Showing papers on "Polystyrene published in 1985"

Plasticization of glassy polymers by CO2

Abstract: A technique is described which uses differential scanning calorimetry to estimate the glass transition of polymers containing a dissolved gas. The technique is simple and appears to give reliable results. The effects of CO2 sorption at pressures up to 25 atm were examined in detail for poly(methyl methacrylate) and its blends with poly(vinylidene fluoride). Less extensive results for polystyrene, polycarbonate, poly(vinyl chloride), and poly(ethylene terephthalate) are also given. Reductions in Tg of up to 50°C are observed. A theoretical relation by Chow predicts results in reasonable agreement with the experimental data. These findings are relevant to various applications such as membrane separation processes for gases.

Particle size control in dispersion polymerization of polystyrene

Abstract: In a dispersion polymerization process, the reaction mixture starts out as a homogeneous solution and the resulting polymer precipitates as spherical particles, stabilized by a steric barrier of di...

Synthesis and Functions of Polystyrene Derivatives Having Pendant Oligosaccharides

Abstract: Polystyrene derivatives with maltose, lactose, and maltotriose substituents on each benzene ring were prepared by coupling the corresponding oligosaccharide lactones with p-vinylbenzylamine, followed by radical polymerization. The polymers were water-soluble and had tightly-coiled conformations in water. Strong interactions with methyl orange and magnesium 1-anilino-8-naphthalenesulfonate were observed and their binding constants were determined and compared. Maltose and maltotriose-containing polymers interacted with concanavalin A specifically.

Monodispersed, micron-sized polystyrene particles by dispersion polymerization

Abstract: Emploi de derives non ioniques de la cellulose comme stabilisants steriques dans la polymerisation par dispersion du styrene et obtention de particules jusqu'a 10 μ sans utilisation d'un costabilisant electrostatique

Study of miscibility and critical phenomena of deuterated polystyrene and hydrogenated poly(vinyl methyl ether) by small-angle neutron scattering

Abstract: Miscibility and critical phenomena were studied on the polymer system of deuterated polystyrene and hydrogenated poly(vinyl methyl ether) by the small-angle neutron scattering technique. The phase diagram was constructed with “light” and “neutron” cloud points as well as spinodal points. It shows a well-known behavior of a lower critical solution temperature. The agreement between the “light” and “neutron” cloud points is fairly good for all compositions. The correlation length, the statistical segment length, and the Flory-Huggins -parameter were obtained as functions of temperature and composition by employing de Gennes’ scattering equation for polymer blends. The -parameter showed not only a temperature dependence but also a composition dependence. Comparison of the -parameter with the lattice fluid theory shows that the composition dependence of results from the lattice fluid nature of the system, i.e., the compressibility and the thermal expansion of the system.

The Structure and Mechanical Properties of Polypyrrole

Abstract: The evidence for the presence of the pyrrole moiety in electro-chemically prepared polypyrrole is reviewed together with structural and IR data obtained for the crystalline dimer and trimer of pyrrole. The modification of the mechanical properties of polypyrrole by formation of graft copolymers with polystyrene, by polymerization of the pyrrole monomer within the matrix of a swellable polymer film and by polymerization of the pyrrole on vitreous carbon electrodes is described.

Surfaces of polymer blends: X‐ray photoelectron spectroscopy studies of polystyrene/poly(vinyl methyl ether) blends

Abstract: The surface compositions of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends have been investigated using x‐ray photoelectron spectroscopy (XPS). The XPS results demonstrate that there are significant differences between the composition of the surfaces (e.g., outmost ∼6 nm) and the bulk of both miscible and immiscible blends. The surfaces of PS/PVME films dip‐coated from either toluene or trichloroethylene solutions are found to be enriched in PVME. An additional enrichment in the PVME content of the surface is also observed when miscible PS/PVME blends are phase separated by heating them above the lower critical solution temperature. The average composition profile of a miscible 50/50(w) blend has been obtained by angular‐dependent XPS measurements. This experiment suggests that the enrichment is the result of a concentration gradient rather than a monolayer coating. These results are discussed in terms of the surface free energies of PS and PVME and the degree of mixing in the surface layer.

The viscoelastic properties of rubber–resin blends. I. The effect of resin structure

Abstract: Blends of elastomers with the proper concentration of appropriate low molecular weight resins exhibit performance as pressure sensitive adhesives. Viscoelastic properties, which may be related to adhesive performance, were measured on 1:l blends of rubber and resin using a mechanical spectrometer. Significant differences in viscoelastic properties were observed depending upon the resin structure. On plots of G′ and tan δ vs. temperature, the addition of a compatible resin produces a pronounced shift of the tan δ peak to a higher temperature and reduces the modulus in the rubbery plateau. An incompatible resin results in a minor shift in the tan δ peak of the elastomer along with the appearance of a second peak at higher temperature, attributed to a second phase which is predominantly resin. Also, the modulus is increased in the rubbery plateau. A polystyrene resin, Mw about 900, is shown to be incompatible with natural rubber but compatible with styrene–butadiene rubber. A cycloaliphatic poly(viny1 cyclohexane) resin, Mw about 650, prepared by hydrogenating the polystyrene resin, is compatible with natural rubber, but incompatible with styrene-butadiene rubber. An alkyl-aromatic poly(tert-butylstyrene) resin, Mw about 850, which is intermediate in aromaticity between the aromatic polystyrene resin and the cycloaliphatic poly(viny1 cyclohexane) resin, is compatible with both natural rubber and styrene-butadiene rubber. Therefore, the structure of the resin is very important in adjusting the viscoelastic properties of a rubber–resin blend to achieve pressure sensitive adhesive performance.

Pyrrole–styrene graft copolymers

Abstract: The first graft copolymer of polypyrrole has been synthesized by electrochemically polymerizing pyrrole in the presence of pyrrole derivatized polystyrene; the copolymer produced exhibited an electrical conductivity comparable to that of polypyrrole.

Compatibilizing effect of random or block copolymer added to binary mixture of homopolymers

Abstract: : When copolymer A-B is added to the mixture of homopolymer A and homopolymer B, the compatibility between the two homopolymers is enhanced under certain conditions. Analysis, based on the Flory-Huggins free energy of mixing, gives the specific conditions under which the critical, spinodal or binodal temperature of the ternary mixture is expected to be lowered linearly with the amount of the added copolymer. Experimental measurements were performed on the changes in the cloud point of the mixtures of polystyrene and polybutadiene to which varying amounts of styrene/butadiene random or diblock copolymer were added. The results agree with the theoretical expectation. From quantitative analysis of the cloud point depression, the temeprature coefficient of the interaction energy density between styrene and butadiene polymers is determined. The temperature coefficient is found to give an excellent agreement with the value previously determined by a curve fitting procedure applied to the cloud point curves of binary mixtures.

Concerning gelation effects in atactic polystyrene solutions

Abstract: Les enchevetrements physiques presents a forte masse moleculaire et haute concentration augmentent la stabilite du gel. Identification de trois regimes distincts sol-gel

Molecular design of multicomponent polymer systems. VII: Emulsifying effect of poly(ethylene-b-styrene) copolymer in high-density polyethylene/polystyrene blends

Abstract: Poly(butadiene–b–styrene) copolymers containing a pure, 1,4-PB block have been synthesized by a “living” coordination process. The complete hydrogenation of the PB chain leads accordingly to a high-density polyethylene (HDPE) block. The emulsifying efficiency of such a copolymer (H-7) in HDPE/PS blends is compared with that of a previously reported poly(ethylene–butene–b–styrene) copolymer (SE-7) obtained by the PB hydrogenation of an anionically prepared PB–b–PS. Microscopy examinations demonstrate unambiguously the interfacial activity of both copolymers in HDPE/PS blends. The tensile mechanical properties of the blends are significantly but also differently modified by the two emulsifiers. The copolymer H-7 gives rise to the highest strengths, but, contrary to the copolymer SE-7, provides a poor ductility to the blends. This different behavior is assumed to result in part from the different characteristics of the hydrogenated PB blocks. The elastomeric HPB chain of SE-7 should form at the interface a more or less extended soft zone whereas a rigid interface would result from the cocrystallization of the HPB chain of H-7 with the HDPE homopolymer.

Blends of polyolefins with polymers containing reactive agents

Abstract: OF THE DISCLOSURE A polyolefin blend comprising, in physical admixture, a major portion of particles of a polyethylene and a minor portion of particles of a composition of a thermoplastic second polymer, is disclosed. The polyethylene is selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and at least one C4 - C10 higher alpha-olefin, and the second polymer is a normally solid thermoplastic polymer having a melting point of less than 185°C and a shear viscosity that is not more than that of the polyethylene when measured at 200°C and a shear rate of 400 sec-1 with the proviso that the second polymer is not a homopolymer or copolymer derived solely from hydrocarbon alpha-olefins having 2-10 carbon atoms. Examples of second polymers are (a) homopolymers and copolymers of unsaturated hydrocarbons in which at least one monomer is other than a C2 - C10 alpha-olefin, e.g.ethylene/propylene elastomers, polystyrene and styrene/-butadiene/styrene copolymers, (b) copolymers of ethylene with ethylenically unsaturated carboxylic acids and anhydrides, and esters thereof, and (c) modified polymers e.g. chlorinated polyethylene, grafted and ionomeric polymers. The composition of the second polymer contains a reactive agent that is capable of reacting with polyolefins that are in a molten state, such agents being cross-linking agents and/or modifying agents. In an alternative embodiment, the polyethylene may be more broadly defined as being a homopolymer or copolymer of hydrocarbon alpha-olefins having 2-10 carbon atoms. The blends may be used in a wide variety of processes, including blow-moulding processes, film and pipe extrusion processes, sheet thermo-forming processes and rotational moulding processes.

Comparisons of Styrene Ionomers Prepared by Sulfonating Polystyrene and Copolymerizing Styrene with Styrene Sulfonate

Abstract: As part of a continuing study of ioncontaining polymers, a comparison has been made on styrene-based sulfonate ionomers obtained by two different processes. Copolymers of styrene with sodium styrene sulfonate (SSS) have been compared with corresponding polymers obtained by the sulfonation/neutralization of preformed polystyrene (S-PS). The former system covered a range of sulfonate level from 1 to 30 mol %, while the latter ranged from about 1 to 7 mol %. The characterization of these materials has been conducted using solubility behavior, dilute solution viscometry, thermal mechanical analysis, density measurements, and water adsorption studies. At low (ca. 1%) levels the solubility behavior of the SSS copolymers and the sulfonated polystyrenes were similar. However, at higher sulfonate levels the solubility behavior in different solvents and the dilute solution viscometry were significantly different for the two systems. Similarly, thermal analysis studies (DSC) showed that the glass transition of the sulfonated polystyrene increased linearly with sulfonate level, while the TR for the SSS copolymer increased modestly, up to about 7 mol % sulfonate content, and then remained constant. Significant differences in the softening behavior and water absorption characteristics were also observed for these two classes of ionomers. Although molecular weights and molecular weight distributions are not now available for these ionomers, the differences in their behavior does not appear to be due simply to differences in molecular weight. It is postulated that the differences in the copolymer and the S-PS ionomers may originate with differences in sulfonate distribution. It is suggested that the SSS monomer units are incorporated as blocks in the copolymer as opposed to a more random distribution in the S-PS ionomer. Indirect evidence in support of his argument is found, for example, in the case of the copolymer in the solubility behavior, the relative independence of T, on sulfonate concentration and the apparent existence of a second, high temperature transition tentatively attributable to an ionrich phase. Additional studies are required to confirm this hypothesis.

The initial stages of adsorption of plasma derived proteins on artificial surfaces in a controlled flow environment.

Abstract: Surfaces of amorphous carbon, polystyrene, and polycarbonate were exposed to solutions of fibrinogen, a modified fibrinogen which lacked the alpha chain protuberance, and serum albumin. The results were studied by electron microscopy. The exposures occurred in a well characterized flow environment at a shear rate of 135/s. All three protein species formed a film when adsorbed to carbon films. When the proteins were adsorbed to polystyrene surfaces, formation of a network was observed. Polycarbonate surfaces adsorbed the proteins both as a network and as a continuous film. It was observed that the nature of the adsorption process depended upon the specific combination of molecule and material. For example, on carbon, individual fibrinogen molecules retain their trinodular structure and adsorb randomly until a monolayer forms. On polystyrene, the individual fibrinogen molecules appear as globules and a network forms before complete coverage occurs.

Surface modification of cellulose fibers. I. Spectroscopic characterization of surface-modified cellulose fibers and their copolymerization with styrene

Abstract: Two coupling agents based on trichloro-s-triazine with different terminal unsaturated groups were synthesized in order to improve the bonding between cellulose fibers and an unsaturated polyester matrix. The products of the reactions between hydroxyl groups of cellulose and reactive species of coupling agents were analysed by Fourier-transform infrared spectroscopy (FTIR) and by elemental microanalyses. ESCA was used for surface characterization of treated fibers. The coupling agents were found to be concentrated on the fiber surface. Polymerization of styrene was carried out in the presence of treated fibers. That the unsaturated groups of the treated fibers were able to copolymrize with styrene was shown by FTIR. Further evidence of the presence of grafted polystyrene on the surfaces of the cellulose fibers was provided by ESCA measurements.

Sulfonated Polystyrene Ionomers Prepared by Emulsion Copolymerization of Styrene and Sodium Styrene Sulfonate

Abstract: Sulfonated polystyrene (S–PS), which is of considerable scientific and technological interest, has been traditionally prepared by the sulfonation of preformed polystyrene. This report describes the preparation and properties of S–PS prepared by emulsion copolymerization of styrene and sodium styrene sulfonate. S–PS prepared by copolymerization gave solubility, solution behavior and thermal characteristics that are consistent with an ionomeric structure. The solubility characteristics indicated some chain-to-chain sulfonate heterogeneity. Thermal analysis studies indicated that the glass transition does not increase with increasing sulfonate content. This is contrary to what has been observed for S–PS prepared by sulfonation and suggests that the S–PS prepared by copolymerization is fundamentally different in structure than S–PS prepared by sulfonation of polystyrene.