Quasiliving Carbocationic Polymerization. XII. Forced Ideal Copolymerization of lsobutylene with Styrene

Forced ideal carbocationic copolymerization of isobutylene/styrene systems has been achieved by continuous addition of mixed monomer feeds to 2-chloro-2,4,4-trimethylpentane/TiCl₄ in n-hexane/methylene chloride charge by keeping the input rate equal to the overall rate of copolymerization. The composition of the copolymers was identical to that of the feeds over the entire monomer concentration range. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at higher isobutylene concentrations in the feed. The molecular weight increase was less pronounced at higher styrene concentration because more methylene chloride had to be used in the solvent system to keep the copolymer in solution. The micro-structure of the copolymers is uniform as determined by gel permeation chromatography (UV plus RI) and ¹³C-NMR spectroscopy According to these studies, true copolymers have formed. The probability of triads in the copolymer has been determined.     

Grafting Vinyl Monomers onto Wool Fibers. VII. Graft Copolymerization of Methyl Methacrylate onto Wool Using Peroxydiphosphate-Thiourea Redox System

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using the potassium peroxy-diphosphate-thiourea redox system as the initiator. The rate of grafting was determined by varying the monomer, peroxydi-phosphate ion, temperature, and solvent. The graft yield increases with increasing peroxydiphosphate ion up to 80 × 10^?-⁴ mol/L, and with further increase of peroxydiphosphate ion the graft yield decreases. The graft yield increases with increasing monomer concentration. The percentage of grafting decreases with increasing thiourea concentration. The rate of grafting increases with an increase of temperature. The effect of acid and water-soluble solvent and certain salts on graft yield has been investigated and a suitable rate expression has been derived.     

Aminobutadienes. VI. Polymerization and Copolymerization of 2-Phthalimido-1,3-butadiene

2-Phthalimido-1,3-butadiene (2-PB) was polymerized either radically or thermally in bulk and in solution. While the polymer obtained by solution polymerization was soluble in some solvents such as halogenated hydrocarbons, dioxane, and dimethylformamide and had a softening point in the range of 160–170°C., that obtained by polymerization in bulk was insoluble in any solvent and only swollen on being immersed in such solvents as above. The reduced viscosity of the soluble polymer obtained by solution polymerization was approximately 1.0, and this value remained almost unchanged with varying polymerization time. Likewise the cationic polymerization in acetylene tetrachloride or in chloroform at 20°C. with the use of cationic catalysts such as boron trifluoride and stannic chloride was attempted, but no formation of polymer was observed. This monomer preferentially reacted with acrylonitrile, methyl methacrylate, styrene, and N-vinylphthalimide to form the respective copolymers; it reacted somewhat less readily with vinyl acetate. The monomer reactivity ratios in the copolymerization with styrene were calculated by the Fineman and Ross method and found to be r₁ (2-PB) = 5.2 and r₂ (styrene) = 0.11, respectively, from which the Q, e parameters were successively evaluated to be Q = 5.0 and e = ?0.05. The fact that e value is close to zero, easily explains why this monomer can copolymerize well both with acrylonitrile, which has a highly positive value of e (1.2) and with styrene, for which e is considerably negative (-0.8).     

Quasiliving Carbocationic Polymerization. IX. Forced Ideal Copolymerization of Styrene Derivatives

Forced ideal carbocationic copolymerization of α-methylstyrene (αMeSt) with p-tert-butylstyrene (ptBuSt) and (αMeSt) with styrene (St) has been achieved by continuous monomer feed addition to a cumyl chloride/BCl₃ charge at -50°C by keeping the feeding rate of the monomer mixtures equal to the overall rate of copolymerization, The composition of the copolymers was identical to the composition of the monomer feeds over the entire concentration range. A quantitative expression has been derived to show that under forced ideal copolymerization conditions the composition of the copolymer can be controlled by the composition of the feed. Further, conditions have been found for forced ideal quasiliving copolymerizations, i.e., the number-average molecular weight of the copolymers increased almost linearly with the cumulative weight of consumed monomers by the use of suitably slow, continuous feed addition in the presence of relatively nonpolar solvent mixtures (60/40 v/v n-hexane + methylene chloride). In polar solvent (methylene chloride) the molecular weight increase was less pronounced due to chain transfer to monomer involving indane-skeleton formation; however, with charges containing large amounts of ptBuSt the molecular weight increase was surprisingly strong. Interestingly, ptBuSt does not homopolymerize in 60/40 v/v n-hexane/methylene chloride but it readily copolymerizes with αMeSt. This observation was explained by examining the relative rates of terminations of the cationic species involved. Conditions have been found for the pronounced quasiliving polymerization of St. In forced ideal quasiliving copolymerizations neither the molecular weights of αMeSt/ptBuSt or αMeSt/St copolymers nor the initiating efficiencies of the initiating systems used show a depression. The microstructure of representative αMeSt/ptBuSt copolymers obtained under forced ideal quasiliving conditions has been analyzed by ¹³C-NMR spectroscopy. According to these studies, true copolymers have formed and resonance peaks for various triads have been deduced.     

Quasiliving Carbocationic Polymerization. XV. Forced Ideal Copolymerization of Isobutylene-lsoprene

Forced ideal carbocationic copolymerization of isobutylene and isoprene has been achieved by continuous addition of monomer mixtures of different compositions to cumyl chloride/TiCl₄ charges at -50°C. The overall rate of copolymerization could be kept equal to that of addition rate with up to 10 mol% isoprene in the mixed monomer feed. In this monomer concentration range the composition of the copolymer was identical to that of the feeds. At higher diene concentrations in the feed, chain transfer to monomer and other side reactions (intramolecular cyclization, gel formation) could not be completely avoided. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at 10 mol% isoprene concentrations in the feed (i.e., in the quasiliving range). According to ¹H-NMR and ¹³C-NMR spectroscopy, the products are random copolymers.     

Copolymerization behavior of vinylimidazolium salts

Copolymerization studies of cationic monomers have been reported in the literature to yield wide variations in reactivity ratios and Q–e values, depending on the comonomer and the nature of the solvent. In this work are presented the copolymerization characteristics of a variety of vinylimidazolium salts in both water and ethanol solution. From these studies, the effect of solvent polarity, of substitution at the imidazolium 2-position, of the type of counterion, and of the hydrophilic–hydrophobic character of the monomeric salts could be ascertained. The results of the study are consistent with other related investigations, in that solvent polarity and comonomer both strongly affected copolymerization.     

Light-scattering studies on solutions of cellulose in the ammonia/ammonium thiocyanate solvent system. I. Classical light-scattering

This article reports the use of classical light scattering to study cellulose in the NH3/NH4SCN solvent system. Three solvent compositions were used, 27.01 73.0,25.5/ 74.5, and 24.51 75.5 weight ammonia/weight ammonium thiocyanate. The coefficient, (dn/dc)_υ, was determined by back calculating using the molecular weight determined by solution viscometry in the solvent system cupriethylenediamine and the classical light-scattering results. Second virial coefficients were found to be similar to those values measured for cellulose in the FeTNa and LiCl/DMAC solvent systems. The characteristic ratios were found to vary with solvent composition with the highest values being at a composition of 25.5/74.5 weight ammonia/ weight ammonium thiocyanate. Persistence lengths were also found to vary with solvent composition with the highest value being 264 × 10^?8 cm at solvent composition 25.5/74.5.     

Metal-Ylide Complex-Initiated Radical Copolymerization of Methylmethacrylate and Styrene

Abstract

Phenacyl dimethylsulfonium ylide complex of mercuric chloride (PDSY-HgCl₂)-initiated radical copolymerization of styrene with methylmethacrylate (MMA) at 85 ± 0.1°C using dioxane as an inert solvent yields random copolymers as evidenced by NMR spectroscopy. The kinetic equation for the present system was R_p α [PDSY-HgCl₂]^0.5 [Sty]^1.0 [MMA]^1.0. The values of energy of activation (ΔE) and k² _p/k₁ were 48.0 kJ mol^?1 and 8.6 × 10^?4 L mol^?1 s^?1, respectively. The mechanism of the reaction has also been proposed for the present system. The properties of copolymer were studied in the form of film. The film was highly absorptive for nitric acid but less absorptive for acetic acid. The film was water impermeable.     

Preconcentration and matrix isolation of heavy metals through a two-stage solvent extraction in a flow system

Metal ions (Cd, Cu, Pb, Co and Ni) in trace amounts were isolated from sample matrices and concentrated by extraction in a flow system. The sample flow was first mixed with buffer and reagent (carbamates) and the combined aqueous flow was next segmented with trichlorotrifluoroethane (Freon 113). The metal complexes were extracted into the organic phase in a 2-m long coil which was followed by a separator with a teflon membrane. The organic phase passed on to a second segmentor where an acidic, aqueous mercury(II) solution was added. Back-extraction to the aqueous solution took place in a 1-m long coil. The Freon was removed in a second membrane separator and the aqueous phase was collected and analyzed by graphite-furnace atomic absorption spectrometer. The enrichment factors were of the order of 15–20 and the recoveries were 90–100% from the sub-μg l^?1 level up to 20–50 μg l^?1. The recoveries decrease at concentrations above 50 μg l^?1, presumably because of slow dissolution of precipitated complexes in the sample solutions. The observed recoveries for copper were generally somewhat lower, being in the range 80–90%.     

Cationic Copolymerization of Propylene Oxide with Tetrahydrofuran. XI. Calculation of Individual Rate Constants

Rate constants (k₁ k₁₁, k₁₂, k₂₂, k₂₁ and k_t) for various steps involved in the copolymerization of propylene oxide (PO) with tetrahydrofuran (THF) have been calculated from reaction rate data obtained with the following catalyst system: (a) triphenyl-methyl cations ((C₆H₅)₃C⁺) associated with hexafluorophosphate (PF₆ ^?), hexafluoroarsenate (AsF₆ ^?) and hexafluoroantimonate (SbF₆ ^?) gegenions; (b) antimony pentachloride (SbCl₅); and, (c) boron trifluoride etherate, BF₃:(C₂H₅)₂O. The latter two systems were studied in the presence of cocatalysts. The effects of several parameters (the cocatalyst concentration and bulk size, the nature of the solvent, and the reaction temperature) on the rate constants are highlighted. The role of entropy in the initiation, propagation and termination steps is discussed in terms of solvation and desolvation processes. Based on termination activation energy considerations, the order of stability for the gegenions used in the copolymerization of PO with THF was found to be: AsF₆ ^? > SbF₆ ^? > HOBF₃ ^?PF₆ ^? > SbCl₆ ^?     

Copolymerization of N-carboxy Nϵ-carbobenzoxy L-lysine anhydride with N-carboxy β-benzyl L-aspartate anhydride in acetonitrile

Copolymerization of N-carboxy N^?-carbobenzoxy L -lysine anydride with N-carboxy β-benzyl L -aspartate anhydride was initiated with n-butylamine in acetonitrile. The copolymerization proceeded almost homogeneously except for the initial stage, when the proportion of N-carboxy anhydride (NCA) in the polymerization mixture varied from 25 to 75 mol %. This was due to the fact that the copolypeptides formed were soluble or highly swollen in the solvent, in contrast to the homopolymerization of NCAs such as N^?-carbobenzoxy L -lysine NCA and β-benzyl L -aspartate NCA in acetonitrile, which proceeds heterogeneously. The compositions of the copolymers obtained were, within experimental error, the same as their monomer feed compositions. The initial rates of copolymerization were almost the same as the rate of homopolymerization of β-benzyl L -aspartate NCA, which propagates with a nonhelical polypeptide, but were slower than the rate of homopolymerization of N^?-carbobenzoxy L -lysine NCA, which propagates with a helical polypeptide.     

Light-scattering studies on solutions of cellulose in the ammonia / ammonium thiocyanate solvent system. II. Quasielastic light-scattering and liquid crystal study

This is the second part of a two–part study of the NH₃NH₄SCN cellulose solvent system. Quasielastic light scattering was used to determine the diffusion coefficients of cellulose in solution and the effective hydrodynamic radius of the dissolved molecules. Additionally, the system was studied using light microscopy to determine the minimum critical volume fraction or liquid crystal formation. Very little change was found in the diffusion coefficients with change in cellulose concentration indicating little interaction between the chains in solution. Values of 7.69 and 2.66 × 10⁸ cm²/s were measured for samples having a degree of polymerization of 153 and 969. The value of the coefficient relating the hydrodynamic volume to the radius of gyration was found to be in the range of 0.33 to 0.53, indicating an extended coil conformation according to the Kirkwood-Riseman theory. The minimum critical volume fractions necessary for liquid crystal formation, υ₂′ were 0.039, 0.038, and 0.048 for the three solvent compositions studied. The values calculated for υ₂′ based on the measured persistence lengths were much larger than the predicted values, indicating strong deviation from theory or possible aggregation in the system.     

Copolymerization of carbon dioxide and N-phenylethylenimine

Copolymerizations of carbon dioxide and N-phenylethylenimine were carried out with the use of various catalysts and solvents. The infrared spectrum of the polymer produced showed the characteristic absorption peak at 1730–1735 cm^?1 based on the urethane linkage. The content of the urethane linkage decreased in the following order: Mn(acac)₂ ≈ MnCl₂4H₂O > Al(OBu)₃ > Ti(OBu)₄ > ZnCl₂ ? BF₃OEt₂ = VCl₃ = Mn(acac)₃ = FeCl₃ = CrCl₃ · 6H₂O = 0. The manganase (bivalent) catalyst in combination with n-hexane solvent was found to be the best system for the copolymerization, and this system received detailed study. Generally speaking, both the polymer yield and the content of the urethane linkage increased with increasing content of carbon dioxide in the feed as well as with increasing polymerization temperature. From the fractionation of polymer in methanol, it was found that the produced polymer is composed of both homopolymer of N-phenylethylenimine and copolymer of N-phenylethylenimine and carbon dioxide. The content of the urethane linkage of the copolymer thus fractionated was as high as about 80%.     

Dissolving of cellulose in PEG/NaOH aqueous solution

Here, a new solvent system for cellulose is reported. The solvent is a mixed aqueous solution of 1.0 wt.% poly(ethylene glycol) (PEG) and 9.0 wt.% of NaOH. Cellulose powder was added into the mixture at room temperature at first, and freezing it at −15 °C for 12 h following a thaw of the mixture at room temperature under strong stirring. There formed a clean solution of cellulose, and the optical microscopy was used to record the dissolving process. ¹³C-NMR, FT-IR, XRD, and intrinsic viscosity measurements revealed that there forms a homogeneous solution of cellulose in the new solvent system. The maximum solubility of cellulose with average molecular weight of 1.32 × 10⁵ g mol⁻¹ in the solvent system is 13 wt.%. The cellulose solution in the new solvent system is stable, even for 30 days storage at room temperature.     

An NMR study of the conformational equilibrium of 5-fluoro-1,3-dioxan in solution. Dependence on solvent

The ¹H and ¹⁹F NMR parameters of 5-fluoro-1,3-dioxan ( 1 ) dissolved in a number of solvent systems are interpreted on the basis of fast inversion between two chair conformations. In cyclohexane solution the two chair conformations are almost equally populated, whereas in more polar solvents, such as chloroform, the conformation having the fluorine substituent in an axial position is strongly preferred. Addition of acetic acid to a solution of 1 in cyclohexane increases the preference of the fluorine substituent for the axial orientation. Possible reasons for these observations are discussed.     

Copolymerization of n‐butylacrylate with methylmethacrylate by a novel photoinitiator, 1‐(bromoacetyl)pyrene

The photopolymerization efficiency of pyrene (Py), 1‐acetylpyrene (AP), and 1‐(bromoacetyl)pyrene (BP) for copolymerization of n‐butylacrylate (BA) with methylmethacrylate (MMA) was compared. A kinetic study of solution copolymerization in DMSO at 30 ± 0.2°C showed that the Py could not initiate copolymerization even after 20 h, whereas with AP as initiator, less than 1% conversion was observed. However, introduction of a Br in α‐methyl group of AP significantly enhanced the percent conversion. The kinetics and mechanism of copolymerization of BA with MMA using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (R_p α [BP]^0.67[BA]¹[MMA]^0.98), and degradative solvent transfer reasonably explains these kinetic nonidealities. The monomer reactivity ratios (MRRs) of MMA and BA have been estimated by the Finemann–Ross and Kelen–Tudos methods, by analyzing copolymer compositions determined by ¹H‐NMR spectra. The values of r₁ (MMA) and r₂ (BA) were found to be 2.17 and 0.44, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 261–267, 2007     

Effect of solvent for vinyl acetate polymerization on microstructure of poly(vinyl alcohol)

The solution polymerization of vinyl acetate was carried out in several solvents at 0 to 100°C, using 2,2′-azobisisobutyronitrile as initiator. For the resulting poly(vinyl alcohol) (PVA), iodinecoloration, 1,2-glycol structure and tacticity were observed. The pentad tacticity of PVA was estimated from its methine carbon spectra by means of ¹³C-FTNMR spectrometer. Iodine-coloration ability of PVA varied markedly with the type of polymerization solvent and decreased in the following order: phenol > aq. phenol > methyl alcohol > ethyl acetate > DMSO, ethylene carbonate. The syndiotactic fraction in PVA also decreased with polymerization solvent in the same order as that of iodine coloration, while 1,2-glycol content of PVA was not almost affected by polymerization solvent except for phenol and aq. phenol. In solution polymerization performed, effect of polymerization temperature on tacticity was less than that of solvent.     

Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives. III. Solvent and Catalyst Effects on Relative Reactivity

Abstract

The change in relative reactivity in the cationic copolymerization of 2-chloroethyl vinyl ether and styrene derivatives was investigated with various catalysts and solvents. p-Methoxystyrene, p-methylstyrene, and a-methyl-styrene were used as styrene derivatives. The styrene content in the co-polymer increased when a polar solvent and/or a strong catalyst was used. The change of relative reactivity in the copolymerization of 2-chloroethyl vinyl ether with styrene derivatives was much greater than that in the copolymerization between vinyl ethers or styrene derivatives. When nitro-ethane was used as a solvent, not only the polarity but also the nucleophilicity influenced the copolymer composition. The results were discussed by two energies, E^π and E_rs, which are measures of complex formation between monomer and carbonium ion, and stabilization energy in the transition state, respectively.     

Dilute solution properties of a polyurethane. I. Linear polymers

A linear polyurethane of high molecular weight was prepared in solution by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). The polymer was fractionated by using a direct sequential extraction procedure, with a solvent–nonsolvent system consisting of N,N′-dimethylformamide (DMF) and acetone (A). The resulting fractions were characterized by viscosity and lightscattering measurements. The relationship between the intrinsic viscosity and molecular weight was found in DMF at 25°C. to be [η] = 3.64 × 10^?4M^0.71. The unperturbed polymer chain dimensions were determined from intrinsic viscosity measurements carried out under experimentally determined theta conditions.     

Copolymerization of 1,3-butadiene and styrene with a neodymium catalyst

Homo- and copolymerization of butadiene and styrene in the presence of the catalyst system Nd(octanoate)₃/CCl₄/Al(iBu)₃ (iBu: isobutyl) were investigated at 60°C in heptane as solvent. The initiating catalyst system is very effective in the polymerization of butadiene. However, the presented copolymerization of butadiene and styrene is only practicable when using a special addition order of the catalyst components and a prescribed ageing phase. Copolymers obtained from various monomer feed ratios were characterized by ¹H and ¹³C NMR spectroscopy and gel-permeation chromatography (GPC). The copolymer characteristics especially microstructure, molar mass and molar-mass distribution (MMD) are strongly dependent on the composition of the monomer mixture.