Polystyrene Coatings Research Articles

Tailoring the Wettability and Substrate Adherence of Thin Polymer Films with Surface-Segregating Bottlebrush Copolymer Additives.

We developed "reactive" bottlebrush polymers based on styrene (S) and t-butyl acrylate (tBA) as additives for polystyrene (PS) coatings. The bottlebrush polymers spontaneously bloom to both the air and substrate interfaces during solution casting. While neat PS films are hydrophobic and poorly adhere to the native oxide on clean silicon wafers, the hydrophilicity and substrate adherence of bottlebrush-incorporating PS films can be tailored through the thermally activated deprotection of tBA to produce acrylic acid (AA) and acrylic anhydride (AH). A critical design parameter is the manner by which tBA is incorporated into the bottlebrush: When the bottlebrush side chains are copolymers of S and tBA, the extent of deprotection is extremely low, even after prolonged thermal annealing at elevated temperature. However, when the bottlebrush contains a mixture of poly(t-butyl acrylate) (PtBA) and PS side chains, nearly all tBA is converted to AA and AH. Consequently, using the "mixed-chain" bottlebrush design with thermal processing and appropriate conditioning, the water contact angle is reduced from over 90° on unmodified PS down to 75° on bottlebrush-incorporating PS films, and the substrate adherence is improved in proportion to the extent of tBA deprotection.

From Blue to White: Sustainable Luminescent Metal Organic Framework for Hybrid Light‐Emitting Diodes

AbstractHybrid light‐emitting diodes based on photon down‐converting filters with metal organic frameworks (MOFs) are mainly restricted to cross‐breed materials (i.e., nonemissive MOFs host and guest emitters) due to the lack of highly photostable and luminescent MOFs (LMOFs). This work reports a sustainable and cost‐effective blue‐emitting Zn‐based MOF with the ligand 1,1,2,2‐tetrakis(4‐(pyridin‐4‐yl)phenyl)ethene (Zn‐2‐LMOF) and their host:guest hybrids with Rhodamine B emitter RhB@LMOF toward blue‐ and white‐emitting hybrid light‐emitting diodes (HLEDs). Zn‐2‐LMOF features blue emission (λem = 480 nm) with impressive photoluminescence quantum yield (ϕ) values of 50% (powder) and 70% (polystyrene coatings). Likewise, hybrid RhB@LMOF features a white emission with ϕ of 30–40% in polystyrene coatings. They lead to blue (Zn‐2‐LMOF; x/y CIE color coordinates of 0.28/0.47) and white (RhB@LMOF; x/y CIE color coordinates of 0.31/0.32) HLEDs with stabilities of 20 and 45 h at 50 mA on‐chip under ambient operation, respectively. Though this device performance is average in HLEDs, the device degradation is mainly attributed to the photoinduced oxidation of the ligand in the MOF structure that further leads to the RhB degradation; a key information for future developments in luminescent MOFs.

Low roughness, elevated stiffness and thickness-modulated surface nanocomposites based on the controlled deposition of polystyrene nanoparticles

A significant interest in the versatile and controlled fabrication of surface coatings is present nowadays in materials science. Here we present a repeatable and efficient method of obtaining polystyrene (PS) layers based on the use of controlled deposition of polystyrene nanoparticles (PS-NPs) in the strictly defined amount and forming a smooth (RMS below 1 nm) coating by melting them. Due to the dependence between the concentration of the applied nanoparticles and the thickness of the obtained homogeneous layer, it is possible to control the thickness of the PS coating straightforwardly. Moreover, in this technique, the initial solvent is quickly evaporated, which results in coatings with a higher DMT modulus (up to 8 GPa) compared to spin- or dip-coated methods. We have obtained PS layers on silicon, glass, gold and steel substrates and we have shown the application of our method to cover highly-rough patterned surfaces. Finally, our method is time- and cost-effective due to the inclusion of only the simple heating process and no need to use any advanced equipment. The topography and thickness of PS coatings were studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM) and all are in good correlation with the theoretical calculations.

Anti-corrosive Polystyrene Coatings Modified with Tannic Acid on Zinc and Steel Substrates

Polystyrene (PS) polymer layers were prepared and studied as anti-corrosive barrier layers on both carbon steel and zinc substrates. To increase the corrosion resistance of the coatings, two different approaches were considered: (i) the use of mesoporous silica-nanocontainers impregnated with a corrosion inhibitor (tannic acid) introduced into the polystyrene matrix and (ii) direct impregnation of polystyrene coatings with the same corrosion inhibitor. The impregnated nanocontainers were characterized by Transmission Electron Microscopy. The thickness and the adhesion of the coatings were measured, and their corrosion behavior was investigated by Electrochemical Impedance Spectroscopy. Results showed that the used inhibitor slightly decreased adhesion, but significantly increased the corrosion resistance of the coatings. The direct introduction of tannic acid into the polymer matrix offers higher corrosion resistance than in the case of polystyrene coatings doped with impregnated silica nanocontainers.

Electrospun highly corrosion-resistant polystyrene\u2013nickel oxide superhydrophobic nanocomposite coating

A key challenge in producing superhydrophobic coatings (SHC) is to tailor the surface morphology on the micro-nanometer scale. In this work, a feasible and straightforward route was employed to manufacture polystyrene/nickel oxide (PSN) nanocomposite superhydrophobic coatings on aluminum alloys to mitigate their corrosion in a saline environment. Different techniques were employed to explore the influence of the addition of NiO nanoparticles to the as-prepared coatings. PSN-2 composite with ~ 4.3 wt% of NiO exhibited the highest water contact angle (WCA) of 155° ± 2 and contact angle hysteresis (CAH) of 5°.Graphic abstractEIS Nyquist plots of 3 g of electrospun polystyrene coatings (a) without and with (b) 0.1, (c) 0.15, and (d) 0.2 g of NiO.

Post-consumption foamed polystyrene coatings for surface tension modification

Foamed polystyrene, commercially known as Icopor, occupies a very important place in the transport systems, and conservation of freight and food, but it is also one of the main polymeric pollutants, due to its low biodegradability, and low reuse. Polystyrene has in its structure aromatic and aliphatic functional groups, which have a high hydrophobicity, which makes them candidates as modifiers of permeability and surface properties, although for this purpose the implementation of solvents is also required. In the following work, polystyrene residues for domestic and food use were used to obtain coatings, which allow surface tension to be modified, on surfaces with high water permeability. For this purpose, the polymeric residue was dissolved in organic type solvents, generating a varnish, which was used to coat the study surface, from which the surface tension with respect to water was previously known by analysing the contact angle; to be compared with those obtained after coating, resulting in an increase in the contact angle, which indicates an increase in surface tension, conferred on the new surface hydrophobicity.

Measuring Force of Droplet Detachment from Hydrophobic Surfaces via Partial Cloaking with Ferrofluids.

This paper presents a new approach to measure the force required to detach a water (a polar liquid) droplet from a hydrophobic surface. This is done by partially cloaking the droplet with a high-surface-tension oil-based ferrofluid and using a magnet to apply a controllable body force to the resulting compound droplet. Placing the assembly on a sensitive scale, the magnet can then be brought closer to the droplet to detach it from the surface while recording the forces applied to the droplet. The work presented here is novel as it uses the concept of partial cloaking in which the solid-droplet contact area is not contaminated by the ferrofluid (and the measured forces do not need postprocessing). Our study is accompanied by numerical simulations aimed at improving our understanding of the interplay between the interfacial forces in a two-phase droplet under the influence of a strong (detaching) body force and at providing additional data for in-depth analyses of these forces. In particular, the minimum ferrofluid volume required for successful water droplet detachment from hydrophobic surfaces is computed for ferrofluids of different surface tensions, and they are compared to experimental data obtained from detaching water droplets from electrospun polystyrene coatings. It is also shown that the detachment force measured via partial cloaking is independent of the volume of the ferrofluid used for the experiment.

Uneven Coating Influences on Electrical Impedance of Quartz Crystal Microbalance

High shear modulus coating material does not provide loading effect to the Quartz Crystal Microbalance sensor. The condition is met when the coating material was glassy and the layer was homogeneous. Polystyrene is considered as a glassy coating material when used on 10MHz Quartz Crystal Microbalance. Homogeneous and compact polystyrene coatings that are glassy can be obtained using the spin coating method. The film’s rigid condition is shown by the sensor impedance value at the series resonance frequency after coating. However, using ultrasonic spray coatings, it was known that polystyrene films are formed not as homogeneous as when coated using spin coatings. We observed that Quartz Crystal Microbalance was damped by the polystyrene film when the coating film was not evenly distributed over the sensor surface, especially on the sensor surface above the electrode. The minimum impedance of the QCM sensor increased significantly. The unevenness of the coating causes the damping effect on the QCM sensor. The minimum sensor impedance before coating was less than 15 Ohms. When the polystyrene layer was uneven, we found that the impedance increased by more than 25 Ohms. The results showed that the distribution of polymer layers on the sensor surface is one of the important factors that must be considered to avoid the effect of damping on the sensor. The measurement results showed that the sensor has a negative mass effect.

Superhydrophobic behavior of polymer-coated nanowire-arrays as a function of interfacial affinity and etching

We have investigated the superhydrophobic behavior of coatings of polydimethylsiloxane (PDMS) and polystyrene (PS) on ZnO nanowire-arrays. PDMS produced a conformal coating on the ZnO nanowires due to high interfacial affinity between ZnO and PDMS, resulting in a large water contact angle of 168.0° (compared to 108.8° for planar PDMS surfaces) and droplet roll-off angles that were too small to measure. The superhydrophobicity of these coatings is among the largest reported for any polymeric coating. PS instead preferentially coated the bases of the ZnO nanowires and valleys between nanowires due to low interfacial affinity between ZnO and PS, resulting in a water contact angle of 149.3° (compared to 90.5° for planar PS surface) and droplet roll-off angles of 5°–8°. If, however, the ZnO nanowires were etched away after PS deposition, hollow tube-like nanostructures of PS were left behind, and exhibited a water contact angle of 164.3° and droplet roll-off angles of 1°–2°. These nanostructured PS coatings offer unique potential for food-safe superhydrophobic coatings because they consist only of PS without any inorganic components.

Droplet Mobility on Hydrophobic Fibrous Coatings Comprising Orthogonal Fibers.

Water droplet mobility on a hydrophobic surface cannot be guaranteed even when the droplet exhibits a high contact angle (CA) with the surface. In fact, droplet mobility on a surface, especially a fibrous surface, has remained an unsolved empirical problem. This paper is a combined experimental-computational study focused on droplet mobility on a fibrous surface. Electrospun polystyrene (PS) coatings were used in this work for their ability to exhibit high CAs simultaneously with low droplet mobility. To simplify this otherwise complicated problem and better isolate droplet-fiber interactions, the orientation of the fibers in the coatings was limited to the x and y directions. As the earth gravity was not strong enough to mobilize small droplets on PS coatings, experiments were conducted using ferrofluid droplets, and a magnet was used to make them move on the surface. Experimentally validated numerical simulations were used to enhance our understanding of the forces acting on a droplet before moving on the surface. Effects of Young-Laplace CA and fiber-fiber spacing on droplet mobility were investigated. In particular, it was found that droplet mobility depends strongly on the balance of forces exerted on the droplet by the fibers on the receding and advancing sides.

Plasma polymerization of styrene using an argon-fed atmospheric pressure plasma jet

In this paper, the authors describe an alternative polymerization process of styrene monomer. Styrene, placed in a Plexiglas crucible to minimize splattering, was treated with an argon-atmospheric plasma jet, at a gas flow rate of 12.5 standard cubic feet per hour for 12 min, using a 450-W neon sign transformer power supply. Treated samples were transferred from the crucible to glass substrates and allowed to dry at room temperature. Solvent washing analysis showed an average product retention of 66.59% proving that polymerization occurred. Contact angle measurements of the treated samples showed an increase in hydrophobicity from 78.12° for untreated styrene to 88.14° for plasma-treated styrene. Fourier transform infrared analysis revealed the absence of the C=C, C=C-H and the presence of the C=O and C-O-C functional groups upon treatment. It was concluded that styrene was polymerized successfully through the use of an argon fed atmospheric pressure plasma jet, and that hydrophobic plasma-polymerized polystyrene coatings were successfully deposited onto glass substrates.

Electromigration properties of capillary columns with polystyrene coating as a stationary phase

Relationships in variation of the surface energy of polystyrene coatings on melted quartz at varied polymer concentration in solution were refined by studying the functional chemical composition and surface structure of model coatings of atactic polystyrene on quartz plates and the electromigration properties of capillary columns with polystyrene coatings. The optimum concentration and temperature-kinetic conditions for preparing polystyrene coatings on quartz capillaries with controllable electrokinetic properties were determined.

Superhydrophobic polysiloxane filament growth on non-activated polymer coatings

Polysiloxane nanofilaments prepared on BA–MMA–MAA (a) and polystyrene (b) coatings via liquid phase reactions.

On the combined use of nanoparticles and a proper solvent/non-solvent system in preparation of superhydrophobic polymer coatings

A novel method including combined use of nanoparticles and non-solvent is proposed for fabrication of superhydrophobic polystyrene coatings. The proposed method results in utterly homogenous and mechanically stable coatings with excellent adhesion to the substrate as compared to the other commonly used solution-based methods. It is proved that individual use of nanoparticles and non-solvent could lead to superhydrophobic behavior but at the price of adding very high contents. Based on water contact angle results, the proposed method causes a significant reduction in the required contents of nanoparticles (150 wt% to 20 wt% with respect to the polymer) and non-solvent (33 vol% to 9–16 vol%) for achieving superhydrophobicity. A thorough investigation of surface composition and morphology is also conducted via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. Moreover, a different approach is employed for evaluation of surface topography using diverse roughness parameters. It was found that a combination of roughness parameters should be considered for a proper surface analysis instead of only using average roughness and root mean square. It was also demonstrated that the surface roughness uniformity is another key factor to achieve a self-cleaning behavior.

Superhydrophobic TiO2 coatings formed through a non-fluorinated wet chemistry route

We present a facile and low cost non-fluorinated wet chemistry route yielding rough and highly hydrophobic surfaces. This procedure is based on a nanosphere lithography (NSL) method using polystyrene (PS) spheres. Multilayer PS coatings were impregnated with a sol–gel TiO2 polymeric sol and then heat-treated at 500°C. Derived NSL-structured TiO2 coatings were then grafted with hexadecyl trimethoxysilane (C16). The morphology of structured coatings was analyzed by optical, scanning electron, and atomic force microscopy, and the water wettability of TiO2 coating grafted with the C16 precursor was studied with respect to NSL features. It is shown that the synergy between the hydrophobicity imparted by the C16 precursor and roughness effects arising from NSL structuration leads to superhydrophobic coatings. In optimized conditions, the static contact angle of 11.6μL water droplets deposited on the surface is around 160° with a corresponding tilt angle as low as 1°.

Fabrication of terahertz hollow-glass metallic waveguides with inner dielectric coatings

Hollow-core glass waveguides (HCWs) with inner coatings of silver and polystyrene (PS) have been fabricated for transmission of terahertz radiation. A liquid-phase chemical deposition process was used to deposit silver and PS thin film coatings inside glass tubing. The PS dielectric layer can substantially lower the loss of the HCW compared to the metal-only waveguide. A polymer coating was chosen because it is possible to deposit the dielectric film thickness required for operation in the terahertz regime. Specifically, the dielectric film thickness is proportional to the wavelength so the PS coatings need to be on the order of 10 to 15 μm to minimize transmission losses at terahertz frequencies. This is much thicker than the submicron thick dielectric coatings needed in the IR region. The thickness of the PS film depends on the concentration of PS in the coating solution and the coating rate. Both of these parameters are studied and related to the losses in the waveguides. The lowest loss of 0.95 dB/m at 119 μm (2.5 THz) was obtained for hybrid HE mode propagation in a waveguide with a 8.2 μm thick PS film deposited inside a 2.2 mm bore, 90 cm long glass tube.

Ion Beam Lithography for Nano-scale Pattern Features

AbstractWith the expected availability of new tools for creating patterned ion beams, containing few-nanometer features, it is important to examine the fidelity of registering such patterns in the receiving medium, such as a photoresist layer in a lithographic fabrication process. In this paper, we report experiments exploring the characteristics of ion beam patterning of poly methyl methacrylate (PMMA) and polystyrene (PS) coatings on silicon substrates, with respect to their response as positive / negative resists to patterned low-energy H+, He+ and Ne+ beams. We examine by AFM the feature profiles thus created after solvent development of the polymer layers, and we examine the dependence of the polymer response upon ion species and fluence. Edge resolution ¡Ü20 nm is readily obtained, and broad process windows are identified in fluence ranges around 1013 ions/cm2. Proximity effects are shown to be negligible, except after exposure at very high ion fluences. Granularity within the final pattern features is shown to be a potential concern for high energy, light ion irradiations. Optimization of edge resolution is clearly possible, by appropriate selection of ion species, energy and fluence to suit the receiving medium.

Gate Dielectric Chemical Structure−Organic Field-Effect Transistor Performance Correlations for Electron, Hole, and Ambipolar Organic Semiconductors

This study describes a general approach for probing semiconductor-dielectric interfacial chemistry effects on organic field-effect transistor performance parameters using bilayer gate dielectrics. Organic semiconductors exhibiting p-/n-type or ambipolar majority charge transport are grown on six different bilayer dielectric structures consisting of various spin-coated polymers/HMDS on 300 nm SiO(2)/p(+)-Si, and are characterized by AFM, SEM, and WAXRD, followed by transistor electrical characterization. In the case of air-sensitive (generally high LUMO energy) n-type semiconductors, dielectric surface modifications induce large variations in the corresponding OTFT performance parameters although the film morphologies and microstructures remain similar. In marked contrast, the device performance of air-stable n-type and p-type semiconductors is not significantly affected by the same dielectric surface modifications. Among the bilayer dielectric structures examined, nonpolar polystyrene coatings on SiO(2) having minimal gate leakage and surface roughness significantly enhance the mobilities of overlying air-sensitive n-type semiconductors to as high as approximately 2 cm(2)/(V s) for alpha,omega-diperfluorohexylcarbonylquaterthiophene polystyrene/SiO(2). Electron trapping due to silanol and carbonyl functionalities at the semiconductor-dielectric interface is identified as the principal origin of the mobility sensitivity to the various surface chemistries in the case of n-type semiconductors having high LUMO energies. Thiophene-based n-type semiconductors exhibiting similar film morphologies and microstructures on various bilayer gate dielectrics therefore provide an incisive means to probe TFT performance parameters versus semiconductor-dielectric interface relationships.

Moisture absorption and wet-adhesion properties of resin transfer molded (RTM) composites containing elastomer-coated glass fibers

Transient water sorption studies were carried out at constant temperature (45 °C) to assess the hydrolytic stability and wet-adhesion properties of glass fiber/epoxy composites having different sizings. Lower effective diffusivity values correlated with improved overall mechanical performance in relation to the control (unsized) samples, and revealed the importance of changing the surface energy characteristics of glass fibers by using distinctively hydrophobic pure polymers. Admicellar polystyrene and styrene-isoprene coatings formed over the inorganic reinforcement appear to create an interface with much higher resistance to moisture attack than the organosilane/matrix interface in composites with commercial sizing. This fact was corroborated by comparing their effectiveness in property retention, which showed the mechanical property (e.g. ultimate tensile strength, stiffness and interlaminar shear strength) increased with respect to the uncoated composites in the dry state as well as after water saturation. Poor wet-adhesion properties of commercial sizings in humid conditions could perhaps be attributed to higher contents of inert material present in these coatings. Fractography analysis was consistent with the previous observations regarding catastrophic failure in composites without coating, and suggested that interfacial debonding, extensive fiber pullout and matrix crazing were the major contributors to the overall failure mechanism. Failed surfaces of both commercial and elastomer-coated composites also showed areas with fiber pullout, but in this case, matrix residues remained on the fiber surfaces, yielding a much rougher appearance. Good fiber-matrix adhesion, particularly in admicellar-coated composites, was also revealed by the presence of hackles and more tortuous failure paths.

Covalent DNA Immobilization on Polymer-Shielded Silver-Coated Quartz Crystal Microbalance Using Photobiotin-Based UV Irradiation

The use of a commercial, silver-coated quartz crystal microbalance (QCM) as a disposable, low-cost, and reliable DNA sensor is presented. This is an incorporation of polymer-based silver electrode shielding and photochemistry-based surface modification for covalent DNA immobilization. To prevent undesired oxidation, the silver electrodes are coated with thin polystyrene films. The polymer surfaces are then modified by a photoreactive biotin derivative (photobiotin) under UV irradiation. The resulting biotin residues on the polymer-shielded surface react with a tetrameric avidin. Consequently a biotin-labeled DNA probe can be immobilized through a biotin–avidin–biotin bridge. A 14-mer single-stranded biotin–DNA probe and a 70-mer single-stranded DNA fragment containing complementary or noncomplementary sequences are used as a model system for DNA hybridization assay on the proposed sensors. The shielding ability of the polystyrene coatings after photo irradiation is investigated. The DNA probe binding capacity, hybridization efficiency, and kinetics are also investigated.