PS Films Research Articles

D-π-A Type [7]Helicene-like Imide Derivatives with Tunable Photophysical Properties and Circularly Polarized Luminescence.

Helicenes and their derivatives show great application prospects as circularly polarized luminescence (CPL) materials, but their fluorescence quantum yields (ΦFLs) need a breakthrough urgently. Herein, we reported a series of D-π-A type helical luminescent emitters by combining the [7]helicene-like imide acceptor with five different donors. The obtained five emitters display blue-to-orange luminescence and markedly enhanced ΦFL. Notably, TPA-NiBTI exhibits the maximum ΦFL in solution, while TPE-NiBTI achieves a maximum ΦFL in the solid state. Their two pairs of enantiomers, (P/M)-TPA-NiBTI and (P/M)-TPE-NiBTI, exhibit remarkable CPL activities, and their doped PS film both displayed doubled ΦFLs. Among them, [(P/M)-TPE-NiBTI]-doped PS film exhibits the maximum luminescence dissymmetry factor (|glum|) value of 9.0×10-4 and the maximum ΦFL of 22%. This molecular design strategy presents a promising approach to improving the ΦFL of helicene derivatives, thereby facilitating their potential application into chiral optoelectronic devices.

Interfacial molecular structure and orientation evolution of the polystyrene under confinement during annealing revealed by sum frequency generation vibrational spectroscopy

The geometrical confinement directly affects many crucial properties of polymer thin films by interfacial interactions. A key to understanding the role of these interfacial interactions is to specifically probe the confined interface at the molecular level and in situ. However, the direct and nondestructive detection of interfacial polymer structures under confinement is very difficult. In this study, specific interface-sensitive sum frequency generation (SFG) spectroscopy was applied to study the deuterated PS (d8-PS) film confined between hydrogenated poly (methyl methacrylate) (PMMA) films at the molecular level and in situ. The results showed that the ordering/orientation of the PS chain (backbone and phenyl group) evolved at the buried d8-PS/PMMA interface during annealing. The tilt angle of the PS phenyl group increased while the twist angle decreased with elevated annealing temperature. Both overall SFG ssp and ppp intensities decreased after annealing at 433 K for 24 h, indicating that PS chains entangled with or penetrated the PMMA chains at the confined interface. This study qualitatively and quantitatively revealed the interfacial structure and structural evolution of the PS chain confined between PMMA films in situ during annealing, which is beneficial to the molecular-level understanding of the interfacial chain conformational relaxation of polymers under confinement.

Rapid stress relaxation of high‐Tg conjugated polymeric thin films

AbstractConjugated polymers consist of complex backbone structures and side‐chain moieties to meet various optoelectronic and processing requirements. Recent work on conjugated polymers has been devoted to studying the mechanical properties and developing new conjugated polymers with low modulus and high‐crack onset strain, while the thin film mechanical stability under long‐term external tensile strain is less investigated. Here we performed direct mechanical stress relaxation tests for both free‐standing and thin film floated on water surface on both high‐Tg and low‐Tg conjugated polymers, as well as a reference nonconjugated sample, polystyrene. We measured thin films with a range of film thickness from 38 to 179 nm to study the temperature and thickness effect on thin film relaxation, where an apparent enthalpy–entropy compensation effect for glassy polymer PS and PM6 thin films was observed. We also compared relaxation times across three different conjugated polymers and showed that both crystalline morphology and higher modulus reduce the relaxation rate besides higher glass transition temperature. Our work provides insights into the mechanical creep behavior of conjugated polymers, which will have an impact on the future design of stable functional organic electronics.

Development of functional, sustainable pullulan-sodium alginate-based films by incorporating essential oil microemulsion for chilled pork preservation

Developing safe, eco-friendly, and functionally edible packaging materials has attracted global attention. Essential oils, can be incorporated into packaging materials as antioxidant and antibacterial agents. However, their high volatility and discontinuous film matrix issues may cause a rough film surface, limiting the application in food packaging. In this study, thyme essential oil microemulsion (TEO-M) was prepared and incorporated into a pullulan-sodium alginate (PS) film. The TEO-M incorporation endowed the PS film with antioxidant and UV protection properties. The antioxidant activities of the TEO-M-incorporated PS film were significantly better than those of the TEO-C (thyme essential oil coarse emulsion)-incorporated PS film. In comparison to TEO-C, the distribution of TEO-M in the film is more uniform. Lipid oxidation and the growth of microorganisms in chilled pork were inhibited by incorporating TEO-M at a concentration of 50 mg/mL in the PS film (PS-50M). After 10 days of storage at 4 °C, the total viable count (TVC) of chilled pork preserved in the PS-50M material was significantly reduced compared to the control group (P < 0.05). This study shows that incorporating TEO-M in the PS film provides a method for applying essential oils in food packaging, which may have great potential in the food industry.

Opportunities and challenges in CsPbX3@Glasses@Film with High Quality for LCD by Process Optimization towards commercialization

Although backlight display screens based on CdSe quantum dots (QDs) have basically solved the remaining problem of small display gamut, its high preparation cost limits its commercial development. In contrast, perovskite nanocrystals (NCs) with narrow band emission, simple preparation and low cost have made leaps and bounds in next-generation backlit displays luminescent material. However, the instabilities are the main issues to solve before we can apply these materials in modern displays. Researchers have precipitated perovskite NCs in inorganic glass substrates and compounded them with PDMS films for backlighting, but the important factors for commercialization have been ignored: Long-term stability under strong blue light irradiation and preparation cost. In this work, a unique melt-water quenching method combined with composition control was applied to prepare a series of glass powder. The optimal photoluminescence (PL) emission and color coordinates in the color coordinates of glasses powder were elaborately regulated by heat treatment temperature control and the introduction of rare earth Tb. Moreover, the passivation of the glass powder surface through special water treatment greatly improves its stability under long time blue light exposure. After irradiation under 20000 cd/m2 blue light (460 nm) for 500 h, the PL intensity retention rate reaches 85% of commercial CdSe film. The red and green-emitting NCs glasses powder with high photoluminescence quantum yield (PLQY) and stability were combined with PET, PS and PDMS to form a composite film, afterwards, combined with Liquid crystal display (LCD)module shows a fuller color image. Finally, after comparison, PS film was demonstrated to be the most suitable choice for commercialization backlighting.

Solvent-Induced Swelling Behaviors of Microphase-Separated Polystyrene-block-Poly(ethylene oxide) Thin Films Investigated Using In Situ Spectroscopic Ellipsometry and Single-Molecule Fluorescence Microscopy.

Block copolymers have attracted considerable interest in the fields of nanoscience and nanotechnology because these polymers afford well-defined nanostructures via self-assembly. An in-depth understanding of solvent effects on the physicochemical properties of these microdomains is crucial for their preparation and utilization. Herein, we employed in situ spectroscopic ellipsometry and single-molecule fluorescence techniques to gain detailed insights into microdomain properties in polystyrene-block-poly(ethylene oxide) (PS-b-PEO) films exposed to ethanol- and water-saturated N2. We observed a quick increase and a subsequent gradual decrease in the ellipsometric thickness of PS-b-PEO films upon exposure to ethanol-saturated N2. This observation was unexpected because ethanol-saturated N2 induced negligible thickness change for PS and PEO homopolymer films. The similarity in maximum thickness gain observed under ethanol- and water-saturated N2 implied the swelling of PEO microdomains. Ethanol vapor permeation through the PEO microdomains was supported by the redshift of the ensemble and single-molecule fluorescence emission of Nile red in PS-b-PEO films. Single-molecule tracking data showed the initial enhancement and subsequent reduction of the diffusion of hydrophilic sulforhodamine B molecules in PS-b-PEO films upon exposure to ethanol-saturated N2, consistent with the spectroscopic ellipsometry results. The higher ethanol susceptibility of the PEO microdomains was attributable to their amorphous nature, as shown by FTIR data.

Wafer-Scale Fabrication and Transfer of Porous Silicon Films as Flexible Nanomaterials for Sensing Application.

Flexible sensors are highly advantageous for integration in portable and wearable devices. In this work, we propose and validate a simple strategy to achieve whole wafer-size flexible SERS substrate via a one-step metal-assisted chemical etching (MACE). A pre-patterning Si wafer allows for PSi structures to form in tens of microns areas, and thus enables easy detachment of PSi film pieces from bulk Si substrates. The morphology, porosity, and pore size of PS films can be precisely controlled by varying the etchant concentration, which shows obvious effects on film integrity and wettability. The cracks and self-peeling of Psi films can be achieved by the drying conditions after MACE, enabling transfer of Psi films from Si wafer to any substrates, while maintaining their original properties and vertical alignment. After coating with a thin layer of silver (Ag), the rigid and flexible PSi films before and after transfer both show obvious surface-enhanced Raman scattering (SERS) effect. Moreover, flexible PSi films SERS substrates have been demonstrated with high sensitivity (down to 2.6 × 10−9 g/cm2) for detection of methyl parathion (MPT) residues on a curved apple surface. Such a method provides us with quick and high throughput fabrication of nanostructured materials for sensing, catalysis, and electro-optical applications.

Composition conversion and parameters influence of nanosecond ultraviolet laser cutting polystyrene film

AbstractPolystyrene (PS) film has great application potential in the electronics industry, optical instruments, and biomedical equipment, for its excellent optical, insulating, and mechanical properties. The composition conversion mechanism of the nanosecond laser cutting PS film process was studied by Raman and thermal analysis simulation. Raman tests verified that laser cutting would not create new solid by‐products and only had an influence on a few chemical bonds. Thermal cracking indicated that the released gas by‐product was mainly Benzene derivatives with benzene ring as the main body, which were harmful to human health. Thermogravimetric‐infrared combined analysis showed that the weight loss reached maximum rate at 405.73°C and remained basically unchanged after 444.85°C. Moreover, a quality evaluation standard composed of cutting kerf zone and heat‐affected zone for nanosecond laser cutting of PS film was established. A three‐factor and five‐level orthogonal experiment was performed for research the cutting processes, and 2 (190 kHz)–4 (0.4 m/s)–4 (65) was the preferable process parameter combination by analysis comprehensively. Interaction analysis was also conducted to clarify the correlation between laser cutting factors. This work has an important guiding role in the industrial application of PS film laser cutting.

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Polypyrrole-coated electrospun polystyrene films as humidity sensors

We report the preparation of flexible polystyrene/polypyrrole (PS/PPy) mats and their successful use as a resistive humidity sensor. These composite membranes were prepared by first obtaining PS films through the electrospinning technique, and then incorporating PPy chains by an in situ chemical polymerization of the pyrrole monomer. The PS fibers were homogeneously distributed, with diameters that obeyed a normal distribution with an average value of (1.04 ± 0.12) μm. The deposition of conducting PPy chains on the surface of the PS fibers was confirmed after characterizing the PS/PPy mats by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), contact angle measurements, and electrochemical impedance spectroscopy (EIS). When used as humidity sensors, the PS/PPy mats exhibited a sensor response of 128.6%, with fast response ((54.9 ± 3.5)s) and recovery times ((76.8 ± 11.1)s), and stable response under different humidity conditions over several days. These performance characteristics compare favorably to those of previous resistive humidity sensors discussed in the literature.

Preparation and Self-Assembling of PLA-b-PNIPAM-b-PS Triblock Copolymer Thin Films.

Polylactide-b-poly(N-isopropylacrylamide)-b-polystyrene (PLA-b-PNIPAM-b-PS) triblock copolymers (tri-BCPs) with various chemical compositions (block ratio) were prepared from the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization. Subsequently, the self-assembling behaviors of these tri-BCP films obtained from spin-coating were investigated by annealing them under different solvent atmosphere. We found that these films could self-assemble into various morphologies due to the microphase separation of incompatible copolymer blocks. Atomic force microscopy confirmed the perpendicular cylindrical morphology self-assembled from PLA4.5k-b-PNIPAM5.2k-b-PS22.4k tri-BCP film under mixed solvent atmosphere of toluene/acetone (7:3, v/v). Self-assembled PLA cylinders are evenly distributed among the PS matrix and perpendicular to the film surface, with PNIPAM component taking place at the PLA/PS interphase. Furthermore, by etching the degradable PLA component, porous PS film decorated with PNIPAM "brushes" hoisting channels were generated. This work provides a facile method and detailed protocol for fabricating stimuli-responsive porous films which are promising for thermoresponsive "smart" separation technologies.

Preparation of Polymeric films containing Schiff base as UV-Absorber with Good Resistance against UV-Photoaging

To increase the photostability of polystyrene, a new Schiff base has been added to the polystyrene mixture. The polystyrene films have been exposed to ultraviolet light for 300 hours. Schiff's base has been utilized as a long-term polystyrene optical stabilizer against ultraviolet radiation. Schiff base efficiency is widely recognized for using different techniques, including weight loss determinations, infrared spectroscopy, and electron microscopy (SEM) of PS films after 300 hours of irradiation. Polystyrene/Schiff base blend surface morphology was investigated by SEM technique, and the images demonstrated the formation of terrestrial crack materials due to the presence of photo-stabilizer within the polymer materials. Moreover, the carbonyl group indices were much lower for PS/stabilizer blend than for the blank polymer. The results showed that adding a Schiff base greatly improved the photostability of polystyrene. Furthermore, many unwanted alternations because of the exposure to ultraviolet light were treated by adding the Schiff base compared to the blank polymeric film. The photo-stabilizer absorbs the light and works as a free radical scavenger segment.

Low-Voltage Operated Organic Thin-Film Transistors With Mobility Exceeding 10 cm²/vs

In this letter, low-voltage operation and high mobility are simultaneously achieved in the OTFTs based on an elaborately constructed tri-layer gate dielectric. The tri-layer gate dielectric consists of the cross-linked poly(4-vinylphenol) (CL-PVP), polyvinylpyrrolidone (PVPy) and poly(styrene) (PS) films. The ultrathin CL-PVP and PS films prevent the charges transferring and trapping in the PVPy dielectric, which improves the performances. The low trap density at the organic semiconductor/dielectric interface contributes to the low-voltage operation and high mobility in the OTFTs. The OTFTs exhibit promising performances with high mobility exceeding 10 cm2/vs, small subthreshold swing of 185 mV/decade on average, high on/off ratio of $10^{{5}}$ , at low operating voltages below 5 V. The measurements on stability and ageing of the OTFTs indicate that the encapsulation is required for practical application.

Effect of Interfacial Adsorption on the Stability of Thin Polymer Films in a Solvent-induced Process

The stability of ultrathin polymer films plays a crucial role in their technological applications. Here, we systematically investigated the influence of interfacial adsorption in physical aging and the stability of thin polymer films in the solvent-induced process. We further identify the stability mechanism from the theory of thin film stability. Our results show that the aging temperature and film thickness can strongly influence the stability of thin PS films in acetone vapor. Physical aging can greatly improve the stability of thin polymer films when the aging temperature Taging1 > Tg. A thinner PS film more quickly reaches a stable state via physical aging. At short aging time, the formation of the adsorbed layer can reduce the polar interaction; however, it slightly influences the stability of thin polymer films in the solvent-induced process. At later aging stage, the conformational rearrangement of the polymer chains induced by the interfacial effect at the aging temperature Taging1 plays an important role in stabilizing the thin polymer films. However, at Taging2 < Tg, the process of physical aging slightly influences the stability of the thin polymer films. The formation of the adsorbed layer at Taging2 can reduce the short-range polar interaction of the thin film system and cannot suppress the instability of thin polymer films in the solvent-induced process. These results provide further insight into the stable mechanism of thin polymer films in the solvent-induced process.

Oligo(ethylene glycol) (OEG) functionalized 2-(2′-Hydroxy benzofuranyl) benzoxazole (HBBO) derivatives: Synthesis, photophysical properties and biomolecules binding studies

Two molecular fluorophores based on a 2-(2′-Hydroxybenzofuranyl) benzoxazole (HBBO) scaffold and presenting an Excited-State Intramolecular Proton Transfer (ESIPT) process are reported herein. These dyes incorporate strongly electrodonating aromatic amino groups on the benzofuranyl side, enabling the appearance of a dual fluorescence emission corresponding to the radiative decay of the excited enol (E*) and keto (K*) tautomers at high and low energy respectively. It was previously demonstrated that dual E*/K* emission could originate from a beneficial decrease of phenolic acidity upon absorption of light leading to a thermodynamic stabilization of the first excited-state. The innovation within these dyes lies in the double functionalization of the aniline moiety with 2-(2-methoxyethoxy)ethyl units which allowed a better solubilization in protic solvents, as compared to their butyl analogs while keeping strong electrodonating capacity. Their intrinsic amphiphilic character leads to a good vectorization in a wide range of solvents from toluene to PBS buffer. The investigation of the photophysical properties of these dyes in solution showed a clear dual emission in apolar solvents with the E* band gradually red-shifting along with the dipole moment of the solvent. Dual emission is also observed in the solid-state when these dyes are doped as 1% wt in PMMA or PS films. Finally, the interactions of one dye with calf-thymus (ct)-DNA and Bovine Serum Albumin (BSA) have been explored and reveal pronounced modifications of the UV–Vis profile of the dye. Additionally, a gradual hypsofluorochromic shift and narrowing of the K* band along with the appearance of the E* fluorescence band upon addition of ct-DNA or BSA is also observed, presumably evidencing an intercalation mode of binding.

Photostabilization of Poly Styrene (Ps) Films with Different Complexes Derived from Various Shif Bases

Photostabilization of Poly Styrene (Ps) Films with Different Complexes Derived from Various Shif Bases

Effect of polystyrene molecular weight and zinc oxide concentration on dewetting behavior of polymeric thin films

The separation between ultra-thin polymer film on metal oxide substrate is called dewetting. Dewetting causes the polymer films to loss their stability and other important properties, for example, the films may short circuit or reduce their transparency. Therefore, the stability of polymer thin films on substrate need to be improved. Addition of nanoparticles is one of the most popular technique used to increase the stability of polymer thin films. The correlation between the different of molecular weight and ZnO concentration on dewetting behavior was studied in this research. The appropriate concentration of ZnO on dewetting suppression in each molecular weight was examined. Furthermore, the variation of dewetting pattern in each molecular weight system was analyzed. In this research, PS (13K and 30K) solutions mixed with ZnO suspension in toluene were prepared. The concentrations of ZnO in PS solution were 0-1.0 wt%. All composite thin films were coated by spin-casting technique and annealed at a temperature of 100°C in a vacuum oven to induce dewetting behavior. The topographies of annealed thin films were studied by using Optical microscope (OM) and Scanning electron microscope (SEM). The thicknesses of thin films were examined by Atomic force microscope (AFM). The surface energies of PS and PS-ZnO composite films were measured and calculated by using contact angle measurement. From the results, we found that addition of ZnO nanoparticles at concentrations 0.7 and 1.0 wt% are the optimum concentration for dewetting inhibition of PS13K and PS30K films, respectively.

Characterization and radiation modification of low density polyethylene/polystyrene/maleic anhydride/magnesium hydroxide blend nanocomposite

Preparation of Low density polyethylene/polystyrene/maleic anhydride/nano Magnesium hydroxide LDPE/PS/MA/Mg(OH)2 blend nanocomposite was carried out. The Mg(OH)2 nanoparticles were investigated by XRD and TEM. The effects of different contents of polystyrene, maleic anhydride and nano magnesium hydroxide on the properties of the prepared blends and blend nanocomposite were investigated. From the mechanical properties the LDPE/PS/MA/Mg(OH)2 blend nanocomposite with composition 70/30/10/5 wt % has higher tensile strength compared with pure LDPE. PS and other blend films. Since polymers used in the biomedical and packaging sectors exposed to ionizing radiation such as gamma rays for sterilization purposes, therefore the selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite films subjected to gamma irradiation at doses 0 up to 40 kGy. The FTIR, TGA analyses and the mechanical properties were used for monitoring changes in properties evaluated by radiation. The selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite films characterized by high chemical, thermal and stable structure against gamma irradiation up to 35 kGy than ordinary LDPE film. The limiting oxygen index (LOI) show that the selected irradiated blend nanocomposite has higher LOI value compared to original PS and nonirradiated blend nanocomposite films. The Field emission- SEM show the accumulation of the nano Mg(OH)2 on the surface of selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite film then reduces to average particle size 153.5 nm by effect of gamma irradiation. The presence of Mg(OH)2 nanoparticles did not alter the mechanical properties of the selected prepared LDPE/PS/MA/MgOH2 blend nanocomposite film, also it increase thermal stability and enhance fire retardency which is better than traditional additives.

Hierarchical patterns on laminated composite bilayer films via surface roughness-mediated buckling instability

This study describes buckling instabilities mediated via surface roughness to generate hierarchical structures on a metal (aluminum)/polymer (polystyrene) laminated composite bilayer film on a rigid substrate. Buckling instability is a non-lithographic approach to generate microscale features in thin films. Metals can buckle over the surface due to compressive stress arising from differences in thermal expansion of the individual layers. The topographies of the buckles characterized by wavelength and amplitude can be manipulated by varying the thickness of the layers and the extent of thermal annealing time. Here, the pre-buckled surface on the laminated composite bilayer film formed via two–step molding resulted in hierarchical patterns via surface roughness-mediated buckling instability. The negative replica of the buckles was generated by poly(dimethyl siloxane) (PDMS) and the positive replica of the buckles was fabricated via molding using a PDMS negative replica onto the PS film. The metal layer was subsequently formed on the PS film and the laminated composite bilayer film enabled patterns with hierarchical topography following thermal treatment. The hierarchically structured surfaces exhibit moderately enhanced hydrophilicity and the elastomeric replica with hierarchical buckles showed stretchable hydrophobicity up to 120% stretching due to partial preservation of the pre-structured buckles on the surface.

Exchange bias in Co/CoO thin films deposited onto self-assembled nanosphere arrays

Looking at the importance of exchange bias (EB) studies in novel magnetic systems, magnetic nanocaps consisting of antiferromagnetic (AF)/ferromagnetic (FM) layers were synthesized using nanosphere lithography, followed by ion beam sputtering. For this, CoO/Co/Si and CoO/Co/polystyrene nanosphere (PS) (800 nm diameter) ultra-thin and thick films were prepared by in-situ oxidation. Room temperature magnetization measurements exhibit a clear distinction between the films on PS and those on plane base Si substrate (reference films). Low temperature field cooled measurements on CoO/Co(5 nm)/PS film show a negative EB in both original (−37.4 mT) and trained hysteresis loops (−31.4 mT). However, corresponding reference films show larger EB values in comparison with those of PS substrate counterparts. Due to a higher Co layer thickness, the CoO/Co(100 nm)/PS film shows a lower EB value (−18.2 mT) in comparison with its corresponding CoO/Co(5 nm)/PS ultra-thin film (−37.4 mT). However, for the corresponding reference films, the ultra–thin film shows a higher EB (−68.5 mT) than the thick film (−12.6 mT), which is a generally observed behavior. The overall results are discussed in terms of the curvature induced modifications in the microstructural properties, which cause drastic changes in the magnetic properties of such nanostructures.