Polystyrene Blend Films Research Articles

Gamma Ray Induced Changes in Polycarbonate/Poly(Methyl Methacrylate)/Polystyrene Blend Films: Linear and Nonlinear Optical Properties

In our research described in this article, we used a solution casting technique to prepare a blend film containing polycarbonate (PC), poly (methyl methacrylate) (PMMA), and polystyrene (PS) polymers. Samples from the prepared PC/PMMA/PS films were irradiated with γ ray doses ranging from 20 to 160 kGy. We used UV-vis spectroscopy to investigate the resulting effects of the γ ray irradiation on the optical properties of the prepared films. When the γ ray dose was increased up to 160 kGy, the maximum dose used, the direct bandgap was decreased from 3.68 to 2.90 eV, associated with an increase of Urbach energy from 0.82 to 1.03 eV. Also, we used the optical dielectric loss (ε″) to detect the type of microelectronic transition for the PC/PMMA/PS blend films, which was found to be a direct allowed transition. The γ ray effects on the absorbance, extinction coefficient, refractive index, dielectric parameters, optical conductivity and the nonlinear parameters of the blend films were studied. The enhancement in the optical properties indicated that the γ radiation is a useful tool that allows the application of the resulting PC/PMMA/PS blend films in optoelectronic devices.

A no-hysteresis TIPS–pentacene:polystyrene blend-based organic field effect transistor by extruded direct ink writing and the application in a resistive load inverter circuit

Organic field effect transistors (OFETs), with the active layer made from 6,13-bis(triisopropylsilylethinyl) pentacene:polystyrene blend films, were fabricated on rigid (glass) and flexible (polyethylene terephthalate) substrates using a motor-controlled extrusion-based Direct Ink Writing printing method.

Molecular orientation anisotropy and hole transport properties of diluted semiconducting films of poly(p-phenylenevinylene) derivative

The electrical and optical properties of certain semiconducting polymers are improved in blend films with inert host materials. The improvements have been attributed to the dilution effect of electron traps and interchain species in semiconductor materials. In this paper, we report on anisotropy in the blend films of poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and its strong dependence on an inert host material, such as polystyrene (PS) or polyvinylcarbazole (PVK). We found that the orientation of the MEH-PPV backbone in the blend film changed from horizontal to random on dilution with PS. Moreover, the in-plane hole conductivity was enhanced in the MEH-PPV:PVK blend film, although the out-of-plane conductivity reduced owing to excessive dilution. Mott–Schottky analysis of the capacitance–voltage characteristics revealed opposite trends for dilution with PS and PVK; i.e., PS increased the accumulated charge density in the bulk of the blend film, whereas PVK reduced it. These results demonstrate that isotropy was induced in the PS blend films, whereas anisotropy was induced in the PVK blend films. Anisotropy is an important factor for understanding the hole transport characteristics in the diluted films. • Anisotropy of hole transport property was found in the diluted polymer films. • Anisotropy in the diluted films strongly depends on the inert host material. • Anisotropy is an important factor for understanding the hole transport properties.

Morphological and structural comparison of TIPS-PEN:PS and neat TIPS-PEN films grown onto cPVP-patterned plastic substrates

In the present study, spray-coated blends of 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) with Polystyrene (PS) insulating polymer were employed to improve the performance of spray-coated neat TIPS-PEN Organic Field-Effect Transistors (OFETs) on plastic substrates. By combining TIPS-PEN with PS insulating polymer, control over the TIPS-PEN crystallization behavior can be achieved. A surface morphology study on the TIPS-PEN blended with PS films at an optimized weight ratio of 0.8:0.2 was carried out, in order to investigate the phase separation phenomena between the two components within the blend. The crystallinity and the crystalline characteristics of the sprayed TIPS-PEN:PS blend films were also investigated and compared to those of the sprayed neat TIPS-PEN films. Finally, these improved characteristics of the blend-based films are correlated with the extracted electrical parameters (mobility value, on/off current ratio, threshold voltage value) of the sprayed TIPS-PEN:PS blend OFETs and are compared with those of the sprayed neat TIPS-PEN OFETs, both in terms of values and inter-device uniformity.

LC alignment behaviors on polystyrene blend alignment films

ABSTRACTWe prepared blend alignment film based on 4-ethylphenoxymethyl-substituted polystyrene (P4EP) and polystyrene (PS) for liquid crystal (LC) alignment. Stable and uniform LC cells having pretilt angles adjustable from 90o to 0o were obtained from these polystyrene blend films having weight contents of P4EP and PS of 1 and 100 weight %, respectively. The LC alignment behavior was well correlated with the wettability of the polymer films. These polystyrene blends having good solubility in many organic solvents and their films having low process temperature can be candidates for LC alignment layer in the flexible display. This study contributes to the latest efforts to develop new alignment layers for pretilt angle control.

The Effects of Compatibilizers on the Morphological, Mechanical, and Optical Properties of Biaxially Oriented Poly(ethylene terephthalate)/Syndiotactic Polystyrene Blend Films

In this study, the effects of three different types of compatibilizers on the morphological, mechanical, and optical properties of poly(ethylene terephthalate) (PET) and syndiotactic-polystyrene (s-PS) (70/30, wt%) blends and biaxially oriented blend films of the two polymers were investigated. The morphological results of the PET/s-PS (70/30) blends revealed that when the 5 phr polystyrene-g-oxazoline (PS-g-OXA) was used as a compatibilizer, the domain size showed minimum. The mechanical studies of the PET/s-PS (70/30) blends showed that when 5 phr PS-g-OXA was used, increased tensile strength was obtained. The transmittance of the blend film showed the highest value (83.7%) for the biaxially oriented PET/s-PS (70/30) blend films with the PS-g-OXA (5 phr), compared with that of the blends without compatibilizer (70.8%), or with the styrene-co-maleic anhydride as a compatibilizer, at the wavenumber of 600 nm. The tensile strength of the biaxially oriented PET/s-PS (70/30) blend films also showed the highest value when PS-g-OXA (5 phr) was used as a compatibilizer. The morphological, optical, and mechanical results of the PET/s-PS (70/30) blends and biaxially oriented blend films of the two polymers showed that PS-g-OXA was the most effective compatibilizer, and that the optimum compatibilizer content was 5 phr.

Capillary Force Lithography Pattern-Directed Self-Assembly (CFL-PDSA) of Phase-Separating Polymer Blend Thin Films.

We report capillary force lithography pattern-directed self-assembly (CFL-PDSA), a facile technique for patterning immiscible polymer blend films of polystyrene (PS)/poly(methyl methacrylate) (PMMA), resulting in a highly ordered phase-separated morphology. The pattern replication is achieved by capillary force lithography (CFL), by annealing the film beyond the glass transition temperature of both the constituent polymers, while confining it between a patterned cross-linked poly(dimethyl siloxane) (PDMS) stamp and the silicon substrate. As the pattern replication takes place because of rise of the polymer meniscus along the confining stamp walls, higher affinity of PMMA toward the oxide-coated silicon substrate and of PS toward cross-linked PDMS leads to well-controlled vertically patterned phase separation of the two constituent polymers during thermal annealing. Although a perfect negative replica of the stamp pattern is obtained in all cases, the phase-separated morphology of the films under pattern confinement is strongly influenced by the blend composition and annealing time. The phase-separated domains coarsen with time because of migration of the two components into specific areas, PS into an elevated mesa region and PMMA toward the substrate, because of preferential wetting. We show that a well-controlled, phase-separated morphology is achieved when the blend ratio matches the volume ratio of the elevated region to the base region in the patterned films. The proposed top-down imprint patterning of blends can be easily made roll-to-roll-compatible for industrial adoption.

Fluorescence imaging of nanoscale domains in polymer blends using stochastic optical reconstruction microscopy (STORM)

High-resolution fluorescence techniques that provide spatial resolution below the diffraction limit are attractive new methods for structural characterization of nanostructured materials. For the first time, we apply the super-resolution technique of Stochastic Optical Reconstruction Microscopy (STORM), to characterize nanoscale structures within polymer blend films. The STORM technique involves temporally separating the fluorescence signals from individual labeled polymers, allowing their positions to be localized with high accuracy, yielding a high-resolution composite image of the material. Here, we describe the application of the technique to demixed blend films of polystyrene (PS) and poly(methyl methacrylate) (PMMA), and find that STORM provides comparable structural characteristics as those determined by Atomic Force Microscopy (AFM) and scanning electron microscopy (SEM), but with all of the advantages of a far-field optical technique.

Fullerene Nanoparticles as Molecular Surfactant for Dewetting of Phase-Separating Polymer Blend Films

We investigate the effects of fullerene nanoparticles (f-NP) on the dewetting morphology in the immiscible temperature regime of blend films of polystyrene (PS) and polybutadiene (PB) on silicon substrate. As in our former work in the miscible temperature regime of this blend film, competitive partitioning of the f-NPs to the polymer–polymer and the substrate interfaces in blend films requires a larger concentration of f-NPs (∼10 mass %) to suppress film dewetting than in homopolymer components (∼2 mass %). In contrast, however, phase-separated blend films rapidly dewet into hemispherical droplets due to finite interfacial tension of internal blend components unlike irregular shape droplets obtained in miscible blend films. The effect of the f-NPs (1 mass % to 5 mass % f-NP) is to simultaneously reduce the size and contact angle of the dewet droplets, but the hemispherical shape of droplets is maintained, suggesting the f-NPs act to (a) only reduce the phase-separated blend interfacial tension but not fully compatibilize it into single phase and (b) reduce the blend substrate interfacial tension progressively. Selective solvent etching of the PS blend component reveals a spherical PS core enclosed within a circular PB shell at all f-NP concentrations. Confocal fluorescence microscopy reveals that the f-NPs are distributed in both phases consistent with the hemispherical shape and calculations that predict only a weak reduction of interfacial tension. The dewet blend droplet contact angle (likewise polymer–substrate interfacial tension) measured by atomic force microscopy shows a bimodal behavior, reducing rapidly (by 40%) at low (0.1 mass %) f-NP levels and significantly slowing down at higher f-NP concentrations. Molecular surfactant like behavior of the f-NPs in the blend films then provides an effective means of tuning dewetting blend film morphology dimensions without compromising phase behavior for potential applications in nanotechnology and nanomedicine.

Anomalous Behavior of Polystyrene Blends Using Thermally Induced Surface Wrinkling

ABSTRACTThe wrinkling of a 50:50 blend of a high molecular mass (Mn = 990 kg/mol) and low molecular mass (Mn = 1.3 kg/mol) polystyrene (PS) film is studied as a function of annealing temperature and film thickness. Both thermal and mechanical wrinkling are utilized to elucidate the apparent modulus of these PS blend films. The PS blend shows a modulus comparable to the high molecular weight PS, ≈ 3.2 GPa for mechanical wrinkling at ambient and thermal wrinkling for T ≤ 50 °C. A sharp decrease in the apparent modulus of the film occurs when thermal wrinkling occurs at 60 °C or higher. The calculated modulus in this case is 0.5 GPa, which is significantly below the modulus determined the neat PS for either Mn when thermally wrinkled at T > 60 °C. This behavior is attributed to a combination of surface segregation of the low molecular weight PS as well as the large difference in bulk glass transition temperature (Tg) of each component. During thermal wrinkling, the high Mn PS vitrifies first, while the surface containing primarily low Mn PS is rubbery; this leads to only the underlayer of PS wrinkling initially and selection of a shorter wavelength due to the effective thickness. The increased thermally induced stresses during cooling when the low Mn PS is vitrified do not change the selected wavelength and instead only leads to an increase in the wrinkle amplitude. These results illustrate a potential method to modulate the wrinkle wavelength without changing the overlayer, which could be useful for patterning applications.

Size Effects on Miscibility and Glass Transition Temperature of PS/TMPC Blend Films: a Simulation and Thermodynamic Approach

The size dependent miscibility of binary polymer blend films of polystyrene (PS) and tetramethylbisphenol-A polycarbonate (TMPC) is studied by the molecular dynamics (MD) simulation in the way of computing Flory-Huggins interaction parameter, χ, of the blend films, which determines the blend films compatibility. It is found that the miscibility of the two polymers decreases as the film thickness D decreases. After that, the size dependent glass transition temperature Tg(w,D) of the two polymers blend films in miscible ranges are determined by computer simulation and the Fox equation where w is the weight fraction of the second component.

Transformation from Ordered Islands to Holes in Phase-Separating P2VP/PS Blend Films by Adding Triton X-100

Our previous investigation showed that the ordered hexagonal island pattern in the phase-separating polymeric blend films of polystyrene and poly(2-vinylpyridine) (PS/P2VP) formed due to the convection effect by proper control of PS molecular weight, solvent evaporation rate, and the weight ratio of PS to P2VP. In this paper, we further illustrate that, by adding a proper amount of the surfactant Triton X-100 to the PS/P2VP toluene solution, the ordered hexagonal island pattern can be transformed to the ordered honeycomb pattern. The effects of the amount of Triton X-100 on the surface morphology evolution and the pattern transformation are discussed in terms of the collapse of Triton X-100, phase separation between Triton X-100/P2VP and PS, the interfacial interaction between Triton X-100/P2VP and the mica substrate, and the Bénard-Marangoni convection.

Tunable ordered droplets induced by convection in phase-separating P2VP/PS blend film

Ordered hexagonal droplets patterns in phase-separating polymeric blend films of polystyrene and poly(2-vinylpyridine) (PS/PVP) formed due to the convection effect by solvent evaporation. The influences of PS molecular weight, solvent evaporation rate, and the weight ratio of PS to PVP on the PVP-rich domains pattern formation and distributions were investigated by atomic force microscope (AFM). Only in an appropriate range of molecular weight of PS, can the ordered pattern form. Too low or too high molecular weight of PS led no ordered pattern due to the viscosity effects. The increase of solvent evaporation rate decreased the mean radius of the PVP-rich domains and the intervals between the centers of the domains due to the enhancement of the viscosity on the top layer of the fluid film. The increase of the weight ratio of PS to PVP decreased mean radius of the PVP-rich domains whereas the intervals between the centers of droplets remained constant. Therefore, the size and the distributions of ordered patterns can be tuned by the polymer molecular weight, the weight ratio of the two components and the solvent evaporation rate. It revealed that the hydrodynamic effects played a significant role on the pattern formation and distributions.

Structures Formed in Spin-Cast Films of Polystyrene Blends with Poly(butyl methacrylate) Isomers

For polystyrene blends with poly(butyl methacrylate), replacing poly(n-butyl methacrylate) by poly(tert-butyl methacrylate) results in modified topography of spin-cast films (holes dominating at a surface are exchanged with islands, or vice versa, such individual surface features are increased), decreased PBMA surface excess, but similar overall domain structure. Two series (PS/PnBMA and PS/PtBMA) of films with constant thickness and PBMA fraction 0 < Φ < 1, cast from toluene onto silicon wafers, were examined with atomic force microscopy, X-ray photoelectron spectroscopy, profiling and mapping mode of dynamic secondary ion mass spectrometry. Topography was analyzed with the integral geometry approach. Film structure formation was postulated to involve surface segregation, phase separation, and instability of the transient PBMA layer [a linear relation between Φ2 and averaged size of holes (islands) was observed for PS/PnBMA (PS/PtBMA)]. Structural changes caused by isomer exchange are related to glass tr...

Control of Birefringence Dispersion of Uniaxially Oriented Poly(2,6-dimethyl 1,4-phenylene oxide)/Atactic Polystyrene Blend Films by Changing the Stretching Parameters

The birefringence dispersion of uniaxially oriented poly(2,6-dimethyl 1,4-phenylene oxide) (PPO)/atactic polystyrene (PS) blend films has been examined as a function of stretching temperature and draw ratio by polarization-modulated transmission spectro-ellipsometry. The normalized dispersion of Δn(450)/Δn(550) of the PPO/PS blends containing 25.6 wt% PPO decreases with increasing temperature between Tg and Tg+15°C at a draw ratio of 3, while it increases above Tg+15°C. The normalized birefringence dispersion as a function of draw ratio at Tg+15°C diverges at a draw ratio between 1.7 and 1.8. These phenomena can be explained by the change of the PS and PPO orientation functions in the birefringence equation of a multicomponent system on the assumptions that the intrinsic birefringence of PS and PPO is not changed by blending and the form birefringence is ignored.

Surface Composition Control via Chain End Segregation in Blend Films of Polystyrene and Poly(vinyl methyl ether)

Surface aggregation states in miscible blends of monodisperse polystyrene (PS) and poly(vinyl methyl ether) (PVME) were studied by X-ray photoelectron spectroscopy (XPS) in conjunction with neutron reflectivity (NR). In the case of symmetric blends in terms of degree of polymerization, N, PVME and PS were preferentially segregated at the film surface and the interface with a silicon wafer, respectively, to minimize free energy of the system. The concentration profile near the surface obtained by experiments was consistent with a mean-field prediction. Also, the surface composition in symmetric blends composed of PS terminated by fluoroalkyl groups at both ends (α,ω-PS(Rf)2) and PVME was examined. In this case, the surface enrichment of PVME was suppressed by virtue of the surface localization of fluoroalkyl end groups, and the composition was strongly dependent on N. The surface in asymmetric α,ω-PS(Rf)2/PVME blend, in which N of α,ω-PS(Rf)2 was much smaller than that of PVME, was mostly covered with the ...

Retardation of enzymatic degradation of microbial polyesters using surface chemistry: effect of addition of non-degradable polymers

The effects of addition of non-degradable polymers on the rate of enzymatic erosion for the poly(3-hydroxybutyrate- co-3-hydroxyvalerate) [P(3HB- co-3HV)] have been studied at 37 °C and pH 7.4 in the aqueous solution of an extracellular PHB depolymerase from Alcaligenes facalis. Polystyrene (PS) or poly(methyl methacrylate) (PMMA) was selected as a minor component (5 wt%) in a blend because of their non-enzymatic activity. Enzymatic degradation behaviors of the “as-cast” and “annealed” blend films were investigated using atomic force microscopy and weight loss measurements. Although the spherulites of P(3HB- co-3HV) cover all blend film surfaces throughout, the retardation of biodegradation in the P(3HB- co-3HV)/PS blend films was detected from morphological observation and weight loss measurement for both as-cast and annealed blend films while there was little difference between the P(3HB- co-3HV)/PMMA blend and pure P(3HB- co-3HV). Since the enzymatic degradation of P(3HB- co-3HV) initially occurs by a surface erosion process, these degradation behaviors were explained by the surface structure of blend films measured by X-ray photoelectron spectroscopy. The surface of P(3HB- co-3HV)/PS blend films revealed an excess of PS, whereas the surface of P(3HB- co-3HV)/PMMA blend films was nearly covered by P(3HB- co-3HV). It was concluded, therefore, that the PS, which exists within P(3HB- co-3HV) spherulites at surface acts as a retardant of enzymatic attack to the surface of the blend film.

Analysis of Extraordinary Birefringence Dispersion of Uniaxially Oriented Poly(2,6-dimethyl 1,4-phenylene oxide)/Atactic Polystyrene Blend Films

The birefringence dispersion of uniaxially oriented poly(2,6-dimethyl 1,4-phenylene oxide) (PPO)/atactic polystyrene blend films has been investigated by polarization-modulated transmission spectro-ellipsometry measurements. The films show reverse birefringence dispersion in the region of PPO volume fraction from 0.21 to 0.29, where the birefringence is negative and close to zero, indicating ordinary refractive index dispersion. The reverse birefringence dispersion can be explained by the birefringence equation of a multicomponent system based on the preconditions that the intrinsic birefringence of each component in the blend is not changed and the form birefringence is ignored. Furthermore, it has been found that the orientation functions change depending on the volume fractions by the new method for obtaining orientation functions from birefringence dispersion.

Retardation Effect of Enzymatic Degradation of Microbial Polyesters at the Surface by Blending with Polystyrene

The enzymatic surface degradation behavior of the blend films of polystyrene (PS) with poly[((R)-3-hydroxybutyrate)-co-((L)-3-hydroxyvalerate)] (P(3HB-co-3HV)) or poly((R)-3-hydroxybutyrate (P(3HB)) were investigated using atomic force microscopy (AFM). It was found that the blends of PS with P(3HB-co-3HV) or P(3HB) are immiscible in both the amorphous and melt states. The degradation of both P(3HB-co-HV) and P(3HB) was significantly retarded at the initial stages of enzymatic attack by hydrophobic PS (up to 20 wt.-%).

Phase ordering in blend films of semi-crystalline and amorphous polymers

A combination of optical and atomic force microscopy (AFM) is used for probing changes in the morphology of polymer blend films that accompany phase ordering processes (phase separation and crystallization). The phase separation morphology of a “model” semi-crystalline (polyethyleneoxide or PEO) and amorphous (polymethylmethacrylate or PMMA) polymer blend film is compared to previous observations on binary amorphous polymer blend films of polystyrene (PS) and polyvinylmethylether (PVME). The phase separation patterns are found to be similar except that crystallization of the film at high PEO concentrations obscures the observation of phase separation. The influence of film defects (e.g., scratches) and clay filler particles on the structure of the semi-crystalline and amorphous polymer films is also investigated.