 7 parameter linear viscoelastic models. It is shown that the 7‐parameter Wiechert model leads to better curve‐fitting results for the magnetic polymer material under ramp‐hold experiments.     

Interfacial and Substrate Effects on Local Elastic Properties of Polymers Using Coupled Experiments and Modeling of Nanoindentation

The mechanical properties of polymers near interfaces are important in a number of different fields. For almost two decades, the local dynamics of thin polymer films have been studied in great detail. However, development of an understanding of local mechanical properties has been hindered by the necessary proximity of stiff substrates: mechanical measurements are confounded by interaction with the substrate, convoluting polymer, and substrate properties. In this paper, local elastic properties of thin polymer films near interfaces are directly probed for the first time via nanoindentation experiments on thin films coupled with finite element modeling. A comprehensive set of experimental and numerical modeling results are presented for poly(methyl methacrylate) (PMMA) revealing separately the effects of substrate and interphase polymer. Results indicate the attractive surface significantly affects the properties up to hundreds of nanometers. This new, direct approach to measure local mechanical properties provides new fundamental understanding of interfacial and small‐scale behaviors in polymers and soft matter for application advances in nanocomposites, microelectronics, and biopolymers.     

Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device Applications

Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano‐, and micro‐structured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD‐based technologies in three fields: electronic devices, surface engineering, and biomedical applications.

     

Plasmapolymerschichten als Basis für maßgeschneiderte funktionale Oberflächen

Plasmapolymer coatings for tailor‐made functional surfaces The tailoring of surface properties via polymer coatings is currently a strongly pursued topic in various fields ranging from microsystem technology to bioanalytics. A precise tuning of surface properties, however, is only possible if chemically well‐defined processes are used that usually require reactive surface moieties to which molecules can be coupled. In this contribution we summarize studies that aimed at the modification of inert surfaces. For this purpose reactive groups at the surfaces are generated by plasma polymerisation of allyl amine which results in layers that contain amino groups. Initiator molecules for free radical polymerization processes are then coupled to these amino groups resulting in surfaces from which polymers can then be grown via surface‐initiated polymerization. Using these processes, polymer monolayers with very different properties can be generated by simply using different monomers.     

Morphology and optoelectronic properties of ZnO rod array/conjugated polymer hybrid films

Vertically aligned zinc oxide (ZnO) nanorods were grown on the ITO glass and then coated with the conjugated polymer poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV) to make the hybrid films. Nanorods with different diameters were synthesized to study the influences of ZnO nanorod morphology and polymer infiltration on the photocurrent and optical properties of the hybrid films. Increasing the growth time leads to the formation of ZnO rod array with large rod diameter, large surface area and small inter-rod distance. Small inter-rod distance hinders the filling of DB-PPV into the porous ZnO rod microstructure and lowers the PN junction area. It leads to lower photocurrent of the hybrid film. The red shift of the photoluminescence spectra suggests that filling the polymer into the ZnO rod microstructure favors more planar molecular orientations of the conjugated polymers and leads to an increase in the effective conjugation length.     

Polymer Carpets

The fabrication of defined polymer objects of reduced dimensions such as polymer‐coated nanoparticles (zero‐dimensional (0D)), cylindrical brushes (1D), and polymer membranes (2D), is currently the subject of intense research. In particular, ultrathin polymer membranes with high aspect ratios are being discussed as novel materials for miniaturized sensors because they would provide extraordinary sensitivity and dynamic range when sufficient mechanical stability can be combined with flexibility and chemical functionality. Unlike current approaches that rely on crosslinking of polymer layers for stabilization, this report presents the preparation of a new class of polymer material, so‐called “polymer carpets,” a freestanding polymer brush grown by surface‐initiated polymerization on a crosslinked 1‐nm‐thick monolayer. The solid‐supported, as well as freestanding, polymer carpets are found to be mechanically robust and to react instantaneously and reversibly to external stimuli by buckling. The carpet mechanics and the dramatic changes of the film properties (optical, wetting) upon chemical stimuli are investigated in detail as they allow the development of completely new integrated micro‐/nanotechnology devices.     

Inorganic–Organic Hybrid Polymers for Information Technology: from Planar Technology to 3D Nanostructures

Sol‐gel synthesis allows inorganic–organic hybrid polymer materials (ORMOCER®s) to be produced, which can be functionalized to tailor their physical and chemical properties such as refractive index or optical loss. A particular material system is discussed here, which is synthesized without addition of water and is applied in optical communications. As examples for 2D and 2.5D technology, planar waveguides, stacked waveguides, and microlenses are shown. Using two‐photon polymerization initiated by femtosecond laser pulses, arbitrary 3D structures can be made in the submicrometer range. In particular, 3D photonic crystal structures are described and discussed.     

High‐ versus Low‐Quality Graphene: A Mechanistic Investigation of Electrografted Diazonium‐Based Films for Growth of Polymer Brushes

Electrografting using aryldiazonium salts provides a fast and efficient technique to functionalize commercially available 3?5 layered graphene (vapour‐deposited) on nickel. In this study, Raman spectroscopy is used to quantify the grafting efficiency of cyclic voltammetry which is one of the most versatile, yet simple, electrochemical techniques available. To a large extent the number of defects/substituents introduced to the basal plane of high‐quality graphene by this procedure can be controlled through the sweeping conditions employed. After extended electrografting the defect density reaches a saturation level (～10¹³ cm^?2) which is independent of the quality of the graphene expressed through its initial content of defects. However, it is reached within fewer voltammetric cycles for low‐quality graphene. Based on these results it is suggested that the grafting occurs (a) directly at defect sites for, in particular, low‐quality graphene, (b) directly at the basal plane for, in particular, high‐quality graphene, and/or (c) at already grafted molecules to give a mushroom‐like film growth for all films. Moreover, it is shown that a tertiary alkyl bromide can be introduced at a given surface density to serve as radical initiator for surface‐initiated atom transfer radical polymerization (SI‐ATRP). Brushes of poly(methyl methacrylate) are grown from these substrates, and the relationship between polymer thickness and sweeping conditions is studied.     

Perfluorocyclobutyl Copolymers for Microphotonics

The copolymerization of aryl bis‐ and tris‐trifluorovinyl ether monomers yields aromatic perfluorocyclobutyl (PFCB) polymers, via thermally initiated step‐growth cycloaddition chemistry. PFCB polymers and their copolymers enjoy a unique combination of attributes well suited for applications in photonic technologies, such as broad tailorability of refractive indices and thermo‐optic coefficients, low transmission losses at 1300 and 1550 nm, high thermal, mechanical, and optical stability, and excellent melt and solution processability. Planar PFCB structures can be processed by direct micro‐transfer molding, which is a first step towards rapid soft‐lithographic fabrication of polymer planar lightwave circuits. Copolymerization chemistry and processing parameters and characterization, including thermal (T_g = 120–350 °C) and optical properties (refractive indices from 1.443 to 1.508 at 1550 nm; thermo‐optic coefficients dn/dT = –7×10^–5 K^–1 to –1.5 × 10^–4 K^–1), birefringence (< 0.003), and temporal stability of refractive index, are described.     

A Hydrogel‐Film Casting to Fabricate Platelet‐Reinforced Polymer Composite Films Exhibiting Superior Mechanical Properties

The fabrication of mechanically superior polymer composite films with controllable shapes on various scales is difficult. Despite recent research on polymer composites consisting of organic matrices and inorganic materials with layered structures, these films suffer from complex preparations and limited mechanical properties that do not have even integration of high strength, stiffness, and toughness. Herein, a hydrogel‐film casting approach to achieve fabrication of simultaneously strong, stiff, and tough polymer composite films with well‐defined microstructure, inspired from a layer‐by‐layer structure of nacre is reported. Ca²⁺‐crosslinked alginate hydrogels incorporated with platelet‐like alumina particles are dried to form composite films composed of horizontally aligned alumina platelets and alginate matrix with uniformly layered microstructure. Alumina platelets are evenly distributed parallel without precipitations and contribute to synergistic enhancements of strength, stiffness and toughness in the resultant film. Consequentially, Ca²⁺‐crosslinked alginate/alumina (Ca²⁺‐Alg/Alu) films show exceptional tensile strength (267 MPa), modulus (17.9 GPa), and toughness (3.60 MJ m⁻³). Furthermore, the hydrogel‐film casting allows facile preparation of polymer composite films with controllable shapes and various scales. The results suggest an alternative approach to design and prepare polymer composites with the layer‐by‐layer structure for superior mechanical properties.     

Chemical vapor phase polymerization deposition of layer-ordered conducting polymer nanostructure for hole injection layer

Layer-ordered and ultrathin films of conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT) was prepared through a chemical vapor phase polymerization method. The chemical polymerization of 3, 4-ethylenedioxythiophene monomer was initiated in as-prepared oxidant LB films,and PEDOT nanofilms with layer-ordered structure was constructed. UV-Vis absorption spectrum and Fourier transform infrared spectroscopy was used to confirm an interface polymerization of PEDOT in as-prepared LB films. The results of X-ray diffraction and secondary ion mass spectrometry revealed that conductive PEDOT ultrathin layers were well located at different planes of LB films. The film deposition surface pressure and chemical polymerization time of PEDOT monomer in as-prepared LB films showed distinct influence on surface morphology and conductive performance of the polymerized PEDOT LB films. This layer-ordered conducting polymer ultrathin films was deposited on ITO surface as hole injection layer for organic light-emitting diodes, and the luminescence performance of devices was improved as well.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 3: Auswertung der experimentellen Ergebnisse und Diskussion

Plasma Pretreatment and Coating of Polymer Films. Part 3: Analysis of the Experimental Results and Discussion The food packaging industry demands cheap polymer films possessing a high barrier against permeation of gases, moisture and flavour. Candidates for the most successful materials fulfilling these requirements are vacuum web coated biaxial oriented polypropylene (BOPP) films containing a thin inorganic barrier layer. For a good adhesion of the barrier layer on the BOPP films, the polymer film must be pretreated. The industry uses the Corona atmosphere plasma. This work is separated in three parts. The first part describes the experimental setup and the properties of vacuum web coated layers on polymer films[1] The next part contains the results of the systematic modification of polymer surface by atmosphere and low pressure plasmas[2]. The influence of the surface properties on the final functionality of the coated films is given. In the last part, the discussion of the results of the first and second part reveals systematic relations between the production parameters of the high barrier films and their final functionality. These results firstly reveal the adhesion mechanism of the inorganic barrier layers of the polymer films and the necessary surface properties of the polymer films, in order to get cheap high barrier films by vacuum web coating.     

Laser microstructuring and scanning microscopy of plasmapolymer-silver composite layers

Laser-induced coalescence of silver nanoparticles embedded in thin plasma polymer films has been used to generate permanent submicrometer structures in the films, which exhibit unusual optical properties. Scanning-electron-microscope images and spatially resolved optical transmission spectra reveal the changes in the nanostructure of the films that are due to the irradiation. The structural modifications result from thermally induced coalescence of the irradiated nanoparticles and are accompanied by significant changes in the optical transmission spectra. A planar micro-optical element has been generated in this way, and its optical properties have been characterized by means of the depth resolution of a confocal microscope.     

Super‐Hydrophobic Surfaces: From Natural to Artificial

Super‐hydrophobic surfaces, with a water contact angle (CA) greater than 150°, have attracted much interest for both fundamental research and practical applications. Recent studies on lotus and rice leaves reveal that a super‐hydrophobic surface with both a large CA and small sliding angle (α) needs the cooperation of micro‐ and nanostructures, and the arrangement of the microstructures on this surface can influence the way a water droplet tends to move. These results from the natural world provide a guide for constructing artificial super‐hydrophobic surfaces and designing surfaces with controllable wettability. Accordingly, super‐hydrophobic surfaces of polymer nanofibers and differently patterned aligned carbon nanotube (ACNT) films have been fabricated.     

Plasmavorbehandlung und Beschichtung von Kunststoffolien. Teil 1: Beschichtung von unbehandelten Kunststoffolien

Plasma Pretreatment and Coating of Polymer Films. Part 1: Coating of Non-treated Polymer Films The food packaging industry demands cheap polymer films possessing a high barrier against permeation of gases, moisture and flavor. Candidates for the most successful materials fulfilling these requirements are vacuum web coated biaxial oriented polypropylene (BOPP) films containing a thin inorganic barrier layer. For a good adhesion of the barrier layer on the BOPP films, the polymer film must be pretreated. The industry uses the Corona atmosphere plasma. This work is separated in three parts. The first part describes the experimental setup and the properties of vacuum web coated layers on polymer films. The next part contains the results of the systematic modification of polymer surfaces by atmosphere and low pressure plasmas. The influence of the surface properties on the final functionality of the coated films is given. In the last part, the discussion of the results of the first and second part reveals systematic relations between the production parameters of the high barrier films and their final functionality. These results firstly reveal the adhesion mechanism of the inorganic barrier layers of the polymer films and the necessary surface properties of the polymer films, in order to get cheap high barrier films by vacuum web coating.