Radiation induced terpolymerization of tetrafluoroethylene with propylene and n-butyl vinyl ether in bulk

Terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and n-butyl vinyl ether (NBVE) induced by γ-rays at room temperature at dose rate 5 × 10⁵ rad/h and P/NBVE molar ratio from 49/1 to 10/40 was carried out. An alternating copolymerization between TFE and two α-olefins was found to take place in this system, so that 50 mole % of TFE containing terpolymer is always formed at various monomer compositions. The terpolymer composition can be explained successfully by the treatment by a complex mechanism. The complex reactivity ratios of r_I (TFE–complex) and r_II (TFE-NBVE complex) were calculated to be 0.5 and 0.6, respectively, assuming a complex mechanism. The polymerization rate and molecular weight increase with NBVE concentration in the monomer mixture. Colorless transparent rubber-like polymers were obtained at each monomer composition. The glass transition temperature sharply decreases with NBVE concentration in the terpolymer but the thermal and chemical resistances of the terpolymer slightly decrease. Considering these results together with the mechanical properties it has been concluded that the 45/48/7 terpolymer of TFE/P/NBVE molar ratio is good as a practical elastomer useful at relatively low temperatures.     

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group—part 8—study of the tetrafluoroethylene-propylene rubber modification by 4,5,5-trifluoro-4-penten-1-ol as a comonomer

The radical terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and 4,5,5-trifluoro-4-penten-1-ol (FA3) for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. The polymerization was carried out in emulsion and in a batch operation, initiated by a redox system containing tert-butylperoxybenzoate. The reaction proceeded without any induction period and in a stationary state at low conversion (up to 12%). The presence of the trifluorovinyl hydroxy monomer in the ternary system sharply decreased the polymerization rate, in contrast to that of the TFE/P binary one. The order of the reaction about FA3 was 1.25. The terpolymer compositions were determined by elemental analysis by ¹H- and ¹⁹F-NMR spectroscopy. An almost equimolar ratio of TFE and P base units in the terpolymer was found, while the FA3 was inserted between TFE/P blocks. The presence of P increased the polymerization rate and lowered the chain transfer coming from FA3 when compared to the TFE/FA3 binary system. Thermal properties were assessed. The glass transition temperatures (T_g) slightly decreased with the FA3 content. The decomposition temperatures were also affected, showing two steps of decomposition related to the amount of FA3 in the copolymer, and is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3991–3999, 1999     

Study of synthesis and properties of tetrafluoroethylene–propylene copolymers

Bulk copolymerization of tetrafluoroethylene (TFE) with propylene (P) initiated by tert-butyl peroxybenzoate (TBPB) in the temperature interval 323–363 K, monomer pressure from 2 to 9 MPa, and TFE and P molar ratio from 20/80 to 90/10 was carried out. The effect of these reaction conditions on the yield, molecular weight, and polymer composition of the copolymer synthesized was studied. Rubber-like alternating copolymers in a wide range of monomer compositions of TFE and P (from 40 to 80 mol %) were obtained. The reaction proceeds in a stationary state without an induction period. Monomolecular chain transfer reaction (C_p = 5 × 10^?4) to propylene takes place. The relative reactivity ratio of P and TFE (0.15 and 0.01, respectively) and apparent activation energy E_α = 75.8 kJ/mol of the reaction were determined.     

Use of samarium (III) acetate as initiator in ring-opening polymerization of trimethylene carbonate

Abstract

In this work was evaluated the activity of samarium acetate (III) (Sm(OAc)₃) as a possible initiator in the polymerization by ring opening of trimethylene carbonate (TMC). All polymerizations were carried out under solvent-free melt conditions in ampoules-like flasks, equipped with a magnetic stirrer. The effects of different parameters of reaction, such as molar ratio monomer to initiator, temperature and reaction time, on typical variables of polymers, e.g., conversion of TMC to poly(trimethylene carbonate) (PTMC), dispersity and molar mass, were analyzed. The molar ratio of monomer to initiator was varied between 0 and 1000?mol/mol and the temperature among 70 and 150?°C. Nuclear Magnetic Resonance (¹H-NMR and HMBC) and Size Exclusion Chromatography (SEC) were used to characterize the polymers. The results indicate that the Sm(OAc)₃ induces the polymerization of TMC to high conversion with number-average molecular weights of 3.11?×?10³ to 38.40?×?10³?Da. Based on the ¹H-NMR end-group analysis of low-molecular-weight PTMC, it was proposed a coordination–insertion mechanism for the polymerization, with a breakdown of the acyl-oxygen bond of the TMC. In according to the kinetic study carried out, the polymerization rate is first-order with respect to monomer concentration with apparent rate constants of k_ap?=?7.02?×?10^?4?mol?×?L^?1?×?h^?1.     

Unsymmetrical N-Heterocyclic Carbene: 1-Isopropyl-3-benzylimidazol-2-ylidene as Catalyst for Ring-Opening Polymerization of ϵ-Caprolactone

An unsymmetrical N-heterocyclic carbene, namely 1-isopropyl-3-benzylimidazol-2-ylidene, is a highly active catalyst for ring-opening polymerization of ?-caprolactone (CL) to give polycaprolactone (PCL) with number average molecular weight (Mn) as high as 2.66 × 10⁴ at 0°C in 100 min in tetrahydrofuran (THF). The effects of monomer/initiator molar ratio ([M]/[I]), catalyst/initiator molar ratio ([C]/[I]), monomer concentration, as well as polymerization temperature and time have been investigated. The kinetic studies of CL polymerization have indicated that the polymerization rate is first-order with respect to both monomer and catalyst concentrations. The apparent activation energy amounts to 56.04 kJ/mol. The proposed mechanism is a monomer-activated process.     

The thermal polymerization of styrene in diethyladipate at temperatures up to 160°

The thermal polymerization of styrene in diethyladipate has been studied dilatometrically at temperatures from 90 to 160°. The rate was found to be directly proportional to (monomer concentration)² and the molecular weight of the polymer formed was controlled mainly by chain transfer to monomer, particularly at the higher temperatures. A value of 86 ± 2 kJ/mol was obtained for the overall energy of activation for the polymerization, and values of 7.16 × 10^?5. 2.0 × 10^?4 and 5.5 × 10^?4 were found for the transfer constant for diethyladipate at 120. 140 and 160° respectively.     

Radiation-induced copolymerization of vinylene carbonate with methyl trifluoroacrylate

Copolymerization of vinylene carbonate (VCA) with methyl trifluoroacrylate (MTFA) was carried out by gamma rays from ⁶⁰Co at dose rates of 1 × 10⁵ rad/h to 1 × 10⁶ rad/h, temperatures of 0°C to 75°C, and molar ratios MTFA/VCA of 30/70 to 90/10 in the monomer mixture. By irradiation, VCA reacted with MTFA to give a white powder copolymer with low molecular weight. The copolymerization rate has a maximum at a concentration of 70 mol % VCA, and is proportional to the 0.92 power of dose rate. The apparent activation energy was 1.3 kcal/mol. Equimolar copolymer was obtained at molar ratio MTFA/VCA of 50/50 to 10/90. The reactivity ratios of both monomers, VCA and MTFA, were determined to be r(VCA) = 0.3 and r(MTFA) = 0.07, respectively.     

Ferric oxide-catalyzed polymerization of methyl methacrylate

The polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10^?5 mole/l.-sec to 11.8 × 10^?5 mole/l.-sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 10⁶ in the absence of ferric oxide to 2.8 × 10⁵ when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 10⁵ at 30°C to 2.2 × 10⁵ at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 10⁴ to 5.3 × 10⁵ and from 3.4 × 10⁵ to 8.9 × 10⁵ as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferric oxide, respectively.     

Radiation-induced terpolymerization of methyl α,β,β-trifluoroacrylate with tetrafluoroethylene and α-olefin

Radiation-induced terpolymerizations of methyl α,β,β-trifluoroacrylate (MTFA) with tetrafluoroethylene (TFE) and α-olefins, such as ethylene, propylene, and isobutylene, were carried out in bulk at 25°C for the purpose of controlling the content of ester group in the MTFA-α-olefin alternating copolymers. These monomers polymerized to form alternating terpolymers which contained 50 mole % α-olefin in a wide range of monomer composition. The content of MTFA, namely, the ester group in polymer, can be varied without destruction of the alternating structures between fluoroolefins (MTFA, TFE) and α-olefin by changing the MTFA/TFE ratio in the monomer mixture. The relative reactivities of MTFA and TFE in the terpolymerization were discussed according to kinetic treatments by free propagating and complex mechanisms. The relation between the MTFA/TFE ratio in the monomer mixture and that in terpolymer was explained favourbly by the complex mechanism. It was also concluded that the relative reactivity of MTFA is larger than that of TFE in the terpolymerizations.     

Radiation-induced copolymerization of methyl trifluoroacrylate with ethylene

Copolymerization of methyl trifluoroacrylate (MTFA) with ethylene in bulk was induced by γ irradiation. The copolymerization was observed to proceed in the liquid monomer mixture of MTFA and ethylene at 25°C with the dose rates ranging from 5.0 × 10⁴ to 1.0 × 10⁶ rad/hr. A wide range of the initial monomer composition gives an almost equimolar and alternating copolymer. The highest polymerization rate was observed at the equimolar monomer composition. The dose rate exponent of the polymerization rate is unity. The reactivity ratios of r₁ (MTFA) and r₂ (ethylene) were determined to be 0.034 and 0.14, respectively.     

Effect of dose rate on radiation-induced polymerization of styrene adsorbed on silica gel

The effect of dose rate on the rate of polymerization and molecular weight distribution of radiation-induced polymerization of styrene adsorbed on silica gel was studied in a wide dose rate range of 4.4 × 10⁴ to 3 × 10⁸ rad/hr by γ rays of ⁶⁰Co and electron beams with a Cockcroft-Walton-type accelerator. Dose rate dependence on the initial rate of polymerization was about 1 below 3 × 10⁷ rad/hr, and it decreased gradually at high dose rates. Throughout the dose rate range, graft polymerizations and homopolymerizations by cationic and radical mechanisms proceeded simultaneously. Dose rate dependence of the cationic polymerization was 1 below 3 × 10⁷ rad/hr, while dose rate dependence of the radical polymerization was 0.65 below 3 × 10⁷ rad/hr. At high dose rates, molecular weight and fraction of graft polymer decreased, and fraction of cationic polymerization increased. A very high-molecular-weight graft polymer was formed above 4.4 × 10⁵ rad/hr at the initial stage of the polymerization. The dose rate dependence of this polymerization was larger than 1 and decreased with increase in dose rate. The polymerization seems to be related to an excitation of monomer or growing chain.     

稀土配位催化马来酸酐-苯乙烯-N-苯基马来酰亚胺三元共聚合

采用稀土配位催化剂研究了马来酸酐、苯乙烯和N 苯基马来酰亚胺的三元共聚合反应 .考察了Al La物质的量的比、不同稀土元素、催化剂浓度、聚合反应时间、单体配比等因素对共聚合反应的影响 .利用核磁、红外、热分析等方法对共聚物进行了初步的表征     

Epoxide polymerization—IV. Ethylene oxide polymerization using the diphenylzinc-water system in benzene at 60°

The diphenylzinc-water system was used as catalyst for ethylene oxide polymerization in benzene solution at 60°. The system is greatly influenced by the molar ratio of water to diphenylzinc. H₂O/Ph₂Zn, the maximum catalyst activity being found for a ratio of unity. Ph₂Zn alone and molar ratios of 0.25, 0.5, 1.5, 1.75 and 2.0 gave very low conversion to polymer. For a molar ratio of unity, the yield of polymer and the molecular weight increase with time. The reaction is first order with respect to monomer with k_P = 5.7 × 10^?5 sec^?1 mol^?1 l.     

单茂钛催化剂的丙烯无规聚合反应及其动力学研究

比较了不同钛化合物／甲基铝氧烷（ＭＡＯ）催化体系的丙烯无规聚合，催化活性次序为ＣｐＴｉ（ＯＲ）３＞ＣｐＴｉ（ＯＰｈ）３＞ＣｐＴｉＣｌ３＞Ｃｐ２ＴｉＣｌ２＞Ｔｉ（ＯＢｕ）４＞ＴｉＣｌ４＞Ｔｉ（ＯＢｕ）２Ｃｌ２，所得聚丙烯用沸庚烷抽提８ｈ，溶解９５％以上，可溶部分经１３Ｃ ＮＭＲ、ＷＡＤＸ、ＦＴＩＲ等分析证明为无规聚丙烯（ａＰＰ），是没有结晶性的弹性体．ＧＰＣ测出其分子量Ｍｗ＝８．０～１０．０×１０４，Ｍｗ／Ｍｎ≈２．０．探索了催化体系ＣｐＴｉ（Ｏ ｎ Ｐｒ）３／ＭＡＯ中钛的浓度、［Ａｌ］／［Ｔｉ］摩尔比，丙烯聚合压力，聚合温度和时间对丙烯聚合反应的影响．研究了该催化体系丙烯聚合反应动力学规律，表观聚合反应速率对催化剂浓度和单体压力（浓度）都呈一级反应关系，表观聚合速率常数ＫＰ＝２９２×１０５ｍｏｌ／Ｌ·ｈ（４０℃）．活化能ΔＥ＝－７．８８×１０３Ｊ·ｍｏｌ－１，碰撞因子Ａ＝１．４１×１０－４ｍｏｌ／Ｌ·ｈ．     

Kinetics of anionic polymerization of methylmetacrylate with caesium and sodium as counterions in tetrahydrofuran

The kinetics of the anionic polymerization of methylmethacrylate in tetrahydrofuran at ?75 are investigated. Cumylcaecium, α-methylstryrylcaesium and α-methylstyrylsodium were used as initiators. The results show that the polymerization proceeds practically without side reactions under these conditions; as for the anionic polymerization of styrene in polar solvents, ion pairs and anions contribute to the propagation. The rate constant of monomer addition to the ion pair has at ?75 values of 60 and 80 for polymethylmethacrylsodium and polymethylmethacrylcaesium, respectively, and for the anion about 5 × 10⁴ l mole^?1 sec^?1. The dissociation constant was measured as 3·5 × 10^?9 for polymethylmethacrylsodium and 2 × 10^?9 mole/l for the caesium compound at this temperature: the corresponding dissociation enthalpies are ?0·3 and ?1·3 kcal mole^?1. The relatively low activation energy for monomer addition to the ion pair of polymethylmethacrylsodium of 2·3 kcal mole^?1 suggests the existence of two types of ion pairs whereas the corresponding value for polymethylmethacrylcaesium of 4·5 kcal mole^?1 does not allow such an interpretation. The kinetic results are compared with those of the corresponding polystyrylcompounds: the differences are explained by the fact that, in the case of the polymethylmethacryl compound, the estergroup competes with the solvent for solvation of the cation.     

Radiation-induced polymerization at high dose rate. I. Isobutyl vinyl ether in bulk

Bulk polymerization of isobutyl vinyl ether was studied at 25°C in a wide dose rate range, 8.2-277 rad/sec by γ rays and 8.8 × 10³-2.2 × 10⁵ rad/sec by electron beams. At low dose rate, 8.2-277 rad/sec, only the radical polymerization took place. At high dose rate exceeding 8.8 × 10³ rad/sec, cationic polymerization was found to occur in addition to the radical polymerization. DP _n of the product at high dose rate was 9-10. Further drying of the monomer increased R_p, and molecular weight of the product formed by cationic mechanism also increased.     

Addition Polymerization of 5-Ethylidene-2-Norbornene in the Presence of Pd N-Heterocyclic Carbene Complexes

New high-performance catalytic systems based on Pd N-heterocyclic carbene complexes for the selective addition polymerization of 5-ethylidene-2-norbornene (ENB) were proposed. With these catalysts, polymerization can be conducted at unprecedentedly high monomer/catalyst ratio (up to 5 × 10⁵/1) and gives high-molecular-weight soluble polymers with good film-forming properties. Varying the polymerization conditions (reaction temperature, monomer and catalyst concentrations, monomer/Pd ratio) makes it possible to prepare soluble ENB-based addition polymers with specified molecular weights in reasonable yields.     

Free‐radical copolymerization of styrene and m‐isopropenyl‐α,α′‐dimethylbenzyl isocyanate studied by 1H NMR kinetic experiments

The free‐radical copolymerization of m‐isopropenyl‐α,α′‐dimethylbenzyl isocyanate (TMI) and styrene was studied with ¹H NMR kinetic experiments at 70 °C. Monomer conversion vs time data were used to determine the ratio k_p × k_t^?0.5 for various comonomer mixture compositions (where k_p is the propagation rate coefficient and k_t is the termination rate coefficient). The ratio k_p × k_t^?0.5 varied from 25.9 × 10^?3 L^0.5 mol^?0.5 s^?0.5 for pure styrene to 2.03 × 10^?3 L^0.5 mol^?0.5 s^?0.5 for 73 mol % TMI, indicating a significant decrease in the rate of polymerization with increasing TMI content in the reaction mixture. Traces of the individual monomer conversion versus time were used to map out the comonomer mixture composition drift up to overall monomer conversions of 35%. Within this conversion range, a slight but significant depletion of styrene in the monomer feed was observed. This depletion became more pronounced at higher levels of TMI in the initial comonomer mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1064–1074, 2002     

19F- and 1H-NMR spectra of tetrafluoroethylene–propylene copolymers

High resolution 94-MHz ¹⁹F- and 100-MHz ¹H-NMR spectra were measured on a series of tetrafluoroethylene (TFE)-propylene (P) copolymers having a range of composition (TFE/P molar ratio = 37/63–55/45) and polymerized at different temperatures (?23, 25 and 65°C). The spectra were analyzed in relation to copolymer compositions. The assignment of ¹⁹F resonance in terms of tetrads proposed previously was confirmed, and the tentative assignment of ¹H resonances was proposed in terms of triads. The spectra thus interpreted revealed the sequence distribution of the copolymers. Copolymer compositions calculated from NMR spectra and elemental analysis agreed rather well with each other. Monomer reactivity ratios were calculated from the sequence distributions and compared with those obtained from the elemental analysis. It was observed that highly alternating copolymers are obtained in this system over a wide range of monomer composition at lower temperatures and that a deviation from alternancy increases slightly with rising polymerization temperature.     

Emulsion copolymerization of tetrafluoroethylene and propylene with redox system containing tert-butylperbenzoate. II. Polymerization mechanism

Emulsion copolymerization of tetrafluoroethylene (TFE) and propylene (P) initiated by trilon-rongalite catalytic system containing tert-C₄H₉OH, initial monomer mixture, emulsifier (C₇F₁₅COONH₄) concentration, and monomer mixture/water ratio on the polymerization rate (R) and molecular weight (M?_n ) was investigated. Both R and M?_n increased considerably with TFE content in monomer mixture up to 75 mol %. Alternating rubber-like copolymers in a wide range of initial monomer mixture (from 55–85 mol %) were obtained. The reactivity ratio was found to be r_TFE = 0.005 ± 0.04 and r_p = 0.17 ± 0.07. Above the critical miscelle concentration, the effects of the initiating system Is and emulsifier Cs on R and M?_n were found to obey the following relations: according to which emulsion copolymerization proceeds by the I case of Smith-Ewart theory. Polymerization mechanism of the reaction studied was suggested. The copolymerization is mainly terminated by degradative chain transfer of the propagating radicals to propylene. © 1994 John Wiley & Sons, Inc.