Novel conductive characteristics of ITO:Ti films deposited by spin coating from colloidal precursor

Transparent semiconducting ITO:Ti thin films, prepared by a sol–gel process, has been deposited by spin-coating technique onto alkali-free glass substrates. The as-coated films were annealed in ambient air at 550 °C for 1 h and further annealed in a reducing atmosphere. The influences of the Ti content in the sol on the surface morphology, microstructure, optical properties and electrical resistivity have been investigated. These properties were found to depend on the Ti content in the coating sol. Ti addition led to dense smooth layers with larger crystallite size (20–30 nm). Double layers synthesized with Ti:ITO = 0.53 wt% and submitted to reducing treatment in forming gas exhibited the lowest sheet resistance R_□ = 60 Ω_□ with an average transmittance of 87% at 550 nm.     

Cathodically deposited polypyridine films: A novel electroactive polyconjugated polymer

Poly-2,5- and poly-2,6-pyridine coatings have been produced on glassy-carbon electrodes by nickelcatalysed reduction of the corresponding dibromopyridine in acetonitrile. Poly-2,5-pyridine films display two reversible cathodic cycles, one of which is due to nickel ions coordinated to pyridine moieties and the other to the polymeric backbone. Both reductions lead to the polymer changing from the insulating to the conductive state. Conversely, Poly-2,6-pyridine films are not reversibly electroactive and the differences are discussed in terms of conjugation along the polymeric chain.     

Ruptured conjugated polymer thin films formed during spin coating

The formation of ruptured poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenyl vinylene] (MEH–PPV) thin films coated from undried tetrahydrofuran (THF) solutions was investigated. Because of the incompatibility of water and MEH–PPV, the polymer films coated from THF/water solutions showed a ruptured film structure. In the photoluminescence (PL) spectra of the polymer thin films, the ruptured polymer films showed a redshifted emission in comparison with continuous polymer thin films. According to a comparison of the PL spectra of polymer solutions and films, MEH–PPV in THF showed a coil–cylinder transition during precipitation from solution. Because of the incompatibility of water and MEH–PPV, an increase in the water content could increase the ratio of polymer chains in the cylinder conformation, resulting in a redshifted emission for the films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 79–84, 2006     

Modulating cell behaviors on chiral polymer brush films with different hydrophobic side groups

Chirality is one of the significant biochemical signatures of life. Nearly all biological polymers are homochiral as they usually show high preference toward one specific enantiomer. This phenomenon inspires us to design biomaterials with chiral units and study their interactions with cells and other biological entities. In this article, through adopting three pairs of aliphatic amino acids with different hydrophobic side groups as chiral species, and using two adhesive cell lines as examples, we show that the chirality of polymer brushes can trigger differential cell behaviors on the enantiomorphous surfaces, and more interestingly, such chiral effect on cellular behaviors can be modulated in a certain extent by varying the hydrophobic side groups of the chiral moieties composing the polymers. This work not only proves the versatility of the chiral effect at the cell level but also demonstrates a method to bridge the gap between organic signal molecules and biomaterials. It thus points out a promising approach for designing novel biomaterials based on the chiral effect, which will be an important complement for conventional strategies in the study of biomaterials.     

Molecular organization in MAPLE‐deposited conjugated polymer thin films and the implications for carrier transport characteristics

The morphological structure of poly(3‐hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin‐casting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side‐chain stacking, π–π stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLE‐deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin‐casting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in‐plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin‐cast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 39–48     

Magnetic characteristics of nanocrystalline GaMnN films deposited by reactive sputtering

The magnetic characteristics of Ga_1−xMn_xN nanocrystalline films (x = 0.08 and x = 0.18), grown by reactive sputtering onto amorphous silica substrates (a-SiO₂), are shown. Further than the dominant paramagnetic-like behaviour, both field- and temperature-dependent magnetization curves presented some particular features indicating the presence of secondary magnetic phases. A simple and qualitative analysis based on the Brillouin function assisted the interpretation of these secondary magnetic contributions, which were tentatively attributed to antiferromagnetic and ferromagnetic phases.     

Surface structure analysis of thin dewetted polymer blend films

The surface structure of thin polymer blend films of deuterated polystyrene (dPS) and polyparamethylstyrene (PpMS) after annealing above the glass transition temperature was investigated. With scanning force microscopy (SFM) the surface topography originated by a dewetting process is detected. The sample surface is covered with small droplets consisting of several polymer molecules. Utilizing grazing incidence small angle neutron scattering (GISANS) the topographical information as well as the in‐plane composition is probed. For thin confined blend films a substructure of the droplets resulting from an additional phase separation process at different length scales is detected.     

Surface patterns induced by laser irradiation on thin polymer bilayer films

We report on the preparation of wavelike surface patterns with characteristic wavelengths on thin bilayers of poly(methyl methacrylate) on azobenzene liquid crystalline polymer films (LCP/PMMA) by irradiation of a single polarized pulsed laser beam. The formation of such patterns was influenced by the thickness of the upper layer and the laser fluence. We were also able to guide the wavelike pattern to have a specific orientation by placing an elastic polydimethylsiloxane (PDMS) mold on the surface of bilayer film prior to laser irradiation. Moreover, the property of the laser irradiation, that is, the selectivity through mask-projection systems, allowed us fabricating complicated micropatterns for novel microdevices.     

Surface structure and photoluminescence properties of AZO thin films on polymer substrates

Al‐doped zinc oxide (AZO) thin films were deposited on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering method at room temperature. The effects of film thickness on the surface structure and the photoluminescence properties of the films were investigated by atomic force microscopy (AFM), secondary ion mass spectroscopy (SIMS) and room temperature photoluminescence (PL). AFM analysis showed that the surface of all films was extremely flat and uniform at nanoscale. Root mean square (RMS) value of the surface roughness which scanned the surface area of 3 µm by 3 µm and grain size increased with increasing the film thickness. Thus, the surface morphology of the films became rough because of the coarse grains. The depth profile of AZO layers was analyzed by SIMS. It was found that the thickness of the AZO layer is almost same with the desired film thickness. The PL intensity of the dominant peak decreased and shifted slightly towards the shorter wavelengths with increasing the film thickness. According to the relationships between luminescence intensity and crystalline characteristics, it was observed that the intensity of the peak decreased by the increased surface area of the grains. Copyright © 2014 John Wiley & Sons, Ltd.     

Self‐assembled honeycomb polycarbonate films deposited on polymer piezoelectric substrates and their applications

Self‐assembled honeycomb polycarbonate films were deposited on polymer piezoelectric (poled polyvinylidene fluoride) substrates under a fast dip‐coating process. Ordered structures with micro‐scaled pores dispersed in the polycarbonate matrix were obtained, demonstrating two‐dimensional (2D) hexagonal packing. A theoretical model explaining the self‐assembling process is proposed. Fabricated structures have a potential as 2D tunable photonic crystals. Photonic bandgap location was estimated. Visible‐IR transmittance spectrum of the self‐assembled films was studied with a FT‐IR spectrometer. Diffraction properties of the honeycomb patterns were investigated. High transparency of the components makes possible IR optics applications of obtained structures. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface forces and friction tuned by thermo-responsive polymer films

Thermo-responsive polymer films have enabled the development of various functional surfaces with switchable interfacial properties. Assessing the surface forces and friction on such films is of paramount importance. On the one hand, it allows us to extract a great deal of information on the interfacial properties of the films, e.g., adhesiveness and lubricity, and how they could be tuned using different stimuli. On the other hand, surface force measurements complement other thin-film analysis methods, e.g., ellipsometry, to better perceive the correlation between the molecular properties of the polymer chains and the interfacial properties of the film. On this basis, we will, herein, provide a concise review of some recent studies on surface forces and friction tuned by thermo-responsive polymer films. This outline comprises a summary of several research works addressing the effects of temperature, solvent composition, and salts on surface forces and friction. In the end, we briefly discuss a few select studies in which the regulation of surface forces by thermo-responsive polymers is examined with an emphasis on the potential applications.     

Novel self-organization of polymer particles on hydrophobic solid surfaces through hydrophobic interaction

A novel technique of particle monolayer fabrication based on hydrophobic interactions in aqueous systems is described in this paper. When alkylated glass plates modified with various silane coupling agents were immersed in aqueous dispersions of submicron-sized polystyrene particles of cationic or anionic surface charges, cationic particle monolayers containing active ester groups were effectively formed at the plate surfaces, whereas no anionic particles were self-organized on the plate surfaces. The coverage of the plates with cationic particles and the morphology of the monolayers varied with the hydrophobicities of the particles and plates as well as with the ionic strength of the medium and temperature. For less hydrophobic methylated glass surfaces modified with methyltriethoxysilane, cationic particles were self-organized at relatively regular intervals, whereas they were self-organized in the form of aggregates for the more hydrophobic octadecylated glass plates treated with n-octadecyltriethoxysilane. Closely packed monolayers were fabricated by adjusting ionic strength and temperature. Fluorescence labelling of cationic particle monolayers was successfully accomplished by the reaction of remaining active ester groups on the monolayers with a fluorescence probe containing amino groups. Cationic particle monolayers were physically stabilized by heating above the glass transition temperature (T _g) of the particles.     

Recognition and determination of bovine hemoglobin using a gold electrode modified with gold nanoparticles and molecularly imprinted self-polymerized dopamine

A molecularly imprinted polymer (MIP) was prepared by self-polymerization of dopamine in the presence of bovine hemoglobin (BHb) and then deposited on the surface of an electrode modified with gold nanoparticles (AuNPs). Scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry were employed to characterize the modified electrode using the hexacyanoferrate redox system as an electroactive probe. The effects of BHb concentration, dopamine concentration, and polymerization time were optimized. Under optimized conditions, the modified electrode selectively recognizes BHb even in the presence of other proteins. The peak current for hexacyanoferrate, typically measured at + 0.17 V (vs. SCE), depends on the concentration of BHb in the 1.0 × 10⁻¹¹ to 1.0 × 10⁻² mg mL⁻¹ range. Due to the ease of preparation and tight adherence of polydopamine to various support materials, the present strategy conceivably also provides a platform for the recognition and detection of other proteins.

Gold nanoparticles and molecularly imprinted self-polymerization dopamine were modified on gold electrode surface to recognize and determine bovine hemoglobin. Under the optimized conditions, the modified electrode showed specific adsorption, selective recognition, and sensitive detection of bovine hemoglobin.

     

Low-temperature-induced swelling of a hydrophobic polymer: a lattice approach

The authors investigate equilibrium properties of a simple model of hydrophobic polymer in aqueous solution by means of dynamic Monte Carlo simulations. The solvent is described by a simplified two-dimensional model, defined on a triangular lattice, which has been previously shown to account for most thermodynamic anomalies of pure water and of hydrophobic solvation for monomeric solutes. The polymer is modeled as a self-avoiding walk on the same lattice. In this framework, the degrees of freedom of water are taken into account explicitly, and in principle there is no need to introduce effective self-contact interactions for the polymer in order to mimic the hydrophobic effect. In certain conditions, the authors observe low-temperature-induced swelling, i.e., expansion of the polymer globule upon decreasing temperature. The authors discuss the relationship between this phenomenon and the anomalous properties of the solvent.     

Surface patterned graft copolymerization of hydrophilic monomers onto hydrophobic polymer film upon UV irradiation

A random copolymer [p(MMA/DMAB)] composed of methyl methacrylate (MMA) and 2,2‐dimethoxy‐1,2‐di(4‐methacryloyloxy)phenylethane‐1‐one (DMAB), which can simultaneously act as a photoradical initiator and crosslinkable monomer, was prepared by free radical random copolymerization. A hydrophobic film on quartz glass was prepared using p(MMA/DMAB) by a spin‐coating technique. Hydrophilic methacrylic acid (MA) and 2‐methacryloyloxyethyl phosphorylcholine (MPC) were graft‐copolymerized from the hydrophobic p(MMA/DMAB) film in water by photo‐cleavage of the DMAB unit. The graft copolymer of MA and MPC was characterized by infrared and X‐ray photoelectron spectroscopies and contact angle measurements. To confirm that MPC can be grafted onto the surface of the film selectively at only UV‐irradiated sites, photoinduced graft copolymerization of MPC using a photomask was performed to prepare a pMPC patterned p(MMA/DMAB) film. The film was stained using a rhodamine 6G dye that can absorb specifically to pMPC to confirm the pMPC pattern. The p(MMA/DMAB) film can be applied to various fields including photolithography and biomedical applications, because the film surface properties can be controlled using various vinyl monomers selectively on UV‐irradiated sites. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2822–2829     

Topographical properties of polymer films deposited in capillaries for electrophoretic separations of large organic molecules

Topography and thickness of hydrophilic polymer coatings of fused-silica capillaries for capillary electrophoresis (CE) were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and profilometry. Three hydrogels, poly(2-hydroxyethyl methacrylate) [poly(HEMA)], poly(diethylene glycol monomethacrylate) [poly(DEGMA)], and poly(triethylene glycol monomethacrylate) [poly(TEGMA)], were deposited using two procedures, either by simple physical sorption of the polymers, or by derivatization of the capillary wall surface with glycidyl methacrylate (EPMA) followed by polymerization of the appropriate monomers. The performance of the modified capillaries was tested under CE conditions (decrease in the electroosmotic flow, EOF dependence on pH, separation of milk and standard proteins). It has been found that the most important property of the polymer coating is its thickness, whereas its topography and the degree of its hydrophobicity are less significant. Film deposition by physical adsorption is preferable to polymerization on the derivatized surface.     

Surface morphology of spin‐coated molecularly imprinted polymer films

The surface morphology of thin molecularly imprinted polymer films has been studied using atomic force microscopy (AFM). The films were produced by spin coating onto glass substrates and examined as a function of host polymer, imprinting template, casting solvent, spin‐coater rotation speed and post‐production treatment. It was observed that the gross features of such films are template controlled. The fine structure is determined by parameters such as solvent, spin speed or subsequent treatment. The relationship between these observations, polymer–template interactions and the mechanism of film formation in spin coating is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Properties of nickel-cobalt-diamond composite coating deposited from a chloride electrolyte

Effect of electrolysis modes and electrolyte composition on physicomechanical properties of nickel-cobalt-diamond composite electroplated coatings deposited from a chloride electrolyte with introduction of an ultradispersed diamond suspension was studied and the possibility of replacement of wear-resistant chromium coatings with these composite coatings was demonstrated.