Polystyrene Molecules Research Articles

Kinetic relationships and mechanism of ozone reaction with polystyrene in CCl4 solution

AbstractIn this work a study is made of the degradation on ozonation of unfractionated polystyrene (PS) in CCl4 solution. It was found that the ozone attack of PS molecules is accompanied by hydrogen abstraction from tertiary CH bonds and by the formation of ozonides due to the reaction of ozone with the aromatic rings. A scheme of PS degradation in solution is suggested; several kinetic parameters are evaluated.

Stabile polyphenoxyle, 5. Sterisch gehinderte vinylphenole zur spinmarkierung von polymeren

AbstractPolystyrene chains containing different amounts of 2,6‐di‐tert‐butyl‐4‐vinylphenylacetat repeating units were deacetylated and dehydrated by means of lead dioxide or potassium hexacyanoferrate(III) to obtain polystyrene molecules containing different amounts of phenoxyl spin‐label radicals. The inter‐ and intramolecular interactions between radical moieties were studied by varying the concentrations of polymer molecules in benzene and toluene solutions and the amounts of radical units in polymer chains. The source of information of these interactions was linewidth analysis of electron spin resonance (ESR) spectra which was carried out by spectral simulations. It was shown that the linewidths of ESR spectra of spin‐labelled polystyrenes in benzene and toluene solutions practically did not change when T > 40°C. It was found that intermolecular interactions are excluded if the polymer concentration is below 250 mg/l. The intramolecular interactions were first observed when the radical concentration in polymer chains was 0,7 mole‐%. This corresponds to a mean distance of 125 repeating units between the radical moieties or a nominal distance of radical units along the polymer chains of about 400 Å. However, the spin‐spin interaction shows that the distance between radicals is at the most about 100 Å under the studied conditions. This is a consequence of random coil conformation of polymer chains in solution.

Ordering phenomena in thin polystyrene films

AbstractOrdering of polystyrene (PS) molecules in thin films collapsed from toluene solutions onto a glass substrate by dip coating is studied in relation to the polymer molecular weight and its distribution. The degree of ordering of chain elements is deduced from measurements of film birefringence, between the normal and parallel directions to the film surface, as a function of film thickness. A technique has been developed for measuring this birefringence by monitoring the intensity of laser light passing through the film, as a function of the angle of incidence. Films of monodisperse low‐molecular‐weight PS exhibit high ordering very close to the substrate, but this ordering decays within 1 μm from the glass surface. Films of monodisperse high‐molecular‐weight PS, on the other hand, exhibit a much smaller, but very long‐range degree of order. In a blend of PS of these two molecular weights, as well as in a polydisperse sample, these effects appear in tandem. The long‐range ordering effect, evident in the 100,000 molecular weight polystyrene films, is much smaller in magnitude in lower‐molecular‐weight films, reflecting probably the importance of chain entanglements.

Untersuchungen zur kettenspaltung und entstehung von π‐bindungen in der vinylkette von polystyrol in lösung unter sauerstoff‐ und lichteinfluß

AbstractThe influence of the solvent on chain degradation of polystyrene (PS) as well as the formation of π‐bonds in the vinyl chain is investigated, the latter caused by irradiation of PS‐solutions with long wave UV light (λ ≥ 270 nm) and reactions of singlet‐oxygen O2 (1Δg). Unambiguous qualitative proof could be given for chain degradation of polystyrene under the given experimental reaction conditions. Quantitative considerations though, based on different oxygen content in the respective solutions, different tension of the macromolecular chain and/or different contraction of the macromolecular coils proved to be not tenable or incomplete. It is shown that under the given experimental conditions formation of π‐bonds in PS results from a reaction of chlorine radicals with PS molecules. The kinetics of π‐bond formation in CCl4 and CHCl3 solutions is investigated by light scattering measurements. The conclusions aim at a quantitative determination of the saturation state in the formation of π‐bonds in both solutions.

Electrical Conduction in Polystyrene–Chloranil System

The charge-transport behaviour in polystyrene–chloranil system has been studied by measuring the dependence of current on voltage, temperature, electrode material, and chloranil concentration. The experimental results are discussed in terms of the Jonscher–Ansari modified Poole–Frenkel mechanism which takes into account the effect of traps. The conductivity was found to increase. with an increase in the chloranil concentration. An explanation for this has been attempted on the basis of charge-transfer-complex formation between chloranil molecules and the phenyl group of polystyrene molecules.

Contraction of Polystyrene Molecules in Dilute Solution below the θ Temperature

Contraction of Polystyrene Molecules in Dilute Solution below the θ Temperature

Etude de la reaction d'addition de polystyrenes ω-vinylsilane avec une molecule-modele des α,ω-dihydrogeno-polydimethylsiloxanes

Three-block copolymers polystyrene-polydimethylsiloxane-polystyrene can be obtained by a hydrosilylation reaction between α,ω-dihydrogeno polydimethylsiloxane and ω-vinylsilane polystyrene molecules. The purpose of the present investigation was to establish by use of a model system, the optical conditions for the synthesis of three-block and multiblock copolymers: reaction temperature and concentrations of reactants and catalyst.

Diffusion of polystyrene in poly(methyl methacrylate)+ benzene solutions measured by photon correlation spectroscopy

A photon correlation spectroscopic investigation has been made of the diffusion of polystyrene molecules in benzene solutions of poly(methyl methacrylate). A subsidiary investigation was made of diffusion in the absence of poly(methyl methacrylate) in both the dilute and concentrated regimes. Results of the latter experiments agree with more detailed studies by others. Diffusion in the presence of poly(methyl methacrylate) of various concentrations has been interpreted as “single labelled chain motion” with the aid of current theories.

Excitation Energy Transfer among Chlorophyll a Molecules in Polystyrene: Concentration Dependence of Quantum Yield, Polarization and Lifetime of Fluorescence

Electronic excitation energy transfer was studied for chlorophyll a in a solid solution of poly­styrene by measuring the concentration quenching of quantum yield, polarization, and lifetime of fluorescence. The concentration quenching of the experimental fluorescence quantum yield is adequately described by Kelly and Porter’s empirical formula (Proc. Roy. Soc., Lond. A 315, 149, 1970), and of polarization of fluorescence by the Jablonski theory (Acta Phys. Pol., 14, 295, 1955). With increasing concentration of chlorophyll a, the fluorescence peak at 672 nm (mainly monomer) is red-shifted, the intensity of the emission peak at ∼730 nm (mainly aggregate) relative to that at the shorter wavelength is increased. The R̅0 values, calculated by using total concentrations, for the emission at 672 nm and 730 nm are 73 ± 2 Å and 45 ±1 Å, respectively. This may suggest that the chlorophyll monomers have a greater efficiency of energy transfer than the aggregates, which fluoresce at ∼ 730 nm.

Molecular interaction and conformation of molecules in polystyrene and styrene-methacrylic acid copolymers

A study was made of universal and specific molecular interaction (MI) and the conformation structure in solid PS and styrene-methacrylic acid (MAA) copolymers, the content of the latter acid varying between 2 and 33 mole %. Experiments were carried out by IR spectroscopy using results of differential scanning calorimetry (DSC) and internal friction (IF). A spectroscopic parameter was selected for the control of variations of universal MI in the polymers studied. Hydrogen bond concentrations in the copolymers were determined according to composition and past thermal history. It was found that in addition to the main effect-increase in the entire MI as a result of hydrogen bonds, the addition of MAA units to PS produces secondary effects, a reduction in universal MI, increase in small scale mobility and chain convolution. These effects are particularly significant starting from MAA concentrations of 10–16%, when average distances between hydrogen bridges become commensurate with the size of the statistical segment.

Eine quantitative, UV‐photometrische bestimmung von Endgruppen in polystyrolen

AbstractStyrene was polymerized in bulk for 45 min at 70°C under a nitrogen atmosphere to a conversion of 6.16 weight‐percent with an aliphatic azo compound, which contained four p‐methoxyphenyl groups per molecule. The polystyrene could be purified easily by column chromatography and was then free of initiator and its decomposing products. It was separated into ten fractions by fractional precipitation (toluene/methanol), and the molecular weights of the polystyrenes were determined osmotically. The ultraviolet absorptions of the polystyrene solutions in dioxane were optically constant and followed the Bouguer‐Lambert‐Beer law. This made it possible to determine the number of absorbing groups per polystyrene molecule, which were constant with a value of 2. Polystyrenes with a number average molecular weight to 106 should be determinable in the same way.

Chain conformation in molten and solid polystyrene and polyethylene by low-angle neutron scattering

Abstract Measurements of radius of gyration, <S2>½and persistence length of polymer molecules in bulk atactic polystyrene have been made by low-angle neutron scattering (LANS) from dilute solutions of protonated polystyrene (PSH) in a deuterated polystyrene (PSD) matrix. The measured values of <S2>½ lie close to those measured in θ solvents and have a molecular weight dependence of M½ + ε = 0.04 ± 0.04. The molecular configuration agrees closely with that of a random coil with a persistence length ∼ 10 Å. These measurements support the model of an unperturbed Gaussian coil in which the distribution of chain segments is random above ∼ 20 Å. Measurements of <S2>½ throughout the glass transition region indicate that the overall conformation of the polymer chain does not change on heating through this region. Chain conformation in molten polyethylene has been measured by (LANS) from dilute solutions of (PED) molecules in a protonated polyethylene (PEH) matrix, and PEH molecules in a PED matrix. The measured values of radii of gyration can be expressed as<S2>½ = k = M½ w with k = 0.63 ±w 0.15, compared to a value of k = 0.45 ± w 0.03. in θ solvent. Thus chain dimensions in the melt appear to again be close to those found in θ solvents. The measurements revealed a tendency to separation (clustering) between PEH and PED molecules, though this tendency is small in the liquid state and does not significantly affect the above result. However, the tendency to clustering is much greater in the solid state and special care is necessary to avoid it. The implications of these findings on recent IR studies of chain reentry in lamallae are discussed.

Influence de la structure conformationnelle sur les spectres de vibration de molécules modèles du polystyrène—II. Région 1000–1200 cm −1

The dependence of the infrared spectra on temperature for some di- and triphenyl-alkanes, model molecules of polystyrene, has been investigated in the range 1000–1200 cm −1. The influence of the conformation of the different isomers on the position of some absorption bands is studied. The origin of these absorption bands seems to be a rocking mode of the terminal methyl groups, more or less coupled with some of the deformation modes of the main chain and influenced by the relative position of the phenyl groups towards the aliphatic substituent.

ORIENTATION OF POLYSTYRENE-GRAPHITE FIBER COMPOSITE

A series of composites were prepared by extruding a mechanical mixture of 90 wt-% atactic polystyrene and 10 wt-% graphite fiber. The orientation degree of both components were determined as functions of processing temperature and demension of extruding orifice by two different methods: The degree of orientation of distributing graphite fiber was evaluated by using an X-ray analyzer; while that of matrix polystyrene was determined by a thermal retraction at a temperature above the glass transition temperature. The orientation of filler, obtained from the intensity distribution curve for the azimuthal scanning of 020 reflection, was at least 80% for all samples, whereas matrix polystyrene was almost always randomly oriented in all composite samples. This may be attributed to the difference in the relaxation times for both components, because the filler fiber is much larger and stiffer than the polystyrene molecules at processing temperature. The dynamic mechanical properties of these composites were measured at temperatures from 20 to 120 C. The effect of graphite fiber was evently observed in both storage and loss moduli: The storage modulus was fairly improved and the loss component was also increased in proportion to the increase of the storage modulus by mixing graphite fiber. The former is simply understood as a reinforcing effect of graphite fiber. The latter, however, is difficult to be explained, but possibly may be interpreted in terms of a weak interaction at the interfacial boundaries between both component materials.

Block and graft copolymers by selective cationic initiation. II. Synthesis and characterization of styrene‐isobutylene block copolymers by use of chlorobrominated alkanes

AbstractThe synthesis and characterization of a new block copolymer, poly(styrene‐b‐isobutylene) (PSt‐b‐PIB), is described. The synthesis involves the initiation of an isobutylene polymerization by a polystyrene molecule containing a terminal tertiary bromine (PSt‐Br), in conjunction with diethylaluminum chloride coinitiator. The species PSt‐Br is in turn synthesized by initiating the polymerization of styrene selectively by the tertiary chlorine of the 2‐bromo‐6‐chloro‐2,6‐dimethylheptane/Et3Al initiator system in the absence of chain transfer. The conditions conducive for selective initiation by tertiary chlorine have been worked out. The pure block copolymer, PSt‐b‐PIB, is obtained by selective extraction and some of its properties were determined, e.g., solubility and film behavior, Tg, and intrinsic viscosity versus temperature. The intrinsic viscosity (in toluene) exhibits a maximum and a minimum in the temperature range from 15 to 55°C.

Measurements of persistence length and temperature dependence of the radius of gyration in bulk atactic polystyrene

Measurements of radius of gyration, 〈S 2〉 1 2 , and persistence length of polymer molecules in bulk atactic polystyrene have been made by means of low angle neutron scattering. The measured values of 〈S 2〉 1 2 lie close to those measured in ϑ-solvents and have a molecular weight dependence of M 1 2 +ϵ where ϵ = 0·04 ± 0·04. The molecular configuration agrees closely with that of a random coil with a persistence length ∼ 10 A ̊ . These measurements support the model of an unperturbed Gaussian coil for this polymer. Measurements of 〈S 2〉 1 2 throughout the glass transition region indicate that the overall conformation of the polymer chain does not change on heating through this region.

Neutron small-angle scattering by mixtures of H and D-tagged molecules of polystyrene and polyethylene

Neutron small-angle scattering by mixtures of H and D-tagged molecules of polystyrene and polyethylene

On the Q-factors for poly-1-olefins in gel permeation chromatography

The Q-factors for ten poly-1-olefins from poly-1-butene to poly-1-octadecene were determined in 1,2,4-trichlorobenzene at 80°C and 135°C using the universal calibration curve and the elution count-extended chain length calibration curve constructed by use of polystyrene standards. These experimentally determined Q-factors were lower than the theoretical ones, except for poly-1-butene, at both temperatures, in contrast to those for polyethylene, polypropylene, and poly-1-butene. Corrected Q-factors for poly-1-olefins were obtained by correlating apparent Q-factors with the number of carbon atoms in the monomer for a series of poly-1-olefins. By assuming that poly-1-olefins in solution exist as quasi-rod-shaped polymers rather than random coils, it would be presumed that the apparent extended chain lengths of poly-1-olefins experimentally determined are longer than the theoretical ones because of the effects of their long pendent groups which influence the elution positions of poly-1-olefins. A molecule of the poly-1-olefins having the same theoretical extended chain length of a polystyrene molecule elutes earlier than the polystyrene molecule, meaning the extended chain length of the poly-1-olefin molecule is supposed to be longer than that of the polystyrene molecule.

Dilute solution behaviour of polymers near the phase separation temperature

Light scattering and viscosity measurements performed in the temperature range between the θ-point and the temperature of phase separation with dilute solutions of polystyrene in cyclohexane and poly(acrylic acid) in dioxane have indicated a different mechanism of precipitation in the two systems. While polystyrene molecules give rise to progressively growing clusters the poly(acrylic acid) coils assume compact forms before precipitating. Phase separation is achieved in the former case by extensive clustering, in the latter by particle coalescence. The dimensions that the compact form of the poly(acrylic acid) molecule can reach before precipitation sets in correspond to a solid-like density inside the molecular domain. From the experimental data the temperatures characteristic for cluster formation ( T c ) and for coil to globule transition ( T g ) have been obtained.

Effects of peroxide bonds and their degradation products on the dielectric relaxations of polystyrene

AbstractPolystyrene radically polymerized in atmosphere of air is composed of bisegment (C‐A) or trisegment (C‐A‐C) block copolymers consisting of styrene segment (A) and styrene peroxide segment (C). Dielectric measurements of a system of copolymers of styrene and oxygen were obtained above the glass temperature. Three primary relaxations, a, b, and c, in order of descending temperature, were found corresponding to three microphases: styrene phase (phase a), styrene peroxide phase (phase c), and an intermediate phase (phase b) which contains a low concentration of peroxide bonds. An alternating copolymer of styrene and oxygen exhibits the relaxation c alone. With heat treatment above the glass temperature, relaxation c and subsequently relaxation b vanish with thermal degradation of peroxide bonds. The sum of relaxation strengths is linearly related to the content of peroxide bonds which was evaluated by the elementary analysis and DTA. Below the glass temperature, the temperature dependence of dielectric loss of carefully purified polystyrene without peroxide bonds shows very weak peaks which correspond to γ (200°K at 10 kHz) and δ (50°K at 10 kHz) peaks, respectively, in the activation plot. When low molecular degradation products of peroxide bonds are occluded or impurities such as benzaldehyde are added into the specimen, the height of the γ peak is appreciably enhanced, indicating that the reorientation of small polar molecules in polystyrene accompanies the vibration of the phenyl group about the CC6H5 bond which gives rise to the γ relaxation.