Pure Polystyrene Film Research Articles

Chain length dependence of ZnO nanofiller–polystyrene blend coating nanofilm: Morphology, surface mechanics, photochemistry, and chain packing

Based on that chain packing which is associated with the number of entanglements per chain and thereby chain length is an influential factor closely related to the properties of polymeric coating film, the nanothin film of zinc oxide (ZnO) nanofiller–incorporated polystyrene (PS) coated on Si substrate important to electronic packaging for protecting electronic material surface is fabricated with different PS molecular weights primarily for heat–resistant coating. Synergistically, through directly–measurable film characteristics obtained using atomic force microscopy (AFM) and spectroscopy (AFS) in conjunction with Raman spectroscopy (RS), the internal structures of the films are evaluated which helps indicate the corresponding film properties tested afterwards. Considering mechanical responses of individual nanoscale surface features together with surface morphology, the optimal PS–ZnO film is pointed out which indicates improved resistance to thermal dewetting compared to pure PS films while providing sub–nanometer roughness and the highest contact area of relatively low–surface–energy sites. Correlated with Raman analysis, chain packing structure encouraging multiple amplification of incident light is ascribed to the films made of the optimal chain length which indicates and describes the observed enhancement of photocatalytic self–cleaning. This study not only contributes to the development of PS–ZnO composite for multi–function coating but also to the design of structure and inspection of nanoparticle–reinforced polymer thin films.

Dewetting Behavior of PS-ZnO Thin Film Coated on Ultrathin Au Layer Grown on Si Substrate

Electronic packaging by coating device component surfaces with polymer thin film is an important step to protect the components from harsh environments. However, along with the device miniaturization to improve its performance, scaling down the coating film can cause a decrease in film durability. Therefore, the thermal stability of pure polystyrene (PS) and zinc oxide-incorporated polystyrene (PS-ZnO) nano-thin films coated on gold (Au) layer with different nano thicknesses on Si substrate were examined to determine the smallest Au thickness at which the polymer films would exhibit optimal stability, and to investigate the effects of the Au component on film resistance to thermal dewetting. With the requirement of having a transparent and conductive Au electrode, the thickness of 20 nm was identified as the optimal value for the Au layer on which both the PS and PS-ZnO films could withstand environment temperatures at 150oC for up to a few hours while the PS-ZnO film exhibited outstanding thermal stability for over 10 days. Such excellent durability was ascribed to the physio-chemical framework in which the coating film can experience forces from the coated layers which potentially affect the mobility of polymer chains. Considering the increase of Au content and Au film roughness with increasing Au film thickness and realizing the similar surface adhesion forces of these Au layers, several possible influences of the Au material on the stability of PS matrix were discussed. The findings provide an insight into heat-resistant coatings for nano-thin Au layers grown on Si, which may also be of benefit in the design and understanding of relevant electronic protection and functional polymeric coatings.

Structure and optical properties of nanocomposites based on polystyrene (PS) and calcium titanate (CaTiO3) perovskite nanoparticles

Polystyrene (PS) thin films containing 4% and 8% calcium titanate (CaTiO3) perovskite nanofiller were prepared by film casting techniques. The influence of CaTiO3 loading on the structure and optical characteristic of PS were studied by using X-ray diffraction and UV-absorption spectroscopy. The XRD analysis showed the addition of CaTiO3 into PS enhanced the formation of crystal structure and resulted in the formation of nano-crystal with a smaller diameter. The optical characterizations showed that the addition of CaTiO3 reduced the transmission and increased the reflection of PS films for UV and visible wavelength of the incident light. Absorption of pure PS films was limited to less than 270 nm, while the absorption of PS/CaTiO3 composites film covered the whole UV -range. The values of the optical energy gap were calculated by using Tauc equation. It was found that the addition of 8% CaTiO3 decreased the values of optical energy gaps from 4.42 eV to 4.26 eV. This is suggested the formation of extra energy levels in the bandgap tails, which aided the transition of electrons from the valence band to these new energy levels in the conduction band.

Allyl and Benzyl Modified Aramid Nanofibers as an Enhancement in Polystyrene-Based Composites.

Aramid nanofibers (ANFs) represent the most promising nanoscale building blocks for high-performance nanocomposites. But their applications are mostly limited to those polymers containing –OH or –NH2 groups that can interact with ANFs through hydrogen bonding or others. In this paper, allyl and benzyl modified ANFs were successfully fabricated using a metallization method followed by functionalization with allyl and benzyl bromide. A series of modified aramid nanomaterials (ANMs) with different degrees of modification were prepared and their morphologies studied. The modified ANFs were added to polystyrene (PS) films as reinforcements. The mechanical properties of the resulting composite PS films including Young's modulus, toughness and yield strength were dramatically improved compared to those of pure PS film. These new types of reinforcement additives for non-polar polymer materials are presented in this paper.

Polystyrene nanocomposites reinforced with phenyl isocyanate-treated cellulose nanofibers

Cellulose nanofibers (CNFs) have attracted much attention as eco-friendly natural nanofillers for thermoplastic-based composites. In this work, we present one possible route to fabricating such a composite based on polystyrene (PS) polymer reinforced with chemically modified CNFs. To achieve a uniform dispersion of CNF fillers in the PS matrix and simultaneously ensure interfacial strength between CNFs and PS in the composite, the surface of CNFs was functionalized with phenyl isocyanates. The composite beads of PS and iCNF were produced by coagulation, followed by thermocompression of the composite beads to produce PS-iCNF composites. Three-point bending flexural tests were performed on the composites to evaluate their mechanical properties according to the CNF loading. The elastic modulus of the PS-iCNF composite increased gradually, while the fracture bending strength decreased as the loading increased, compared to those for the pure PS film. SEM analysis of the fracture surface revealed that the failure behavior of the composite changed from ductile to brittle fracture with increasing iCNF loading. Optical transmittance of the composites was also investigated as a function of the iCNF loading.

Enhancing the stability of polystyrene ultrathin films by using star-shape polymers as dewetting inhibitors

This contribution introduces a new class of materials for improving the stability of polystyrene (PS) ultrathin films. Two types of three-arm polystyrenes (TA-PS) with different arm lengths are added into PS thin films with thicknesses of 7 and 23 nm. Concentration of the TA-PS additives is varied from 0 to 40 wt%. The morphological change of PS films upon annealing above its glass transition temperature is followed by utilizing optical and atomic force microscopy. Our results show that the addition of TA-PS into PS films leads to significant improvement of the film stability. The dewetting rate of PS film containing only 5 wt% of TA-PS is 3 times slower than that of the pure PS film. The increase of TA-PS concentration results in systematic decrease of the dewetting rate. We also observe that the dewetting-suppression efficiency of the TA-PS depends significantly on its arm length.

Effect of Three Arm Polystyrene on Polystyrene Film Stability

This research studied ways to increase the stability of a polymer thin film with a thickness of approximately 10 nm. Our system consisted of a polystyrene (PS) thin film filled with three arm polystyrene (TAP) as additives. Formation of dewetting was investigated by atomic force microscopy and optical microscopy which showed that complete dewetting of the pure PS film occurs after being annealed at 120 oC for 5 h. The dewetting dynamics were dramatically suppressed when a small amount of TAP polymer was added into the PS thin film. We hypothesize that the nitrogen atom in the TAP polymer provides dipolarity between the polymeric thin films and the substrate followed by an increase in the interfacial interaction of the TAP/PS thin films, which in turn leads to increased film stability. However, if the concentration of TAP is too high, this leads to phase separation of the thin films. We also observed that the amount of TAP within the PS thin film largely affected the efficiency of inhibiting dewetting. This method could be utilized for the study of the mechanism in a blended polymer film.

Effect of Polyethylene Packaging Modified with Silver Particles on the Microbial, Sensory and Appearance of Dried Barberry

Low‐density polyethylene (LDPE) packages containing submicrometre‐sized silver particles (Ag‐LDPE) were produced by extrusion method and used as packaging material for barberry packaging. The effects of Ag‐LDPE packages on the microbial factors, apparent color and sensory factors of dried barberry were investigated in comparison with the pure polystyrene packages. Ag‐LDPE packages showed antimicrobial effects on barberry compared with pure polystyrene packages. In comparison with pure polystyrene packages, Ag‐LDPE film with 2 weight percent (wt%) of silver particles revealed antimicrobial activity against mold and total bacteria count of approximately 2.3 and 2.84 log10 reductions in colony‐forming units, respectively. Ag‐LDPE packages in concentration of more than 1 wt% of silver particles preserved the appearance quality of the barberry better than pure polystyrene packages. The barberries packaged in Ag‐LDPE film with 1 wt% of silver particles retained their red color and brightness for approximately 2 to 3 weeks more than barberries packaged in pure polystyrene films. Ag‐LDPE packages assisted in the improvement of aroma, taste and total acceptance of barberry in comparison with pure polystyrene packages except in the low concentration of silver particles of approximately 0.02 wt%. The taste, aroma, appearance and also total acceptance of barberries packaged in Ag‐LDPE film with 1 wt% silver particles were preserved for approximately 2 to 3, 1 to 4, 2 to 5 and 2 to 4 weeks, respectively, more than barberries packaged in pure polystyrene films. Copyright © 2012 John Wiley & Sons, Ltd.

Improved properties of highly oriented graphene/polymer nanocomposites

AbstractA kind of molecular‐level dispersed and highly oriented graphene monolayer nanocomposite film was successfully obtained by in situ reduction of phenyl isocyanate functionalized graphite oxide (RPIGO) in N,N‐dimethylformamide in the presence of polystyrene (PS). Atomic force microscopy and transmission electron microscopy results show that the RPIGO monolayers were not only homogeneously intercalated into the PS matrix but also arranged parallel to the surface of the nanocomposite films. Because of the efficient interaction between the graphene monolayers and PS matrix, the mechanical properties of the graphene‐based nanocomposite films improved significantly. Compared with the pure PS film, a 28.4% increase in the Young's modulus and a 27.8% improvement in the tensile strength of the RPIGO–PS nanocomposites films were obtained with the addition of only 0.5 wt % graphite oxide. The glass‐transition temperature and onset degradation temperature of PS also increased from 96.6 and 427°C to 103.2 and 439°C, respectively. The improvement of the properties was mainly due to the large lateral thickness ratio and the high orientation of graphene monolayers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Photoluminescence developed from polystyrene and CdS/polystyrene nanocomposite films in picosecond time range by repetitional irradiation of excitation femtosecond pulses in PL up conversion measurements

A CdS/SPS nanocomposite film in which CdS nanoparticles were embedded into partially sulfonated polystyrene (SPS) was synthesized and its subpicosecond time resolved photoluminescence (photoluminescence up conversion: PL Up-C) measurements were carried out. A similar measurement was also done for pure SPS and polystyrene (PS) films that were used as the matrix. For a CdS/SPS, PL Up-C signals (sum frequency signal; SFS) were observed at the first measurement. They were also observed for pure SPS and PS films by repetitional measurements though they were not observed at the first measurement. It seems that the development of SFS for SPS and PS films is due to relatively stable luminescent substances formed from themselves by exposing them to intense femtosecond laser pulse (for excitation) during the measurements. The SFS development process was also readily observed for a CdS/SPS film by reducing excitation pulse intensity in the measurements. Therefore, PL that was observed for a CdS/SPS film is also mainly due to luminescent substances formed from the SPS matrix but CdS nanoparticles. CdS nanoparticles embedded into a SPS film may act as an accelerator for PL development from the SPS matrix. The origin of PL may be several luminescent substances formed by photo- or thermal-degradation of SPS via multiphoton (probably two photons) absorption of SPS itself and/or photo-excitation of CdS nanoparticles. Although the luminescent substances could not be assigned, they might be oxidative decomposition products of SPS that have long conjugated π bonds with a PS main polymer chain that absorbs the excitation femtosecond pulse ( λ max = 396 nm).

Effect of γ‐irradiation on the physical properties and dyeability of poly(vinyl butyral) blends with polystyrene and poly(ethylene glycol)

AbstractCast films of polymer blends essentially based on poly(vinyl butyral) (PVB) and equal ratios of polystyrene (PS) and poly(ethylene glycol) (PEG) were prepared from benzene and butyl alcohol solutions of the individual polymers. The effect of γ‐irradiation on the thermal decomposition and tensile mechanical properties was investigated. Moreover, the effect of γ‐irradiation on the dye affinity of PVB/PS and PVB/PEG for basic and acid dyestuffs was studied. The thermogravimetric analysis (TGA) study showed that the unirradiated PVB polymer films prepared in benzene displayed higher thermal stability than the same polymer films prepared in butanol. However, in all cases the thermal stability was found to increase with increasing γ‐irradiation dose. On the other hand, PVB/PS blend possesses higher thermal stability than PVB/PEG, as shown from the determination of the weight loss (%) at different heating temperatures, the temperatures of the maximum rate of reaction and the activation energy. While, pure PS films showed the stress‐strain behavior of brittle polymers, PVB/PS films showed the behavior of tough polymers with yielding properties. The results of dyeing clearly showed that the solvent type, blend composition, and irradiation dose are determining factors for the dye affinity for basic or acid dyes. For example, unirradiated PVB films prepared from butanol displayed a higher affinity for the basic and acid dyes than the same polymer prepared from the same benzene. However, PVB prepared from butanol showed higher affinity to the dyes than PS prepared from the same solvent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Amphiphilic Gold Nanoparticles Grafted with Poly(N-isopropylacrylamide) and Polystyrene

Two types of amphiphilic gold nanoparticles (AuNP-1 and -2) grafted with a mixture of poly(N-isopropylacrylamide) (PNIPAM) and polystyrene (PS) chains in two different compositions have been successfully prepared with the “grafting-to” method in a homogeneous THF phase. These AuNPs were thoroughly characterized by FTIR, 1H NMR, UV−vis, high-resolution transmission electron microscopy, thermogravimetric analysis, and dynamic light scattering to determine the total number of polymer chains bound to the gold nanoparticles, the ratio between PNIPAM and PS chains, and the size of the gold core. Langmuir monolayer experiments at the air−water interface of the two types of AuNPs revealed different compression isotherms of the surface pressure vs particle area (π−A curve) conducted at 20 °C. These amphiphilic gold nanoparticles can be regarded as analogues of amphiphilic diblock copolymers at the air−water interface. The compression isotherm of AuNP-2 with a PNIPAM:PS ratio of 2:1 showed several characteristic regions that can be attributed to the polymer conformational transitions from the pancake, the pancake to brush transition, to the brush. However, the monolayer of AuNP-1, with a ratio of 5:1 of PNIPAM:PS, never reaches a brush stage but showed an extension of the pseudoplateau region upon compression. These differences may be due to the more hydrophilic nature and the more stretched PNIPAM chains. Furthermore, the sessile drop contact angle measurements, conducted at room temperature on both upper and lower surfaces of the AuNP-2 monolayer transferred at 35 mN/m onto either hydrophilic or hydrophobic substrates, are slightly different, 82 ± 2° and 77 ± 2°, respectively. After comparing with the literature data of the contact angles of water on either the pure PS film or the PNIPAM brush, we concluded that the chemically different PNIPAM and PS chains grafted on the surface of the gold core tend to be phase-separated.

Solid state solvation in amorphous organic thin films.

The photoluminescence (PL) of the red laser dye DCM2, doped into blended thin films of polystyrene (PS) and the polar small molecule camphoric anhydride (CA), redshifts as the CA concentration increases. The DCM2 PL peaks at 2.20 eV (lambda=563 nm) for pure PS films and shifts to 2.05 eV (lambda=605 nm) for films with 24.5% CA (by mass). The capacitively measured electronic permittivity also increases from epsilon=2.4 to epsilon=5.6 with CA concentration. These results are consistent with the theory of solvatochromism developed for organic molecules in liquid solvents. To our knowledge, this work is the first application of a quantitative theory of solvation to organic molecules in amorphous thin films with continuously controllable permittivity, and demonstrates that "solid state solvation" can be used to predictably tune exciton energies in organic thin film structures.

Infrared absorption spectra of polystyrene doped with some charge-transfer complexes

The IR absorption spectra of thin films of pure polystyrene (PS) and PS doped with acceptors [tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE) and chloranil], donors (anthracene, Rhodamine 6G and Acridine Orange) and acceptor-donor systems have been investigated. Close comparison of the IR spectra PS films doped with donor or acceptor with the films doped with donor-acceptor systems showed that new bands appeared in spectra of the complexed donor-acceptor PS films. These bands were assigned to molecular interaction between acceptor and donor molecules on the one hand and the interaction of acceptor and donor molecules separately with PS molecules on the other. The results indicate that some bands in the IR spectra of donor-acceptor PS films show frequency and intensity changes when compared with the absorption bands of PS. The molar energies possessed by PS, PS donor or acceptor complexes and donor-acceptor complexes were calculated. From these calculations the stabilities of the complexes formed in PS films were determined.

Picosecond transient grating studies of polymeric thin films

Picosecond transient grating experiments have been performed on a 5-μm-thick polystyrene film doped with naphthalene and on a 700-μm-thick pure polystyrene film at room temperature. In both cases, the observed acoustic modulation of the diffracted signal is explained by the formation of a thermal grating. No detectable acoustic attenuation is observed within the time delay of 6 ns, and the speed of sound obtained from the acoustic modulation period is in excellent agreement with that reported by an ultrasonic measurement. The coherent third order nonlinear electronic response observed at zero-time delay is found to be shorter than 2 ps.

Effect of carbonyl compounds on long‐wave UV photooxidation of polystyrene films

AbstractIt was found that the rate of secondary photooxidation reactions initiated by light not absorbed by polystyrene (PS) is related to the concentration of carbonyl compounds produced initially in pure PS films. Photochemical experiments carried out with a group of twelve low‐molecular‐weight compounds as models of the most likely carbonyl products of PS photooxidation showed that mainly diketones sensibilize the long‐wave UV photooxidation of polystyrene.