Band structure of nonclassical polymers

It is shown that fully conjugated alternant nonclassical polymers are comparatively stable systems as a result of the considerable delocalisation energy.The energy characteristics of the polymers are strongly determined by the electron spin distribution of the degenerate nonbonding molecular orbitals; the full spin configuration,S>0, is favoured. The spin densities depend on the electron correlation and alternate; this corresponds to a ferrimagnetic state of the polymer at 0°K.     

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.     

Surface characterizations of spin-coated films of ethylcellulose and hydroxypropyl methylcellulose blends

Films of pure ethylcellulose (EC) and hydroxypropyl methylcellulose (HPMC) polymers and EC/HPMC blends were prepared from solutions by spin coating where isopropyl alcohol (IPA), water, and IPA/water cosolvent were used as solvents. Surface structures of the films were investigated using optical microscopy, atomic force microscopy (AFM), and Raman mapping and spectroscopy. For the films prepared from EC/HPMC blend solutions using the IPA/water cosolvent, different domain structures such as islands or pits and phase separation between EC and HPMC were observed by optical microscopy and AFM. The nature of the polymer components on the surface of the films was identified by Raman mapping and spectroscopy. Experimental results also indicated that polymer composition, solvent, and temperature during spin coating had significant impacts on surface structures of the films.     

Effect of film thickness controlled by ink‐jet printing method on the optical properties of an electroluminescent polymer

Ink‐jet printing (IJP) represents a highly promising liquid processed polymer deposition method for the film preparation of functional polymers in photo‐electronic devices. In this report, the results on the IJP of a fluorene‐based electroluminescent polymer, poly(9,9‐dihexylfluorene‐alt‐2,5‐dioctyloxybenzene) (PF6OC8), from a piezoelectric droplet generator are presented. The polymer film thickness has been found to show an approximate linear relation with the number of droplets per unit area; it is thus convenient to control the film thickness by the space of printed dots in IJP process. In comparison, spin coating approach is also used to prepare polymer films with different thicknesses by varying solution concentration and spinning speed. However, it is found that spin coating is difficult to control the film thickness quantitatively. The influence of film thickness on the photoluminescence (PL) properties of PF6OC8 films prepared by IJP and spin coating is comparatively investigated. For both ink‐jet printed and spin coated films, the intensity of PL spectra first increases and then decreases with increase in the film thickness, probably due to the exciton quenching in thicker films. When the polymer film thickness is at nanoscale, the major peak in the PL spectrum is the 0–0 vibronic emission at about 420 nm, and with increase in the film thickness, the 0–1 vibronic peak at about 440 nm becomes dominant. The red‐shifted PL spectra with increase in film thickness show the change from the 2D exciton state to the 3D one. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal analysis and free volume study of polymeric supermolecular structures

Positron annihilation lifetime measurements were performed on samples cut down from commercially available polyethylene (PE) and poly(4-methyl-1-pentene) (PMP). The effect of a free volume on the segmental relaxation behaviour was examined. The samples were isothermally annealed at different temperatures. In order to study the effect of annealing on supermolecular structures of the polymers, the annealing temperatures were chosen between the polymers transition temperatures of the polymers. All thermodynamic parameters varied as compared to the parameters of the samples which were not annealed. A slight change of the free volume was observed. The idea of two miscellaneous amorphous fractions in polymer was under consideration. Differential scanning calorimetry, dynamic mechanical thermal analysis were used to study the effect of specimen heat treatment on both glass transitions, too. The degree of crystallinity of the PE and PMP samples was determined. An attempt to estimate this parameter from positron annihilation data was undertaken. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrochemical sensing with electrodes modified with molecularly imprinted polymer films

This article summarises our work on the development of voltammetric sensors based on molecularly imprinted polymers. Several recognition elements and integration strategies were used:1.membranes electropolymerised at the electrode surface; 2.casting of polymeric membranes by drop-coating a solution of pre-formed polymer (polyphosphazene) and template in a low-boiling-point solvent on to the electrode surface; 3.preparation of composite membranes containing conductive material (graphite or carbon black), acrylic-type molecularly imprinted polymers (small particle size), and PVC as binder; and 4.in-situ polymerisation of a thin layer of acrylic imprinted polymer deposited on the electrode surface by spin coating.All the options evaluated offer the possibility of controlling electrode characteristics such as hydrophobic/hydrophilic character, permeability, or film thickness, which are essential for obtaining good sensor performance.     

Photolabile carboxylic acid protected terpolymers for surface patterning. Part 1: Polymer synthesis and film characterization

We present the synthesis and characterization of a series of photolabile phenacyl derivative polymers and their subsequent thin film preparation. These systems are composed of up to three methacrylate units: a photolabile component including a p-methoxyphenacyl moiety which after selective irradiation (UV/laser) can provide free carboxylic groups in specific areas for further modification; an anchoring unit, trimethoxysiloxane or glycidyl methacrylate derivative, which allows the covalent attachment of the polymer to the substrate; and a spacer, methyl methacrylate or styrene, which in the appropriate proportion ensures the formation of films with good quality. Structural and thermal properties of these materials have been analyzed by means of NMR, FTIR, elemental analysis, UV, gel permeation chromatography, differental scanning calorimetry, and thermogravimetric analysis. The polymers have been subsequently processed by spin coating to render ultrathin films (<50 nm). Topographic and structural characterization studies of the films have been carried out with atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. The extent of the substrate attachment of the polymers depending on the nature of the anchoring groups have been studied by ellipsometry and FTIR.     

Synthesis and characterization of water-swellableα,β-polyasparthydrazide derivatives

The synthesis of a new crosslinked polymer by reaction of , -polyasparthydrazide and glutaraldehyde is reported. Different crosslinking degrees were obtained by varying the ratio between the aldehyde and the starting polymer. The crosslinked polymer was characterized by water swelling tests and thermal analysis. In particular, the crosslinking density and its effects on the glass transition temperature of the material were studied. Finally, the microstructure of the obtained polymer was observed using scanning electron microscopy.     

Thermal annealing combination with pulse Nd-YAG laser treatment of ITO on polycarbonate using spin coating process

This work, we report a cost effective method to decompose ITO thin layer on polycarbonate as flexible substrate by means of spin coating technique. Three calcinations techniques were carried out. The coating were deposited by spin and cured by heat, ultraviolet (UV) irradiation and Nd-YAG pulse laser. The resistivity change on annealing of the amorphous film by thermal, UV and laser was investigated by X-ray diffraction, scanning electron microscopy, atomic force spectroscopy and UV–Vis spectrometer. It is shown that the resistance of coated film on polymer decreases dramatically to less than impedance spectroscopy (600 Ω) when using combination of low heat treatment and laser irradiation with a wavelength of 1,100 nm and energy of 6–25 J.     

Mucoadhesive Sustained Drug Delivery System Based on Cationic Polymer and Anionic Cyclodextrin/Triclosan Complex

In this study the interactions between a cationic polymer and an anionic cyclodextrin were investigated. The system has the potential for use in a sustained release dosage forms for use on mucous membranes. As mucous membranes are negatively charged the objective of this study was to investigate whether a drug delivery system based on a cationic polymer and an anionic cyclodextrin would be more mucoadhesive than a system containing a cationic polymer and a neutral cyclodextrin. For this purpose the cationic polymer hexadimethrine bromide (HDMBr) and anionic sulfobutylether -cyclodextrin (SBECD) were utilized as well as the neutral hydroxypropyl-cyclodextrin (HPCD). Triclosan was used as a model drug. The drug delivery system was formulated as a solution or semi-solid and its adhesion to porcine buccal mucosa and cation exchange media was measured. In addition the release of triclosan from the system was quantified. No difference was observed between the two systems when they were applied to the mucosal surface. However, the formulations showed improved adhesion, compared to the neutral cyclodextrin/drug delivery system, when they could also reach the underlying surface of the excised tissue. The drug delivery system was much better retained on the cation exchange media than the uncharged system. Significant interactions were observed between the negatively charged cyclodextrin and the positively charged polymer. The results indicate that the interactions could be used to obtain a mucoadhesive sustained drug delivery system under certain circumstances. The positive charge of HDMBr did not have the expected effect on the buccal mucosa and it can be concluded that although a positive charge is likely to promote mucoadhesion, other attributes of polymers, such as molecular weight and viscosity, may have equally beneficial effect.     

Spin coating process of sol-gel silicate films deposition: Effect of spin speed and processing temperature

The effect of two factors having the most important influence on spin coating process of sol-gel films: the spin speed and the temperature (of the substrate and the applied solution) during film deposition is discussed. It is shown, that film thickness and thickness uniformity are determined by centrifugal driving force dynamics, viscous polymer rheology, solvent evaporation dynamics, and film porous microstructure.     

Preparation of TiO2 Thin Film Photocatalysts by Dip Coating Using a Highly Viscous Solvent

TiO₂ thin film photocatalysts coated onto soda lime glass were prepared by a dip coating process using a highly viscous solvent. The source of the TiO₂ was tetraisopropyl orthotitanate, and -terpineol was used as the solvent. Two types of thin film preparation procedures based on dip coating (a sol-gel system and thermal decomposition system) were used to prepare the samples. TiO₂ thin films were obtained after calcination at 450°C for 1 hour. The film thickness obtained with a single dipping was proportional to the viscosity of the dip coating solutions. The obtained thin films were transparent with a thickness of 1 m. The crystal form of the obtained photocatalyst films was anatase alone. The thin films were formed with aggregated nano-sized TiO₂ single crystals (7–15 nm). The photocatalytic activity of the TiO₂ thin films, as evaluated by the photooxidation of NO (1 ppm) in dry air, was as high as our previous TiO₂ thin films prepared by the sol-gel method.     

Epoxy polymer coating to prevent the corrosion of aluminum nanoparticles

Aluminum nanoparticles were coated by epoxy polymer in order to prevent the corrosion reaction. The coverage of the epoxy polymer film was controlled from 0% to 100%, which changed the corrosion rate of nanoparticles quantitatively. The surface of the polymer coating was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the corrosion resistance of these nanoparticles was estimated by the wet/dry corrosion test on platinum (Pt) plate with a NaCl solution. From a TEM analysis, 10 mass% polymer‐coated Al particles in the synthesis were almost 100% covered on the surface by a polymer film of 10 nm thick. On the other hand, 3 mass% polymer‐coated Al was partially covered by a film. In the AFM–Kelvin force microscopy, the potential around the Al particles had a relatively low value by the polymer coating, which indicated that the conductivity of the Al was isolated from Pt plate by the polymer. Both the corrosion and H₂ evolution reaction rates were quantitatively reduced by the mass% of polymer coating. In the case of 10 mass% coated sample, there was very little corrosion of Al nanoparticles. This fact suggested that the electrochemical reaction was suppressed by the polymer coating. Thus, it was found that the corrosion reaction rate of Al nanoparticles could be quantitatively suppressed by the mass% of epoxy coating. Copyright © 2015 John Wiley & Sons, Ltd.     

Sector spin coating for fast preparation of polymer libraries

The feasibility of sector spin coating (or combinatorial spin-coating) is demonstrated (i.e., spin coating of various samples onto one single substrate using a metal template to divide the substrate into sectors). Film thickness increases in an angular direction against the sense of rotation. In the radial direction, the film thickness is constant within 2%. A library of 8 poly(methyl methacrylate)/polystyrene-blends with varying composition was spin coated and subsequently analyzed using automated atomic force microscopy: 24 measurements could be performed within 72 min. The contact angles of a library of 16 polyoxazoline diblock copolymers were measured using one substrate with 16 spin-coated sectors. Forty-eight measurements could be performed within 50 min. On the basis of the surface energies calculated using the Owens-Wendt-Rath-Kaeble method, the library can be divided into three groups of polymers: those containing a dispersive nonyloxazoline block, those containing a polar phenyloxazoline block, and those containing neither.     

Enantiomer separations with chromatographic supports based on β-cyclodextrin polymers immobilized on porous silica. Role of the polymer structure in separating ability

Summary Two -cyclodextrin (-CD)-containing polymers have been prepared either by condensation of -CD molecules with a bifunctional reagent or by grafting a -CD derivative on to a linear polymer (polyvinylimidazole). HPLC stationary phases were obtained by adsorption of the -CD polymers on to silica. The ability of these chromatographic supports to resolve racemic mixtures of organic compounds such as amino acid derivatives, phenylhydantoins, barbiturates, and hydroxycoumarin derivatives has been investigated. Results were found to depend on the chemical structure of the -CD polymers     

Protective coatings for stainless steel for SOFC applications

In this paper, a coating procedure based on spin coating of metal oxide polymer precursors on stainless steel, which decreases the oxide scale growth rate, is evaluated. The yttrium and cobalt solutions were used as polymer precursors, while a ferritic stainless steel Crofer 22 APU was used for the deposition of protective coatings. The thickness of deposited protective film was about ~500 nm. The effectiveness of protective layer was evaluated by cyclic thermogravimetry, oxide scale electrical conductivity, and X-ray diffractometry. The results show that steel coated with yttrium polymer precursor has better properties than uncoated or cobalt-coated sample.     

In Situ Crystallization of Bacterial Cellulose III. Influences of Different Polymeric Additives on the Formation of Microfibrils as Revealed by Transmission Electron Microscopy

Effects of polymer additives on the formation of microfibrils of bacterial cellulose have been examined by transmission electron microscopy. Among additives with different degrees of polymerization (DP) or substitution (DS), carboxymethyl cellulose sodium salt (CMC) with DP = 80 and DS = 0.57 is the most effective in producing separate, smaller-size microfibrils. By increasing the concentration of this CMC from 0.1 to 1.5%, the percentage of microfibrils measuring 3–7 nm wide is increased and levels off at around 1.0%. Other polymer additives such as xyloglucan are less effective than CMC in producing microfibrils with smaller sizes and the resulting microfibrils still tend to aggregate. The number of charged substituents and the molecular weight seem to be important factors in the production of highly separate smaller-size microfibrils. The reduction in average microfibril size is well correlated to the decrease in mass fraction of cellulose I in bacterial cellulose crystals. On the basis of these results, the mechanism of the crystallization of celluloses I and I is discussed. The effect of colony types, smooth and rough, on the formation of microfibrils in the presence of CMC is also described.     

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

We have studied the dewetting process of thin polystyrene films on nonwettable substrates in the viscoelastic regime slightly above the glass transition temperature. The evolution of the shape of the dewetting rim for varying film thickness, molecular weights and dewetting temperatures allowed us to determine the relaxation rates of residual stresses, which originated from nonequilibrated polymer chain conformations formed during film preparation by spin‐coating. For long chain polymers, we found rates notably faster than the longest bulk relaxation processes, highly independent of molecular weight and temperature. Our study demonstrates that dewetting is a powerful tool for sensitive characterization of nonequilibrium properties of thin polymer films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 515–523     

Porogen formulations for obtaining molecularly imprinted polymers with optimized binding properties

This paper examines the formulation of new porogenic mixtures used to prepare molecularly imprinted polymers (MIPs) in both thin film and bulk monolith formats. Films were cast by using spin coating to spread a pre-polymerization mixture onto a substrate, and rapid curing of the films was achieved with UV photolysis. The use of a low volatility solvent in combination with a linear polymer porogen resulted in a porous morphology and a 60-fold enhancement in the binding capacity, relative to a non-porous film prepared with a highly volatile solvent and in the absence of the polymer porogen. The opposite effect was seen in MIPs that were prepared in the traditional bulk monolith format, for which the binding efficiency of the MIP decreased monotonically with the concentration of the linear polymer porogen. Furthermore, bulk MIPs that were prepared in the presence of linear polymer porogens exhibited significantly decreased specific surface areas (from 620 to 8 m²/g for samples prepared with pure solvent and 50% polymer porogen, respectively). Despite the change in binding capacity and morphology, the selectivity of the bulk MIPs remained unaffected by the presence of the polymer porogens (approximately 50% chiral selectivity for all bulk MIPs considered). This difference in behavior of the two systems was attributed to the large difference in the kinetics of polymerization.     

反应性聚合物微凝胶的合成及应用

反应性聚合物微凝胶是一种具有反应活性,分子内交联的高分子。它具有优良的加工性能,涂膜的力学性能及耐久性也十分优异,主要应用于制备高档涂料或对涂料进行改性,本文着重介绍了反应性聚合物微凝胶的合成方法及其在涂料改性方面的应用。