Direct through anionic,cationic, and radical active species: Terminal carbon–halogen bond for “controlled”/living polymerizations of styrene

In this work, we examined the synthesis of novel block (co)polymers by mechanistic transformation through anionic, cationic, and radical living polymerizations using terminal carbon–halogen bond as the dormant species. First, the direct halogenation of growing species in the living anionic polymerization of styrene was examined with CCl₄ to form a carbon–halogen terminal, which can be employed as the dormant species for either living cationic or radical polymerization. The mechanistic transformation was then performed from living anionic polymerization into living cationic or radical polymerization using the obtained polymers as the macroinitiator with the SnCl₄/n‐Bu₄NCl or RuCp^*Cl(PPh₃)/Et₃N initiating system, respectively. Finally, the combination of all the polymerizations allowed the synthesis block copolymers including unprecedented gradient block copolymers composed of styrene and p‐methylstyrene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 465–473     

Ab initio quantum-mechanical calculations of the propagation enthalpies for the radical and anionic polymerizations of formaldehyde and methanimine

The gas phase enthalpies of formation for oligomeric radicals and anions H(CH₂NH)_n^* and H(CH₂O)_n^* were theoretically determined by ab initio quantum-mechanical calculations with n in the range 1 to 6. From these results, the reaction enthalpies for each of the first five propagation steps of the polymerization were estimated for methanimine (H₂C = NH) and formaldehyde (H₂C = O). At the same step of oligomerization, enthalpies associated with anionic polymerizations are always more negative than enthalpies corresponding to radical polymerizations, but the difference between them decreases with increasing n. Both Delta;H (propagation) vs. n curves tend rapidly, particularly for radical polymerizations, towards an asymptotic value independent of the mode of polymerization and equal to - 12 kcal/mol for formaldehyde and - 14 kcal/mol for methanimine. Experimental data for the gas phase polymerization of formaldehyde are in good agreement with our theoretical value. These results demonstrate that heats of polymerization can be reasonably estimated by intensive calculation methods if a careful choice of the reaction mimicking the propagation step is done.     

Kinetics and mechanism of acetylene polymerization

The kinetics of acetylene polymerization initiated by Ti(OBu)₄/4AlEt₃ catalyst was studied by radioquenching with C^*O to count the number of active sites [C] and by CH₃OT^* to determine the total metal polymer bonds [MPB] and M?_n of the polymer. The amount of quenching agent and time of reaction required and the kinetic isotope effect for CH₃OT^* were determined. The effects of Al/Ti ratio, catalyst aging, catalyst concentration, temperature, and monomer pressure on the polymerization were investigated. Detailed kinetic data on the variation of rate of polymerization, R_p, [C] [MPB], and M?_n with time were obtained at 298 and 195°K. The results required the assumption that the catalytic species C, is initially active and within less than 30 min all are converted by bimolecular kinetics to a far less active species. Analysis of the data yielded rate constants of propagation and termination and their energies of activation. Estimates of chain transfer efficiency were obtained. The mechanisms for the propagation, termination, and transfer processes were discussed. By drawing on our earlier EPR results we propose probable structures for the catalytically active species.     

Precision synthesis of acrylate multiblock copolymers from consecutive microreactor RAFT polymerizations

Well‐defined acrylate RAFT polymers and multiblock‐copolymers have been synthesized via the use of a continuous‐flow microreactor, in which polymerizations could be executed in 5?20 min reaction time. First, Poly(n‐butyl acrylate) (PnBuA) was synthesized in the micro‐flowreactor by using two different trithiocarbonate RAFT agents. Reaction time and reaction temperature were optimized and collected samples were directly studied with NMR, SEC and ESI‐MS to determine conversion, molar mass and end group fidelity. Using the continuous flow technique, highly reproducible and fast polymerizations yielded quantitatively functionalized PnBuA in a very facile and efficient manner. One batch of RAFT acrylate polymer with a molar mass of 1100 g mol^?1 and excellent end group fidelity was employed as a macro‐RAFT agent for the subsequent copolymerization with different acrylate monomers (2‐ethylhexyl acrylate, t‐butyl acrylate, n‐butyl acrylate). Using this procedure, a sequential multiblock‐copolymer (M_n = 31,200 g mol^?1, PDI = 1.46) consisting of five consecutive acrylate blocks was synthesized. This study clearly demonstrates the potential of using a continuous‐flow microreactor for subsequent RAFT polymerizations towards well‐defined multiblock‐copolymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 2366–2374     

Living cationic polymerization of vinyl ethers with a functional group. VII. Polymerization of vinyl ethers with a silyloxyl group and synthesis of polyalcohols and related functional polymers

Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?_n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?_w/M?_n around or below 1.1. Desilylation of the polymers under mild conditions (with H⁺ for MeSiVE and F^? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers.     

Lifetime of living polymers in cationic polymerization. III. Living polymerization of isobutyl vinyl ether initiated by a cationogen/etalcl2 system in the presence of 1,4-dioxane as an added base

The concentration ([P^*]) and lifetime (half-life) of the propagating species were measured in the living cationic polymerization of isobutyl vinyl either initiated by the 1-(isobutoxy) ethyl acetate [CH₃COOCH (OiBu) CH₃]/ethylaluminum dichloride (EtAlCl₂) system in the presence of excess 1,4-dioxane in n-hexane at 0 to +70°C; the acetate serves as a cationogen that forms an initiating vinyl ether-type carbocation. The measurements were based on the end-capping reaction with sodiomalonic ester [Na^⊕?CH (COOEt)₂], which was shown to react rapidly and quantitatively with the living growing end. From the terminal malonate group of the quenched polymers, [P^*] was determined by ¹H-NMR spectroscopy. In contrast to its constancy during the polymerization, [P^*] progressively decreased with time after the complete consumption of monomer. The postpolymerization decay was first order in [P^*], and the lifetime (half-life) of the living end was determined from the decay rate constant. The lifetime increased on lowering polymerization temperature, decreasing EtAlCl₂ concentration, and increasing dioxane concentration. In particular, the “base-stabilized” living ends, generated by the CH₃COOCH (OiBu) CH₃/EtAlCl₂/dioxane system, turned out extremely stable at 0°C (half-life > 5 days in the absence of monomer).     

Molecular structure parameters in certain semiconducting polymers

The condensation polymers formed by condensing aromatic hydrocarbons or their derivatives with aromatic acids are quite conductive. The room temperature resistivities of 42 polymers studied here range from 10² to 10¹² ohm-cm. It is found that the resistivities are inversely related to the number of fused rings in the hydrocarbon portion of the monomer for either the homopolymers or copolymers. The resistivities are strongly dependent, inversely, upon the acid strength of the acid monomer reactants. For all the polymers studied, the conductivity σ depended upon the pressure P as ln(σ/σ₀) = (b^*/k)P^1/2 where b^* is seen to be an inverse function of the number of fused rings in the monomer in accord with theory. The resistivity ρ varied with absolute temperature T, as ln ρ ∞ (1/T) for all polymers. Thermoelectric powers were determined, and the various relationships established among energy interval, resistivity at “infinite temperature,” carrier concentrations and mobility ratios, number of fused rings, and pressure coefficients are discussed. The polymers are p-type. Doping by Be⁺⁺ or Cu⁺⁺ has a small effect, increasing the conductivity slightly. Electron spin concentrations and carrier concentrations are directly related among the polymers, being found nearly equal for the most conductive but differing by up to nine orders of magnitude in the least conductive polymers.     

Kinetics of the exothermic decomposition of 1-nitro-3-(β,β,β-trinitroethyl)-4,5-dinitroiminoimidazolidine-2-one

The kinetic parameters of the exothermic decomposition of the title compound in a temperatureprogrammed mode have been studied by means of DSC. The DSC data obtained are fitted to the integral, differential, and exothermic rate equations by the linear least-squares, iterative, combined dichotomous, and least-squares methods, respectively. After establishing the most probable general expression of differential and integral mechanism functions by the logical choice method, the corresponding values of the apparent activation energy (E _a), preexponential factor (A), and reaction order (n) are obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential form and the values of E _a and A of this reaction are (1 − α)^−4.08, 149.95 kJ mol⁻¹, and 10^14.06 s⁻¹, respectively. With the help of the heating rate and kinetic parameters obtained, the kinetic equation of the exothermic decomposition of the title compound is proposed. The critical temperature of thermal explosion of the compound is 155.71°C. The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal explosion rule of the title compound. The text was submitted by the authors in English.     

Synthesis and characterization of isoprene polymers with polar groups via reversible addition-fragmentation chain-transfer polymerization

Homo and copolymerization of isoprene (IP) with small amounts (1% wt) of glycidyl methacrylate) were conducted using the reversible addition-fragmentation chain-transfer process (RAFT) at 125 °C in a solution polymerization process using toluene as solvent. Suitable reaction conditions to avoid Diels–Alder dimerization of IP and crosslinking were determined; and 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl] pentanoic acid was found to be the best transfer agent among those tested. Theoretical calculations were used to understand why some RAFT agents work better than others in these polymerizations. Molecular weights M_n higher than 100,000 Da were reached by successive chain extension experiments, confirming the livingness of the intermediate polymers. All the successful polymerizations yielded average molar masses (M_n) of about 75% compared to the theoretical M_n (M_n,theo) depending on the agent used for control. The dispersity (Ð) ranged from 1.20 to 1.70 being a function of the control agent. The polymers were characterized by FTIR spectroscopy, ¹H NMR, and gel permeation chromatography. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2463–2474     

Analysis of the equations of state of polyolefin melts in terms of the simha-somcynsky hole theory

Pressure–volume–temperature data on melts of low-density polyethylene, polypropylene (PP), poly(butene-1) (PBT), and poly(4-methylpentene-1) (PMP) previously reported by us have been evaluated in terms of the Simha–Somcynsky hole theory of polymeric liquids by a determination of the reducing parameters P^*, V^*, and T^* for each system. Literature data on the reducing parameters of linear polyethylene and of a branched polyethylene of intermediate density are also considered. Agreement with theory is best for the polyethylenes and deteriorates markedly in the series PBT:PP:PMP. These higher polyolefins have very low values of P^*, thus suggesting a deficiency of the Simha–Somcynsky theory at high reduced pressures P? = P/P^*. In these polyolefins, systematic variations of the reducing parameters (and molecular parameters derived therefrom) are noted and discussed. Correlations found previously between T^* and the moleculer weight M₀ of the effective segment of the theory or its hard-core volume M₀V^* are obeyed by the polyethylenes only. The higher polyolefins show serious deviations from these correlations.     

Free volumes in simple and polymeric liquids

Values of ε₀ν₀ the vaporization energy and volume in the hypothetical liquid state at 0°K., are derived for some simple polar and nonpolar molecules used as models for vinyl polymers. The following empirical relationship between the free volume fraction, f = (v ? v₀)/v, and the liquid compressibility coefficient β is demonstrated: ?f² ∝? This is applied to several vinyl polymer liquids near their glass transition temperatures, T_g, giving. f_g ? 0.17, if the “hard-core” volume v^* is considered to be independent of pressure and temperature, (i.e., v^* = v₀); or, f_g ?0.12, if the P,T dependence of v^* is considered to be the same as that of the glass. These agree with f_g values derived by Simha and Boyer from thermal expansion coefficients for the two analogous cases. An empirical viscosity-free volume equation of the Doolittle form: η = ATⁿe^b/f is applied to the glass transition, on assuming that this is an isoviscosity state and with the use of reported values for the expansion and compressibility coefficients and dT_g/dP for three polymers: polystyrene, poly(methyl methacrylate), and poly(vinyl acetate). Reasonable values of b/n are thus obtained. This viscosity equation is critically examined in the light of molecular theories of liquid viscosity.     

Ion Transport in a Three-Layered Ion-Exchange Membrane: A Mathematical Model

An ion transport model is considered. The model is based on the Nernst–Planck equations, the elements of nonequilibrium thermodynamics, the principle of local equilibrium, and the concept of a virtual solution. The model is applied to an ion-exchange membrane with two diffusion layers for the cases of electrotransport of two and three types of ions. To determine transfer coefficients L ^* _j in the Nernst–Planck equations, two approaches are used. In the phenomenological approach, L ^* _j are found from experimental data on the electroconductivity and transport numbers. In the modeling approach, values of L ^* _j are sought for from a model of a microheterogeneous membrane. The obtained boundary-value problem is solved using a numerical method of parallel shooting developed earlier, which perfectly fits specific features of the problem formulation (utilizing the Nernst–Planck equations in all the three layers and the concept of a virtual solution).     

Catalytic inhibition in free radical polymerizations

Free radical polymerizations of methyl methacrylate and methacrylamide in DMF solution were found to be catalytically inhibited by the addition of the boron fluoride derivative of cobaloxime to the system. The nature of this inhibition is examined and equations which describe the kinetics of these catalytically inhibited polymerizations are developed. Using these equations estimates of the inhibition constants (C_z) of 7.23 × 10² and 2.27 × 10² were estimated for methacrylamide and methyl methacrylate, respectively.     

Universal xanthate‐mediated controlled free radical polymerizations of the “less activated” vinyl monomers

The living free radical polymerizations of three “less activated” monomers (LAMs), vinyl acetate, N‐vinylcarbazole, and N‐vinylpyrrolidone, were successfully achieved in the presence of a disulfide, isopropylxanthic disulfide (DIP), using 2,2′‐azoisobutyronitrile (AIBN) as the initiator. The living behaviors of polymerizations of LAMs are evidenced by first‐order kinetic plots and linear increase of molecular weights (M_ns) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions, respectively. The effects of reaction temperatures and molar ratios of components on the polymerization were also investigated in detail. The polymerization proceeded with macromolecular design via interchange of xanthate process, where xanthate formed in situ from reaction of AIBN and DIP. The architectures of the polymers obtained were characterized by GPC, ¹H NMR, UV–vis, and MALDI‐TOF‐MS spectra, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Lifetime of living polymers in cationic polymerization. II. Living polymerization of isobutyl vinyl ether initiated by the hydrogen iodide/zinc halide systems

In the living cationic polymerization of isobutyl vinyl ether (IBVE) initiated by the hydrogen iodide/zinc halide (HI/ZnX₂; X = I, Br, Cl) systems, the concentration ([P^*]) of the living propagating species was determined by quenching with sodiomalonic ester ( 1 ). The quenching reaction was shown to be clean, instantaneous, and quantitative to give poly (IBVE) with a terminal malonate group from which [P^*] was obtained by ¹H-NMR spectroscopy. In the polymerizations in toluene below +25°C, [P^*] was constant and equal to the initial concentration ([HI]₀) of hydrogen iodide, independent of the type and concentrations of ZnX₂ as well as monomer conversion. At 0 and +25°C, however, the living species started decaying immediately after the complete consumption of monomer. In contrast, such a decay process was absent at ?15°C even in the absence of monomer until about an hour (depending on the conditions) after the end of polymerization. The deactivation reaction was first order in [P^*], and the lifetime (half-life) of the living species was longer at lower temperature and at lower ZnX₂ concentration. On the basis of these [P^*] and lifetime measurements, the HI/ZnX₂ systems were also compared with the HI/I₂ counterpart.     

Combination of nitroxide‐mediated polymerization and SET‐LRP for the synthesis of high molar mass branched and star‐branched poly(n‐butyl acrylate) characterized by size exclusion chromatography and rheology

Branched and star‐branched polymers were successfully synthesized by the combination of two successive controlled radical polymerization methods. A series of linear and star poly(n‐butyl acrylate)‐co‐poly(2‐(2‐bromoisobutyryloxy) ethyl acrylate) statistical copolymers, P(nBA‐co‐BIEA)_x, were first synthesized by nitroxide‐mediated polymerization (NMP at T > 100 °C). The subsequent polymerization of n‐butyl acrylate by single electron transfer‐living radical polymerization (SET‐LRP at T = 25 °C), initiated from the brominated sites of the P(nBA‐co‐BIEA)_x copolymer, produced branched or star‐branched poly(n‐butyl acrylate) (PnBA). Both types of polymerizations (NMP and SET‐LRP) exhibited features of a controlled polymerization with linear evolutions of logarithmic conversion versus time and number‐average molar masses versus conversion for final M_n superior to 80,000 g mol^?1. The branched and star‐branched architectures with high molar mass and low number of branches were fully characterized by size exclusion chromatography. The Mark–Houwink Sakurada relationship and the analysis of the contraction factor (g′ = ([η]_branched/[η]_linear)_M) confirmed the elaboration of complex PnBA. The zero‐shear viscosities of the linear, star‐shaped, branched, and star‐branched polymers were compared. The modeling of the rheological properties confirmed the synthesis of the branched architectures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Novel synthesis of high molecular weight polymers with extremely low polydispersity by the unique initiation properties of organo-lanthanide complexes

Organolanthanide(III) complexes such as |(C₅Me5₅)₂SmH|₂ and (C₅Me₅)₂SmMe(THF) were found to initiate the living polymerizations of methyl methacrylate (MMA) to give high molecular weight polymers (M _n > 500 × 10³) with extremely low polydispersity (M _w/M_n = 1.04). The syndiotacticity increased up to 95.2% by lowering the temperature to −95°C. The molecular structure of the 1:2 adduct of (C₅Me₅)₂SmH with MMA determined by X-ray method indicates that this intermediate assumes the 8 membered ring conformation where the Sm atom is bound to MMA in an enolate form and the ester of penultimate MMA is coordinated to the metal. Based upon these results, an anionic coordination mechanism has been proposed for the present reaction. Organolanthanide(II) complexes also exhibit high activity and proceed the living polymerizations. Organolanthanide(III) complexes also initiate the living polymerizations of lactones such as ϵ-caprolactone and δ-valerolactone. The stoichiometric reactions indicate that real active species assumes the alkoxylanthanide(III) form.     

IR and electronic spectra of complex Co<Superscript>2+</Superscript> groups in chloride-fluoride and carbonate-chloride melts

The IR and electronic absorption spectra of molten mixtures in the NaCl-CsCl-NaF-CoCl₂, NaCl-KCl-NaF-CoCl₂, and NaCl-KCl-NaKCO₃-CoCl₂ systems have been studied. The spectral data show that, for all molten mixtures, the composition ranges exist in which chloro fluoro Co(Cl _n F _m )(n + m = 4–6) and carbonato chloro CoCl(CO₃)_{4 − n} (n = 1–3) complex groups are formed at δ₁ < δ₁^* and δ₂ < δ₂^* (δ₁^* = F/Co and δ₂^* = CO₃/Co). At δ₁ ≥ δ₁^* and δ₂ ≥ δ₂^*, the mixtures contain complexes homoligand Co and CoF₆⁴⁻ and Co(CO₃)₄⁶⁻.     

Isotactic rac‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR¹=N,N‐dimethylamino ethoxide, OR²=2‐pyridyl methoxide), are active for the polymerization of rac‐lactide at ambient temperature in benzene to yield polymers with M_w/M_n=1.0–1.2. X‐ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR¹ provided only atactic polylactide, LCuOR² produced partially isotactic polylactide (P_m=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR² in contrast to a mononuclear species for LCuOR¹.     

Substitution kinetics of chelate complexes as studied by isotopic exchange

The fact that isotopic exchange reactions take place at chemical equilibirum makes this type of reaction useful for kinetic studies. In the case of chelate complexes [M(chel)_n] isotopic exchange reactions can be classified as metal exchange reactions. [M(chel)_n]+^*M⇆[^*M(chel)_n]+M and ligand exchange reactions [M(chel)_n]+^*chel⇆[M(chel)_n−1 ^*chel]+chel The literature on type (a) and type (b) reactions of mainly transition metal complexes is reviewed with respect to the kinetic information obtained. The value and the limitations of isotopic exchange studies as a kinetic technique are discussed.