Synthesis of polypropene-block-poly(ethylene-co-propene) by short-period polymerization with MgCl2-supported Ziegler catalyst

The short-period polymerization method was successfully applied to the synthesis of a novel diblock copolymer, polypropene-block-poly(ethylene-co-propene). The polymerization was carried out for ca. 0,1 s with a MgCl₂-supported Ziegler catalyst. The copolymers obtained showed unimodal curves in gel-permeation chromatography without any peak in the low-molecular-weight region. After extraction with heptane, the fraction of poly(ethylene-co-propene) remained unchanged in the copolymer but disappeared in a commercial so-called block-type copolymer. All the results the formation of polypropene-block-poly(ethylene-co-propene), in which poly(ethylene-co-propene) is chemically linked with polypropene.     

High-Pressure phase behavior of mixtures of poly(ethylene-co-methyl acrylate) with low-molecular weight hydrocarbons

Cloud-point data to 180°C and 2,800 bar are presented for three poly(ethylene-co-methyl acrylate) copolymers [10, 31, and 41 mol % methyl acrylate (MA)] and for polyethylene in ethylene, ethane, propylene, and propane. At low concentrations of MA in the backbone of the copolymer, the saturated hydrocarbons are better solvents for the copolymer than their olefinic analogs because polarizability drives the phase behavior. For the higher MA-content copolymers, which have more polar repeat units, the unsaturated hydrocarbons are better solvents owing to favorable quadrupolar interactions between the solvent and the polymer segments. The cloud-point curves of the high MA-content copolymers in the unsaturated hydrocarbons are shifted to very high temperatures to overcome strong acrylate-acrylate interactions in the polymer. In fact, the 41 mol % MA copolymer cannot be dissolved in propane at temperatures to 180°C and pressures to 2,800 bar even though the copolymer is predominantly ethylene, while the same copolymer dissolves in propylene at 40°C and at pressures as low as 1,400 bar. Although the Sanchez-Lacombe equation of state is used to model the cloud-point curves, two temperature-dependent mixture parameters are needed for a good fit of the data. © 1992 John Wiley & Sons, Inc.     

Synthesis and near infrared properties of rare earth ionomers

Fully exchanged, anhydrous ionomers of ethylene-co-acrylic acid (EAA) copolymers and ethylene-co-methacrylic acid (EMAA) copolymers containing Dy⁺³, Er⁺³, Sm⁺³, Tb⁺³, Tm⁺³, and Yb⁺³, and mixtures of them, were synthesized and studied in the near infrared region by reflection and Fourier Transform Laser Raman spectroscopies. The EAA copolymers ranged from 1.4 to 8.7 mol % acid and the EMAA copolymers were 7.3 and 16.2 mol % acid. The ionomers were shown to be essentially free of carboxylic acid groups, water, or other forms containing O (SINGLE BOND) H groups and were characterized by infrared and other methods. They are light and heat stable, and become thermoplastic and moldable at ca. 220°C under pressure. When excited at 1.064 μ with a Nd: YAG laser, these ionomers exhibit novel, lanthanide-dependent near infrared luminescence and strong Raman scattering in the near infrared region. The strongest luminescence is observed with Sm⁺³ ionomers. The Dy⁺³ ionomer Raman-shifts this source to emit light most strongly in the 1.53–1.55 μ range where the ionomer also transmits light well. © 1996 John Wiley & Sons, Inc.     

Polymer-supported Ziegler–Natta catalysts. I. A preliminary study of catalyst synthesis

Polymer-supported Ziegler–Natta catalysts based on various polymer carriers were synthesized by different methods, including (1) loading TiCl₄ directly onto the polymer supports; (2) loading TiCl₄ onto the polymer supports modified by magnesium chloride (MgCl₂); (3) loading TiCl₄ onto the polymer supports modified by Grignard reagent (RMgCl); and (4) loading TiCl₄ onto the polymer supports modified by magnesium alkyls (MgR₂). The activity and kinetic features of the catalysts for ethylene polymerization were examined. Among the combinations tested, the best was found to be TiCl₄/n-Bu₂Mg.Et₃Al/poly(ethylene-co-acrylic acid) (92:8), which produced a catalyst of very high activity for ethylene polymerization. © 1994 John Wiley & Sons, Inc.     

A novel synthesis of acrylic acid containing polymers

A novel synthesis of linear acrylic acid containing polymers, poly(styrene-co-acrylic acid) and poly(acrylic acid), was accomplished through hydrolysis of the respective parent polymers, i.e. poly(styrene-co-methyl acrylate) and poly(methyl acrylate), with trimethylsilyl iodide under mild conditions. Combination of ¹H NMR, ¹³C NMR, FTIR, DSC and chemical titration confirms that the conversion from methoxycarbonyl to carboxyl is almost complete. This method is further successfully applied to synthesize poly-(ethyl methacrylate-co-acrylic acid) through selective hydrolysis of the methyl acrylate units in poly(ethyl methacrylate-co-methyl acrylate).     

IR laser ablative modification of poly(ethylene-co-acrylic acid) zinc salt

IR laser-induced ablative degradation of poly(ethylene-co-acrylic acid) zinc salt (PEAZn) leads to cleavage of both polyethylene backbone and CO₂H group. It yields carbon oxides and volatile hydrocarbons (ethene as a major product) and affords ablative deposition of solid ionomeric films in which the initial ratio -CO₂H/-CO₂Zn is decreased due to higher thermal stability of the -CO₂Zn group. The laser-induced process differs remarkably from conventional degradation of similar polyethylene chain-based metal methacrylate ionomers that are known to yield cold ring fraction containing only -CO₂H group. The cleavage of the polyethylene backbone in the laser-induced degradation becomes more important at higher fluences. The presence of sodium metasilicate is shown to accelerate the decomposition of the CO₂H group.     

Synthesis and properties of poly(oxyethylene)s containing thioether,sulfoxide, or sulfone groups

Poly[oxy(ethylthiomethyl)ethylene] (ETE) was prepared from poly[oxy (chloromethyl)ethylene] (CE) by reaction with sodium ethanethiolate. Sulfoxide and sulfone analogues were synthesized by oxidation of the poly[oxy(ethylthiomethyl)ethylene]. By changing the chloromethyl/sodium ethanethiolate ratio, poly[oxy (chloromethyl)ethylene-co-oxy(ethylthiomethyl)ethylene] (CE-ETEs) were easily made. Poly[oxy(ethylsulfinylmethyl)ethylene] (ESXE), poly[oxy(chloromethyl)ethylene-co-oxy(ethylsulfinylmethyl)ethylene] (CE-ESXEs), poly[oxy(ethylsulfonylmethyl)ethylene] (ESE), and poly[oxy(chloromethyl)ethylene-co-oxy(ethylsulfonylmethyl)ethylene] (CE-ESEs) were obtained by oxidation of ETE or CE-ETEs. There was little if any chain degradation. The (co)polymer structures were confirmed by FTIR and ¹H-NMR spectroscopic studies. Their thermal properties were studied by DSC and TGA. T_gs of ETE, ESXE, and ESE were -57, 36, and 57°C, respectively, and T_d,os (initial decomposition temperature, TGA) were 331, 198, and 308°C, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 793–801, 1998     

Nuclear magnetic resonance and high-performance liquid chromatographic evaluation of polymer-based stationary phases immobilized on silica

Three poly(ethylene-co-acrylic) acid copolymers (–CH₂CH₂–)_x[CH₂CH(CO₂H)–]_y with different chain lengths and mass fractions of acrylic acid were covalently immobilized as stationary phases on silica via two variants of spacer molecules (3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane). Different mobilities of the alkyl chains in the stationary phases were observed using ¹³C solid-state NMR spectroscopy. The stationary phases with more rigid trans-ordered alkyl chains had better selectivity for geometric -carotene and xanthophyll isomers (provitamin A derivatives). Also, all the separations of the analytes were affected by polar interactions with the chromatographic sorbent. This was further proved by separating more polar cis/trans retinoic acid isomers (vitamin A derivatives). ¹³C high-resolution/magic-angle spinning (HR/MAS) NMR measurements of the chromatographic sorbents suspended in the mobile phase confirmed a dependence of molecular shape recognition ability on alkyl chain conformation.     

Cosolvency effects on copolymer solutions at high pressure

Cloud-point data to 180°C and 2800 bar are presented for polyethylene, poly(methyl acrylate), and two poly(ethylene-co-methyl acrylate) copolymers (10 and 31 mol % methyl acrylate) in propane and chlorodifluoromethane with two cosolvents, acetone and ethanol. The addition of small amounts of either cosolvent to the copolymer–solvent mixtures shifts the cloud-point curve to lower pressures and temperatures, as both cosolvents provide favorable polar interactions with the acrylate group in the backbone of the copolymer. Ethanol has a larger effect than acetone since ethanol hydrogen bonds to the acrylate group. However, if the concentration of ethanol is increased above ca. 10 wt %, it self-associates and reverts to antisolvent behavior, forcing the copolymer out of solution. For nonpolar polyethylene–propane mixtures, the polar cosolvents behave as traditional an-tisolvents. In poly(methyl acrylate)–chlorodifluoromethane mixtures, both polar cosolvents enlarge the single-phase region. The cloud-point curves for the (co)polymer–propane–acetone mixtures are modeled reasonably well using the Sanchez–Lacombe equation of state with two adjustable mixture parameters. No attempt is made to model the mixtures that exhibit hydrogen bonding. © 1993 John Wiley & Sons, Inc.     

Surface tension of polymer mixtures and copolymers

Contact angles θ of liquids of different polarity were measured on a series of mixtures of solid high polymers and a series of copolymers. The mixtures were composed of an alternating poly(ethylene-co-maleic anhydride) (EMA), and its addition product with n-octadecylamine, poly(ethylene-co-N-n-octadecylmaleamic acid) (EOM). The co-polymers were composed of the same monomeric units as the mixtures. The surface tension γ_s of EOM, calculated from θ by the Good-Fowkes-Owens-Wendt treatment, decreased slightly with increasing molecular weights and then reached a limiting value. Plots of γ_s against EOM concentration indicated large negative excess surface tension of the units with lower surface tension, EOM, in both series studied. For the mixture series, γ_a first sharply decreased with the EOM concentration; then it reached a limiting value, the γ_s of pure EOM, at a very low EOM concentration. This indicates phase separation of the two polymers, and the thickness of a monomolecular surface layer was calculated from these data. For the copolymers, γ_s varied logarithmically with the EOM concentration. Throughout the whole concentration range, the data fitted the equation developed by Belton and Evans for ideal mixtures.     

Contact-angle,ellipsometric, and spin-diffusion solid-state nuclear magnetic resonance spectroscopic investigations of copolymeric stationary phases immobilized on SiO<Subscript>2</Subscript> surfaces

SiO₂ surfaces—silica gel particles and silica wafers—were modified by covalently immobilizing three poly(ethylene-co-acrylic acid) copolymers, (–CH₂CH₂–)_x[CH₂CH/(CO₂H)–]_y, with different chain lengths and mass fractions of acrylic acid. ¹³C solid-state NMR spectroscopy on the modified silica gel particles revealed both mobile gauche and rigid trans aligned alkyl chains in the copolymers. For copolymers attached to silica wafers via a 3-aminopropyltriethoxysilane spacer molecule, ellipsometric measurements revealed a mean value of the layer thickness distribution of 6.5 and 4.3 nm, respectively, for the more acidic and the shorter copolymers with mobile alkyl chains mostly in the gauche conformation. For the longest and least acidic copolymer with more rigid trans ordered alkyl chains, however, a mean phase thickness of 10.6 nm was found. When this copolymer was immobilized via a 3-glycidoxypropyltrimethoxysilane spacer molecule we measured a mean layer thickness of 9.9 nm. A model of the surface morphology of this immobilization strategy was derived using spin-diffusion ¹³C NMR measurements on the corresponding modified silica. It was thereby proven that the trans and gauche-aligned alkyl chains occur in distinct domains of certain sizes on the silica surface. The surface polarity of all modified silica wafers was also investigated by measurement of contact-angle.     

New Approach to Determine the Phase Transition Temperature,Cloud Point,of Thermoresponsive Polymers

In this study, a novel method to determine the cloud point temperature variation in aqueous solutions of thermoresponsive homo- and copolymers was developed. Poly(N-vinylcaprolactam) (PVCL) and triblock copolymers of poly(t-butyl acrylate-co-acrylic acid)-b-poly(N-vinylcaprolactam)-b-(t-butyl acrylate-co-acrylic acid) (P[(tBA-co-AA)-b-PVCL-b-P(tBA-co-AA)] were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and used as models. The incorporation of AA units (hydrophilic segments) into the polymeric chain of PVCL influenced the phase transition, increasing the cloud point temperature of the final copolymer. The cloud point temperatures of the PVCL and the triblock copolymer P(tBA-co-AA)-b-PVCL-b-P(tBA-co-AA) were determined by measuring the transmittance of aqueous solutions of the polymers in a Turbiscan Lab instrument in the range of 29 to 40 C. This is the first study in which Turbiscan Lab is used to determine the cloud point temperature.     

Intermolecular potential parameters and combining rules determined from viscosity data

The law of corresponding states has been demonstrated for a number of pure substances and binary mixtures and provides evidence that the transport properties viscosity and diffusion can be determined from a molecular shape function, often taken to be a Lennard–Jones 12‐6 potential, that requires two scaling parameters: a well depth ε_ij and a collision diameter σ_ij, both of which depend on the interacting species i and j. We obtain estimates for ε_ij and σ_ij of interacting species by finding the values that provide the best fit to viscosity data for binary mixtures and compare these to calculated parameters using several “combining rules” that have been suggested for determining parameter values for binary collisions from parameter values that describe collisions of like molecules. Different combining rules give different values for σ_ij and ε_ij, and for some mixtures the differences between these values and the best‐fit parameter values are rather large. There is a curve in (ε_ij, σ_ij) space such that parameter values on the curve generate a calculated viscosity in good agreement with measurements for a pure gas or a binary mixture. The various combining rules produce couples of parameters ε_ij, σ_ij that lie close to the curve and, therefore, generate predicted mixture viscosities in satisfactory agreement with experiment. Although the combining rules were found to underpredict the viscosity in most of the cases, Kong's rule was found to work better than the others, but none of the combining rules consistently yields parameter values near the best‐fit values, suggesting that improved rules could be developed. © 2010 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 42: 713–723, 2010     

Modeling the vapor–liquid equilibria of polymer–solvent mixtures: Systems with complex hydrogen bonding behavior

The vapor–liquid equilibria of binary polymer–solvent systems was modeled using the Non-Random Hydrogen Bonding (NRHB) model. Mixtures of poly(ethylene glycol), poly(propylene glycol), poly(vinyl alcohol) and poly(vinyl acetate) with various solvents were investigated, while emphasis was put on hydrogen bonding systems, in which functional groups of the polymer chain can self-associate or cross-associate with the solvent molecules. Effort has been made to explicitly account for all hydrogen bonding interactions. The results reveal that the NRHB model offers a flexible approach to account for various self- or cross-associating interactions. In most cases model's predictions (using no binary interaction parameter k_ij = 0) and model's correlations (using one temperature independent binary interaction parameter, k_ij ≠ 0) are in satisfactory agreement with the experimental data, despite the complexity of the examined systems.     

Mechanism of the Formation of Palladium(II) Maleate Complex: A DFT Approach

In this work, a mechanism of the reaction between palladium(II) and maleic acid has been theoretically investigated in detail. Upon spectroscopic studies, a structure for this complex had been proposed in which the hydrogen maleate was coordinated to palladium through a C=C double bond and one carboxylic group. Experimentally, a three‐pathways mechanism had been proposed for this process, which consists of a slow ring closure (k_SRC) and two bimolecular processes (k₃, k₄). The k_SRC pathway is the direct and dominant route. The k₃ and k₄ pathways commence with the attack of a maleic acid to hydrogen maleate in the palladium complex. Using the quantum mechanical approach, different pathways were investigated. Considering the solvent effects, the activation energies of three pathways and other contingent pathways were calculated and compared with each other and experimental results.     

The role of polydispersity in the lamellar mesophase of model diblock copolymers

High-resolution small angle X-ray scattering (SAXS) measurements were performed on two series of poly(ethylene-alt-propylene)-b-poly(D ,L -lactide) (PEP-PLA) diblock copolymer materials exhibiting differences in the widths of the poly(D, L -lactide) block molecular mass distributions as measured by their polydispersity indices (PDI_PLA). At symmetric compositions of PEP-PLA (f_PLA ≈ 0.5), all SAXS data were successfully fit to an established model describing the small angle scattering from lamellar mesostructures. According to this model, the increase in the PDI_PLA negligibly affected the amount of lattice disorder. The apparent asymmetry of the poly(ethylene-alt-propylene)-block lamellae (ϕ), also determined by the fitting procedure, were more substantially affected; increasing the PDI_PLA resulted in a decrease in ϕ. At asymmetric compositions of PEP-PLA (f_PLA ≈ 0.67), only the data at the highest values of the PDI_PLA could be reasonably fit to this model. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3386–3393, 2007     

Anionic polymerization of oxirane in the presence of the polyiminophosphazene base t-Bu-P4

The use of the polyiminophosphazene base t-Bu-P₄ (1) for the anionic polymerization of ethylene oxide is described. Polymerization initiated by a monoalkoxide of the protonated base leads to well-defined poly(ethylene oxide)s with low polydispersity (M _w/M _n ≈ 1.1). Furthermore, graft copolymers of poly[ethylene-co-(vinyl alcohol)] (PEVA) with poly(ethylene oxide) and a star macromolecule were synthesized from multifunctional polyalkoxides in high yields.     

Kinetics of polyesterification: Adipic acid with ethylene glycol, 1,4-butanediol,and 1,6-hexanediol

Polyesterifications of adipic acid with ethylene glycol, 1,4-butanediol, and 1,6-hexanediol in the absence and presence of the foreign acid (p-toluene sulfonic acid) as catalyst were carried out under constant reaction temperatures of 140–180°C (rather than at constant oil-bath temperatures) and at ratios of diol to diacid of 0.9867–3.5880. The experimental data fit the rate equations proposed by Chen and Wu: d(RCOOR′)/dt = k_ae^αp(RCOOH)²(R′OH) – k_h(H₂O)(RCOOR′) and d(RCOOR′)/dt = k_ac(AH)e^αp(RCOOH)(RO′H) – k_h(H₂O)(RCOOR′) for self-catalyzed and acid-catalyzed reactions, respectively; the data did not fit the other equations appearing in the literature. Here p is the conversion of acid, and α is the constant related to dielectric constants. The reaction rate constants and activation energies for self-catalyzed and acid-catalyzed reactions are calculated. The activation energy is found to decrease with chain length of the alkyl group of the diol. This result is consistent with that observed by Brauman and Blair using ion cyclotron resonance spectroscopy for the variation of acidity of alcohols with chain length of the alkyl group.     

Atomic distributions in liquid copper-tin alloys

Abstract

Molten copper-tin alloys have been studied by X-ray diffraction, using a focusing theta-theta diffraetometer and Mo-Kα radiation (monochromator in the diffracted beam). Five alloys with 20, 35, 45, 55 and 78 atomic percent Sn, and pure Cu and Sn were measured at temperatures about 20 °C above the liquidus, and at 1100 °C. The total interference functions I(K), where K = 4π sin θ/δ, were obtained from the observed scattered intensities I_a(K) per atom and the theoretical atomic scattering factors. Splitting of the first peak in I(K) has been observed in the Cu-55 at% Sn alloy at the liquidus temperature.

The partial interference functions I_tj(K) at the liquidus temperature and at 1100°C were evaluated (assuming that they are independent of atomic concentration) using the five total I(K) of the alloys. The functions I_ij(K) are in reasonable agreement with those obtained by Enderby, North and Egelstaff from neutron diffraction data of a Cu-45 at % Sn alloy.

The reduced partial distribution functions G_ij(r) = 4πρ₀ r{g_ij(r) ? 1} and the probability functions g_ij(r) = ρ _ij(r)/c_j ρ₀, where ρ _ij(r) is the number of j-type atoms per unit volume at the distance r from an i-type atom, c_j is the atomic fraction of j-type atoms and ρ₀ is the average atomic density, have been evaluated by Fourier transformation of {I_ij(K) ? 1} K.

The electrical resistivities ρ _R of the alloys, calculated with the Faber-Ziman equation using the measured I_ij(K) and Animalu-Heine pseudo-potential elements U_i(K), are in good agreement with the experimental values of Roll and Motz. Assuming that U_i (2k _F) is independent of the values of the Fermi diameter 2k _F of the alloys, the concentration dependence of (3 - X)ρR, where X is the thermoelectric parameter measured by Enderby and Howe, is well reproduced when using the X-ray values of I_ij (2k _F).     

Isentropic Compressibility Changes of Mixing for 1,3-Dioxolane or 1,4-Dioxane + Water + Propanol Ternary Mixtures

Speed of sound data, u_ijk, of 1,3-dioxolane or 1,4-dioxane(i) + water(j) + propan-1-ol or propan-2-ol(k) ternary mixtures and their sub-binary mixtures, u_ij, of 1,3-dioxolane or 1,4-dioxane(i) + water or propan-1-ol or propan-2-ol(j) and water(i) + propan-1-ol or propan-2-ol(j) mixtures have been measured over the entire composition range at 308.15 K. Isentropic compressibility changes of mixing, (κ_s^E)_ij and (κ_s^E) _ijk, for the binary and ternary mixtures have been determined by employing the observed speeds of sound data and densities (calculated from their molar excess volumes data). The (κ_s^E) _ij and (κ_s^E) _ijk values have also been predicated by the graph theoretical approach and the Flory theory. It has been observed that (κ_s^E) _ij and (κ_s^E) _ijk predicted by the graph theoretical approach compare well with their corresponding experimental values.