Radiation-Induced Polymerization of Methyl Vinyl Ether

The radiation- induced polymerization of methyl vinyl ether under super-dry and wet conditions was studied. Little difference in the rates of polymerization was found. It seems clear that only an extremely slow free-radical polymerization was taking place. Possible reasons for the lack of concurrent cationic polymerization are discussed.     

Cationic Polymerization of Isobutyl Vinyl Ether in Solution by Radiation

The radiation-induced cationic polymerization of isobutyl vinyl ether in solutions of diethyl ether and methylene chloride was investigated under conditions where the monomer and solvents were dried with molecular sieves to high levels of dryness. The investigation covered the temperature range from -16 to 90° C, the dose-rate range from 10¹⁵ to 10²⁰ eV/ (g)(sec) (using both gamma rays and electrons), and the influence of diethyl ether and methylene chloride as solvents for the monomer.

For the solution of the monomer in diethyl ether, a very high overall activation energy of 29.7 kcal/mole was found, which decreased sharply to a value of 1.2 kcal/mole above 30° C. No such change was found for the monomer solution in methylene chloride.

The dose-rate dependence of the rate of polymerization for the monomer solution in methylene chloride was found to be close to unity over the entire dose-rate range investigated.     

Radiation-Induced Polymerization of Ethyl Vinyl Ether in n-Pentane and Neopentane

The radiation-induced polymerization of ethyl vinyl ether was studied in n-pentane and neopentane solutions under super-dry conditions. The free ion yields of these solvents are reported to be 0.16 and 1.0, respectively. The rate of polymerization in neopentane was about twice as fast as in n-pentane. The dose-rate dependence of the rate of polymerization was found to be nearly 0.50 in both solutions. It seems clear that the free solvent ions do, indeed contribute to the initiation. Regenerative chain transfer to monomer played a more important role in n-pentane than in neopentane as revealed by the molecular weight of the polymers.     

乙烯基单体正离子聚合中链增长速率常数的研究进展

碳正离子聚合中,聚合速率常数的测定方法通常包括电导法、绝热量热法、胺抑制法、止流光谱法及扩散计时法。在烷基乙烯基醚、苯乙烯及其衍生物和异丁烯等几种常见乙烯基单体的正离子聚合中,本文介绍不同测定方法得到的不同结构碳正离子(包括自由离子和离子对)的链增长速率常数(kp 和kp±)。     

Photo-induced Living Cationic Copolymerization of Isobutyl Vinyl Ether and Vinyl Ether with Carbazolyl Groups

In this work, a fluorescent monomer 2-（9-carbazolyl） ethyl vinyl ether（CEVE） was synthesized in our lab, and its photo-induced living cationic copolymerization behavior with isobutyl vinyl ether（IBVE） was investigated in detail using diphenyliodonium chloride（DPICl）/2,2-dimethoxy-2-phenylacetophenone（DMPA） and zinc bromide（Zn Br2） initiating system in dichloromethane solution at 5 °C, -5 °C, and -15 °C, respectively. The living nature of this copolymerization system was confirmed by adding fresh comonomer method after the copolymerization almost finished. In addition, the obtained fluorescent copolymer poly（IBVE-co-CEVE） has a low glass transition temperature（Tg）, below -10 °C.     

Radiation-Induced Ionic Grafting of Ethyl Vinyl Ether to Polypropylene Film

The radiation-induced grafting of ethyl vinyl ether to polypropylene film in bulk has been investigated under super-dry conditions. The per cent grafting increased linearly with increasing dose without an induction period. The grafting did not take place in the presence of traces of water, indicating that the grafting proceeds by an ionic mechanism. The dose-rate dependence of the rate of grafting was found to be 0.25. The grafting was also examined in n-pentane and neopentane solutions. Although the per cent grafting in the solution system was lower than that in the bulk system, n-pentane was found to increase the grafting efficiency.     

Radiation-Induced Grafting of Ethyl Vinyl Ether onto Polyvinyl Chloride)

The radiation-induced graft polymerization of ethyl vinyl ether (EVE) onto polyvinyl chloride) (PVC) was studied under a variety of conditions. Graft copolymer and homopoly(EVE) were formed in all cases. The presence of water reduced overall polymerization rates, percentage grafting, and homopoly(EVE) molecular weights. With “superdry” EVE, grafting reached 29% at a total dose of 6.9 Mrad. Grafting to PVC films was less efficient than grafting to PVC powder. Application of a relatively poor swelling agent for PVC resulted in an increase in the efficiency of grafting. From a comparison of studies of radiation-induced EVE homopolymerization and the present work, it was concluded that dry and superdry EVE are grafted to PVC by a cationic mechanism and wet EVE is grafted mainly by a free-radical mechanism.     

Absolute Rate Constants in Free-Radical Polymerization. III. Determination of Propagation and Termination Rate Constants for Styrene and Methyl Methacrylate

A spatially intermittent polymerization (SIP) reactor has been used for determination of absolute rate constants in photo-initiated, free-radical polymerization of styrene (STY) and methyl methacrylate (MMA). Experimental data are reported in the temperature range 15-30°C and in the high molecular weight region for MMA and STY. Additional experimental data are reported at 30° C and various lower molecular weights for STY which indicate that the propagation rate constant K is independent of polymer molecular weight, and K is dependent on molecular weight, especially at low molecular weight, approaching an approximately constant value at high molecular weight.     

Quasiliving Carbocationic Polymerization. VIII. Quasiliving Polymerization of Methyl Vinyl Ether and Its Blocking from Quasiliving Poly(isobutyl Vinyl Ether) Dication

Quasiliving carbocationic polymerization of methyl vinyl ether (MVE) was achieved with the p-dicumyl chloride (p-DCC)/AgSbF₆ initiator system by the slow and continuous monomer-addition (quasiliving) technique. A polar solvent (CH₂Cl₂) and a low reaction temperature (-70°C) were optimum for the quasiliving MVE polymerization. Under these conditions, the number-average molecular weight (M _n) of poly(MVE) increased linearly with the cumulative weight of added monomer (W_MVE), and linear M _n versus W_MVE plots passed through the origin. M _n's were inversely proportional to the initial initiator (p-DCC) concentration. Reactions in a nonpolar solvent (toluene) at -70°C or in a polar solvent (CH₂Cl₂) at ?30°C resulted in deviations from these quasiliving characteristics. Block polymerization of MVE from quasiliving poly(isobutyl vinyl ether) dications by the quasiliving technique (p-DCC/AgSbF₆ initiator, CH₂Cl₂ solvent,(-70°C) led to novel isobutyl vinyl ether (IBVE)-MVE block polymers in high yield (>93 wt%) and at high blocking efficiency. The block polymers, most likely poly(MVE-b-IBVE-b-MVE), having M _n = 10,900–14,000 [M _n(center block) = 6,200–9,0001, were soluble in n-heptane and insoluble in water, and gave hazy homogeneous solutions when dissolved in methanol at room temperature.     

Radiation-Induced Heterophase Polymerization of Vinyl Chloride: Influence of Additives on the Particle Morphology

Investigations were carried out on the particle morphology of polyvinyl chloride) obtained in quiescent conditions in the early stages of radiation-induced bulk polymerization at 50°C and 70°C of vinyl chloride with methanol added in small     

Kinetics of Living Polymerization with Propagation Rate Constants Depending on Degree of Polymerization

A study is presented on the kinetics of living polymerization in which the propagation rate constants decrease to zero at a certain degree of polymerization of the propagating chain. The general solution for the distribution function and the rate of polymerization is given and two special cases are discussed. When all the propagation rate constants are the same up to a critical degree of polymerization and null beyond it, the polymerization proceeds approximately as a normal living polymerization until the number-average degree of polymerization reach 85 to 90% of the critical value. When the propagation rate constants decrease linearly with the degree of polymerization, the distribution of living polymer is narrower than the usual Poisson distribution and the reaction order of the rate of polymerization with respect to monomer concentration is between first and second and is affected by the initial monomer and catalyst concentrations.     

Radiation-Induced Solid-State Polymerization in Binary Systems. VI. Polymerization of Vinyl Compounds in the Supercooled Liquid Phase

Abstract

The radiation-induced polymerization of glass-forming systems containing vinyl monomers was investigated. Irradiation below the secondorder transition temperature (T_g) of the systems causes no in-source polymerization but does cause a very rapid postpolymerization in the course of heating above T_g. Differential thermal analysis was carried out to estimate T_g and to follow the postpolymerization.     

Radiation-Induced Polymerization of Tetrafluoroethylene

Polymerization of tetrafluoroethylene was carried out in bulk at low temperatures by initiation with γ-rays from a ⁶⁰ Co source. It was found that a remarkable postpolymerization takes place even in the liquid phase. Kinetical analysis has been made of the in-source and postpolymerizations. An activation energy of 2.7 kcal/mole was obtained for the in-source polymerization and 10.3 kcal/mole for the postpolymerization. The long lifetime of polymer radicals in the liquid phase at -78°C seems to be due to the slow recombination rate of the polymer radicals, based on the rodlike shape of the polymer radicals.     

Solvent Effects on the Rate of Radiation-Induced Grafting of Vinyl Monomers on Polymeric Films

Earlier work indicated that in the radiation-induced grafting of vinyl monomers on polymeric films, the plasticity of the film being grafted is determined by the Hildebrand solubility parameter of the grafting solution. Film plasticity affects the termination step of the grafting reaction, and thus strongly influences the overall rate of monomer grafting on the polymeric film.

In the grafting of styrene on nylon film, a sequence of irradiation runs was made at selected volume ratios of styrene/benzene/methanol, all grafting solutions having a constant solubility parameter value of 9.5 Under these conditions, a linear plot of grafting rate vs volume percent styrene in the grafting solution was obtained. A similar sequence of runs grafting pentafluorostyrene on nylon film at constant solubility parameter also produced a linear plot of grafting rate vs volume percent PFS.

Styrene was grafted on polyethylene film in a sequence of four runs using styrene dissolved in methanol, ethanol, 1-propanol, and 1-butanol, each solution having the same solubility parameter of 10.4. A straight-line plot of grafting rate vs volume percent styrene was obtained under these conditions.     

Crown Ether As The Phase-Transfer Catalyst for Free Radical Polymerization of Hydrophobic Vinyl Monomers

Various crown ethers were used as phase-transfer catalysts for free radical polymerizations of some water-insoluble vinyl monomers such as acrylonitrile, methylmethacrylate and styrene with persulfate as initiator. The catalytic abilities of these crown ethers for free radical polymerization of acrylonitrile with S₂O₈^2?ion as an initiator were in the order: 18-crown-6 > 15-crown-4 > 12-crown-4 > benzo-15-crown-5 > dibenzo-18-crown-6. Among various persulfates such as Na₂S₂O₈ K₂S₂O₈ and (NH₄)₂S₂O₈, ammonium persulfate was the optimum initiator for the polymerization of acrylonitrile catalyzed by 18-crown-6 or 15-crown-5. Among the organic solvents used, chloroform seems to be the best solvent for the catalytic polymerization of acrylonitrile. An apparent activation energy of 72.9 kJ mol^?1 was observed for the polymerization of acrylonitrile. The catalytic reaction rates of free radical polymerization for these hydrophobic vinyl monomers were in the order: acrylonitrile > methylmethacrylate > styrene > isoprene. Effects of concentrations of crown ether, initiator, and nitrogen on the polymerization of these vinyl monomers were investigated.     

Radiation-Induced Polymerization of Styrene Oxide

Radiation-induced polymerization of styrene oxide in the liquid and solid states was carried out by initiating with γ-rays from ⁶⁰Co and electrons from a Van de Graaff accelerator.

Effects of dose rate, a radical inhibitor, and temperature on the polymerization were examined. Infrared spectra and viscosities of polymers obtained were measured.

From these experiments, the following results were obtained:

1. Apparent activation energies are 6.2 kcal/mole for the liquid-state polymerization and 0.17 kcal/mole for the solid-state polymerization, respectively.

2. The polymerization in liquid state is inhibited and retarded by p-ben-zoquinone.

3. The rate of polymerization is approximately proportional to the dose rate.

4. The viscosity of polymers obtained increases with irradiation dose.

5. Infrared spectrum of polymers obtained varies with the polymerization temperature.

It is emphasized in this paper that the chain-transfer and isomerization reactions are rapid and play an important role in the polymerization of styrene oxide, and that the polymer-forming process is not so rapid, owing to a step-by-step type of growing.     

Quasi “Tacticity” of Rigidly Alternating Copolymers of Isobutyl Vinyl Ether and Maleic Anhydride

Since the copolymers of maleic anhydride, a cyclic monomer, and vinyl ethers, such as isobutyl vinyl ether, are made of rigidly alternating monomer unit sequences, quasi "isotactic" and quasi "syndiotactic" configurations for the monomer unit diads and triads are proposed considering the relative orientation of the cyclic anhydride group and the ether side chain with respect to the copolymer backbone.     

Kinetic Models for Bulk Polymerization of Vinyl Chloride and Their Rate Expressions

The various models and their rate expressions developed for the bulk polymerization of vinyl chloride are checked against carefully evaluated experimental data. Only Ugelstad's and Olaj's models yield rate expressions consistent with experiment.     

Predicting Absolute Rate Constants for Huisgen Reactions of Unsaturated Iminium Ions with Diazoalkanes

The kinetics and stereochemistry of the reactions of iminium ions derived from cinnamaldehydes and MacMillan's imidazolidinones with diphenyldiazomethane and aryldiazomethanes were investigated experimentally and with DFT calculations. The reactions of diphenyldiazomethane with iminium ions derived from MacMillan's second‐generation catalysts gave 3‐aryl‐2,2‐diphenylcyclopropanecarbaldehydes with yields >90 % and enantiomeric ratios of ≥90:10. Predominantly 2:1 products were obtained from the corresponding reactions with monoaryldiazomethanes. The measured rate constants are in good agreement with the rate constants derived from the one‐center nucleophilicity parameters N and s_N of diazomethanes and the one‐center electrophilicity parameters E of iminium ions as well as with quantum chemically calculated activation energies.     

Estimation of Rate Constants of Bimolecular Decomposition of Redox Initiators in Radical Polymerization

A rigorous statistical method is established to compute the rate constants of the bimolecular decomposition of redox catalysts used to initiate polymer chains. Results obtained for the systems styrene-dimethylaniline-benzoyl peroxide and acrylamide-thio-glycollic acid-potassium bromate compare favorably with those reported by other workers. The merits of this error-in-variable technique, which outperforms conventional nonlinear least-square analysis and the dead-end polymerization method, are discussed.