Phase equilibrium and rheology of poly(1-trimethylsilyl-1-propyne) solutions

The phase equilibrium and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions obtained with tantalum catalysts are studied. For three polymers with different molecular masses, phase diagrams are determined in a number of solvents. From these diagrams, the Hansen solubility parameters of poly(1-trimethylsilyl-1-propyne) are calculated by the method proposed in this work. Dilute solutions of poly(1-trimethylsilyl-1-propyne) behave as Newtonian liquids, whereas the viscosity of viscoelastic concentrated systems decreases as the shear rate grows. The molecular and rheological characteristics of studied poly(1-trimethylsilyl-1-propyne) samples are compared with the samples prepared with NbCl₅ catalysts. Poly(1-trimethylsilyl-1-propyne) obtained with a catalytic system involving tantalum pentachloride is characterized by high intrinsic viscosity and solution viscosity compared to poly(1-trimethylsilyl-1-propyne) prepared with niobium catalyst. The difference in properties is due to the dissimilar ratios of cis and trans units in the samples.     

Chromatographic and adsorption properties of the mixed stationary phase poly(1-trimethylsilyl-1-propyne)/poly(1-phenyl-1-propyne)

Adsorption and chromatographic properties of the mixed stationary phase poly-(1-trimethylsilyl-1-propyne)/poly(1-phenyl-1-propyne) (PTMSP/PPP) composed as 97: 3 by weight have been investigated by methods of low-temperature nitrogen adsorption and gas chromatography on packed columns. The resultant phase has uniform mesoporous structure. The chromatographic properties of the mixed phase are significantly different from the properties of the original porous polymers PTMSP and PPP. The adsorbent obtained by modifying Chromosorb P NAW with a mixture of polymers provides the selective separation of chlorosubstituted, saturated, and aromatic hydrocarbons.     

Rheological properties of poly(1-trimethylsilyl-1-propyne) solutions

The phase state and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions in toluene and cyclohexane are studied. Samples of poly(1-trimethylsilyl-1-propyne) have the same backbone structure (cis-trans configuration ratio) but different molecular masses. Phase diagrams of these systems are derived via optical interferometry. It is found that they have an upper critical mixing temperature (UCMT) whose value exceeds the boiling points of the individual solvents. The two solvents exhibit limited solubility with respect to the studied polymer, and this parameter decreases with an increase in the molecular mass of the polymer. In the transition from dilute to concentrated solutions, the pattern of the rheological behavior changes from Newtonian to pseudoplastic. The concentration dependences of the zero-shear-rate viscosity of the solutions are typical for flexible-chain polymers. The viscous behavior of the poly(1-trimethylsilyl-1-propyne)-solvent system can be described through a single generalized viscosity-concentration relationship if dimensionless reduced values that take into account the contribution of the molecular mass, the nature of the solvent, and the pattern of intermolecular interactions in the solutions are used as the argument and the function.     

The effect of solvent nature upon the optical anisotropy of poly-(1-trimethylsilyl-1-propyne)

Optical properties of poly-(1-trimethylsilyl-1-propyne) in solvents with different refractive indices and optical anisotropies have been studied by the dynamic birefringence method. An optical shape-effect has been detected in solvents characterized by refractive indices n_s different from those of dry polymer n_k. It was revealed that this effect is an effect of the macromolecule segment shape; this allowed us to estimate thermodynamic rigidity of the molecular chains under study (A = 82 × 10⁻⁸ cm). It has been found that the optical shear coefficient of the studied polymers solutions in anisotropic solvents exceeds considerably the same parameter in an isotropic solvent. It has been shown that this difference is caused by the solvent anisotropic molecules orientation by the axis of maximal polarizability along the macromolecule backbone. The assumption that the solvent molecules orientation order with respect to chain molecules does not depend on the chain molecule thermodynamic rigidity allowed us to obtain independent estimate of the sizes of static segments of the macromolecules under study (98 × 10⁻⁸ cm).     

Synthesis and properties of homo- and copolymers of trifluoropropyldimethylsilyl-1-propyne with trimethylsilyl-1-propyne

Homopolymerization of 1-(3,3,3-trifluoropropyldimethylsilyl)-1-propyne is investigated in the presence of catalysts based on tantalum (V) chloride and niobium (V) pentachloride with various cocatalysts. As a result of homopolymerization, an insoluble polymer is formed. It is established that the insolubility of the homopolymer is connected with the presence in the polymer of “pseudocrystalline” regions playing the role of physical links. Copolymerization of 1(3,3,3-trifluoropropyldimethylsilyl)-1-propyne and trimethylsilyl-1-propyne under the action of the TaCl₅-Ph₃Bi system is studied. The relative activity constants of monomers, whose ratio points to the formation tendency of copolymers enriched with trimethylsilyl-1-propyne at the early stages of polymerization, are estimated. It is shown that the structures and solubilities of the obtained copolymers depend on their compositions. Gas-transport and hydrophobic-hydrophilic properties for soluble samples are studied. Soluble copolymers have good film-forming properties, improved hydrophobicity, stability against hydrocarbons, and high levels of gas permeability: properties that make them promising materials for the separation of various liquids and gaseous water-organic media.     

Chromatographic properties of poly(1-phenyl-1-propyne)

The chromatographic properties of poly(1-phenyl-1-propyne) (PPP) were studied by separating the C₁–C₁₀ hydrocarbons, alcohols, aromatic, and sulfur-bearing compounds. The influence of the phase percentage for polymer adsorbent (Polysorb-1) on the process of component retention was investigated. A comparison of PPP and the nonpolar liquid phase SE-52 widely used in gas chromatography was performed.     

Living Polymerization of 1-Trimethylsilyl-1-propyne and 4-Methyl-2-pentyne by NbCl5-Based Catalysts

Sequential homopolymerization of disubstituted acetylenes 1-trimethylsilyl-1-propyne and 4-methyl-2-pentyne by NbCl₅–Ph₃SiH was investigated and the main evidence of living polymerization, namely, continuation of chain propagation after addition of a new portion of monomer was observed. AB and BA type block copolymers of 1-trimethylsilyl-1-propyne and 4-methyl-2-pentyne were synthesized by sequential polymerization of these monomers in presence of NbCl₅–based catalytic systems.     

Copolymerization of 4-methyl-2-pentyne with 1-trimethylsilyl-1-propyne and 1-trimethylgermyl-1-propyne with Nb-containing catalysts

It has been shown that the copolymerization of 4-methyl-2-pentyne with 1-trimethylsilyl-1-propyne or 1-trimethylgermyl-1-propyne with the use of niobium pentachloride-based catalytic systems in the presence of Ph₃Bi, Et₃SiH, and Bu₄Sn as cocatalysts yields corresponding copolymers of various compositions. The technique of determining the composition of copolymers from their IR spectra has been developed. The reactivity ratios of the monomers have been estimated. It has been demonstrated that these values increase in a sequence 4-methyl-2-pentyne > 1-trimethylsilyl-1-propyne > 1-trimethylgermyl-1-propyne.     

Cyclo- and Cyclized Diene Polymers. XIX. Polymerization of Butadiene with the C2H5AlCl2 + TiCl4 Catalyst

Abstract

The polymerization of butadiene with an EtAlCl₂-TiCl₄ catalyst system yields cyclopolybutadiene with varying amounts of trans-1, 4 units, depending upon the Al/Ti ratio and the solvent. Apparently different active centers are produced at Ti > Al and Al > Ti ratios. When the catalyst system has Ti > Al, there is a rapid decrease in the initial polymerization rate and the cyclopoly butadiene contains large amounts of methyl groups, 10–12% of trans-1, 4 units, 2–3% of 1, 2 units, and, when the polymerization is carried out in aromatic solvents, aromatic moieties are incorporated in the structure. When the catalyst system has Al > Ti, there is a very slow decrease of the initial polymerization rate, and the cyclopoly butadiene contains up to 40% of trans-1, 4 units, less than 1% of 1, 2 units, and methyl groups and solvent moieties are essentially absent even when the polymerization is carried out in aromatic solvents. Cocatalytic amounts of iodine greatly increase the initial rate of polymerization. The Ti > Al catalyst may promote 1, 3-cation-radical propagation with transoid monomer to yield a perhydrophenanthrene structure while the Al > Ti catalyst may promote 1,2 cation-radical propagation with cisoid monomer to yield a perhydroanthracene structure.     

Polymerization of acenaphthylene by transition metal catalysts

The polymerization of acenaphthylene (ACN) was examined in the presence of the group V and VI transition metal salts such as WCl₆, MoCl₅, TaCl₅, and NbCl₅, as catalysts under various reaction conditions. These transition metal salts were found to be effective catalysts for the polymerization of ACN. The polymerization of ACN by WCl₆ in chlorobenzene proceeded at a high initial rate when the monomer to catalyst mole ratio was 200. In addition, it was observed that aromatic solvents generally were found to be superior to aliphatic solvents for both conversion and molecular weight. The structure of the resulting polymers was characterized by means of NMR, IR, UV, and x-ray diffraction. Emission properties were also investigated. Fluorescence emission spectra of the polymers obtained by WCl₆ as a catalyst varied strongly depending on the polymerization solvent. Thus, it appears that the polyacenaphthylene produced by WCl₆ was a different configuration dependent on the polymerization solvents used.     

Synthesis of hyperbranched poly(ether nitrile)s by one‐step polycondensation of an AB2 monomer

Hyperbranched poly(ether nitrile)s were prepared from a novel AB₂ type monomer, 2‐chloro‐4‐(3,5‐dihydroxyphenoxy)benzonitrile, via nucleophilic aromatic substitution. Soluble and low‐viscous hyperbranched polymers with molecular weights upto 233,600 (M_w) were isolated. According to the ¹H NMR and GPC data, the unique polymerization behavior was observed, which implies that the weight average molecular weight increased after the number average molecular weight reached plateau region. Model compounds were prepared to characterize the branching structure. Spectroscopic measurements of the model compounds and the resulting polymers, such as ¹H, DEPT ¹³C NMR, and MS, strongly suggest that the ether exchange reaction and cyclization are involved in the propagation reaction. The side reactions would affect the unique polymerization behavior. The resulting polymers showed a good solubility in organic solvents similar to other hyperbranched aromatic polymers. The hydroxy‐terminated polymer was even soluble in basic water. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5835–5844, 2009     

Assistance d'un groupe voisin pour des tosylates secondaires β substitues diequatoriaux dans l'hexafluoroisopropanol 97%

Solvolysis rates in methanol and 97% hexafluoroisopropanol (HFIP) for four β-methyl and β-phenyl bicyclic tosylates, show that solvent nucleophilic assistance is operating in the former solvent. However, in 97% HFIP, for three of the mentioned compounds, the mechanism involves π or σ neighboring group assistance. The factors influencing the occurrence of these processes are discussed. Owing to these possible neighbouring group assistances in non-nucleophilic solvents used to obtain k_c reference mechanisms, it is concluded that the k_a/k_c ratio which was proposed as a quantitative evaluation of solvent nucleophilic assistance must be used with caution.     

Correlations of the rate constants of phosphorylation reactions with the empirical parameters of the solvent polarity

Regression analysis of the solvent effects on the rate constants of nucleophilic substitution at the phosphoryl group was performed with the use of the empirical parameters of solvent polarity which characterize the ability of the solvents to electrophilic and nucleophilic solvation. The nucleophilic solvation of reagents by solvents, as a rule, favors the phosphorylation reactions. In the phosphorylation reactions of anionic nucleophiles, the electrophilic solvation of anions influences negatively the reactions rates. The phosphorylation of amines by chlorides of phosphorus acids is facilitated by the electrophilic solvation of a separated anion. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 271–274, February, 1998.     

Chemical modification of poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) using highly reactive metallating systems

Poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) are metallated using normal and secondary butyllithium chelate complexes with tetramethylethylenediamine and superbases based on complexes of normal and secondary butyllithium with potassium tert-pentoxide as metallating agents. Optimal conditions ensuring metallation of poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) with a high yield without degradation of macrochains are determined. Poly(vinyltrimethylsilane) and poly(1-trimethylsilyl-1-propyne) are functionalized via reactions of metallated polymers with CO₂, trimethylsilyl chlorosulfone, diethyl disulfide, and ethylene oxide. COOH, SO₃H, OH, and thioester groups are introduced into poly(vinyltrimethylsilane), and SO₃H and COOH groups are incorporated into poly(1-trimethylsilyl-1-propyne). Upon introduction of carboxyl groups into poly(vinyltrimethylsilane), its hydrophilicity and permselectivity with respect to H₂O/N₂, H₂O/H₂, and H₂O/CH₄ pairs increase. The introduction of SO₃H groups into poly(1-trimethylsilyl-1-propyne) and poly(vinyltrimethylsilane) leads to the appearance of proton conductivity of these polymers.     

Synthesis of Poly(arylene ether amine)s from a Monomer Containing an Electron‐Donating Amine Group in a Nucleophilic Aromatic Substitution Reaction

Summary: Poly(arylene ether amine)s were synthesized by a nucleophilic aromatic substitution polycondensation of bis[4‐fluoro‐3‐(trifluoromethyl)phenyl]amine with several bisphenols. Even though the monomer has an electron‐donating diphenylamine moiety, which normally deactivates a nucleophilic aromatic substitution (S_NAr) reaction, the polymerization proceeded by a S_NAr reaction to give high‐molecular‐weight polymers. The polymers show good solubility in common organic solvents and have T_gs in the range of 123 °C to 177 °C.

High‐molecular‐weight poly(arylene ether amine)s synthesized by a S_NAr reaction with the monomer containing an electron‐donating diphenylamine moiety.     

Living polymerization of 4-methyl-2-pentyne and 1-trimethylsilyl-1-propyne initiated by NbCl5-Ph4Sn catalyst

The polymerization of 4-methyl-2-pentyne and 1-trimethylsilyl-1-propyne initiated by catalytic systems based on niobium pentachloride and Et₃SiH, Bu₄Sn, Ph₄Sn, and Ph₃SiH as cocatalysts has been investigated. Direct evidence for the living polymerization of 4-methyl-2-pentyne and 1-trimethylsilyl-1-propyne with the NbCl₅-Ph₄Sn catalytic system is derived. These are the linear molecular mass dependence on conversion and the continuation of chain propagation after introduction of a new monomer portion.     

Macrochain configuration, stucture of free volume and transport properties of poly(1-trimethylsilyl-1-propyne) and poly(1-trimethylgermyl-1-propyne)

The relationship between poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(1-trimethylgermyl-1-propyne) (PTMGP) microstructure, gas permeability and structure of free volume is reported. n-Butane/methane mixed-gas permeation properties of PTMSP and PTMGP membranes with different cis-/trans-composition have been investigated. The n-butane/methane selectivities for mixed gas are by an order higher than the selectivities calculated from pure gas measurements (the mixed-gas n-butane/methane selectivities are 20?C40 for PTMSP and 22?C35 for PTMGP). Gas permeability and n-butane/methane selectivity essentially differ in polymers with different cis-/trans-composition. Positron annihilation lifetime spectroscopy investigation of PTMSP and PTMGP with different microstructure has determined distinctions in total amount and structure of free volume, i.e. distribution of free volume elements. The correlation between total amount of free volume and gas transport parameters is established: PTMSP and PTMGP with bigger free volume exhibit higher n-butane permeability and mixed-gas n-butane/methane selectivity. Such behavior is discussed in relation to the submolecular structure of polymers with different microstructure and sorption of n-butane in polymers with different free volume.     

N‐Heterocyclic Carbene Catalyzed Concerted Nucleophilic Aromatic Substitution of Aryl Fluorides Bearing α,β‐Unsaturated Amides

Concerted nucleophilic aromatic substitution (CS_NAr) has emerged as a powerful mechanistic manifold, in which nucleophilic aromatic substitution can proceed in one step without the need to form a Meisenheimer intermediate. However, all of the CS_NAr reactions reported thus far require a stoichiometric strong base or activating reagent, and no catalytic variants have yet been reported. Herein, we report an N‐heterocyclic carbene (NHC)‐catalyzed intramolecular cyclization of acrylamides that contain a 2‐fluorophenyl group on the nitrogen through a CS_NAr reaction. By using this catalytic method, it is possible to synthesize an array of quinolin‐2‐one derivatives, which are common structural motifs in pharmaceuticals and organic materials. DFT calculations unambiguously revealed that this reaction proceeds through the concerted nucleophilic aromatic substitution of aryl fluorides, in which a stereoelectronic σ (C_ipso‐C_β)→ σ*(C_ipso‐F) interaction critically contributes to the stabilization of the transition state for the cyclization.     

Studies of polymers from cyclic dienes. V. Cationic polymerization of cyclopentadiene,influence of polymerization conditions on the polymer structure

Cationic polymerization of cyclopentadiene was studied with several Friedel-Crafts catalysts, and the influence of polymerization conditions on the polymer structure was investigated. Polycyclopentadiene contained higher amounts of the 1,2 structure when a stronger catalyst and a more polar solvent were used. This fact is discussed in terms of the tightness of the growing ion pair. The polymer structure did not vary with polymerization temperature in toluene solvent. In methylene chloride at around 0°C. the structural variation with catalysts was much smaller, suggesting a freer nature of the growing ion pair. The viscosity data also support the change in the structure of the ion pair under similar conditions. The use of aliphatic hydrocarbon solvents gave the highest contents of the 1,2 structure. This results was ascribed to the lack of solvation, considering the dependence of the polymer structure on the monomer concentration, which was found only in this solvent. Furthermore, isomerization during propagation was observed in polar solvents at higher temperature.     

Solvent Control over Supramolecular Gel Formation and Fluorescence for a Highly Crystalline π‐Conjugated Polymer

In π‐conjugated polymers (πCPs), crystallinity and fluorescence typically exhibit a trade‐off relationship. Here, we have synthesized a highly crystalline and fluorescent π‐conjugated polymer with a simple alternating structure of 1,2,4,5‐tetrafluorophenylene and 3,3′‐dihexyl‐2,2′‐bithiophene units. In film, the polymer exhibited efficient red‐colored fluorescence, an improved quantum yield (Φ_sol=13 %→Φ_film=23 %) and a crystalline structure. Interestingly, supramolecular gel formation occurred in appropriate solvents, and the macrostructure and fluorescence properties of the gel could be directly controlled by the choice of the solvent. The polymer self‐assembled into a spherical form that exhibited red fluorescence in non‐aromatic solvent (1,2‐dichloroethane) and into a fibrous form that exhibited yellow fluorescence in aromatic solvent (mesitylene).