An Approximate Kinetic Treatment of Slow‐Initiated Living Polymerization. I. First‐Order Initiation and Propagation

A new method for deriving the initiation rate constant for a slowinitiated living polymerization process in which all reactions are first order with respect to all participants is presented. The method is based upon an approximate analytical solution of the set of differential equations modeling this class of processes. The solution is found by asymptotic expansion of the unknown functions, using a dimensionless parameter which characterizes the process.     

Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Kinetic Study of the Al-Schiff's Base Initiated Polymerization of ε-caprolactone and Synthesis of Graft Poly(methylmethacrylate-g-caprolactone)

Graft copolymers of polycaprolactone (PCL) on polymethacrylate (PMMA) backbone have been successfully synthesized and characterized by SEC, ¹H and ¹³C NMR spectroscopy. The strategy used consisted of polymerizing ε-CL, followed by end-functionalization of the resulting PCL using methacryloyl chloride. Free radical polymerization of the methacryl double bond lead to the C-C polymer backbone and an overall graft copolymer. The polymerization of ε-caprolactone was achieved using Al-Schiff's base isopropoxide (HAPENAlOⁱPr) in DCM at ambient temperature. SEC and MALDI analysis of the polymers confirmed that mostly linear chains were obtained with the Al initiator, up until high monomer conversion. The low molar mass PCL was then end-capped with a methacryloyl group, in a quantitative manner, as evidenced by ¹H NMR. The macromonomer thus obtained was copolymerized in small proportions with methyl methacrylate by conventional free radical polymerization and atom transfer radical polymerization (ATRP). Analysis of the products by NMR and SEC showed the presence of true graft copolymers and the absence of homopolymers.     

Atom Transfer Radical Polymerization of MMA Initiated by 2‐(4‐chloromethyl‐phenyl)‐benzoxazole and Fluorescent Property of PMMA

Atom transfer radical polymerization (ATRP) of MMA was conducted using 2‐(4‐chloromethyl‐phenyl)‐benzoxazole as initiator, CuCl as catalyst, and PMDETA as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (Mn/Mw range from 1.30 to 1.45). The structure of PMMA was analyzed by ¹H‐NMR and proved the polymerization could be controlled to some degree. The optical property of the initiator was well preserved in the resulting PMMA, and the end‐functionalized PMMA exhibited fluorescent emission at 360 nm whether in DMF solution or in film state.     

Kinetic Study of Radical Polymerization v. Determination of Reactivity Ratio in Copolymerization of Acrylonitrile and Itaconic Acid by 1H‐NMR

Many reports exist in the literature about the application of ¹H and ¹³C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line ¹H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well.     

Oligomerization and Polymerization of Ethylene Initiated by a Novel Ni（II）-Based Acetyliminopyridine Complexes as Single-Site Catalysts

Novel Ni(II)-based acetyliminopyridine complexes 1b, 2b, 3b (1-3b), which are synthesized from ligands 1a, 2a, 3a (1-3a) and [NiCl2(DME)], are suitable precursors for the catalysts that are neces- sary for ethylene oligomerization and polymerization reactions, activated by methylaluminoxane (MAO). The MAO-treated 1-3b presents an active catalytic center, which may oligomerize and polymerize ethylene to produce linear α-olefins and polyethylene, respectively. The molecular weight distributions of oligomers that are obtained are in good agreement with the Schulz-Flory rules for oligomers>C4. The activity of 3b-MAO complex is 6.3E7 g/(molNi·h) at 50 ℃. The activities and molecular weight distributions of oligomers show significant reliance on the structures of catalyst precursors.     

Kinetic Study of Radical Polymerization VIII. A Comprehensive Study of Solution Copolymerization of Vinyl Acetate and Methyl Acrylate by 1H‐NMR Spectroscopy

Radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) was performed in a solution of benzene‐d₆ using benzoyl peroxide (BPO) as the initiator at 60°C. Kinetic studies of this copolymerization reaction were investigated by on‐line ¹H‐NMR spectroscopy. Individual monomer conversions vs. reaction time, which was followed by this technique, were used to calculate the overall monomer conversion, as well as the monomer mixture and the copolymer compositions as a function of time. Monomer reactivity ratios were calculated by various linear and nonlinear terminal models and also by simplified penultimate model with r _2(VA)=0 at low and medium/high conversions. Overall rate coefficient of copolymerization was calculated from the overall monomer conversion vs. time data and k _p  . k _t ^?0.5 was then estimated. It was observed that k _p  . k _t ^?0.5 increases with increasing the mole fraction of MA in the initial feed, indicating the increase in the polymerization rate with increasing MA concentration in the initial monomer mixture. The effect of mole fraction of MA in the initial monomer mixture on the drifts in the monomer mixture and copolymer compositions with reaction progress was also evaluated experimentally and theoretically.     

Note a Kinetic Study of the Photopolymerization of N,N Methylenebisacrylamide Initiated by N‐Bromo‐Succinimide in the Presence and Absence of Isopropyl Alcohol

The photopolymerization of N,N′‐methylenebisacrylamide has been studied with N‐bromosuccinimide as photoinitiator in the presence and absence of isopropyl alcohol (ISP). The rate of polymerization in the presence of ISP was found to be very high, and this is explained on the basis of the relative reactivities of the initiating radicals. A probable mechanism consistent with the observed results is proposed and discussed.     

Living Cationic Polymerization of α-Methylstyrene. 2. Synthesis of Block and Random Copolymers with 2-Chloroethyl Vinyl Ether and End-Functionauzed Polymers†

Abstract

Both AB and BA block copolymers of α-methylstyrene (αMeSt) and 2-chloroethyl vinyl ether (CEVE) were synthesized by the sequential living cationic polymerization initiated with the HCl-CEVE adduct (1a)/SnBr₄ system in CH₂Cl₂ at -78°C. αMeSt-CEVE (AB) block copolymers with narrow molecular weight distributions ([Mbar]_w/[Mbar]_n ～ 1.15) were obtained when αMeSt was polymerized first, followed by addition of CEVE to the resulting αMeSt living polymer solution. The reverse order of monomer addition, from CEVE to αMeSt, also led to a BA-type block copolymer. In the polymerization of a mixture of the two monomers, almost random copolymers were obtained. Living polymerizations of αMeSt were also induced with functional initiating systems, HCl-functionalized vinyl ether adducts (1b-1d)/SnBr₄, to give end-function-alized poly(αMeSt)s with a methacrylate, an acetate, or a phthalimide terminal.     

Catalytic Effect of Dimethylsulfoxide Complexes of Rh(III) and Ru(II) on the Polymerization of Vinyl Monomers Initiated by 2,2′-Azobisisobutyronitrile

Transition metal salts and complexes catalyze the polymerization of vinyl monomers in the presence or absence of 2,2′-azobisisobutyronitrile (AIBN). In this article the effect of some dimethyl sulfoxide complexes of Rh(III) and Ru(II) on the polymerization of vinyl monomers such as methyl methacrylate (MMA) and methyl acrylate (MA) initiated by AIBN is reported. The percentage conversion and the rate of polymerization of MMA and MA are found to increase rapidly with time. At the critical concentrations of the complexes, the percentage conversion and the rates of reaction are found to be higher than those with AIBN alone, which significantly proves their accelerating effect. At concentrations above and below that of the critical value, the percentage conversion and the rates of polymerization of MMA and MA are found to decrease from those with AIBN alone. The trend of the increase and decrease of the percentage conversion and the rate of reaction with both types of complexes are similar. The solvent used in the polymerization of MMA and MA is dimethylsulfoxide (DMSO) and the temperature of the reaction is 60°C. A precise mechanism for the catalytic reaction is suggested.     

Functional Monomers and Polymers. 165. Dehydrochlorination of Head‐to‐Tail 1,4‐rans‐Poly‐(‐1‐Chlorobutadiene) Prepared by Inclusion Polymerization in Deoxycholic Acid Canals

Thermal and chemical dehydrochlorination of head‐to‐tail 1,4‐trans‐poly(‐1‐chlorobutadiene) prepared by inclusion polymerization in deoxycholic acid canals resulted in formation of a trans‐polyacetylene‐type polymer. The dehydrochiorinated polymer was characterized by UV/VIS, IR, Raman, and ESR spectroscopy. The number of conjugated double bonds in the polymer was about 10–20. Doping with iodine was also studied.     

Carbohydrate Derivative from Baylis–Hillman Adduct. An Easy and Short Synthesis of 2‐Deoxy‐2‐C‐methylene‐D‐erythro‐pentono‐1,4‐lactone

Abstract

A simple and straightforward approach for the synthesis of an α‐methylene‐δ‐butyrolactone from a Baylis–Hillman adduct obtained from a chiral α‐hydroxy aldehyde, is described.     

Removal of Lead (II) Ions by Poly(2‐octadecyl butanedioic acid): Isothermal and Kinetic Studies

Poly(2‐octadecyl‐butanedioic acid), prepared from polyanhydride PA‐18, possesses novel heavy metal adsorption characteristics. The adsorption capacity of this water insoluble polymer for lead (II) was substantially higher than other heterogeneous adsorbants and is equivalent to those obtained with homogeneous sorbants. The polymer exhibited pseudo‐second‐order kinetics and nearly complete adsorption of lead occurred in 15 min with initial lead (II) concentrations greater than 100 mg · L^?1. Adsorptive behavior was accurately predicted by the Dubinin‐Radushkevich isotherm model. The mean free energy of adsorption of lead (II) onto poly(2‐octadecyl‐butanedioic acid) was determined to be 31.6 kJ · mol^?1, suggesting an ion exchange component to the adsorption mechanism. Gibb's free energy values for this process indicate that it is spontaneous. Adsorption was relatively independent of pH in the range of 3–5, due to the utilization of the sodium carboxylate form of the chelating groups, and was not influenced by high Na⁺ concentration and moderate concentrations (up to 200 mg · L^?1) of Ca⁺². Lead (II) solutions containing 2000 mg · L^?1 Ca⁺² did reduce the adsorption of 2000 mg · L^?1 lead (II) by 28%.     

An Extension and New Interpretation of Ościk's Equation for Describing Liquid Chromatography with Mixed Mobile Phases. II. Partition and Adsorption Effects

Abstract

Previously [J. Liquid Chromatogr. 8 (1985) 1363] it was shown that an equation having a form similar to O?cik's classical equation was derivable from a model involving solute partitioning (with no solute and solvent displacement) between a bulk-liquid mobile phase and a surface-influenced stationary liquid layer. Based on a recent general theory, we now propose a solute retention model which reveals an alternative molecular basis of O?cik's equation, which has been successfully applied to a range of liquid adsorption chromatographic systems. According to this model, solute is distributed between the     

An ESR study of the copper(II)–glycyl-l-serine and copper(II)–l-seryl-glycine systems by the simultaneous analysis of multi-component isotropic spectra. Formation constants and coordination modes

The formation constants and the isotropic ESR parameters (g-factors, ⁶³Cu, ⁶⁵Cu, ¹⁴N hyperfine coupling constants and relaxation parameters) of the various species were determined by the simultaneous analysis of a series of spectra, taken in a circulating system at various pH and ligand-to-metal concentration ratio. For both systems the new [CuLH]²⁺ complex was identified in acidic solutions. With the glycyl-l-serine ligand below pH 11.5 the same complexes and coordination modes are formed than with simple dipeptides. The side-chain donor group is bound only over pH 11.5 in the complex [CuLH₋₂(OH)]²⁻, where it is deprotonated and substitutes the carboxylate O in the third equatorial site. For the bis complex [CuLH₋₁(L)]⁻ an isomeric equilibrium was shown, where the difference between the isomers was based on which of the donor atoms of the ‘L’ ligand, the peptide O or the amino N, occupies the fourth equatorial position, and which one is coordinated axially. The l-seryl-glycine ligand forms the same species as simple dipeptides and glycyl-l-serine up to pH 8. The only difference is that the axial binding of the alcoholic OH group fairly stabilizes the bidentate equatorial coordination of the ‘L’ ligand through the amino N and peptide O atoms in the [CuL]⁺ complex as well as in the major isomer of the [CuLH₋₁(L)]⁻ complex. For this system we showed that (1) proton loss and the equatorial coordination of the alcoholic OH group occurs at relatively low pH (over pH 8–9), which results in the [CuL₂H₋₂]²⁻ complex with excess ligand, and also the newly identified species [Cu₂L₂H₋₄]²⁻: (2) this process is in competition with the proton loss of a coordinated water molecule. For both systems, the ESR-inactive species [Cu₂L₂H₋₃]⁻ was also shown.     

In-situ High Resolution NMR Investigation on Polymerization Mechanism. II. Comparison between BF3·Bu2O and CI-N2PF6 as Catalysts in Homopolymerization of Trioxane and Copolymerization with Ethylene Oxide

A comparison of BF₃ ·Bu₂O and Cl-N₂PF₆ as catalysts for cationic homopolymerization and copolymerization of trioxane has been made by employing high resolution nuclear magnetic resonance techniques. While no substantial difference was detected for the homopolymerization, two important differences were observed for the copolymerization with ethylene oxide; viz., 1) with Cl-NPF₆ there is a lower build-up of formaldehyde concentration; 2) with Cl[sbnd]N₂PF₆, a lesser amount of cyclic compounds containing ethylene oxide units is formed (e.g., 1,3-dioxolane). Both observations suggest that depolymerization occurs to a lesser extent with the cl-N₂PF₆ catalyst.     

Molecular Engineering of Liquid Crystal Polymers by Living Polymerization. VIII. Influence of Molecular Weight on the Phase Behavior of Poly {ω-[(4-Cyano-4′-biphenyl)-oxy]alkyl Vinyl Ether}s with Ethyl,Propyl, and Butyl Alkyl Groups

The synthesis and living cationic polymerization of 2-[4-cyano-4′-biphenyl)oxy]ethyl vinyl ether (6–2), 3-[4-cyano-4′-biphenyl)oxy]-propyl vinyl ether (6-3), and 4-[4-cyano-4′-biphenyl)oxy]butyl vinyl ether (6-4) are described. The mesomorphic behaviors of poly(6–2), poly(6-3), and poly(6-4) with different degrees of polymerization and narrow molecular weight distributions were compared to those of 6–2, 6–3, and 6–4 and of 2-[(4-cyano-4′-biphenyl)oxy]ethyl ethyl ether (8–2), 3-[(4-cyano-4′-biphenyl)oxy]propyl ethyl ether (8–3), and 4-[4-cyano-4′-biphenyl)oxy]butyl ethyl ether (8–4) which are model compounds of the monomeric structural units of poly(6–2), poly(6–3), and poly(6–4). In the first heating scan, all three polymers exhibit an x (unidentified) mesophase which overlaps the glass transition temperature, and an enantiotropic nematic mesophase. In the second and subsequent heating and cooling scans, poly(6–3) and poly(6–4) display only the enantiotropic nematic mesophase. Both in the first and subsequent scans, only poly(6–2) with degrees of polymerization lower than 4 exhibits an enantiotropic nematic mesophase.     

Sulphur-nitrogen chelating agent—II. Mixed-metal binuclear (Cu2, Ag+) and mononuclear (Cu2+) solid state complexes of 1,4-diazo-7-thiaoctane and 1,5-diazo-8-thianonane. An infrared and reflectance spectral analysis

A series of CuLX₂, CuL₂X₂, CuLYZ and AgCuL₂Z₃ {X⁻ = Cl⁻, Br⁻, NO⁻₃; Y⁻ = OAc⁻; Z⁻ = NO⁻₃ or ClO⁻₄; L = 1,4-diaza-7-thiaoctane [2,2-NNS(Me)] or 1,5-diaza-8-thianonane [3,2-NNS(Me)]} have been prepared and characterized by means of elementary analysis, i.r. and electronic spectroscopy. All 1 : 1 complexes containing polyanions (NO⁻₃, OAc⁻, ClO⁻₄) are five-coordinated species with the meridionally arranged thiadiamine acting as a tridentate. The remaining coordination positions are occupied by an asymmetric bidentate nitrate or acetate group. In contrast, in the 1 : 2 complexes, the thiadiamines are incompletely coordinated leaving one or even two sulphur donors free. These free sulphide-groups readily coordinate with the Ag(I) ions to form mixed-metal AgCuL₂Z₃-compounds.