PS Films Research Articles

Influence of Zinc Oxide Nanoparticles on the Optical, Dielectric and Electromagnetic Interference Shielding Performance of Polystyrene Films

In the present work, Zinc oxide (ZnO) nanoparticles are synthesized using solvothermal technique. Polystyrene-ZnO (PS/ZnO) nanocomposite films are synthesized by solution casting procedure. PS/ZnO films are analyzed by XRD, FTIR and UV-Vis spectroscopic techniques. The addition of ZnO into the PS film is found to decrease the optical band gap (OBG) from 4.07 eV to 1.86 eV. Frequency dependence of dielectric constant (ε′), loss tangent (tanδ), ac conductivity (σac) and electromagnetic (EM) interference shielding effectiveness (SE) studies have been undertaken on the pure PS and PS/ZnO films. Insertion of ZnO into pure PS polymer matrix is found to enhance ε′, tanδ, σac, and SE considerably. The ε′ and tanδ were reduced with an enhancement in the frequency. σac of PS/ZnO nanocomposites was enhanced with rise in frequency and electrical conduction process in PS/ZnO film is in agreement with an electron-hopping model. EM interference SE is reduced with rise in the frequency. PS/ZnO films were proven as a favorable functional substance for the absorbing of EM waves at lower frequencies.

Amphiphilic Block Copolymer Micelles in Selective Solvents: The Effect of Solvent Selectivity on Micelle Formation.

We investigated the micellar behavior of a series of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers in different P4VP-selective alcoholic solvents. The micellar behavior was further correlated with the spectroscopic ellipsometry results obtained on swelling of PS and P4VP polymer films in the corresponding solvent vapors. The time-resolved (in situ) dynamic light scattering (DLS) measurements, in combination with (ex situ) electron microscopy imaging, revealed information about the aggregation state of PS-b-P4VP BCP in different alcohols and the effect of heat treatment. The ellipsometry measurements allowed us to estimate the difference in solvent selectivity toward PS/P4VP pair. Both DLS and ellipsometric studies suggested that less polar alcohols (i.e., 1-propanol, 1-butanol, and 1-pentanol) are likely to be close to each other in terms of their selectivity toward PS/P4VP pair, whereas more polar ethanol and methanol show the highest and the lowest affinity toward P4VP, respectively.

Study of nonlinear optical properties of TiO2 – polystyrene nanocomposite films

We consider an ex-situ prepared TiO2 − polystyrene (TiO2 − PS) nanocomposite, with different concentration of TiO2 nanoparticles (NPs), deposited by the spin-coating method on quartz substrates. Nonlinear optical properties of the TiO2 − PS nanocomposite films are studied using the Z-scan technique. Structural properties of the films are investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The optical band gap energy of the TiO2 − PS films are determined from the optical absorption spectra. The relation between the optical nonlinearities and the bandgap energy, as a microscopic electronic property of the semiconductor nanocomposite, is established. It is shown that an increase in the content of TiO2 NPs in the nanocomposite films results in bandgap narrowing and concomitant enhancement of optical nonlinearities. It is proposed that bandgap narrowing and enhancement of optical nonlinearities can be ascribed to the introduction of mid-gap states as a result of the formation of surface defects in TiO2 NPs. The results of this work indicate that incorporation of TiO2 NPs in the PS polymeric matrix can be a new way for bandgap narrowing of TiO2 NPs toward the visible light region, which is of great interest for their application in this part of the spectrum. Furthermore, enhancement of the optical nonlinearities of the spin-coated TiO2 − PS films by increasing the TiO2 NP content can open up new avenues for their use as nonlinear optical films in photonics applications.

Proton Beam Induced Modification of Luminescence Properties of Polystyrene/Al2O3 Polymer Nanocomposites.

Polystyrene polymer (PS)/Al2O3 nanocomposite films were synthesized from PS:Al2O3 (1-x):x mixtures (x = 3wt%) via solution casting method. These nanocomposite films were exposed to 5MeV proton beam of different fluences. The proton beam induced changes in optical and luminescence properties of PS and PS:Al2O3 films have been investigated using FTIR, UV-visible, Photoluminescence and thermoluminescence studies. FTIR studies concede reduction in the peak intensity due to doping of Al2O3 and proton irradiation. The UV-visible spectra show shifting of absorption edge with increasing fluence. This can be attributed to creation of conjugated system of bonds. The band gap of PS and 3wt% Al2O3 doped PS is observed to be 4.38eV and 4.34eV, respectively, whereas the band gaps of proton irradiated 3wt% Al2O3 doped PS films are found to be 4.28eV and 4.23eV at the fluences of 1 × 1012 ions/cm2 and 1 × 1013 ions/cm2, respectively. The photoluminescence emission spectra show three peaks, wavelength at 411nm, 435nm and 462nm corresponding to the PS in violet-blue region when excited with near UV wavelength of 380nm. The intensity of emission peaks was found to increase with increasing fluence. The thermoluminescence curves of PS/Al2O3 were analysed using glow curve deconvolution method (GCD). The increase in TL peak intensity of the glow curve was observed as fluence increase.

Biodegradation of mixture of plastic films by tailored marine consortia.

This work sheds light on the physicochemical changes of naturally weathered polymer surfaces along with changes of polymer buoyancy due to biofilm formation and degradation processes. To support the degradation hypothesis, a microcosm experiment was conducted where a mixture of naturally weathered plastic pieces was incubated with an indigenous pelagic community. A series of analyses were employed in order to describe the alteration of the physicochemical characteristics of the polymer (FTIR, SEC and GPC, sinking velocity) as well as the biofilm community (NGS). At the end of phase II, the fraction of double bonds in the surface of microbially treated PE films increased while changes were also observed in the profile of the PS films. The molecular weight of PE pieces increased with incubation time reaching the molecular weight of the virgin pieces (230,000 g mol-1) at month 5 but the buoyancy displayed no difference throughout the experimental period. The number-average molecular weight of PS pieces decreased (33% and 27% in INDG and BIOG treatment respectively), implying chain scission; accelerated (by more than 30%) sinking velocities compared to the initial weathered pieces were also measured for PS films with biofilm on their surface. The orders Rhodobacterales, Oceanospirillales and Burkholderiales dominated the distinct platisphere communities and the genera Bacillus and Pseudonocardia discriminate these assemblages from the planktonic counterpart. The functional analysis predicts overrepresentation of adhesive cells carrying xenobiotic and hydrocarbon degradation genes. Taking these into account, we can suggest that tailored marine consortia have the ability to thrive in the presence of mixtures of plastics and participate in their degradation.

Biomimetic Polymer Film with Brilliant Brightness Using a One‐Step Water Vapor–Induced Phase Separation Method

AbstractThe scales of the white Cyphochilus beetles are endowed with unusual whiteness arising from the exceptional scattering efficiency of their disordered ultrastructure optimized through millions of years of evolution. Here, a simple, one‐step method based on water vapor–induced phase separation is developed to prepare thin polystyrene films with similar microstructure and comparable optical performance. A typical biomimetic 3.5 µm PS film exhibits a diffuse reflectance of 61% at 500 nm wavelength, which translates into a transport mean free path below 1 µm. A complete optical characterization through Monte Carlo simulations reveals how such a scattering performance arises from the scattering coefficient and scattering anisotropy, whose interplay provides insight into the morphological properties of the material. The potential of bright‐white coatings as smart sensors or wearable devices is highlighted using a treated 3.5 µm film as a real‐time sensor for human exhalation.

Observation of the Polystyrene Swelling Effect using Quartz Crystal Microbalance

A polystyrene film can swell in contact with the buffer solution. It will affect the microstructure of PS during the contact and resulted in a frequency change of the QCM coated with polystyrene. Phosphate buffered saline and tris-hydrochloride solutions were used to observe the swelling behavior of 192 kDa PS coating annealed from 100 °C to 200 °C. The result showed that the frequency of QCM/PS in contact with the buffer solution was decreased. This result showed that the QCM could be used as a simple and low-cost system to observe a swelling effect of a PS film.

Fabrication of large scale PS monolayer colloidal crystal film by using a novel secondary self-assembly method for nanoimprint technique

PS microspheres emulsions with different PS diameters of 207 and 378 nm were prepared by using an emulsifier-free polymerization method. A novel secondary self-assembly method which combined the spin coating and the lifting-up method was used to prepare the close-packed PS MCC films. During the process, the PS MCC film was firstly assembled on a glass substrate by a spin coating technique. Secondly, the obtained PS MCC film was transferred on the air-water interface by immersing the PS glass substrate in water using a dip-coater. Thirdly, the floating close-packed PS MCC films on the air-water interface was transferred to a new glass substrate by using a lifting-up method. During the spin-coating and the self-assembly process, some SDS solution was added in the PS films to improve the uniformity of the PS layer. Effects of the spin-coating speeds, the SDS solution concentration and the lifting-up rates on the morphology of PS MCC films have been discussed. Scanning electron microscopy was used to observe the morphological properties of the PS colloidal crystal films. Results indicate that a relatively close-packed and large scale PS MCC films can be obtained when the spinning speed is 2000 rpm for 60 s, the SDS solution concentration is 2 wt% and the lifting-up rate is 2 mm/min. Furthermore, the polydimethylsiloxane soft mold was replicated from the-fabricated PS MCC films and was then imprinted onto the photosensitive hybrid film under UV-irradiation and thus the micro-lens arrays built in the photosensitive hybrid sol–gel film were obtained.

1,8‐Substituted Pyrene Derivatives for High‐Performance Organic Field‐Effect Transistors

There have been many reports on the application of pyrene derivatives as organic semiconductors, but 1,8-subsituted pyrene semiconductors are less well-developed. Two p-type 1,8-substituted pyrene derivatives were synthesized that were composed of a pyrene core, thiophene or bithiophene arms, and end-capped octyl chains. These structures were not completely symmetrical and the dihedral angles between the pyrene core and the adjacent thiophene units had a difference of approximately two degrees. The field-effect performance of these materials was tested on a variety of dielectric surfaces. The performance of both materials with a spin-coated polystyrene layer on SiO2 (PS-treated SiO2 ) was better than that with an octadecyltrichlorosilane self-assembled monolayer on SiO2 (OTS-treated SiO2 ), which was mainly attributed to the presence of large grains on the low-leakage and high-capacitance PS films. The thiophene-contained compound presented a hole mobility of up to 0.18 cm2 V-1 s-1 on PS-treated SiO2 , which was 45 times that of the bithiophene-contained compound, owing to less steric hindrance, high crystallinity, and large grain size.

Thickness Dependence of the Young’s Modulus of Polymer Thin Films

The Young’s modulus of polymer thin films was measured from bulk films that are micrometers in thickness down to films having a thickness of ∼6 nm, which is less than the radius of gyration, Rg. A simple, noninvasive technique in the same geometry, i.e., the wrinkling of a free-floating film on a water surface with a droplet of water on the surface of the film, was used to determine the modulus over this very large range of film thicknesses. Unlike a solid substrate, there are no in-plane stresses exerted on the film by the underlying liquid substrate except at the boundary of the film. Using recent theoretical developments in the treatment of wrinkling phenomena, we extracted the film modulus from measurements of the wrinkle length. The Young’s modulus does not show any systematic change with film thickness, from the thickest bulk films down to films with a thickness of ∼Rg for both PS and PMMA, although a slight increase of the Young’s modulus was found for the thinnest sub-Rg thick PS film.

Preparation and Characterization of ATO/PS Bilayer Films with Superior Hydrophilicity

The hydrophilic films are widely used in industrial and domestic fields. Here, we report a Tin oxide film doped with antimony and Potassium silicate (ATO/PS) hydrophilic bilayer films deposited on aluminum substrates. The ATO film was prepared first on the substrates by spray pyrolysis and then PS film was deposited on ATO film by a simple dip-coating method. The structure, morphologies, wettability, stability of hydrophobicity and thermal conductivity of four kinds of samples have been analyzed in detail, including Al substrates (Al), Al substrate with ATO film (ATO), Al substrate with PS film (PS) and Al substrate with ATO/PS bilayer films (ATO/PS). The results show that the hydrophobicity of ATO/PS bilayer films is superior with contact angle of 12.5°. And the angle of ATO/PS sample is approach to 20° after being immersed in water for 48h, while 44.5° is obtained for the PS sample. The thermal conductivity value of ATO/PS sample is almost the same as the Al substrate, and also better than PS film. These results indicate that ATO/PS bilayer films have potential application in heat exchanger and other heat dispersing fields.

Detection the Degradation of PS Thin Films Containing Triazole Complexes by FTIR Techniques

4-amino-5-(pyridyl)-4H-1,2,4-triazole-3-thiol (X) with Ni2+, Cu2+, Zn2+, Cd2+ and Sn2+ has been synthesized also used as PS photostabilizers. In chloroform solvent, these complexes mixed with PS to form modified PS, which involving (0.5 % wt) of complexes were prepared using casting method. At room temperature the intensity of light (6.02×10-9 Ein Dm-3 S-1) and wavelength 365 nm with utilized to irradiate polymeric films. PS films irradiation with UV light led to obvious changes in infrared spectra. The photostabilization activity of these polymeric films was investigated by observation the indices using FTIR spectroscopy.

Tailoring uniform gold nanoparticle arrays and nanoporous films for next-generation optoelectronic devices

High-density arrays of gold nanodots and nanoholes on indium tin oxide (ITO)-coated glass surfaces are fabricated using a nanoporous template fabricated by the self-assembly of diblock copolymers of poly (styrene-block-methyl methacrylate) (PS-b-PMMA) structures. By balancing the interfacial interactions between the polymer blocks and the substrate using random copolymer, cylindrical block copolymer microdomains oriented perpendicular to the plane of the substrate have been obtained. Nanoporous PS films are created by selectively etching PMMA cylinders, a straightforward route to form highly ordered nanoscale porous films. Deposition of gold on the template followed by lift off and sonication leaves a highly dense array of gold nanodots. These materials can serve as templates for the vapor-liquid-solid (VLS) growth of semiconductor nanorod arrays for next generation hybrid optoelectronic applications.

Optical Characterization of Transmitted Visible Photoluminescence of Bragg‐resonanced Porous Silicon

The investigation and optical characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and sharp photoluminescence (PL) at the Bragg resonance wavelength were reported. Two types of Bragg reflector porous silicon (BR PS) samples which exhibit strong reflection in visible or near infrared region and broad red PL were fabricated. When the Bragg reflection wavelength places in the range of emission wavelength, BR PS starts to exhibit narrowing of PL behavior. The optimization of Bragg resonance phenomenon of PL to generate sharp Bragg‐resonated PL by changing the number of repeats of Bragg‐stack layers. BR PS showing the reflection wavelength of 640 nm with 50 repeats exhibited sharp PL at the Bragg resonance wavelength with broad weak PL. BRL PS having 70% porosity with 1.45 refractive index displayed the second‐order reflectivity peak at 640 nm, thus sharp PL peak at 640 nm was the second‐order transmitted and amplified PL peak at the Bragg resonance wavelength. The optical properties of free‐standing BR PS film were investigated. The front side surface of BR PS shows both reflectivity and PL, however the back side surface of free‐standing BR PS shows only reflectivity without PL.

Formation of Hierarchical Porous Structure via Breath Figure Method

The porous structure films of PS containing silica nanoparticles of different hydrophobicity were obtained from breath figure method. For the porous films, the pores at the peripheral region and the center region were compared. It was found that the pores at the peripheral region appeared more uniform in size and showed higher degree of ordering. In addition, the patterns of the porous film became more disordered with the enhancing concentration of nanoparticles, and the pore size of the pore was increased. With the increase of the content of SiOH, that is, decrease in particle hydrophobicity, the Si elements were aggregated at the surface of the film and the interior of the pores. A hierarchical porous structure had been obtained at appropriate humidity and particle concentration. Finally, a possible mechanism of the hierarchical structure was proposed.

Continuously tunable organic solid-state laser based on the adjustment of effective refractive index

We report a facile way for continuously tuning the lasing wavelength of an organic solid-state laser by varying the effective refractive index. The effective refractive index of the organic gain medium can be fine controlled by the dopant concentration in the DCJTB:PS film. Continuous wavelength tuning of laser and amplified spontaneous emission (ASE) are achieved in the distributed feedback (DFB) gratings and planar waveguides, respectively. In the DFB laser, laser emission is demonstrated in the red spectral region with a tunable wavelength range of 30 nm, centered at 612 nm. The laser exhibits a well-defined pump threshold and good emission characteristics. Furthermore, ASE with a large wavelength range of 40 nm is also achieved by varying the dopant concentration, thus giving one the freedom to set or tune the lasing wavelength to meet a particular purpose with a common structure. Our results allow for a simple, broadband continuous tuning of the laser emission wavelength.

Spectroscopic and photochemical stability of polystyrene films in the presence of metal complexes

Five metal complexes containing Ni(II), Cu(II), Zn(II), Cd(II) and Sn (II) metals and 4-amino-5-(pyridine-4-yl)-4H-1,2,4-triazole-3-thiol have been prepared for use as polystyrene photostabilizers. The additives (0.5% by weight) were mixed with polystyrene in chloroform to produce modified PS using the casting method. PS films were irradiated (λ=250–380nm) with a light absorption intensity of 6.02×10−9eindm−3s−1 at room temperature. The photostabilization activity of the films was determined by monitoring various changes, such as the carbonyl index, hydroxyl index, weight loss, viscosity average molecular weight, surface morphology and quantum yield of the chain scission.

Plateau-Rayleigh Instability Morphology Evolution (PRIME): From Electrospun Core-Shell Polymer Fibers to Polymer Microbowls.

Electrospun core-shell fibers have great potentials in many areas, such as tissue engineering, drug delivery, and organic solar cells. Although many core-shell fibers have been prepared and studied, the morphology transformation of core-shell fibers have been rarely studied. In this work, the morphology evolution of electrospun core-shell polymer fibers driven by the Plateau-Rayleigh instability is investigated. Polystyrene/poly(methyl methacrylate) (PS/PMMA) core-shell fibers are first prepared by using blend solutions and a single axial electrospinning setup. After PS/PMMA core-shell fibers are annealed on a PS film, the fibers undulate and sink into the polymer film, forming core-shell hemispheres. The evolution process, which can be observed in situ by optical microscopy, is mainly driven by achieving lower surface and interfacial energies. The morphologies of the transformed structures can be confirmed by a selective removal technique, and polymer microbowls can be obtained.

Vapochromic features of new luminogens based on julolidine-containing styrene copolymers.

We report on vapochromic films suitable for detecting volatile organic compounds (VOCs), based on new polystyrene copolymers containing julolidine fluorescent molecular rotors (JCAEM). Poly(styrene-co-hydroxyethylmethacrylate) copolymers functionalized with cyanovinyl-julolidine moieties of different compositions were prepared, (P(STY-co-JCAEM)(m) with m = 0.06-0.61). The sensing performance of the spin-coated copolymer films demonstrated significant vapochromism when exposed to VOCs characterized by high vapour pressure and a favourable interaction with the polymer matrix, such as Et2O and CH2Cl2. It is worth mentioning that the fluorescence decrease rate was 7 times faster than that of previously investigated julolidine-based fluorescent molecular rotors dispersed in PS films. This phenomenon was attributed to the better control of the JCAEM moiety distribution in the polymer matrix conferred by the covalent approach, combined with a minimal film thickness of 4 microns. These factors, in concert, strongly accelerate the deactivation pathways of the JCAEM units in the presence of VOCs which interact well. Overall, the present results support the use of julolidine-enriched styrene copolymers as effective chromogenic materials suitable for the fast detection of VOCs.

Morphology control in thin films of PS:PLA homopolymer blends by dip-coating deposition

In this work, smooth polymer films of PS, PLA and their blends, with thicknesses ranging from 20nm up to 400nm and very few defects on the surface were obtained by dip-coating. In contrast to the process of spin-coating which is conventionally used to prepare thin films of polymer blends, we showed that depending on the deposition parameters (withdrawal speed and geometry of the reservoir), various morphologies such as layered films and laterally phase-separated domains could be formed for a given blend/solvent pair, offering much more opportunities compared to the spin-coating process. This diversity of morphologies was explained by considering the superposition of different phenomena such as phase separation process, dewetting and vitrification in which parameters such as the drying time, the compatibility of the polymer/solvent pairs and the affinity of the polymer towards the interfaces were suspected to play a significant role. For that purpose, the process of dip-coating was examined within the capillary and the draining regimes (for low and high withdrawal speed respectively) in order to get a full description of the thickness variation and evaporation rate as a function of the deposition parameters.