Polymer-bound crown ethers. III. effect of polymeric matrix properties on the rate of crotonization

Condensation of aromatic aldehydes with nitromethane or fluorene in the presence of polymer-bound crown ethers complexed with alkali metal or ammonium salts and hydroxides was used to study the kinetics of these catalytic reactions. The course of the reactions was found to depend on the properties of the polymeric matrix used, the rate of condensation being affected by the sorption of substrates and reaction products and by the swelling capacity of the matrix.     

Optical properties of injection‐molded polystyrene scintillators. I. Processing and optical properties

Scintillating tiles for the Tilecal/Atlas calorimeter can be produced by injection molding, an alternative to mold casting via in situ polymerization. This new production method, which leads to a much faster production rate, introduces a number of additional variables that affect the optical yield of the scintillators and that have not yet been reported in the literature. In this work, the effect of processing‐induced orientation on the optical properties of the scintillators is analyzed and discussed. For this purpose, the birefringence across the thickness of the scintillator has been measured. The variations of the birefringence may be correlated with the orientation and, therefore, related to the optical performance, that is, the average light output and its nonuniformity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2706–2713, 2003     

Synthesis and optical properties of novel, thermally stable phenanthrolines bearing an arylthienyl-imidazo conjugation pathway

Six new hyperpolarizable chromophores based on functionalized arylthiophene donors and an imidazo-phenanthroline acceptor moiety have been designed and synthesized for the first time in good to excellent yields by condensation of 5,6-phenantroline-dione with formyl-arylthiophene derivatives in the presence of ammonium acetate in glacial acetic acid. The thermal stability, solvatochromic and nonlinear optical properties of these compounds were evaluated.     

Thermodynamic properties of phosphorus compounds. II. Low-temperature heat capacity and entropy of sodium mono-, di-, and tri-phosphates

Heat capacities from 10–320°K of nine sodium phosphates have been measured by adiabatic calorimetry and the entropies of the compounds have been calculated. The values of S₂₉₈ found were: NaH₂PO₄ 30.47; Na₂HPO₄ 35.97; Na₃PO₄ 41.54; Na₂H₂P₂O₇ 52.63; Na₄P₂O₇ 64.60; Na₃P₃O₉ 68.47; Na₅P₃O_10.6H2_O146.1; Na₅P₃O₁₀ (I) 91.25; Na₅P₃O₁₀ (II) 87.37 cal/deg. mole. The estimation of thermodynamic properties of other sodium phosphates is discussed.     

Investigation of the impact of insoluble diluents on the compression and release properties of matrix based sustained release tablets

In the present study the effect of insoluble diluents such as microcrystalline cellulose (MCC) and dibasic calcium phosphate (DCP) on the compression characteristics and release profile of sustained release tablets containing Hydroxypropylmethylcellulose (HPMC) matrices was investigated. The effect of diluents on the compression characteristics was studied using Heckel and Kawakita equations. The effect of compression forces on the release profile was also investigated. Diclofenac Sodium (DS) was used as a model drug. Tablets were prepared using wet granulation method. It was found that there is a decrease in the drug release as the concentration of these insoluble diluents is increased. From the Heckel and Kawakita analysis it was concluded that the compressed granules of formulations containing microcrystalline cellulose showed higher plastic deformation, densification and granule fragmentation as compared to DCP. Also a relationship was evaluated between the compression force and the release profile i.e. an increase in compression force causes decrease in the release rate of the drug from the formulation irrespective of change in the diluent.     

Polymerization of organic compounds in an electrodeless glow discharge. V. Amines and nitriles

Polymerizations of amines and nitriles in a glow discharge generated by inductive coupling of 13.5-MHz radio frequency are investigated by employing the measurement of closed-system pressure change. It is found that nitrogen in those compounds are incorporated into polymer in a nearly stoichiometric manner and that the polymerization of those compounds are very much similar to that of hydrocarbons. Hydrogen detachments, opening of double bond and/or cyclic structure, opening of triple bond including C?N, and opening of aromatic and heteroaromatic structures contribute to polymerization of amines and nitriles.     

Investigation of a combination of novel polyphosphoramide and boron-containing compounds on the thermal and flame-retardant properties of polystyrene

A novel phosphorus, nitrogen-containing compound, poly(4, 4′-diaminodiphenyl methane phenyl dichlorophosphate) (PDMPD) with high thermal stability was synthesized. The PDMPD was then incorporated into polystyrene (PS) to be used as halogen-free flame retardant. Moreover, small amounts of two boron-containing compounds, Zinc borate (ZnB) and boron phosphate (BP) were combined with PDMPD,to explore effective flame-retardant formulations for PS. The flammability and the thermal properties of the composites were evaluated using limiting oxygen index (LOI) test, microscale combustion calorimeter (MCC) and thermogravimetric analysis (TGA) respectively. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer (TG-IR) was also used to study the gas phase from the degradation of PS composites. Furthermore, the char residues of the samples were investigated by scanning electron microscopy (SEM) and FTIR. The results showed that the incorporation of PDMPD can significantly decrease the flammability of virgin PS, and enhance the thermal stability at high temperature region, in both nitrogen and air atmosphere. A combination of PDMPD with small amounts of boron compounds can further decrease the flammability.     

Investigation of a combination of novel polyphosphoramide and boron-containing compounds on the thermal and flame-retardant properties of polystyrene

Novel, predominantly alternating poly(ether ester)s, poly(butylene-3/4-hydroxy benzoate)s (PBHB)s were synthesized by the hydrogenation of the corresponding unsaturated polymers obtained by forming ether and ester linkages under one pot conditions. The ether substitution caused a reduction in glass transition temperature, T_g. The melting transition was also lowered by more than 100°C compared to poly(butylene terephthalate) as studied by the differential scanning calorimetry (DSC). Crystallization was observed during heating as well as cooling in the DSC studies. Wide angle X-ray diffraction (WAXRD) analysis also indicated that PB-4-HB was semi-crystalline in nature. The thermal stability of hydrogenated polymer was better than that of the unsaturated polymer.

Effect of aluminum oxide nanoparticles additives and gamma irradiation on the structural and optical properties of syndiotactic polystyrene

Aluminum oxide nanoparticles (Al₂O₃) were prepared and the obtained structure and size of the prepared Al₂O₃ nanoparticles were studied via X‐ray diffraction (XRD) and transmission electron microscopy. The effect of adding various concentrations of the Al₂O₃ and gamma radiation on the structural and optical properties of syndiotactic polystyrene (sPS) were investigated using XRD and UV‐spectroscopy. XRD data showed that the addition of the various concentrations of the Al₂O₃ influenced the crystallinity of the nanocomposites. A significant change in the lattice structure and the optical parameters were observed. The results showed that a sample with the Al₂O₃ concentration of 10% achieved a higher refractive index and optical conductivity. Effect of gamma irradiation on sPS sample loaded with 10% Al₂O₃ was studied. The results showed several changes in the structure and optical properties of the resulting films due to crosslinking between the polymer chains. This result reflects that the polymer suffered from structural rearrangement due to the irradiation treatments. POLYM. ENG. SCI., 59:555–565, 2019. © 2018 Society of Plastics Engineers     

Formation of CdS nanoparticles in the matrix of silicate glass and its optical properties

CdS nanoparticles of an average diameter of ~2.7 nm have been synthesized in silicate glass by two stage heat treatment. As was demonstrated using the methods of spectrophotometry and luminescence in the ultraviolet and visible optical ranges, semiconductor phase nuclei were formed at the first stage of thermal treatment, and they grew at the second stage. The image of the spatial distribution of CdS nanoparticles in the glass network has been obtained by computer simulation. The calculated pair distribution function revealed that the average distance between nanoparticles was ~15 nm, which appears sufficient to isolate them from each other in the dielectric matrix and to ensure reliable confinement of electrons inside each nanoparticle.     

On the interesting optical properties of highly transparent,thermally stable,spin‐coated polystyrene/zinc oxide nanocomposite films

In the present work, polystyrene/zinc oxide (PS/ZnO) nanocomposite films are prepared by simple mixing followed by film deposition, using spin‐coating technique. Although there are a few reports on the UV‐shielding properties of PS/ZnO nanocomposite films, these reports deal with rather thick films obtained by solution casting. Spin coating is a more advantageous technique where one can control the film thickness by suitably adjusting the viscosity of the solution and the spinning speed and get homogeneous films with thickness around a few hundreds of nanometers. These aspects provide the motivation for the present work where emphasis is given to investigating the optical properties of PS/ZnO nanocomposite films obtained by spin coating and analyzing the effects of each component of the composite (PS/ZnO) on the properties of the other. The nanocomposite films are found to be highly transparent throughout the visible region and the thermal stability is better compared with PS. The optical absorption of the composite films in the UV region is quite high, and this aspect highlights the prospects of applications of these films in UV shielding. The PS matrix brings about considerable surface modification of ZnO nanoparticles, resulting in the reduction of defect states within ZnO and facilitating sharp, near band edge photoluminescence emission. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly(methyl methacrylate)

Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of ?0.6 · 10^?3 to ?2.6 · 10^?3. Both the height and position of this point are influenced by M?_w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.     

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.     

Acetylenic compounds. II. Preparation and properties of stearolic acid and the related substances

1. 9,10-Dibromostearic acid has been prepared in different grades of purity through urea-inclusion compounds from natural sources of fatty acids. This facilitated preparation of stearolic acid.
2. The degree of separation of stearolic acid from other fatty acids and polymers by means of ureainclusion compounds was ascertained.
3. The attempts at preparation of behenolic acid by dehydrobromination of 13,14-dibromobehenic acid ended in failure.
4. Stearolic acid could not be reduced by sodium in liquid ammonia. Debromination of 9,10-dibromooleic acid yielded stearolic acid whereas reduction of 3, hexyne and debromination of 3,4-dibromohexene resulted in the formation oftrans, 3-hexene. Hence a reaction sequence involving debromination of vinylic dibromides and subsequent reductive hydrogenation has been proposed.

     

The effect of cobalt complex addition on the cure and properties of an epoxy matrix resin

The effects of adding various cobalt complexes to a tetraglycidyl methylene dianiline-based epoxy resin were determined. The addition of cobalt(III) acetylacetonate was found to alter the epoxy cure and improve the flexural strength and fracture toughness of the cured resin. These effects were not duplicated by the addition of various other cobalt complexes.     

A study on the optical properties of three‐armed polystyrene and poly(styrene‐b‐isobutyl methacrylate)

Atom transfer radical polymerization (ATRP) of three‐armed polystyrene[PS] and poly(styrene‐b‐isobutyl methacrylate)[PS‐b‐PiBμMA] were accomplished using an initiator with tri‐active C‐Br end group function and cuprous (I) bromide/2,2′‐bipyridyne catalytic system. The characterization obtained by FT‐IR, ¹H‐NMR, and GPC techniques. The average molecular weight and polydispersity of PS and PS‐b‐PiBμMA were determined as 19,800, 29,300 and as 1.37 and 1.15, respectively, which indicates that the constant concentration of growing chains are present throughout the polymerization. The refractive index and extinction coefficient of the samples were determined in the visible range as a function of wavelength. The refractive index dispersion curves of the thin films were fitted by the Cauchy‐Sellmeier model. The width of localized states (E_u) values changed inversely with optical band gaps (E_g) of the films. While the calculated E_u values of films for initiator, PS and PS‐b‐PiBμMA were determined as 2.72, 2.98, and 2.94 eV, the E_g values were determined as 3.43; 3.11, and 3.16 eV, respectively. The dispersion parameters of thin films were determined. These parameters changed in the investigated wavelength ranges. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

A study on the preparation and properties of the heterogeneous cation-exchange membranes of sulfonated polystyrene/divinyl benzene on an acetal base

The heterogeneous acetal-based membranes containing 50, 60, 70, 80, and 90% (w/w) of the sulfonated polystyrene crosslinked with 7% divinyl benzene were fabricated and studied. In addition, the heterogeneous acetal-based membranes of 85% (w/w) sulfonated polystyrene crosslinked with 1, 4, and 7% divinyl benzene were also prepared and studied. The gel water content, dimensional stability, ion-exchange capacity, area and specific ohmic resistance, permselectivity, and rate of ion exchange of the acetal-based membranes were determined. The sulfonated polystyrene crosslinked with 7% divinyl benzene resin was found to be the better material for preparing the acetal-based membrane with comparable good characteristics. A commercially available heterogeneous membrane (Shanghai Chemicals, 3361) of dry-molding sulfonated polystyrene–divinyl benzene resin was used as the reference membrane for the present investigation. © 1995 John Wiley & Sons, Inc.     

Effect of ammonium derivatives of oligoamidephosphates on the vulcanization characteristics and mechanical properties of some rubber compounds. 1. Isoprene rubber compounds

IR compounds containing ammonium derivatives of oligoamidephosphates were studied with respect to vulcanization and mechanical characteristics. The ammonium derivatives were obtained as neutral analogues of the corresponding oligoamidephophates. The results indicate an improved efficiency of the neutral products and the possibility of a partial replacement of traditional sulphenamide accelerators with the studied ammonium derivatives, leading to a strong improvement of the fatigue resistance (by more than one order). The addition of such products without reducing the level of the basic accelerator led to additional acceleration—the cure rate increased and the cure time decreased up to three times. Ageing resistance showed a tendency to improve.     

Polymerization of organic compounds in an electrodeless glow discharge. IX. Flow-rate dependence of properties of plasma polymers of acetylene and acrylonitrile

Properties (free-radical concentration, gas permeabilities, internal stress, and contact angle of water) of plasma polymers of acetylene and of acrylonitrile were investigated as a function of flow rate of monomer in an electrodeless glow discharge. It was found that the monomer flow rate has a strong influence on free-radical concentration, gas permeabilities, and internal stress but little influence on the contact angle of water. The discharge power has little effect on properties when the full glow is maintained in the reactor. Gas permeabilities decrease with increasing concentration of free radicals in plasma polymers.