Formation Of Polymer Films Research Articles

Spontaneous photoinduced formation of hybrid polymer films with functionalized macroporous patterns

Sol–gel phase separation of 3-(glycidyloxypropyl)trimethoxysilane (GPTMS) in presence of a long-chain hydrophobic precursor ((H3C(CH2)n−1Si(OCH3)3), n=12–16) served to synthesize macroporous hybrid films, without the requirement of any template or additives. The method used was both simple and fast; proceeding through a sol–gel process triggered by UV light, and based on efficient Brönsted supercid photocatalysts. The film surface was characterized by a three-dimensional network of relatively well-defined and homogeneously dispersed micro- or nanopatterns as assessed by a variety of microscopy techniques. The concentration and structure of the n-alkylsilane as well as the film thickness were critical parameters in controlling the macrostructuration and the size of the perforations. Time-resolved Fourier transformed infrared spectroscopy allowed to probe in situ the compositional changes during the sol–gel process. By using spatially-resolved confocal Raman spectroscopy, we showed a preferential localization of the condensed n-alkylsiloxane species at the surface of the pores to form conformationally ordered monolayers. This self-assembly process was presumably driven by the surfactant properties of the hydrolyzed alkylsilane species formed in situ and stabilizing the macropores.

EFFECT OF WATER SOLUBLE POLYMER AND FIBER ON THE EARLY-AGE SHRINKAGE CRACKING OF CEMENTITIOUS COMPOSITES

Both polymeric fiber and water soluble polymer (WSP) have been reported effective in reducing early-age shrinkage cracking. The synergistic effect of cellulose based WSP and fiber on reducing early-age shrinkage cracking of cementitious composite exposed to a constant evaporation rate of 1 kg/(h.m2) environment was investigated in this paper. A fixed ratio of WSP was employed in the poly-acrylic fiber reinforced cementitious composites with various fiber content and aspect ratios. Results indicate that the addition of polymeric fibers reduced plastic shrinkage cracking, such as the total crack area, the average crack width and cracks wider than 1.5 mm. Further reductions on both the crack width and the total crack area were achieved when WSP was used in combination with fibers with an aspect ratio of less than 420. The synergistic reduction on the early-age shrinkage cracking may be attributed to the improvement of the fiber-matrix bond strength and polymer film formation on the drying front. Nevertheless, when fibers with an aspect ratio greater than 420 the synergistic effect provided by the WSP might be masked by the decreased fiber spacing or stronger crackbridging capability. In practical terms, preventing early-age shrinkage cracking by adding WSP not only can reduce fiber requirement but may also keep mixture workable.

Effects of swelling on the viscoelastic properties of polyester films made from glycerol and glutaric acid

AbstractViscoelastic properties have been determined for poly(glycerol‐co‐glutaric acid) films synthesized from Lewis acid‐catalyzed polyesterifications. The polymers were prepared by synthesizing polymer gels that were subsequently cured at 125°C to form polymer films. The polymers were evaluated for the extent of reaction before and after curing by Fourier transform infrared spectroscopy. They were subsequently immersed in dimethylsulfoxide, tetrahydrofuran, water, methanol, and hexane for 24 h. The amounts of solvent absorbed were monitored and recorded. Dependent up the solvent used, the polymers were able to absorb 9.5–261% of its weight. The effects of the solvent absorption on the viscoelastic properties of the polyester films were evaluated by determining their elastic modulus (G′), viscous modulus (G″), tan δG″/G′, and complex viscosity (η*) by performing oscillatory frequency sweep experiments. The elastic modulus (G′) and viscous modulus (G″) were both higher for the dry polymers than the solvent‐absorbed polymers. However, the polymer films were all higher in elastic (G′) character than viscous (G″) character. Therefore, tan δG″/G′ < 1 before and after immersion in solvents. Values for η* decreased with angular frequency for all of the polyesters tested in this study. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Investigating the self healing process on coated steel by SVET and EIS techniques

AbstractMicroencapsule was incorporated into an interpenetrating polymer network and applied over steel surface. A scratch was made on the coated surface and its self healing ability was studied using scanning vibrating electrode technique (SVET) and electrochemical impedance spectroscopy (EIS). Results of SVET studies show that the current density increases in the initial stage. After 24 h, the current density decreases, which indicating the formation of passive polymer film due to the diffusion of core polymer present in the microcapsules through the holidays. Increase in the resistance (107 Ω/cm2) of the self healing coating was observed after 24 h in EIS studies confirming the formation of the passive film. The results of the studies are discussed in this article. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Autonomic Shutdown of Lithium‐Ion Batteries Using Thermoresponsive Microspheres

AbstractAutonomic, thermally‐induced shutdown of Lithium‐ion (Li‐ion) batteries is demonstrated by incorporating thermoresponsive polymer microspheres (ca. 4 μm) onto battery anodes or separators. When the internal battery environment reaches a critical temperature, the microspheres melt and coat the anode/separator with a nonconductive barrier, halting Li‐ion transport and shutting down the cell permanently. Three functionalization schemes are shown to perform cell shutdown: 1) poly(ethylene) (PE) microspheres coated on the anode, 2) paraffin wax microspheres coated on the anode, and 3) PE microspheres coated on the separator. Charge and discharge capacity is measured for Li‐ion coin cells containing microsphere‐coated anodes or separators as a function of capsule coverage. For PE coated on the anode, the initial capacity of the battery is unaffected by the presence of the PE microspheres up to a coverage of 12 mg cm−2 (when cycled at 1C), and full shutdown (>98% loss of initial capacity) is achieved in cells containing greater than 3.5 mg cm−2. For paraffin microspheres coated on the anode and PE microspheres coated on the separator, shutdown is achieved in cells containing coverages greater than 2.9 and 13.7 mg cm−2, respectively. Scanning electron microscopy images of electrode surfaces from cells that have undergone autonomic shutdown provides evidence of melting, wetting, and resolidification of PE into the anode and polymer film formation at the anode/separator interface.

Poly(2‐aminobiphenyl), preparation, characterization, mechanism, and kinetics of the electropolymerization process

AbstractElectropolymerization of 2‐aminobiphenyl was carried out on glassy carbon, gold, and platinum electrodes, in aqueous–organic solvent mixtures, using a potentiodynamic technique. The choice of organic solvent strongly influences the film formation. In a mixture of 60% acetonitrile and 40% 1.0M HClO4, stable films were obtained. The poly(2‐aminobiphenyl) films were characterized with cyclic voltammetry, where the electrochemical activity of the formed polymer films was investigated in acidic and neutral aqueous solutions containing perchlorates or in potassium ferrocyanide. The prepared films posses a remarkable stability in acidic aqueous solutions and are also stable in some organic solvents. The stability of the polymer films depends on the pH of the solution, and the mechanism of the polymerization process involves deprotonation and head‐to‐tail coupling of oxidized monomers with its oligomeric radical cations. The kinetics of the electropolymerization process was investigated by determining the charge consumed during the electropolymerization as a function of time at different concentrations of the electrolyte components. The electropolymerization process follows first‐order kinetics with respect to the monomer and negative order with respect to HClO4. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

MICROSTRUCTURAL OBSERVATION AND SIMULATION OF POLYMER CEMENT WATERPROOFING MEMBRANE

A polymer-modified cement waterproofing membrane is formed by simultaneous cement hydration and polymer film formation, these rates are affected by the moisture content of the polymer emulsion used. The moisture content gradually decreases due to cement hydration and evaporation from the surface. This study focused on the changes caused in the waterproof layer by differences in the moisture environment. Four test pieces with different cement, polymer, and moisture contents were prepared and cured at 20 °C and relative humidities of 25, 60, and 98 %. The basic physical properties of the test pieces were studied in tensile tests; the structures were observed using an EPMA. Furthermore a simulation was carried out using a model that considers cement hydration, polymer film formation, and moisture evaporation rate. The simulation results well reproduced the experimental results.

Electrochromic films with high optical contrast prepared by oxidative electropolymerization of a novel multi-functionalized cyclometalating ligand and its neutral-charged Pt(II) complexes

A novel multi-functionalized cyclometalating ligand (H L) and its two neutral-charged Pt(II) complexes, i.e., [( L)PtCl] ( C1) and [( L)Pt(C CC 6H 5)] ( C2) (H L = 4-{ p-[N-(4-(9-carbazole))butyl-N-phenyl]anilino}-6-phenyl-2,2′-bipyridine), have been successfully synthesized and verified by 1H NMR, 13C NMR, elemental analysis and/or X-ray crystallography. The introduction of the electron-donating arylamino unit at the 4-position of the electron-withdrawing 6-phenyl-2,2′-bipyridine ligand forms the D–A system, resulting in the enhanced 1MLCT bands in the absorption spectra and intense orange emissions in the PL spectra of C1 and C2. The carbazole units grafted through alkyl chain in H L, C1 and C2 electrochemically trigger the efficient cross-linking reaction to form polymer films, which have been characterized by AC impedance, SEM and spectroelectrochemistry. Each of the poly-H L and poly- C1 films exhibits reversible oxidation with significant color change having a high contrast ratio (81.8% for poly-H L film and 67.3% for poly- C1 film), a reasonable coloration response time (6.3 s for poly-H L film and 3.1 s for poly- C1 film) and a comparable coloration efficiency (158 C −1 cm 2 for poly-H L film and 132 C −1 cm 2 for poly- C1 film) that can be switched by modulation of the applied potential.

A case study exploring the impact of an oxygen barrier coating on formulation stability, in-vitro dissolution and bioperformance

The impact of a carmellose sodium (sodium carboxymethycellulose)-based coat (Opaglos 2) on the stability of an oxygen-sensitive compound A and in-vitro dissolution and bioperformance of compound B has been investigated. Tablets containing compounds A and B were coated with various weight gains of Opaglos 2 and a comparative elegance coating (poly(vinyl alcohol)-based Opadry II). Film-coated tablets were assessed for oxidative degradation under accelerated stability conditions (30°C/65% RH and 40°C/75% RH). An apparent rank order of restriction of oxygen (O(2) ) permeability afforded by the coatings was observed, with only higher Opaglos 2 coating weight gains (6 and 8% w/w) providing adequate oxidative degradation stability for up to 52 weeks. Improved stability at the higher coating weight gains was attributed to incomplete polymeric film formation at lower coating weight gains. The 6% and 8% w/w Opaglos 2 formulations showed dissolution retardation compared with elegance-coated formulations in USP dissolution apparatus II, predicting significant impact on formulation bioperformance. However, pharmacokinetic studies in Beagle dogs showed similar bioperformance for all formulations. The Opaglos 2 coating system evaluated in these studies afforded adequate protection from oxidative degradation with no negative impact on bioperformance as compared to elegance coating. However, further studies are needed using several compounds to assess the broader applicability of these coatings.

High-Quality Inherently Organic Conducting Polymers Electrosynthesized from Fused-Ring Compounds in a New Electrolytic System Based on Boron Trifluoride Diethyl Etherate

Many efforts have been focused on the decrease of oxidation potentials of monomers in order to prepare high-quality inherently organic conducting polymers (IOCPs) from the fused-ring aromatic monomers. Boron trifluoride diethyl etherate (BFEE), a middle strong Lewis acid, is a co-ordination complex obtained from BF3 and diethyl ether (EE) in 1:1 equiv. proportion. The interactions between BFEE and the fused-ring aromatic monomers can lower their corresponding oxidation potentials and the catalytic effect of BFEE facilitates the formation of high-quality polymer films. Recent important works on the high-quality IOCPs electrosynthesized from fused-ring aromatic compounds in BFEE-based electrolytic system at low potentials are reviewed.

Formation of Ag Nanoparticle-Doped Foam-like Polymer Films at the Liquid–Liquid Interface

The composite poly(2-vinylpyridine) (P2VP)-Ag(+) foam-like thin films were prepared at the interface between AgNO(3) aqueous solution and polymer chloroform solution at 25 °C. An X-ray photoelectron spectroscopy (XPS) investigation indicated that Ag(+) ions in the composite films were partially transformed to Ag atoms after irradiated by UV-light and completely transformed to Ag atoms after being treated with KBH(4) aqueous solution. Ag nanoparticles with the average sizes of 2.71 ± 0.82 and 3.28 ± 1.20 nm were generated in these two transferred films with different treatments, respectively. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images showed clearly that the composite films were composed of microcapsules whose walls had multilayer structures, and the nanoparticles were incorporated in the walls. The formation of the composite films at the liquid-liquid interface was attributed to the adsorption of the polymer molecules at the interface, coordination between the pyridine groups and Ag(+) ions, and self-assembly of the composite molecules. Furthermore, the catalytic activity of the composite films was evaluated using the reduction of 4-nitrophenol (4-NP) by KBH(4). The results demonstrated that the composite thin films have high and durable catalytic activity.

Photoacoustic monitoring of thermal wave interference effects during the formation of polymeric thin films from solutions

In this work, the potential of photoacoustic (PA) technique in the analysis of the formation of polymer films by evaporation from aqueous solutions is explored. Experiments are performed using different aqueous volume fractions of two different polymers, PEDT:PSS and a white liquid glue. The liquid sample is deposited on a metallic substrate attached to a modified PA cell that allows the monitoring of the evaporation process and development of the polymeric film. It is shown that when the thickness of the sample is of the order of the thermal diffusion length, maxima and minima of the PA signal, due to thermal wave interference effects, are observed. In the last stage of the process, the PA signal reaches a stable value which depends on the thickness of the formed film. The kinetics of the polymeric film formation, the dependence of the evaporation rate of the solvent as well as the final thickness of the polymeric film is discussed. These results can be useful in establishing a methodology for the photothermal monitoring and thermal characterization of the development of polymeric films from solutions.

Formation of ultrathin protective films for ophthalmological use from aqueous solutions of polymers and taurine

Aqueous dextran solutions, polyhexamethyleneguanidine hydrochloride and Sovidone and their mixtures with taurine were used to form stable ultrathin protective films for ophthalmological use. Addition of taurine to dextran and polyhexamethyleneguanidine solutions induced an association between polymer macromolecules in the two-dimensional film and a decrease in the surface activity of the solution. Addition of taurine to Sovidone solutions altered the conformation of macromolecular globules and increased the surface activity of the solution. Use of these solutions as the bases for eye drops did not harm the lipid layer of the tear film, and that rapidly formed polymer films could successfully be replaced by natural lipids via natural processes during recovery of the functions of the tear glands.

Synthesis, Spectroscopic Properties, and Electropolymerization of Azulene Dyads

Four azulene dyads have been synthesized and studied by spectroscopic and electrochemical methods. A triarylamine, a boron-dipyrromethene (BDP or BODIPY), a porphyrin, and an isoalloxazine moiety have been linked to an extended π electron system at the 2-position of azulene, leading to the dyads 1-4, respectively. For the synthesis of 1-4, first 2-(4-ethynyl-phenyl)azulene (EPA) was prepared, which was further reacted with the halogenated chromophores by Pd-catalyzed cross-coupling reactions. The dyads 1-4 exhibit strong absorption bands in the visible range, which are dominated by the absorption spectra of the individual subchromophores. Fluorometric studies of 2-4 revealed that after excitation of the subchromophoric unit attached to the parent azulene moiety, quenching mainly through energy transfer to azulene is effective, whereas possible charge-transfer interactions play only a minor role. Potentiodynamic oxidation of the dyads 1-4 leads to the formation of polymer films, which are deposited at the electrode. The polymer film derived from 1 was further characterized by spectroelectrochemistry. During positive doping of poly-1, a strong absorption band appears at 13,200 cm(-1), which is typical for triarylamine radical cations. This band is overlapping with a broad absorption band in the low-energy region that might be caused by charge-transfer interactions within the polymer.

Preliminary investigation of factors determining self-organised structures preparation in polymer layers

Factors determining creation of self-organized structures, Bénar–Marangoni cells, during the process of solvent evaporation from the polymer solution and formation of polymer film were studied. Examined parameters were temperature, temperature gradient, rate of drying, height of a liquid layer, area for film preparation, viscosity, molecular weight distribution, etc. A special apparatus, micro condensation drying system, was engineered for this study. As a model system, hydroxyethyl cellulose aqueous solution was used for its excellent film-forming ability and the tendency to self-aggregation. Experimental results, presented in a wide spectrum of self-organized patterns, show the complexity of the problem and the crucial role of molecular weight distribution of the polymer in the fixation of organized structures under highly non-equilibrium conditions.

Development of manipulation technology of ferroelectric polymer film: Photo-lithographic patterning and multilayer formation

The micrometer-scale patterning of ferroelectric polymer film of poly(vinylidene fluoride-trifluoroethylene) was performed using an ordinary photo-lithographic method with a commercialized photoresist, developer and photoresist stripper. To hinder the ferroelectric polymer film from dissolving at the photoresist stripper, the solubility of the photoresist stripper was controlled by dilution with an insoluble solvent, in this case water. In addition, patterning of the top electrode on the ferroelectric polymer film was completed by a lift-off process, which also used the diluted photoresist stripper. From the polarization–voltage relationships, no thermal and chemical degradation was found during the patterning and lift-off process. Another new process for the multilayer formation of ferroelectric polymer film was performed by a detach-and-transfer method with ferroelectric polymer film. From the polarization–voltage relationships, ferroelectricity was shown in detach-and-transferred ferroelectric polymer film. Therefore, it is concluded that the two conditions of photolithographic patterning and the multilayer formation of ferroelectric polymer film were established successfully and that these methods will be helpful for variable device fabrications and applications with ferroelectric polymer film.

Formation of novel polymeric films derived from 4-hydroxybenzoic acid

This work reports electrochemical and morphological studies of formation of poly(4-hydroxybenzoic acid), prepared in different pH, on the graphite surface. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance (EQCM) and atomic force microscopy (AFM) have been carried out to study the modified electrodes formed. The electrodes modified with poly(4-HBA), prepared in pH 0.5 and 7.0, presented oxidation/reduction peaks, but no peak was detected to modified electrodes prepared in pH 12.0. Voltammetric studies showed decrease in oxidation/reduction currents and slower electron transport across the polymer for all pH values, however, the electron transport was higher when the polymer was prepared in acid medium. EIS analysis indicated that the charge transfer resistance for poly(4-HBA) electropolymerized at pH 12.0 was about 2 and 1.4 times higher when compared to pH 0.5 and 7.0, respectively. Studies through EQCM showed higher amount of polymer mass deposited in acid medium. Images by AFM indicated that the topography is affected by pH value, whereas films prepared in acidic pH conditions presented higher roughness.

Interfacial properties of polymethyl alpha-cyanoacrylate and polybutyl alpha-cyanoacrylate.

Several physical properties of two polyalkyl alpha-cyanoacrylates relevant to their use in pharmaceutical dosage forms have been investigated. Formation of polymer films at several oil-water interfaces reveals films of diverse morphology. The retardation of solute transfer across an oil-water interface caused by the presence of polymer films formed in situ from the monomers has revealed that the methyl derivative forms the more effective barrier to the test solute, gentian violet. The emulsion-stabilizing properties of the methyl polymer have been studied, and the film-forming properties of the monomers spread from benzene onto water surfaces have been examined using a surface balance.

Electrochemistry of Conductive Polymers 47: Effects of Solubilizers on 3,4-Ethylenedixoythiophene Oxidation in Aqueous Media and Properties of Resulting Films

Effects of a few solubilizers on electrochemical oxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous media and on electrochemical, morphological, and electronic properties of its resultant thin polymer (PEDOT) films have been investigated by Fourier transform electrochemical impedance spectroscopic and current sensing atomic force microscopic experiments. Two different types of solubilizers including hydroxypropyl-β-cyclodextrin (HpβCD) forming an inclusion complex with a hydrophobic species and two anionic surfactants forming micelles, sodium dodecylsulfate (SDS) and sodium dodecylsulfonate (SDBS), were used due to the low solubility of the EDOT monomer in aqueous media. Results indicate that anionic surfactant micelles protect electrogenerated cationic species of monomers and oligomers by encapsulating them, leading to formation of polymer films of better properties. The polymer growth characteristics were shown to be closely related to electrical properties of resultant polymer films; PEDOT films...

Effect of mineral admixtures and viscosity modifying admixtures on plastic shrinkage cracking of cementitious composites

The effects of mineral admixtures (MAs) and cellulose-based viscosity modifying admixtures (VMA) on bleeding and plastic shrinkage cracking of cementitious mortar exposed to a windy environment were examined for this article. Cementitious composites containing 25% of three types of MAs, i.e. fly ash and two finenesses of slag were incorporated with two molecular weights of VMA with various mixing ratios in the mortar specimens. Plastic shrinkage cracking tests were conducted on the restrained plate subject to a constant evaporation rate of 1000 g/(m2 h) using a speed adjustable fan in an environment chamber. Bleeding and total crack areas (TCA) and crack widths and crack width distribution were evaluated. In addition, the viscosity of cementitious composite and surface tension of pore solution were also investigated. Without VMA, with the addition of slag, viscosity increased and bleeding reduced, and thus TCA increased. The opposite was found when fly ash was added. With the addition of VMA, bleeding and surface tension reduced significantly. Cementitious mortars with specified VMA dosages appeared to be significantly effective in reducing TCAs, average crack width, and large cracks. The crack reductions are fairly well correlated with surface tension, VMA dosage, and polymer film formation.