Lyotropic liquid crystal formation of polystyrene polymacromonomers in dichloromethane

Liquid crystallinity of dichloromethane (DCM) solutions of five samples of polymacromonomer F65 consisting of 65 styrene residues in each side chain was studied by birefringence observation and phase separation experiments at different temperatures in a molecular weight range from 9.4 × 10⁵ to 4.1 × 10⁶. Dilute-solution characterization was also made by light scattering and viscometry in DCM at 20 °C. The polymer concentration c_I on the phase boundary between the isotropic and biphasic regions was lower than the previously determined c_I for a polymacromonomer with a shorter side-chain length of 33 styrene residues at the same molecular weight, reflecting the higher chain stiffness and larger diameter of the F65 polymer. The molecular weight dependence of c_I for the two polymacromonomers (at 20 °C) was explained almost quantitatively by the scaled-particle theory for worm-like cylinders with the model parameters (the Kuhn length, the linear mass density, and the chain diameter) describing gyration radius and intrinsic viscosity data in DCM but without chain-end effect. It was concluded that this theory is capable of predicting the phase boundary concentration of brush-like polymers with essentially the same degree of accuracy as that known for linear, stiff chains.     

Synthesis and characteristics of polymacromonomers composed of alternating binaphthalene-phenylene main chain and polystyrene side chains

Well-defined polystyrene (PSt) based polymers containing middle- or end-chain 2,5- or 3,5-dibromobenzene moieties, prepared by Atom Transfer Radical Polymerization (ATRP) were implied in Suzuki type couplings with 1-naphthalene boronic acid. The resulting polymers, containing a conjugated sequence with 1-naphthyl groups at the extremities, were used as macromonomers in chemical oxidative polymerization in the presence of anhydrous FeCl₃. Polyarylenes, with a hairy-rod structure, having binaphthyl groups in the main chain and the respective PSt chains as lateral substituents, were obtained.All the starting, intermediate or final polymers were structurally analyzed by spectral methods (¹H NMR, IR) and GPC measurements. Thermal behavior of the macromonomers and final polymers was investigated by Differential Scanning Calorimetry (DSC) analyses. Optical properties of the polymers were followed by UV and fluorescence spectroscopies. The absorption spectra of the polymers indicate only a limited extend of conjugation as compared to the naphthalene functionalized polystyrenes. However, in the emission spectra of the polymers, a bathochromic shift with respect to the monomers was observed in all cases.     

Electrical studies of nanocomposites consisting of MWNTs and polystyrene

Multi-wall carbon nanotubes (MWNTs)/polystyrene (PS) nanocomposites containing different concentrations of MWNTs were prepared by the solution evaporation method. Dispersion of MWNTs in PS was achieved by using ultrasonic energy. The structure of nanocomposites was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The dielectric constant (ε′), dielectric loss (ε″), and ac conductivity (σ _ac) were measured from room temperature to 100 °C over the frequency range 10³ Hz–1.2 MHz. The results show that the dielectric properties depend on both frequency and temperature and they are enhanced by increasing the MWNTs content.     

Solution properties of comb‐like polymers consisting of dimethylsiloxane monomer units

A series of comb‐like polymers consisting of dimethylsiloxane monomer units and differing by side‐chain length have been studied in hexane solution using analytical ultracentrifugation, translational diffusion and viscometry. Analysis of the hydrodynamic parameters and their molar mass dependences based on the Fixman–Stockmayer theory or wormlike spherocylinder model shows that with side chain lengthening, the Kuhn segment length A of the polymers under study increases from the value of A for linear polydimethylsiloxane to values typical for semi‐rigid chain polymers A = 8–10 nm. © 2016 Society of Chemical Industry     

Dielectric properties of sulphonated polystyrene

Polystyrene was sulphonated with chlorosulphonic acid and the dielectric properties of the films were measured as a function of degree of sulphonation and water content at 27°C at frequencies of 10³ to 10⁶ Hz. The sulphonated samples have a high dielectric constant as compared to the unsulphonated polystyrene. The hydration of polystyrene sulphonic acid is a stepwise process.     

Thermodynamic and hydrodynamic properties of the the systems polymer—tetrahydrofuran—water: 1. Solution properties of polystyrene

Tetrahydrofuran (THF) is a solvent widely applied in polymer science and technology. However, because of its hygroscopic nature THF may often contain water considerably influencing the properties of the corresponding polymer solutions. In the first part of a series devoted to this problem, cloud point titrations and viscosity measurements were performed in the system polystyrene (PS)-THF-water. The limiting viscosity numbers of polystyrene considerably depended on the water content already in the domain of azeotropic composition, i.e. at about 4.5 vol.% of water. The constants of the Mark—Houwink equation, K and a were determined in pure THF and in mixtures containing up to 8.2 vol.% of water and compared with those for PS-THF found in the literature. The corresponding unperturbed dimensions were determined by various extrapolation procedures and were found to depend on solvent composition. Simultaneously, polymer-mixed solvent interaction parameters B were determined and discussed. Two theta compositions were observed: at about 7.7 vol.% of water for second virial coefficient A₂ = 0, and about 8.12 vol.% for a = 0.5. This agrees with the hypothesis of Dondos and Benoit and indicates the presence of preferential solvation in the system.     

Comparison of optical properties of thermally reversible light scattering films consisting in dispersions of polystyrene/naphthalene domains or polystyrene/liquid crystal (EBBA) domains in epoxy matrices

Summary Thermally reversible light scattering (TRLS) films are materials that can be reversibly switched from opaque to transparent states by varying temperature. TRLS films containing different types of dispersed domains in an epoxy matrix: a) naphthalene/polystyrene (NP/PS), and b) liquid crystal (EBBA/PS), were synthesized by polymerization-induced phase separation. The intensity of transmitted light was measured as a function of temperature in successive heating/cooling cycles. Transparent states were observed during heating cycles at temperatures close to the melting point of NP (81 °C) or the nematic-isotropic transition of EBBA (at about 70 °C). The NP crystallization from their polystyrene solutions in the course of cooling cycles required large undercooling (about 30 °C). In the temperature range comprised between melting and crystallization, optical properties depend on the cooling rate and the thermal history of the material. The situation was quite different for TRLS films based on EBBA. In this case, the generation of a nematic phase from the polystyrene solution required a small undercooling (about 2–3 °C), leading to a relatively sharp transition between opaque and transparent states, independent of the thermal history. This constitutes a significant advantage of the use of liquid crystals compared to organic crystals in the manufacture of TRLS films.     

Preparation of physical gel consisting of syndiotactic polystyrene and poly(ethylene glycol)

Syndiotactic polystyrene (s-PS) was blended with poly(ethylene glycol) (PEG) in 1,2-dichloroethane (DCE) solvent. The mixture became a homogeneous solution at 155 °C depending on the composition ratio of PEG to DCE. When the solution was cooled at the rate of 5 °C/min to room temperature, a thermoreversible gelation was occurred. Wide angle X-ray diffraction (WAXD) measurements revealed that the polymer chain of s-PS in the obtained gel was crystallized with a helical conformation, while that in the non-gelated sample was done with an all-trans planar zigzag conformation.After drying gelated samples at 70 °C for 24 h, a novel polymer blend type of the physical gel consisting of s-PS and PEG was obtained. Dynamic mechanical analysis (DMA) revealed that the physical gel had a high modulus and a long elastic plateau in the temperature range of −80-270 °C.     

Solution properties of polyelectrolytes. I. Exclusion chromatography of sodium polystyrene sulphonate in salt-free water as eluent

The effect of concentration of sodium polystyrene sulphonate on the elution volume in exclusion chromatography has been investigated using salt-free water as eluent. A non-linear increase in the elution volume has been observed with increasing injected sample concentration. Concentration-dependent calibrations have been obtained which approach the universal calibration for uncharged polymers (dextrans) as polyelectrolyte concentration increases. The separation mechanisms are interpreted in terms of electrostatic and hydrodynamic interactions. A semi-empirical model is proposed to predict concentration effects of linear polyions in exclusion chromatography and good agreement has been found between experimental and calculated elution volumes.     

Solution viscosity–molecular weight relationship for polystyrene

The 10% solution viscosity has been used extensively as a measure of molecular weight for the commercial production of polystyrene. Recently, poor correlations have been observed between 10% solution viscosity and molecular weight as measured by gel permeation chromatography. Lowering the concentration improves the correlation. At 0.2%, the log–log plot of viscosity versus molecular weight becomes linear.     

Preparation and properties of selectively p-chlorinated polystyrene

Polystyrene has been chlorinated in the liquid phase by SbCl₃ catalyst combined with 10-trifluoroacetylphenothiazine to afford a polymer, which is represented by the formula . The aromatic substitution reaction (x > 1) occurs predominantly at the p-position, the ratio of p- to o-chlorination being 10-12. The intrinsic viscosity of the toluene solution at 30°C decreases with content of chlorine, x. The refractive index, n_D, increases with x. The n_D value of a 25.05% chlorine-containing polymer (x ? 1) is 1.6041.     

Preparation and properties of magnetic polystyrene microspheres

Magnetic polystyrene nanospheres were efficiently prepared by using a new indirect process based on miniemulsion polymerization of styrene. The samples were characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and vibrating‐sample magnetometry (VSM), respectively. The experimental results clearly show that the 3‐methacryloxypropyltrimethoxy silane was anchored onto the surface of the magnetic particles to form the vinyl end. The size of the magnetic particle is about 6–30 nm. The size of the magnetic particle capped with polystyrene is about 1–2 μm. The magnetic polystyrene spheres exhibit multidomain character, whereas the pure magnetic particles show single domain character. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3660–3666, 2007     

Solution behavior of Na sulfonated polystyrene: Dipole moment determinations

Solution behavior of Na sulfonated polystyrene (NaSPS) ionomers with different percentages of sulfonate was studied by viscosity and dipole moment measurements. Two solvents of different character were chosen, i.e. dioxane (? = 2.22) and dimethyl formamide (DMF, ? = 36) and their mixtures. The reduced viscosity as a function of concentration in polar solvents reflects the ‘polyelectrolyte’ behaviour of the ionomers. Mean-squared dipole moment (<μ²>/x) values were calculated over a temperature range of 20–100°C, in dioxane and in a mixture of 4% DMF in dioxane. The results confirm the ‘polyelectrolyte’ behavior of ionomers by the addition of a small amount of polar cosolvent. The effect of increasing temperature on <μ²>/x in the DMF-dioxane mixture is attributed to the formation of a coordination complex.     

Solution blending of polystyrene and poly(methyl methacrylate)

Blends of poly(methyl methacrylate) (PMMA) and polystyrene (PS) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were made of a low molecular weight PS with three PMMAs having number-average molecular weights of (1) 18,300, (2) 37,000, and (3) 211,000, The blend was found to be partially miscible. The composition-dependent values of the polymer-polymer interaction parameter (g₁₂) were determined and found to be from 0.015 to 0.029 for solution casting at 25°C. The interaction parameter (g₁₂) increases with increasing PMMA molecular weights in the PMMA/PS blend systems. This result is consistent with the behavior of the glass transition temperatures and with the microscopy study which indicate that compatibility is greater in the PMMA-1/PS blends having the low molecular weight of PMMA than in the PMMA-3/PS blends having the higher molecular weights of PMMA.     

Simulation of mechanical properties of oriented glassy polystyrene

Mechanical properties of processed polymers depend sensitively on their microstructure. In order to understand how different processing conditions affect the mechanical properties of polymers, one needs a means to describe the process-induced microstructure. Because the characteristic relaxation times of processed polymer chains often span several orders of magnitude, it is commonly the case that partial relaxation of the chains is frozen into the final product. We report results of molecular simulations by the Semi-Grand Canonical Monte Carlo (SGMC) method to study the orientation-dependent elasticity of glassy polystyrene as a function of both the system-average degree of orientation and the degree of relaxation of chain ends at a constant average orientation, in accord with the tube model of Doi and Edwards. Our simulations reproduce quantitatively the experimentally observed trends in the tensile modulus E₁₁ as a function both of the system-average orientation and of the inhomogeneity of the orientation along the chain due to rapid relaxation of chain ends. The results show that the partial relaxation of the polymer chains is sufficient to explain the observed variation of mechanical properties for samples that differ in processing history, yet have the same observed birefringence.     

Sintering properties of composites consisting of carbon filler and binder

The sintering properties of composites consisting of coke and coal pitch are considered. The coke yield from pitch cannot be used to assess the sintering properties. The increase in coke yield from the pitch in the presence of filler is found to be correlated with increase in sintering properties and strength of the composite.     

间规聚苯乙烯热性能研究

对间规聚苯乙烯（sPS）的热性能（包括熔点、晶型及热稳定性等）进行了差示扫描量热、热重分析和动态力学性能等的测量和分析,发现sPS中存在着不同的晶型,它理想晶体的热力学临界分子量熔点为270．13℃,sPS在静态和动态时间的使用温度可达250℃,说明sPS具有良好的热性能。研究结果有助于sPS的进一步加工和应用。     

酰化间规聚苯乙烯的合成与热性能

采用异相反应合成了乙酰化间规聚苯乙烯,用FTIR,NMR,DSC对乙酰化间规聚苯乙烯的结构与性能进行了研究.结果表明,乙酰化间规聚苯乙烯与间规聚苯乙烯相比,玻璃化转变温度升高,熔融温度和熔融热焓下降.     

Polymorphism and mechanical properties of syndiotactic polystyrene films

The dynamic-mechanical behaviour and the tensile moduli of unstretched and stretched semicrystalline s-PS films, presenting different polymorphic forms (α, γ, δ and clathrate) but similar crystallinity and orientation, have been compared. The main aim is to elucidate the possible influence of different crystalline phases, being largely different in chain conformation and density, on mechanical properties of s-PS semicrystalline samples. For unstretched films presenting a preferential perpendicular orientation of the chain axes, the highest elastic modulus is observed for films with the high density γ phase while for uniaxially oriented films the highest modulus is observed for films with the trans-planar α phase. As for the clathrate films, the guest molecules when only included into the crystalline clathrate phase, have no plasticizing effect.