Anionic polymerization of one-ended “living” strontium-polystyrene in tetrahydropyran in the presence of tetraglyme and in benzene

The anionic polymerization of the strontium salt of one-ended living polystyrene (SrS₂) was investigated at 20°C in tetrahydropyran (THP) in the presence of two different concentrations of added tetraglyme. Similarly to BaS₂ in tetrahydrofuran (THF) and to SrS₂ in THF and in pure THP, the observed pseudo-first-order rate constant of propagation, k_obs, was nearly independent of the total concentration of salt, their values being 7,5.10^?3 s^?1 and 9 · 10^?3 s^?1, respectively, i. e. about 100 to 120 times higher than in pure THP. This indicates that the propagation occurs mainly via an increased but constant amount of free S^? anions resulting from the two already known equilibria SrS₂ ? (SrS)⁺ + S^?(K₁) and 2 SrS₂ ? (SrS)⁺ + (SrS₃)^? (K₂) and the equilibrium of glymation (SrS⁺) + G ? G, (SrS)⁺ (K_i). A small not exactly determinable contribution of glymated ion-pairs and/or triple ions, whose rate constants would then probably be of the order of 18 l · mol^?1 · s^?1 and 80 l · mol^?1 · s^?1, respectively, could not be excluded. The glymation constant K_i was found to be about 3 · 10⁶ 1 · mol^?1, i.e., approximately 17 times greater than for the Na⁺ cation. Finally, a kinetic experiment with SrS₂ at 20°C in pure benzene (contaminated, however, with some remaining THP from the preparation of SrS₂) indicated that propagation by ion-pairs is possible with a bimolecular apparent rate constant K_app = 1,1 · 10^?1 l · mol^?1 · s^?1.     

Dependence of the kerr constants of benzene,p-dioxane and poly(oxydiethylene terephthalate) on temperature

The Kerr constants of benzene, p-dioxane, and of poly(oxydiethylene terephthalate) (PDET) in p-dioxane solution were measured at several temperatures. As in the case of some other pure liquids reported in the literature, the values obtained for benzene and p-dioxane are fitted by equations of the type _mK = a + b · T^?1 with a = (0,3 ± 0,6) · 10^?26 m⁵ · V^?2 · mol^?1 and b = (16,0 ± 1,8) · 10^?24 m⁵ · V^?2 · mol^?1 · K for benzene and a = (3,9 ± 0,9) · 10^?26, b = ?(8,2 ± 2,6) · 10^?24, in the same units, for p-dioxane. The values of the mean molar Kerr constant per repeating unit 〈_mK〉/x extrapolated to infinite dilution in the case of PDET yield a values of d(〈_mK〉/x)/dT = (13,5 ± 0,9) · 10^?27 m⁵ · V^?2 · mol^?1 · K^?1, in excellent agreement with the calculated result of 13,2 · 10^?27 (in the same units) reported in the literature.     

Evaluation of the rate constant for primary radical termination in free radical polymerization

Styrene and methyl methacrylate were polymerized with azodiisobutyronitrile (AIBN) at 50, 60, and 70°C. The average degree of polymerization was kept constant while changing the initiator concentration, by using 1-butanethiol as a chain transfer agent. In these polymerizations, a deviation from the simple kinetic rate law was noticed. This deviation was explained in terms of primary radical termination considering the effect of size dependence of the termination rate constant on the kinetics of free radical polymerization and taking into account the fraction of thermal polymerization. The temperature dependence of the characteristic constant, K_tpr/K_pK_i, was estimated to be 5,408 · 10^?5 exp (12915 cal mol^?1/RT) and 7,52 · 10^?3 exp (7791 cal mol^?1/RT) for styrene/AIBN and methyl methacrylate/AIBN, respectively.     

Rate coefficients of the free-radical polymerization of 1,3-butadiene

Rate coefficients of termination and transfer in the free-radical polymerization of 1,3-butadiene in chlorobenzene were determined in the temperature range 318 K < T < 333 K. On the basis of an earlier published temperature dependence of the rate coefficient of propagation, for the termination reaction the Arrhenius equation K_t = 1,13 · 10¹⁰ · exp(? 711 K/T) L · mol^?1 · s^?1 was obtained. For the transfer to monomer the experiments yielded the Arrhenius equation K_tr,M = 4,22 · 10⁶ · exp(? 5140 K/T) L · mol^?1 · S^?1 and for the transfer to the solvent K_tr,S = 2,25 · 10⁸ · exp(? 7050 K/T) L · mol^?1 · S^?1.     

Solvent effect on the propagation rate constant in the radical polymerization of bis(2-ethylhexyl) itaconate

Polymerization of bis(2-ethylhexyl) itaconate ( 1 ) with dimethyl azobis(isobutyrate) ( 2 ) was carried out at 50°C in various solvents. Polar solvents caused a significant decrease in the polymerization rate (R_p) and the molecular weight of resulting poly( 1 ). The propagating poly( 1 ) radical could be observed as a five-line ESR spectrum in the actual polymerization systems used. The stationary concentration of poly( 1 ) radical was determined by ESR to be 4,2–6,4 · 10^?6 mol · L^?1 at 50°C when the concentrations of 1 and 2 were 1,03 and 3,00 · 10^?2 mol · L^?1. Using R_p the monomer concentration and the polymer radical concentration, the propagation rate constant (K_p) was estimated to be 1,4–6,8 L · mol^?1 · s^?1, depending on the solvents used. The k_p value was smaller in more polar solvents. The solvent effect is explained in terms of the solvent affinity for the propagating polymer chain.     

Synthesis,Characterization, and Photopolymerization of Novel Phosphonated Resins, 2

New phosphonated cross‐linked polymers were synthesized from telomers obtained by reaction between 10‐undecenol and dialkyl hydrogenphosphonates. Telomers were studied using MALDI‐TOF MS. It was proven that side products were produced, corresponding to cross‐esterification reactions of dialkyl hydrogenphosphonate on telomers and to radical additions of telomer on 10‐undecenol. The same behavior was also observed with allyl alcohol. Telomers were then converted to resins by methacrylation reactions. Finally, photopolymerization of the different resins synthesized was achieved and influence of the nature of the phosphonate group (diester, monoacid and diacid) was also evaluated.

     

Evaluation of unperturbed dimensions parameter from intrinsic viscosity data of any binary or ternary polymer system

Taking into account the dependency on molar mass of the viscometric interaction parameter B, the modified Stockmayer-Fixman-Burchard equation ([η]/M^1/2) = K_Θ + C″ · A₂ · M^1/2 is obtained. It relates the intrinsic viscosity, [η], to the second virial coefficient, A₂, and to the unperturbed dimensions parameter, K_Θ, with C″ being a constant. Hereupon, K_Θ can be determined from [η] and A₂ data of any binary (solvent/polymer) and/or ternary (solvent 1/solvent 2/polymer) system, BPS and/or TPS. Because of the scarcity of reliable sets of [η] and A₂ values mostly for TPS, the application of the above equation to obtain K_Θ coefficients rests limited. This limitation can be surmounted by an A₂ evaluation from [η] data and trial K_Θ values through two-parameter theories taking into account the interpenetrating factor between chains, ψ, as evaluated from the Flory-Krigbaum-Orofino (FKO) theory, from a modified FKO theory, or from the Kurata-Yamakawa theory. An interative process is followed until coincidence between assumed and evaluated K_Θ values is reached. The method has been applied to the K_Θ evaluation from [η] with literature data for diverse BPS and TPS of polystyrene, poly(methyl methacrylate), poly(dimethylsiloxane), poly(2-vinylpyridine) and poly(1-vinyl-2-pyrrolidone), with the respective K_Θ values 7,5 · 10^?2, 5,8 · 10^?2, 8,2 · 10^?2 and 6,4 · 10^?2, 7.2·10^?2 and · 6,4 · 10^?2 mL · mol^1/2 · g^?3/2 being obtained. Moreover, a single C″ value, mainly C″ = 0,52, holds for all five polymers.     

PLP‐SEC Study into the Free‐Radical Propagation Rate Coefficients of Partially and Fully Ionized Acrylic Acid in Aqueous Solution

Summary: Propagation rate coefficients, k_p, for acrylic acid (AA) polymerization at 6 °C in aqueous solution were measured via pulsed laser polymerization (PLP) with the degree of ionization, α, varied over the entire range between 0 and 1. These measurements were carried out in conjunction with aqueous‐phase size‐exclusion chromatography (SEC). Strictly speaking, the reported k_p's are “apparent” propagation rate coefficients deduced from the PLP‐SEC data under the assumption that the local monomer concentration at the radical site is identical to overall monomer concentration. At an AA concentration of 0.69 mol · L^?1, the apparent k_p decreases from 111 000 L · mol^?1 · s^?1 at α = 0 to 13 000 L · mol^?1 · s^?1 at α = 1.0. The significant lowering of k_p with higher α is attributed to the repulsion between both monomer molecules and macroradicals becoming negatively charged. Addition of up to 10 mol‐% (with respect to AA) sodium hydroxide to the fully ionized aqueous AA solution leads to an enhancement of k_p up to 57 000 L · mol^?1 · s^?1.

Dependence of apparent k_p values on the degree of ionization of acrylic acid (a) and on pH (b) for aqueous polymerizations of acrylic acid.     

Synthesis and Characterization of New Methacrylic Phosphonated Surface Active Monomer

Summary: The synthesis of novel methacrylic phosphonated surface‐active monomer by an original method is described. The crucial stage is the telomerization of undec‐10‐enyl acetate with dialkyl (alkyl = methyl or ethyl) hydrogenphosphonate. The phosphonated acetate obtained is selectively hydrolysed to give dialkyl(11‐hydroxyundecyl)phosphonate as a precursor. The alcohol function allows setting of methacrylic side, which is highly reactive in radical polymerization. Particularly, by mono‐dealkylation of dimethyl phosphonate in a selective and quantitative way, the potassium iodide permits to get, at one stage, the expected salt of sodium methyl phosphonate. The new surface‐active sodium methyl(11‐methacryloyloxyundecyl)phosphonate is characterized by ¹H and ³¹P NMR. Its critical micelle concentration evaluated by conductometry is 2.4 × 10^?2 mol · l^?1.

Synthesis of dialkyl(11‐methacryloyloxyundecyl)phosphonate (DAHP) without protection of alcohol function.     

Termination Kinetics of Dibutyl Itaconate Free‐Radical Polymerization Studied via the SP–PLP–ESR Technique

Summary: The termination kinetics of dibutyl itaconate (DBI) bulk polymerization was studied via SP–PLP–ESR single pulse–pulsed laser polymerization with time‐resolved detection of free‐radical concentration by electron‐spin resonance, at temperatures between 0 and 60 °C. As is characteristic of PLP experiments, termination rate coefficients, k_t(i,i), are measured for radicals of (almost) identical chain length (CL) i. CL‐averaged 〈k_t〉, for chain lengths up to 200 monomer units, and also kequation/tex2gif-stack-1.gif referring to termination of very small‐size radicals are directly deduced from measured DBI radical concentration vs time traces. At 45 °C, 〈k_t〉 is (3.4 ± 0.6) · 10⁵ L · mol^?1 · s^?1 and kequation/tex2gif-stack-2.gif is (7.2 ± 1.0) · 10⁵ L · mol^?1 · s^?1. Both rate coefficients are independent of monomer conversion up to the highest experimental conversion of 18%. The associated activation energies are E_A(〈k_t〉) = 23.0 ± 3.2 kJ · mol^?1 and E_A(kequation/tex2gif-stack-3.gif) = 27.6 ± 2.8 kJ · mol^?1, respectively. “Model‐dependent” and “model‐free” analyses of radical concentration vs time profiles indicate a pronounced CL dependence of k_t(i,i) for DBI radicals of moderate size, 5 < i < 50. The lowering of k_t(i,i) with CL corresponds to an exponent α close to 0.5 in a power‐law expression k_t(i,i) = kequation/tex2gif-stack-4.gif · i^?a. At higher chain lengths, the variation of k_t(i,i) with CL becomes weaker and may be represented by an α value of 0.16 or even below. These results are consistent with models according to which α varies to a larger extent at low CL and to a smaller extent at high CL with the crossover region between the two ranges being located somewhere around i = 100.

Conversion‐dependence of 〈k_t〉 and kequation/tex2gif-stack-5.gif from laser‐induced photopolymerization of DBI.     

N‐tert‐Butyl‐1‐diethylphosphono‐2,2‐dimethylpropyl nitroxide as counter radical in the controlled free radical polymerization of styrene: kinetic aspects

The controlled free radical polymerization of styrene with N‐tert‐butyl‐1‐diethylphosphono‐2,2‐dimethylpropyl nitroxide (DEPN) as counter radical was studied. Polymerizations were performed in bulk, with a DEPN‐capped polystyryl as alkoxyamine initiator, in the presence of an excess of DEPN nitroxyl free radicals. Kinetics of the polymerization were followed at 115°C, 125°C and 130°C. The equilibrium rate constant K = k_d/k_c of exchange between dormant and active species was determined experimentally from the slope of Ln([styrene]₀/[styrene]) versus time. The obtained Arrhenius relation was the following: K (mol·L^–1) = 1.45×10⁷exp (–113.5 kJ·mol^–1/RT), i.e., K = 1.9×10^–8 mol·L^–1 at 125°C. This result is consistent with a much faster polymerization of styrene with DEPN than with Tempo as nitroxyl counter radical (K = 2.1×10^–11 mol·L^–1 at 125°C determined previously by Fukuda).     

Telomerization of styrene with dialkyl hydrogenphosphonates

Radical telomerization of styrene with phosphonated telogens has been studied. The transfer agents used are dialkyl hydrogenphosphonates HP(O)(OR)₂ (R = Me, Et). We first compared the activity of the three following initiators: 2,2′‐azoisobutyronitrile (AIBN), benzoyl peroxide (BPO), and tert‐butyl peroxide (tBu₂O₂) and the better results are obtained with tBu₂O₂. We have used the latter to realize a kinetic study. Our results first show that we obtained phosphonated telomers either with diethyl‐ or dimethyl hydrogenphosphonate. They have been characterized by size exclusion chromatography (SEC) and by NMR (¹H and ³¹P). The important length of the telomers is explained by the small value of the transfer constant (C_T = 9 · 10⁻⁴ for HP(O)(OEt)₂), so this kind of telogens is not an efficient transfer agent to styrene.

     

Viscosity and intrinsic viscosity/temperature relationships for dilute solutions of poly(2-biphenylyl methacrylate) and poly(4-biphenylyl methacrylate)

The actual viscosity η and the intrinsic viscosity [η] of six fractions of poly(2-biphenylyl methacrylate) {poly[1-(2-biphenylyloxycarbonyl)-1-methylethylene], (POB); weight average molecular weight M?_w: 4,0 · 10⁴ to 1,42 · 10⁶, polydispersity ratio M?_w/M?_n ≈ 1,4} and of three fractions of poly(4-biphenylyl methacrylate) {poly[1-(4-biphenylyloxycarbonyl)-1-methyl-ethylene], (PPB); M?_w : 8,1 · 10⁴ to 5,3 · 10⁵, M?_w/M?_n ～ 1,4} in benzene have been determined at different temperatures between 20 and 60°C. Values of the apparent activation energy of the viscous flow Q and the pre-exponential term A in the expression η = A · exp[Q/(RT)] have been obtained. Q varies with M?_w and concentration c according to Moore's equation: Q = Q₀ + K_e · M · c, where Q₀ refers to the solvent and K_e depends on polymer and solvent. The numerical value of K_e for POB and PPB is 1,6 · 10^?4 (6,7 · 10^?4) and -8,1 · 10^?4 cal · dl · g^?1 (-3,4 · 10^?3 J · dl · g^?1), resp. From all polymethacrylates studied POB is the only polymer with a positive K_e value. The positive value of K_e for POB may possibly be related to the more extended form of POB in benzene and also may be connected, at least partly, with its low flexibility. The temperature coefficient of the unperturbed dimensions dln〈r₀²〉/dT for POB estimated from the viscosity data using the Burchard-Stockmayer-Fixman relation, is 0,14 · 10^?3, much lower than for PPB (2,3 · 10^?3 between 22 and 40°C and 1,2 · 10^?3 between 40 and 60°C). The positive values of dln〈r₀²〉/dT indicate that extended conformations of these polymers in benzene must be associated with higher energies.     

Elementary reactions in the cationic polymerization of oxepane. Comparison with the polymerization of tetrahydromfuran

In the polymerization of oxepane (OXP), initiated with derivatives of trifluoromethanesulfonic acid, covalent and ionic active centers were simultaneously observed by ¹H and ¹⁹F NMR spectroscopy. A higher proportion of secondary oxonium ions (these species detected by ¹⁹F NMR were independently observed by proton trapping with R₃P in the ³¹P NMR spectrum). The proportion of ionic species decreases with monomer conversion, indicating a substantial contribution of bimolecular ionization of the monomer. The effective molarity in oxepane polymerization [OXP]_eff ? 1 mol ·I^-1 was found to be lower by a factor of 10² than [THF]_eff in the polymerization of THF. The rate constant of the covalent propagation in the polymerization of OXP is similar to that measured for THF, however, due to the reduced reactivity of the oxepanium cation, the relative reactivity of the covalent active centers becomes higher than that of the ions. Thus, for OXP, in CH₃NO₂ at 25°C, K_pc = 3 · 10^?4 mol^?1 · 1 · s^?1, k_pi = 2 · 10^?4 mol^?1 · 1 · s^?1 whereas for THF k_pc = 5 · 10^?4 mol^?1 · 1 · s^?1 and k_pi = 2 · 10^?2 mol^?1 · 1 · s^?1 under similar conditions. The rates of ionization and temporary termination, measured by the “temperature jump” technique, allow to determine the contributions of inter-and intramolecular ionizations. These rates becomes equal at [OXP] = 1 mol · 1^-1 (= [OXP]_eff).     

Macroion-pairs and macroions in the kinetics of polymerization of hexamethylene oxide (oxepane)

Cationic polymerization of oxepane (hexamethylene oxide) ( 1 ) in CH₂Cl₂ and C₆H₅NO₂ as solvents was initiated with 1,3-dioxolan-2-ylium hexafluoroantimonate ( 2 ). Dissociation constants (K_D) of the ion-pairs of polyoxepane into ions were measured: K_D (in CH₂Cl₂, T = 25°C) = 2,8·10^?5 mol·l^?1 [ΔH_D = ?3,8 kJ·mol^?1 (?0,9 kcal·mol^?1), ΔS_D = ?98 J·mol^?1·K^?1 (?23,4 cal·mol^?1·K^?1)]; K_D (in C₆H₅NO₂, T = 25°C) = 1,6·10^?3 mol·l^?1 [ΔH_D = ?7,1 kJ·mol^?1 (?1,7 kcal·mol^?1), ΔS_D = ?78 J·mol^?1·K^?1 (?18,7 cal·mol^?1·K^?1)]; these values are close to those of the ion-pairs of polytetrahydrofuran. Rate constants k_p⁺ and k_p^±, determined from the kinetic measurements for degrees of dissociation of macroion-paris ranging from 0,02 to 0,21 (in CH₂Cl₂) and from 0,09 to 0,7 (in C₆H₅NO₂), were found to be identical within an experimental error of kinetic measurements. The activation parameters of propagation were measured and their dependences on the polarity of the polymerization mixtures are discussed.     

Study of the mechanism of propagation and transfer reactions in the polymerization of olefins by Ziegler-Natta catalysts, 2. The influence of polymerization temperature on the kinetic characteristics of propagation

By quenching polymerization with radioactive carbon monoxide (¹⁴CO) data on the number of propagation centers (C_p) and the propagation rate constant (K_p) were obtained for the ethylene and propene polymerization in the presence of titanium trichloride at different temperatures. The values of K_p for ethylene and propene polymerization were found to be 8,0·10⁵ e^?13/(RT) and 3,0·10⁵ e^?23/(RT) l mol^?1 S^?1, respectively (activation energies in kJ mol^?1). It was further found that at increasing polymerization temperature the steady-state concentration of propagation centers increased when using Al(C₂H₅)₃ and Al(C₂H₅)₂Cl as cocatalysts, whereas it did practically not change in the case of Al(isobutyl)₃. On the basis of these data several conclusions were drawn on the mechanism of propagation and the role of organoaluminium cocatalysts in this reaction.     

Study of the mechanism of propagation and transfer reactions in the polymerization of olefins by Ziegler-Natta catalysts, 1. Determination of the number of propagation centers and the rate constant

The number of propagation centers (C_p) and the propagation rate constant (K_p) in the polymerization of ethylene and propene in the presence of heterogeneous TiCl₃ derived Ziegler-Natta catalysts of different composition were determined using the method of quenching the polymerization by radioactive carbon monoxide (¹⁴CO). The values of K_p, (1,2±0,3)·10⁴ l mol^?1 s^?1 at 75°C for ethylene and (90±20) l mol^?1 s^?1 at 70°C for propene polymerization, significantly exceed those ones obtained by use of tritium tagged alcohols as quenching agents. Further, for the polymerization of olefins in the presence of TiCl₃ based catalysts, the influence of catalyst composition, polymerization conditions, and monomer nature on C_p and K_p was studied.     

EPR Investigations into the Kinetics of Trithiocarbonate‐Mediated RAFT‐Polymerization of Butyl Acrylate

Electron paramagnetic resonance (EPR) spectroscopy is used for measuring rate coefficients of addition, k_ad, and fragmentation, k_β, together with the associated equilibrium constants, K_eq, for butyl acrylate polymerizations mediated by S‐ethyl propan‐2‐ylonate‐S’‐propyl trithiocarbonate (EPPT) and by S‐S’‐bis(methyl‐2‐propionate) trithiocarbonate (BMPT). Experiments at ?40 °C yield k_ad = (3.4 ± 0.3) × 10⁶ L mol^?1 s^?1, k_β = (1.4 ± 0.4) × 10² s^?1, and K_eq = (2.6 ± 0.8) × 10⁴ L mol^?1 for EPPT and k_ad = (4.1 ± 0.9) × 10⁶ L mol^?1 s^?1, k_β = (4.5 ± 0.5) × 10¹ s^?1, and K_eq = (8 ± 4) × 10⁴ L mol^?1 for BMPT. The K_eq values are in satisfactory agreement with data from ab initio calculations.

     

A Novel Approach for Investigation of Chain Transfer Events by Pulsed Laser Polymerization

Pulsed laser polymerization (PLP) with subsequent analysis of molecular mass distribution (MMD) is used to determine the rate coefficient of chain transfer to an agent A, k_trA, by varying pulse repetition rate such that the contributions of PLP‐induced and chain‐transfer‐induced peaks to the MMD change to a significant extent. It is shown by simulation that the relative heights of these peaks may be used to estimate k_trA. The method is applied to evaluation of the rate coefficient of chain transfer to dodecyl mercaptan with butyl methacrylate polymerizations at ?11, 0, 20 and 40 °C. The Arrhenius parameters for this coefficient are determined to be: A(k_trA) = (2.2 ± 0.6) × 10⁶ L · mol^?1 · s^?1 and E_a(k_trA) = (22.1 ± 0.7) kJ · mol^?1.

     

Einfluß des temperns auf die negative thermische ausdehnung von polyethylen

The linear thermal coefficient of expansion for high density polyethylene, extended to draw ratios λ = 8 to 16 is α = ?24·10^?6 K^?1 at 20°C. This value results from the orientation of crystallites with an expansion coefficient α_c = ?12·10^?6 K^?1 and from stresses in the amorphous phase. Using the model of series coupling of crystalline and amorphous parts the value α_am ≤ ?50·10^?6 K^?1 is calculated for a crystallinity x_v = 70%. From measurements of Young's modulus the fraction of tie-molecules χ_tie = 0,4% of the sample is assessed and the expansion coefficient α_tie = ?90·10^?6 K^?1. Annealing of the samples leads to shrinkage while the density ρ increases slightly and the expansion coefficient α increases considerably. Samples annealed at temperatures closely below the melting point show a slight decrease of the density at 20°C but a value of α exceeding that of isotropic samples. This effect can be explained by preferred orientation of the crystal a-axis in fibre direction as soon as orientation starts to break down.