SiO2 nanoparticles as scatterers for random organic laser action in red fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran doped polystyrene films

Random multimode lasers are achieved in 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped polystyrene thin films by introducing silicon dioxide (SiO2) nanoparticles as scatterers. The devices emit a resonance multimode peak at a center wavelength of 640 nm with a mode linewidth less than 0.87 nm. The threshold excitation intensity is as low as 0.25 mJ pulse(-1) cm(-2). It can be seen that the microscopic random resonance cavities can be formed by multiple scattering of SiO2 nanoparticles.

Single mode and multimodes lasing emission from MEH-PPV doped polystyrene thin films with surface ripples formed by vapour-induced phase separation

We report single mode and multimodes lasing emission from conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) doped polystyrene ( PS) thin films with surface ripples. Surface ripples were formed by water vapour-induced phase separation. A single mode lasing emission at 606 nm with a line-width of less than 0.4 nm was obtained. The laser threshold was as low as 3.5 mu J pulse(-1). The side mode suppression ratio was 5.76 dB. The periodic changes of the refraction index in the MEH-PPV : PS blending film due to the phase separation should be attributed to the lasing actions.

Branched polystyrene with abundant pendant vinyl functional groups from asymmetric divinyl monomer

Branched polystyrenes with abundant pendant vinyl functional groups were prepared via radical polymerization of an asymmetric divinyl monomer, which possesses a higher reactive styryl and a lower reactive butenyl. Employing a fast reversible addition fragmentation chain transfer (RAFT) equilibrium, the concentration of active propagation chains remained at a low value and thus crosslinking did not occur until a high level of monomer conversion. The combination of a higher reaction temperature (120 degrees C) and RAFT agent cumyl dithiobenzoate was demonstrated to be optimal for providing both a more highly branched architecture and a higher polymer yield.

Mechanism on flame retardancy of polystyrene/clay composites-The effect of surfactants and aggregate state of organoclay

Effects of organically modified montmorillonites (OMMTs) with different type and amount of modifiers on flame retardancy of polystyrene (PS) have been studied. The results from morphology analysis, gas chromatography-mass spectrometry and cone calorimeter have showed different mechanisms for the flame retardancy of PS/OMMTs composites, depending on surface property of OMNTrs. One is the catalysis of acid sites formed on the surface of octadecylammonium modified MMT (c-MMT) via Hoffman decomposition on the carbonization of degradation products, which promotes the formation of clay-enriched char barrier.

Crystal Growth Transition from Flat-On to Edge-On Induced by Solvent Evaporation in Ultrathin Films of Polystyrene-b-Poly(ethylene oxide)

The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment Was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation tit the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer-substrate interaction.

Lamella reorientation in thin films of a symmetric poly(L-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(L-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (T-g(PLLA)), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (T-c), the glass transition temperature of PS (T-g(PS)), the peak melting point of PLLA crystals (T-m(PLLA)), and the end melting point of PLLA crystals (T-m,end(PLLA)). When annealed at (T-c =) 80 degrees C (T-c < T-g(PS) < T-ODT, order-disorder transition temperature), 123 degrees C (T-g(PS) < T-c < T-m(PLLA) < T-ODT). 165 degrees C (T-g(PS) < T-m(PLLA) < T-c < T-m,end(PLLA) < T-ODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced.

Orientation of Syndiotactic Polystyrene Crystallized in Cylindrical Nanopores

Syndiotactic polystyrene (sPS) nanorods with different diameters have been prepared by using anodic aluminum oxide templates, and the orientation of the sPS crystals in the nanorods has been investigated by FT-IR spectroscopy. It is found that the c axis of the beta' crystals preferentially oriented perpendicular to the axis of the nanorod, and the degree of orientation is lower as the diameter of the nanorod decreases. This unexpected result is attributed to nuclei formed at the surface of the nanopores and their subsequent growth, in addition to the preferential growth compatible with the pore direction by the nuclei formed in the bulk film and in the nanorods.

Probing structural changes of spin-coated polystyrene film after swelling and precipitation by synchrotron GIUSAXS and AFM

Polystyrenc film of about 50 nm in thickness on silicon wafer was obtained by spin-coating in tetrahydrofuran solution.The film exhibits a rough surface as shown by atomic force microscopy images and ellipsometry data.

Electrochemiluminescence sensor based on partial sulfonation of polystyrene with carbon nanotubes

Herein, homogenously partial sulfonation of polystyrene (PSP) was performed. An effective electrochemiluminescence (ECL) sensor based on PSP with carbon nanotube (CNTs) composite film was developed. Cyclic voltammetry and electrochemical impendence spectroscopy were applied to characterize this composite film. The PSP was used as an immobilization matrix to entrap the ECL reagent Ru(bpy)(3)(2+) due to the electrostatic interactions between sulfonic acid groups and Ru(bpy)(3)(2+) cations. The introduction of CNTs into PSP acted not only as a conducting pathway to accelerate the electron transfer but also as a proper matrix to immobilize Ru(bpy)(3)(2+) on the electrode by hydrophobic interaction. Furthermore, the results indicated the ECL intensity produced at this composite film was over 3-fold compared with that of the pure PSP film due to the electrocatalytic activity of the CNTs. Such a sensor was verified by the sensitive determinations of 2-(dibutylamino)ethanol and tripropylamine.

Pressure effects on thermodynamics of phase behavior in polystyrene/methylcyclohexane solutions

The calculations presented in this paper are based on the Sanchez-Lacombe (SL) lattice fluid theory. The interaction energy parameter, g*(12)/k, required in this approach was obtained by fitting the cloud points of polystyrene (PS) /methyleyclohexane (MCH) polymer solutions under pressure. The SL lattice fluid theory was used to calculate the spinodals, the binodals, and the Flory-Huggins (FH) interaction parameter of the solutions. The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well. However, the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions. Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.

Synthesis of Arm-6 polystyrene by atom transfer radical polymerization

A new initiator for atom transfer radical polymerization (ATRP), (Cl-2 HCCOO)(3) -C-6 H-3, (TrDCAP),has been designed and successfully synthesized. ATRP of styrene was carried out by using TrDCAP as hexafunctional initiator and the CuCl/bpy catalyst at 130 degrees C in 30% THF via core-first strategy. The Arm-6 PS-AAP was synthesized by etherealization of Arm-6 PS and 4-(4'-methoxyphenylazomethine) phenol (AAP). The initiator and the architectures of the Arm-6 PS were confirmed by H-1-NMR, FT-IR, UV-Vis and GPC.

Crystallization and orientation of syndiotactic polystyrene in nanorods

Syndiotactic polystyrene (sPS) nanorods of 200 and 80 nm diameters were prepared by infiltrating porous anodic alumina oxide templates with polymer melt, and the crystallinity and orientation of various forms of sPS crystals in the nanorods were studied by FTIR spectroscopy and electron diffraction. For sPS crystallized from amorphous state at lower temperatures, a-form crystals were found in the nanorods with random orientation and the same degree of crystallinity as that in the bulk. However, for sPS crystallized from molten state at 260 degrees C, while no preferred orientation was found for the chains in the melt, the beta-crystals formed in the nanorods oriented preferentially with the c-axis aligning perpendicular to the axial direction of the nanorod, and the degree of crystallinity was significantly lower than that in the bulk. The crystallinity decrease was more profound for nanorods of smaller diameter. These results were also supported by electron diffraction data and can be attributed to competition between nucleation and crystal growth in the nanotemplates.

Dewetting of thin polystyrene films under confinement

The dewetting behavior of thin polystyrene (PS) film has been investigated by placing an upper plate with a ca. 140 nm gap from the underlying substrate with the spin-coated thin polymer films. Three different kinds of dewetting behaviors of thin PS film have been observed after annealing according to the relative position of the PS film to the upper plate. Since the upper plate is smaller than the underlying substrate, a part of the polymer film is not covered by the plate. In this region (I), thin PS film dewetting occurs in a conventional manner, as previously reported. While in the region covered by the upper plate (III), the PS film exhibits unusual dewetted patterns. Meanwhile, in the area right under the edge of the plate (II) (i.e., the area between region I and region III), highly ordered arrays of PS droplets are formed. Formation mechanisms of different dewetted patterns are discussed in detail. This study may offer an effective way to improve the understanding of various dewetting behaviors and facilitate the ongoing exploration of utilizing dewetting as a patterning technique.