STM observations of the first polymerization steps between hexahydroxy-tri-phenylene and benzene-di-boronic acid molecules

To understand the first polymerization steps between benzene-diboronic acid (BDBA) and hexahydroxy-triphenylene (HHTP) molecules, the peculiar self assemblies of HHTP molecules on an Ag(111) surface have been investigated in terms of substrate temperature during evaporation. Interaction of these different molecular structures with BDBA moieties has been researched. The results show that polymer tecton is based on an oligomer composed of one BDBA surrounded by two HHTPs, its shape being independent of the surrounding HHTP network. The geometry and functionality of this tecton determines the shape of the final structures obtained after covalent bonding.     

Direct opal-like structures consisting of monodisperse polymer particles and synthesis of the related inverse structures

Three-dimensional periodic solid-state film structures with a face-centered cubic lattice and a high degree of perfection have been prepared from monodisperse particles of styrene copolymers with methacrylic acid. It has been shown that these structures can be successfully used not only as model objects for studying specific features of light propagation in photonic crystals but also as templates for synthesizing inverse opal-like structures. The influence of the degree of hydrophilization of the surface layer of polymer particles forming a polymer template and the template synthesis conditions on the quality of an inverse opal-like TiO₂-based structure has been analyzed.     

Atomic force microscopy, Raman spectroscopy and nonlinear absorption properties of femtosecond laser irradiated CR-39

Investigations have been performed to explore ultrashort laser irradiation effects on the surface topography as well as structural and nonlinear absorption properties of a polymer CR-39. For this purpose, a CR-39 target was exposed in air to 25 fs, 800 nm Ti:sapphire laser radiation at fluences ranging from 0.25 J cm⁻² to 3.6 J cm⁻². The surface features, structural changes and nonlinear absorption were explored by AFM, Raman Spectroscopy and a Z-scan technique, respectively. Several topographical structures like bumps, explosions and nano cavities have been observed on the irradiated surface. Raman spectroscopy reveals changes in the fundamental structure of the polymer after the irradiation. Nonlinear absorption data contained by the Z-scan technique predict the dominance of three-photon absorption in case of pristine CR-39. Furthermore, nonlinear absorption (three or two photon) increases with increasing laser fluences and is well correlated with surface and structural changes revealed by AFM and Raman spectroscopy.     

Phase separated composite films of liquid crystals

Phase separation of liquid crystals from a solution with polymers has long been studied and used to prepare polymer stabilized and polymer dispersed structures. They are formed by spatially isotropic phase separation. A new mode, in which the phase separation proceeds anisotropically, has recently been discovered. Known as phase separated composite films (PSCOF), the resultant structures are made of adjacent parallel layers of liquid crystal and solidified polymer. PSCOFs have been made with nematic, ferroelectric (FLC), and antiferroelectric (AFLC) liquid crystals. Liquid crystals in PSCOFs exhibit electro-optical properties not observed in devices prepared by conventional methods, polymer dispersion, or polymer stabilization methods. Devices incorporating FLCs possess grey scale and switch 100 times faster at low fields than conventional surface stabilized devices. This method makes it possible to prepare very flexible devices and devices with liquid crystal film thickness comparable to optical wavelengths with great ease.     

On the morphological similarities between networklike structures in viscoelastic polymer systems and the large-scale structure of the universe

Networklike structures are observed in various materials and nature. The networklike structures in viscoelastic phase separation of polymer mixtures have been explained by a model with a couple of hydrodynamic equations. On the other hand, the large-scale structure of the universe has been explained by a multi-dimensional extension of the Burgers equation. The networklike structures of the two very different systems have some morphological similarities. To see origins of the similarities and differences, the Burgers equation is derived from the model of the polymer mixtures using several approximations. The meaning of the approximations is discussed in connection with the morphology.     

Spontaneous formation of polymer nanoparticles by good-solvent evaporation as a nonequilibrium process

In recent years, polymer nanoparticles have been investigated with great interest due to their potential applications in the fields of electronics, photonics, and biotechnology. Here, we report the spontaneous formation of polymer nanoparticles from a clear solution containing a nonvolatile poor solvent by slow evaporation of a volatile good solvent. During evaporation of the good solvent, the solution gradually turns turbid. After evaporation, polymer nanoparticles of homogeneous shape and size are dispersed in the poor solvent. Homogeneous nucleation and successive growth of polymer particles takes place during the dynamic nonequilibrium process of solvent evaporation. The size of the particles, ranging from tens of nanometers to micrometer scale, depends on both polymer concentration and the solvent mixing ratio. Because of the physical generality of the particle formation mechanism, this procedure is applicable to a wide variety of polymers with suitable combinations of solvents. Here, we also show unique features, surface structures and surface properties of polymer nanoparticles prepared by this method.     

Directed assembly of nanostructured carbon materials on to patterned polymer surfaces

Directed assembly of single-walled carbon nanomaterials on to polymer surfaces has been achieved. The approach relies on selective interactions of the polymer functionalities with the surface structures present on the carbon materials. The successful immobilization of the carbon structures was confirmed by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. By generating patterned polymer surfaces with chemically distinct components through the control of polymer–polymer or polymer–substrate interactions, directed assembly of single-walled carbon nanohorns and single-walled nanotubes was demonstrated. This new type of carbon assembly might open up new avenues in the construction of functional polymer/carbon composites and flexible nanocarbon nano-electronics.     

新型含偶氮聚合物薄膜表面微结构的刻写研究

基于偶氮苯聚合物的光致异构和光致取向特性,开展了双偶氮苯功能化聚合物薄膜表面微结构的"刻写"研究.利用两束相干光照射,在样品表面"刻写"出了亚微米量级的光栅结构;利用分步法在样品表面制作出了清晰的"三角格子"等花样微结构,证明了双偶氮苯功能化聚合物对于表面微结构的制作有较强的可操作性.通过对比单偶氮和双偶氮材料的实验结果,证明了双偶氮聚合物具有响应时间快、衍射效率高等特点,并由此讨论了偶氮苯聚合物薄膜表面微结构的形成机理及其偏振选择性.     

Morphology and electronic structure of platinum-containing polymer nanosystems

Morphological characteristics and electronic structures of platinum-containing nanosystems obtained during a redox reaction in water medium at different concentrations of a stabilizing polymer and platinum were studied by atomic-force microscopy (AFM), X-ray photoelectron spectroscopy, and dynamic light scattering. It was shown that individual and associated structures of different morphologies were formed on the silicon substrate surface. Comparison of the dimension characteristics of nanoclusters in the Pt nanoparticle-polymer systems (in solution by means of molecular optics, on the silicon substrate surface in air by means of AFM) for ionogenic and nonionogenic polymer matrices upon the change of the mass ratio ν has shown that the nanocluster sizes in solution are two to three times larger than those in a thin film formed on the substrate surface. The size dependences of the nanoclusters on ν obtained by these methods exhibit the same character.     

Fabrication of three-dimensional electrical patterns by swollen-off process: An evolution of the lift-off process

We present a novel process to fabricate three-dimensional (3D) metallic patterns from 3D printed polymeric structures utilizing different hygroscopic swelling behavior of two different polymeric materials. 3D patterns are printed with two different polymers as cube shape. The surface of the 3D printed polymeric structures is plated with nickel by an electroless plating method. The nickel patterns on the surface of the 3D printed cube shape structure are formed by removing sacrificial layers using the difference in the rate of hygroscopic swelling between two printing polymer materials. The hygroscopic behavior on the interfaced structure was modeled with COMSOL Multiphysics. The surface and electrical properties of the fabricated three-dimensional patterns were analyzed and characterized.     

Polymer surface patterning by laser scanning

Proposed work develops method of polymer surface patterning, suggested in our laboratory. Surface structures with different symmetry and shape are prepared on PMMA and photoresist (Su-8) surface. For surface modification, periodic laser scanning from confocal microscope was used. For optical response improvement meso tetraphenylporphyrine was added either in the polymer bulk or on the top of pristine polymer by vacuum evaporation method. Applications of vacuum deposition methods allow increasing applicability of the technique and preparation of more complex structure. Parameters of the created structures were studied with the aim to better understand the driving forces of the surface modification. Application of prepared structures in photonics as diffraction grating or light coupling elements is also given.     

Contact electrification of polymers due to electron transfer among mechano anions,mechano cations and mechano radicals

Many studies have been reported for contact electrification based on the electron transfer from donors to acceptors. However, the chemical structures of donors and acceptors have not been identified. Here we calculated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of model structures of mechano anions, mechano cations and mechano radicals which were produced by the heterogeneous and homogeneous scissions of covalent bonds comprising polymer main chain in vacuum at 77 K. We identified the donors are mechano anions(HOMO) and mechano radicals(HOMO), and the acceptors are mechano cations(LUMO) and mechano radicals(LUMO). The contact electrification is due to the electron transfer from the donors to the acceptors during contacting on the friction surface, and produces mosaic nano-scopic domains with opposite sign. The sign of the net charge of polymer was deduced from the number of paths of electron acceptance reaction. The relative sign of charge and position on the triboelectric series were deduced from their chemical structure.     

Polymer self-assembled nano-structures and surface relief gratings induced with laser at 157 nm

Surface relief gratings (SRG) and self-organized nano-structures induced by laser light at 157 nm on the fluoropolymer poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA), films were obtained under well-controlled light exposure conditions. Regular and semi-regular spaced self-organized grating-like structures were created on polymeric films for ∼7.5-100 mJ/cm² laser energy fluence. For lower laser fluence, the surface morphology of light exposed/non-exposed areas exhibited irregular-like structure morphologies, while polymer surface irradiation with energy fluence higher than 150 mJ/cm² causes progressively fading out of the regular patterns. Under the specific experimental conditions, the SRG and self-organization patterning have their origin in the development of a surface thermal instability (Rayleigh's instability), which is resolved itself into regular patterns on the surface of the fluoropolymer film. The thermal instability is due to the explosive polymer surface photo-dissociation at 157 nm and the build up of longitudinal and periodic surface stress, which eventually create the SRG and the self-assembled structures on the polymer.     

Surface wave generation and propagation on metallic subwavelength structures measured by far-field interferometry

Transmission spectra of metallic films or membranes perforated by arrays of subwavelength slits or holes have been widely interpreted as resonance absorption by surface plasmon polaritons. Alternative interpretations involving evanescent waves diffracted on the surface have also been proposed. These two approaches lead to divergent predictions for some surface wave properties. Using far-field interferometry, we have carried out a series of measurements on elementary one-dimensional subwavelength structures with the aim of testing key properties of the surface waves and comparing them to predictions of these two points of view.     

Structural and electronic properties of cubic SrHfO3 surface: First-principles calculations

Structural, electronic and chemical bonding properties of the (0 0 1) surface of cubic SrHfO₃ have been investigated with both SrO and HfO₂ termination using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory. The relaxed structures of two slabs have been analyzed, which shows the interplanar distance of two slabs has the same changed trend. The electronic band structures and density of states of two slabs have been discussed, showing the reduced band gaps by comparison with those of bulk system. The chemical bonding between Sr and O between the surface layer and subsurface layer as well as Hf and O has been increased. The surface energy, work function and stability have been calculated, which indicates SrO-terminated slab is more stable.     

Effect of Polymer-Substrate Interactions on the Surface Morphology of Polymer Blend Thin Films

Surface structures and compositions of poly(Styrene-block-Ethylene/Butylene-block-Styrene) (SEBS)/Poly(Methyl Methacrylate) (PMMA) blend films have been studied by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). Substrates with different hydrophobicity and SEBS with and without Maleic Anhydride (MA) grafting were used to study the effect of polymer-substrate interactions. It is indicated that the surface energy of the substrate (substrate/air) plays a crucial role on the surface composition of the polymer component. For a fixed surface, the adsorption of polymer on the substrate is also important. The hydrophilic sites of SEBS-g-MA can prevent the dewetting of the SEBS-g-MA from the substrate. The dewetting of PMMA from the SEBS-g-MA will make the PMMA protrusions more pronounced, and the SEBS-g-MA phase domains are enlarged after annealing treatment. An adsorption scheme is suggested to explain the phase inversion and height difference observed in the various polymers used. In addition, SEBS triblock copolymers form wormlike and meshlike microphase separation morphologies on the hydrophilic and hydrophobic substrates, respectively.     

Disorder-order transition in microporous oriented polyethylene films

Spatial correlations on the surface of microporous polyethylene films obtained by extrusion of the polymer melt with the subsequent stages of annealing, uniaxial extension, and thermal fixation have been studied using scanning electron microscopy. It has been shown that, as the degree of orientation of the melt increases, the formation of the periodic superlattice of oriented lamellae occurs in the films as a result of the disorder-order transition. This transition is preceded by the formation of two mutually complementary percolation clusters, which reflect the pores and the solid phase of the polymer.     

Nanostructural self-organization and dynamic adaptation of metal–polymer tribosystems

The results of investigating the effect of nanosize modifiers of a polymer matrix on the nanostructural self-organization of polymer composites and dynamic adaptation of metal–polymer tribosystems, which considerably affect the wear resistance of polymer composite materials, have been analyzed. It has been shown that the physicochemical nanostructural self-organization processes are developed in metal–polymer tribosystems with the formation of thermotropic liquid-crystal structures of the polymer matrix, followed by the transition of the system to the stationary state with a negative feedback that ensures dynamic adaptation of the tribosystem to given operating conditions.     

The Spatial-Temporal Lamellar Structures in the Confined Ideal Polymer Blends

We consider the formation of self-organized spatial-temporal oscillating structures in symmetric binary polymer blends confined by two flat walls. An influence of these walls on the formation of the oscillating volume structures is studied. This phenomenon is simulated by an initial boundary-value problem for the conserved order parameter (or the concentration of one of the components in a binary mixture). Under a special choice the dynamical Puri-Binder’s boundary conditions these structures look like the lamellar structures. The behavior of the order parameter is described by the modified Cahn-Hilliard equation which models so-called the non-Fickian diffusion in the symmetric binary polymer blends. The nonlinear dynamical boundary conditions correspond to the process of adsorption-desorption on the walls. As a result, these nonlinear surface processes induce into the volume the spatial-temporal asymptotically periodic structures of relaxation, pre-turbulent or turbulent type with finite, countable or non-countable points of discontinuities on the period correspondingly. The frequency of oscillations on the period follows a power-law for the relaxation type and increases exponentially in the other cases.     

Comparative study of sub-micrometer polymeric structures: Dot-arrays, linear and crossed gratings generated by UV laser based two-beam interference, as surfaces for SPR and AFM based bio-sensing

Two-dimensional gratings are generated on poly-carbonate films spin-coated onto thin gold-silver bimetallic layers by two-beam interference method. Sub-micrometer periodic polymer dots and stripes are produced illuminating the poly-carbonate surface by p- and s-polarized beams of a frequency quadrupled Nd:YAG laser, and crossed gratings are generated by rotating the substrates between two sequential treatments. It is shown by pulsed force mode atomic force microscopy that the mean value of the adhesion is enhanced on the dot-arrays and on the crossed gratings. The grating-coupling on the two-dimensional structures results in double peaks on the angle dependent resonance curves of the surface plasmons excited by frequency doubled Nd:YAG laser. The comparison of the resonance curves proves that a surface profile ensuring minimal undirected scattering is required to optimize the grating-coupling, in addition to the minimal modulation amplitude, and to the optimal azimuthal orientation. The secondary minima are the narrowest in presence of linear gratings on multi-layers having optimized composition, and on crossed structures consisting of appropriately oriented polymer stripes. The large coupling efficiency and adhesion result in high detection sensitivity on the crossed gratings. Bio-sensing is realized by monitoring the rotated-crossed grating-coupled surface plasmon resonance curves, and detecting the chemical heterogeneity by tapping-mode atomic force microscopy. The interaction of Amyloid-β peptide, a pathogenetic factor in Alzheimer disease, with therapeutical molecules is demonstrated.