Showing papers in "Journal of Polymer Science Part A in 1985"

An electrically conductive plastic composite derived from polypyrrole and poly(vinyl chloride)

Abstract: An electrically conductive plastic material was obtained by the electrochemical polymerization of pyrrole in a poly(vinyl chloride) matrix. The transmission electron microscopy shows that polypyrrole is uniformly distributed in the matrix. The conductivity of the composites fall in the range of 5 to 50 S/cm, and their mechanical properties, as measured in a stress—strain test, are very similar to those of pure poly(vinyl chloride). These can be further improved by addition of poly(chloroprene) rubber as a plasticizer.

Homogeneous Ziegler–Natta catalysis. II. Ethylene polymerization by IVB transition metal complexes/methyl aluminoxane catalyst systems

Abstract: Homogeneous Ziegler-Natta systems for the ethylene polymerization, deriving from R2R2′M complexes (R = cyclopentadienyl; R′ = alkyl, aryl; M = Ti, Zr, Hf) and oligomeric oxoalane compounds, were studied Further results concerning the methyl aluminoxane synthesis and the related chemistry are reported On the basis of spectroscopic data a delocalized electronic structure could be inferred for these compounds Results from polymerization experiments showed that the highest productivities are obtained only by oxoalane cocatalysts having a high degree of oligomerization The catalytic activity of the systems under investigation was strongly affected also by changing both the σ-alkyl and the π-cyclo-pentadienyl ligands Furthermore, it was found that in the presence of methyl aluminoxane, the homoleptic σ-alkyl derivatives of IVB transition metals, such as Zr(CH2C6H5)4, are also able to polymerize ethylene with a fairly high productivity Active species containing ZrOAl bonds have been postulated

Polymerization of styrene miniemulsions

Abstract: Polymerization of styrene miniemulsions, prepared using a mixed emulsifier system comprising sodium lauryl sulfate and cetyl alcohol, was carried out using both water-soluble (potassium persulfate) and oil-soluble [2,2′-azobis-(2-methyl butyronitrile)] initiators. The effects of variation of initiator concentration, polymerization temperature, and added inhibitor on the kinetics and particle-size distributions were investigated to obtain more quantitative evidence concerning the locus of polymerization in miniemulsion systems. Experimental results for the kinetics and particle-size distributions clearly showed that monomer droplets became the main source of polymer particle formation. This was attributed to the fact that stable emulsions with droplet diameters in the range of 0.05 to 0.15 μm were produced using this mixed-emulsifier system. In this size range, droplet initiation could effectively compete with other mechanisms due to their large surface area. Their size was indeed similar to the corresponding latex particle size obtained after polymerization.

Ethylene propylene diene terpolymers produced with a homogeneous and highly active zirconium catalyst

Abstract: EPDM terpolymers with ethylidene norbornene as diene monomer could be prepared by means of a soluble Ziegler catalyst formed from biscyclopentadienyl zirconium dimethyl and methylaluminoxane. The overall activities lie between 100 and 1000 kg EPDM/(molZr h bar), obtainable at zirconium concentrations as low as 5 × 10−7 mol/L. After an induction period (0.5–5 h) the polymerization rates increased and then leveled to a value which was constant for several days. From copolymerization kinetics reactivity ratios r12 = 31.5, r21 = 5 × 10−3, and r13 = 3.1 could be derived, and by 13C-NMR spectroscopy r12 · r21 = 0.3 was found (1: ethylene, 2: propylene and 3: ethylidene norbornene). The regiospecifity of the catalyst toward propylene leads exclusively to the formation of head-to-tail enchainments. The diene polymerizes via vinyl polymerization of the cyclic double bond, and the tendency to branching is low. Molecular weights were estimated between 40,000 and 160,000. The average molecular weight distribution of 1.7 is remarkably narrow. Glass transition temperatures of −60 to −50°C could be observed. The cure behavior and the physical properties of cured samples were also tested.

Polymerization of glycidol and its derivatives: A new rearrangement polymerization

Abstract: Anionic (KOH) polymerization of glycidol, or its trimethylsilyl ether (TMSGE) followed by hydrolysis, gives a low molecular weight, largely amorphous polymer that is not the reported 1,3-polyglycidol but, based on 13C-NMR, largely a 1,4-poly(3-hydroxyoxetane) with much branching. This result is achieved by a simple rearrangement of the usual, propagating secondary oxyanion to a primary one. Substantial amounts of four dimers (5–10%), four trimers, and some tetramers were also found. One dimer was isolated and shown to be glycidyl glycerin, the usual thermal dimer from glycidol. Possible structures of the other dimers are proposed. The polymerization appears to begin with the rapid formation of the glycidoxy anion , formed by base abstraction of a proton from glycidol and by nucleophilic displacement of the SiMe3 group from TMSGE. Other bases such as KOtert-Bu give similar 1,4 polymer for glycidol but, with TMSGE, there is considerable 1,3 polymerization. Detailed mechanisms are proposed. The polymer perpared from R-TMSGE with KOH was highly crystalline, high melting (166°C), H2O soluble, isotactic poly(3-hydroxyoxetane). The cationic polymerization of tert-butyl glycidyl ether (TBGE) and TMSGE gave low molecular weight 1,3 polyethers. The TBGE polymer was all head-to-tail whereas the polyglycidol from TMSGE contained extensive head-to-head chain units with considerable branching. Mechanisms for these interesting differences are proposed.

Polymerization of surface-active monomers. I: Micellization and polymerization of higher alkyl salts of dimethylaminoethyl methacrylate

Abstract: Micellization of cationic salts of dimethylaminoethyl methacrylate (DMAEMA) quaternized with n-alkyl bromides such as octyl, lauryl, myristyl, and stearyl bromide and their polymerizations were investigated. The critical micelle concentration (cmc) in water at 25°C was determined by electrical conductivity and dye(azobenzene) solubilization methods and the relation log(cmc) = 1.46–0.31N was obtained, where cmc is in mmol L−1 and N corresponds to carbon number of alkyl bromides used for the monomer preparations. All of these monomeric salts exhibited a high radical polymerizability in water and benzene. The polymerizations in water appeared to proceed with a higher rate with increasing a chain length of the alkyl moiety of the monomers and those in benzene gave the polymers with a remarkably high viscosity. The rate of polymerization of lauryl bromide salt in anisotropic solutions (in water and benzene) was exceedingly fast as compared with that in isotropic solution(in acetonitrile). All of the polymers obtained here were insoluble in water. Solubility characteristics of these monomers and polymers in other solvents were also presented. The reduced viscosity, in dimethylformamide and methanol, of poly(lauryl bromide salt) prepared in water increased with dilution but that for the polymer obtained in benzene exhibited an inverse concentration dependence. Some discussions were made on the peculiarities of the polymerizations of these monomers and the resulting polymers.

Polyetherimides. I. Preparation of dianhydrides containing aromatic ether groups

Abstract: A general synthetic method and characterization of bis(ether anhydride)s, the ether containing aromatic dianhydrides of the following structure, are presented. The method involves aromatic nitro-displacement of N-substituted 3- or 4-nitrophthalimide with bisphenoxides to form N-substituted arylene-bis(phthalimido)ethers or bis(ether imide)s. Sixteen structurally different bis(ether imide)s have been prepared and subsequently converted to the corresponding bis(ether anhydride)s. Bis(ether anhydride)s are stable crystalline compounds of a moderate reactivity. Unlike highly reactive dianydrides such as pyromellitic and benzophenonetetracarboxylic dianhydrides bis(ether anhydride)s are semipermanently stable against hydrolysis in the presence of atmospheric moisture.

O‐nitrobenzyl photochemistry: Solution vs. solid‐state behavior

Abstract: The efficiency of various 2-nitrobenzyl groups in the photogeneration of carboxylic acid from nitrobenzyl esters has been determined, and the solution vs. solid polymer matrix photochemistry is compared. Generally, the quantum yield for photoreaction is lower in the solid state, probably due to decreased conformational mobility. The substitution that affords the largest increase in quantum yield (ϕ) is at the α-carbon atom. The value of ϕ for α-methyl-2-nitrobenzyl trimethylacetate in solution is 0.65 vs. 0.13 for the parent 2-nitrobenzyl ester.

Plasma polymerization investigated by the substrate temperature dependence

Abstract: Plasma polymerization of tetra fluoroethylene (TFE), perfluoro-2-butyl-tetrahydrofuran (PFBTHF), ethylene, and styrene were investigated in various combinations of monomer flow rates and discharge wattages for the substrate temperature range of −50 to 80°C. The polymer deposition rates can be generally expressed by k0 = Ae−bt, where k0 is the specific deposition rate given by k0 = (deposition rate)/(mass flow rate of monomer), A is the preexponential factor representing the extrapolated value of k0 at zero absolute temperature, and b is the temperature-dependence coefficient. It was found that the value of b is not dependent on the condensibility of monomer but depends largely on the group of monomer; that is, perfluorocarbons versus hydrocarbons. The values of A are dependent on domains of plasma polymerization. In the energy deficient region A is given by A = α(W/FM)n, where α is the proportionality constant, W is discharge wattage, FM is the mass flow rate, and n is close to unity. In the monomer deficient region A becomes a constant. The kinetic equation is discussed in view of the bicyclic rapid step-growth polymerization mechanisms.

Surface modification of polypropylene with CF4, CF3H, CF3Cl, and CF3Br plasmas

Abstract: ESCA and contact angle measurements were used to characterize the surfaces of polypropylene and glass substrates exposed to CF4, CF3H, CF3Cl, and CF3Br plasmas. The use of both organic and inorganic substrates allowed clear distinction between treatments which led to plasma polymerization and treatments which caused grafting of functional groups directly to the substrate surfaces. CF4 plasmas were the only treatments studied which fluorinated polypropylene surfaces directly, without the deposition of a thin, plasma-polymerized film. CF3H polymerized in a plasma, while CF3Cl and CF3Br plasmas caused chlorination and bromination of polypropylene surfaces, respectively. Correlations were made between the active species present in the plasmas and the surface chemistry observed on the treated polypropylene substrates.

A kinetic model for predicting oxidative degradation rates in combined radiation-thermal environments

Abstract: A general theoretical model has been derived for the case of oxidative degradation dominated by the slow breakdown of hydroperoxide species. The model has been used to predict the general dose-rate behavior for this mechanism. The model also suggests a method for creating isothermal dose-rate curves through a time-temperature-dose-rate superposition procedure which utilizes no adjustable parameters. The superposition procedure and the kinetic model are quantitatively verified using accelerated aging laboratory data and real-time nuclear power plant aging data on a PVC material.

Heterogeneous oxidative degradation in irradiated polymers

Abstract: : When polymeric materials are irradiated in the presence of air, oxygen-diffusion effects can, depending upon dose rate, lead to oxidative degradation which occurs only near the edges. This report describes the use of several recently developed techniques which are of general use for studying heterogeneous degradation in commercial polymeric materials. The techniques discussed are: optical evaluation of cross-sectioned, polished samples; cross-sectional profiling of changes in relative hardness; and profiling of density changes. Oxidation penetration depths are given for a number of major polymer types as a function of dose rate. A detailed example is given graphically illustrating the effects of differing oxidative penetration depths on the radiation-degradation behavior of a Viton(R) O-ring material; this particular material becomes hard and brittle when irradiated at high dose rate. but soft and stretchable when irradiated at low dose rates. jg p4

Halomethyl octyl ethers: Convenient halomethylation reagents

Abstract: Chloromethylation du polystyrene soluble par ClCH 2 OC 8 H 17 . Bromomethylation du polystyrene soluble et d'une polysulfone soluble par BrCH 2 OC 8 H 17

Effect of carboxyl end groups on hydrolysis of polyglycolic acid

Abstract: Dye interaction analysis in hexafluoroisopropanol was used to determine end carboxyl groups in polyglycolic acid (PGA). The rate of heterogeneous hydrolysis of purified PGA in water at 37°C shows a first-order dependence on carboxyl end group concentration at levels above 12 meq/kg. Reaction of molten PGA with a tetraarylorthocarbonate or a triarylketenimine gave end-capped PGA with carboxyl levels as low as 1 meq/kg. These samples were somewhat more resistant to hydrolysis than untreated PGA despite an increased initial rate at the lower carboxyl levels.

Organogermane homopolymers and copolymers with organosilane

Abstract: The first high molecular weight soluble, formable organogermane homopolymer (n-Bu2Ge)n was synthesized by the sodium coupling of n-Bu2GeCl2 in toluene. Soluble organogermane/organosilane copolymers [(X2Ge)x(YZSi)y]n were prepared by sodium coupling of X2GeCl2 and YZSiCl2 in different molar ratios (X = n-bu, Ph; Y = n-hexyl, cyclohexyl; Z = Me). Germanium-containing polymers and copolymers with organosilanes are highly absorbing between 300–360 nm, with the absorption maxima dependent on the nature of the substituent and the ratio of X2Ge:YZSi in the polymer. These polymers are photoactive and display bleaching behavior with photoscission.

Structure and phase transitions in poly(diethylsiloxane)

Abstract: The structure changes accompanying phase transitions in poly(diethylsiloxane) (PDES) have been studied by WAXS and SAXS techniques using oriented and isotropic samples. PDES may exist in two low-temperature modifications (the monoclinic α1-form and presumably the “tetragonal” β1-form) and two high-temperature modifications (the monoclinic α2-form and the “tetragonal” β2-form). In linear PDES the crystal - crystal transitions α1–α2 and β1–β2 occur near 214 and 206 K, respectively. At higher temperatures α2 (280 K) and β2 (290 K) forms transform into the mesomorphic phase αm that gradually melts at 280–300 K giving an amorphous phase. According to x-ray and density data, αm phase is also characterized by monoclinic structure slightly different from hexagonal packing.

13C‐NMR spectral studies on the distribution of substituents in water‐soluble cellulose acetate

Abstract: The degree of substitution (DS) and distribution of O-acetyl groups of water-soluble cellulose acetate (CA) were investigated by 13C-NMR For this purpose, three different series of CA samples with low DS were prepared by respective homogeneous reaction, ie, (1) deacetylation of cellulose triacetate (CTA) in acetic acid—water solution (D-series), (2) reaction of CTA with hydrazine (H-series), and (3) acetylation of cellulose with acetic anhydride in a 10% LiCl-dimethylacetamide solution (A-series) It was found that (i) water-soluble CA can be obtained only from D-series products, (ii) the DS value of water-soluble CA ranges from 05 to 11, (iii) the D-series products exhibit little difference between the relative DS values at C-2, C-3 and C-6 hydroxyl groups, and (iv) the relative DS at C-6 hydroxyl groups is very high compared to those at C-2 and C-3 hydroxyl groups in H- and A-series products Aqueous solution of water-soluble CA (D-series sample) showed no gel—sol transition, even when the temperature was raised to 95°C X-ray diffraction observations revealed that the water-soluble D-series samples were essentially noncrystalline, but the water-insoluble A-series samples were crystalline It was also found that the relative ease of acetylation is C-6 > C-2 > C-3

Spectroscopic study on chemical structure of plasma‐polymerized hexamethyldisiloxane

Abstract: A plasma-polymerized material was produced from hexamethyldisiloxane vapor by a glow discharge polymerization technique. Spectroscopic interpretation of the chemical structure of the polymerized hexamethyldisiloxane was studied by spectroscopic means such as IR, XPS, and NMR. The plasma polymer was barely soluble in the usual organic solvents, although it contained a small amount of the monomer and its oligomers. The IR spectrum indicated that the polymer consisted of SiCH3, SiO, SiCH2, and SiH groups. The surface of the polymer was found to retain structural units similar to the monomer from the XPS measurement. On the other hand, the 13C and 29Si high-resolution, solid-state NMR measurements revealed that the plasma polymer was highly crosslinked with a variety of conformations and a number of O atoms surrounding a Si atom. Results from the XPS and NMR spectra suggested that the bulk of the polymer was more oxidized than the surface layer; Si atom was preferentially oxidized. A hypothetical chemical structure was proposed for the polymerized hexamethyl-disiloxane.

Kinetics and mechanism of emulsifier‐free emulsion polymerization: Styrene/surface active ionic comonomer system

Abstract: The emulsifier-free emulsion polymerizations of styrene in the presence of the surface active comonomer, undecylenic isethionate sodium salt (at concentration below its critical micelle concentration), and of the initiator, potassium persulfate, indicate that the number of polymer particles and the rate of polymerization at steady state is dependent on 1-power of the comonomer concentration and 1/2-power of the initiator concentration. This result suggests a homogeneous nucleation mechanism by which particles are formed from coiled-up oligomeric radical chains originally dissolved in the aqueous phase. Size distribution of the particles is rather narrow and has a uniformity very close to one (ca. 1.02) after 30% conversion. Addition of salt such as sodium sulfate to increase the ionic strength in the aqueous phase results in a formation of micelles (which can grow to become polymer particles) in addition to the formation of polymer particles through the homogeneous nucleation mechanism. Variation of the ionic strength leads to a variation in the number of polymer particles due to a competition between these two nucleation mechanisms and gives a minimum of the number of polymer particles and a maximum of the average particle diameter.

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.

Polyaromatic Ether-Ketones and Ether-Keto-Sulfones Having Various Hydrophilic Groups,

Abstract: : Polyaromatic ether-ketones and polyaromatic ether-keo-sulfones were sulfonated by suspending the polymer powders in dichloroethane containing liquid sulfur trioxide and trialkyl phosphate at room temperature. It was found that more than one sulfonic group can be introduced per each repeating unit of the polymers without degradation. The sulfonated polymers were soluable in various organic solvents, and solubility and mechanical properties depended on the initial molecular weight of polymers as well as the degrees of sulfonation. Strong films can be cast from their dimethylformamide solutions.

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.

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.

Dehydrofluorination of poly(vinylidene fluoride) in dimethylformamide solution: Synthesis of an operationally soluble semiconducting polymer

Abstract: The reaction of poly(vinylidene fluoride) with several different bases in dimethylformamide solution yields dehydrofluorinated products with conjugated polyene structures. The extent of elimination can be controlled by varying the amount of added base. The structural properties of dehydrofluorinated materials depend on the base used. Polymer films cast from DMF solution exhibit electronic conductivity upon iodine doping; the conductivity is also a function of the base used.

Binding of metal ions by polyethylenimine and its derivatives

Abstract: Mesures de la fixation d'ions metalliques bivalents, Cu 2+ , Ni 2+ , Co 2+ et Zn 2+ sur le polyethyleneimine et ses derives acetyl et alkyl par la technique de la dialyse d'equilibre

The emulsion copolymerization of styrene and sodium styrene sulfonate

Abstract: The emulsion copolymerization of styrene and sodium styrene sulfonate has been shown to be a feasible preparative route to ionomeric sulfonated polystyrene. The properties of these copolymers are reported elsewhere. The copolymerization rate was found to be dramatically enhanced when compared to that for the emulsion copolymerization of styrene under identical conditions. This copolymerization was studied in detail and two mechanisms were proposed to account for these rate differences. An increase in the number of polymerizing particles in the copolymerization with consequent rate enhancement was substantiated by electron microscopy. However, the data indicate that the rate differences cannot be fully accounted for by this effect. In addition, a gel effect is proposed as a second contributor to the enhanced rate. This gel effect is believed to result from the intermolecular association of the incorporated metal sulfonate units in the growing polymer particles. When a third monomer that plasticizes the ionic interactions is used the polymerization rate decreases. This supports the gel effect hypothesis.