Radiation-Induced Polymerization of Tetrafluoroethylene in Solution

Polymerization of tetrafluoroethylene in monochlorodifluoromethane was carried out at low temperatures with -prays from a ⁶⁰Co source. An activation energy of 4.3 kcal/mole was obtained for the in-source polymerization, and this is higher than that of bulk polymerization, 2.7 kcal/mole. It was found that a remarkable postpolymerization takes place even if the reaction system is in liquid state. A kinetic treatment for the postpolymerization is described.     

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.     

Radiation-Induced Copolymerization of Tetrafluoroethylene and Propylene. 2. Copolymerization in Solution

Copolymerization of tetrafluoroethylene and propylene in chlorofluorohydrocarbon solvents was carried out below room temperature with γ-rays from a ⁶⁰Co source. A remarkable rate-accerelating effect was observed in these solution systems, although the activation energies and the compositions of copolymers were almost the same as those in bulk system. The most effective solvent was found to be trichlorotrifluoroethane. Kinetic results of the copolymerization in trichlorotrifluoroethane solution system revealed the role of solvent to be complicated, with the possibility of affecting almost all reaction steps of the polymerization.     

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.     

Radiation-Induced Solid-state Polymerization in Some Methacrylates

This paper presents a comparison of some of our results on the polymerization of methacrylic acid, octadecyl methacrylate, zinc methacrylate, and barium methacrylate monohydrate in the solid state. Polymerization was initiated by cobalt-60 γ rays, both in-source and post-irradiation polymerization techniques being used. Electron spin resonance studies showed that the polymerization proceeded by a free radical mechanism in all cases. The initial radicals formed by irradiation at low temperatures added a first monomer unit about 100° below the temperature of long-chain polymerization. Some radical decay occurred in the early stages of polymerization. The rate of polymerization increased rapidly, approaching the melting point or other phase change in the monomer.     

辐照法制备交联聚丙烯酰胺涂层毛细管电泳柱及评价

采用辐照法制备交联聚丙烯酰胺毛细管电泳涂层柱。毛细管先经双功能团试剂γ－甲基丙烯基氧丙基三甲基硅烷预处理，然后柱内充入丙烯酰胺溶液进行辐照聚合，得到线性涂层柱；再经动态涂覆交联剂甲叉双丙烯酰胺，二次辐照交联，采用随机试验设计方法，对辐照剂量率，辐照时间和交联剂浓度几个因素进行了优化。     

Graft Polymerization of a Polymer Matrix: Grafting of Tetrafluoroethylene

Graft polymerization of tetrafluoroethylene on polyethylene preirradiated by γ-rays from a cobalt-60 source at ?196°C has been investigated in the region of PE devitrification. A calorimetric technique made it possible to establish that 1.5-2% of monomer dissolves in the amorphous regions of PE at low temperatures. Efficient grafting proceeds in the temperature range directly adjoining the PE devitrification region. The graft copolymer yield amounts to ca. 1200%. The intensification of grafting is apparently caused by the following: (1) because of previous solution of TFE in the PE amorphous regions and filling of the micropores, the reaction in the initial stage is not limited by diffusion; (2) and the initiation efficiency is increased by slow passage through the PE devitrification region. The breaking strength of the graft copolymer is higher than that for the PE copolymer irradiated by the same dose.     

Radiation-Induced Polymerization of Urea Canal Complex. Part 4. Radiation-Induced Polymerization of Acrylonitrile in Urea-Ethylene Glycol Supercooled Liquid System

Abstract

Using elementary analysis, NMR on ^{3 1}P and ¹H nuclei, and electroconductivity methods, the acrylonitrile, methacrylonitrile, formaldehyde, and β-propiolactone anionic polymerization in the presence of triethylphosphine is shown to follow the macrozwitterion mechanism: quartary phosphonium being on one end of a polymer chain and the growing anion on the other. The number of covalent bonds through the whole polymer chain between charges forming the active center increases with the propagation reaction. The active centers stationary concentration in the system is low when connected with both the slow initiation reaction and with the fast active centers termination reaction. Thus the ion interaction of different growing polymer chains can be ignored. The active centers parts occurring in the form of ion pairs (the ends are near and form the “cyclic”) and of free ions (the ends are separated) are determined by the monomolecular equilibrium, and its constant depends upon the macro-zwitterion polymerization degree K_d ⁽ⁿ⁾ = K_d ^(I)n^3/2. Such constant depends upon the chain length affords the macrozwitterion self-accelerated propagation with its length, as the free ion reactivity is more than that of ion pairs. The self-accelerated chain propagation effect shows up as an increase of polymerization initial rate order and polymer molecular weight in the monomer concentration. This effect can be avoided by the introduction of electrolyte into the system, which dissociates into ions and transforms all cyclic ion pairs into the linear form, the latter dissociating independently of chain length. The strict mathematical analysis of stationary and nonstationary polymerization kinetics made it possible to determine all the elementary constants separately: K_i = 5.6 × 10^?4 liters/ (mole) (min); K_- = 2.5 × 10⁴ liter/ (mole) (min); K_± = 2.0 liters/ (mole) (min); K_t = 0.84/min; K_t ¹ = 4/min; K_d ^(I) = 10^?4; K₃ = 0.07 × 10^?4 mole/liter.     

Radiation-Induced Polymerization of Methyl Methacrylate at High Pressure

Radiation-induced polymerization of methyl methacrylate (MMA) was studied up to 7500 kg/cm² at 20°C. The rate of polymerization increased to 3000 kg/cm² with overall activation volume ΔV_pol? of -23.6 cm³/mole, and then the pressure dependence of the rate was very small in the pressure range between 3000 and 3700 kg/cm². The rate of polymerization increased again above 3700 kg/cm² up to the crystallization pressure of MMA (5500 kg/cm²) with ΔV_pol? of -13.7 cm³/ mole with increasing pressure. The volume contraction by polymerization decreased with increasing pressure up to 3000 kg/cm² but hardly decreased with increasing pressure above 3000 kg/cm². The stereoregulzarity (triad probability) of PMMA changed slightly at 3000 kg/cm; above 3000 kg/cm², syndiotactic addition decreased and heterotactic addition increased. Marked change in P-V isotherms of MMA, however, was not observed about 3000 kg/cm². We concluded from these facts that an alignment of monomer molecules, which does not cause large volume change, was realized about 3000 kg/cm². Polymerization proceeded above the crystallization pressure by long time irradiation, and isotactic addition increased clearly in the solid-state polymerization.     

Radiation-Induced Polymerization of Urea Canal Complex. Part 3. Radiation-Induced Polymerization of Acrylonitrile-Urea Canal Complex in the Frozen State

Radiation-induced polymerization of acrylonitrile-urea canal complexes formed in frozen ethylene glycol or tert-butyl alcohol media was investigated. Formation of canal complexes in the frozen state was prolonged. The initial rate of polymerization was enhanced in the frozen state. The degree of polymerization of polymers obtained is found to show no depression at high conversions and is higher in the frozen state, suggesting stabilization of canal complexes by the frozen medium.     

The Radiation-Induced Polymerization and Copolymerization of Butadiene in Emulsion

Abstract

The polymerization of butadiene in emulsion initiated by ^{6 0}Co gamma radiation has been studied in some detail. Similar studies with styrene and styrene-butadiene comonomer mixtures were also conducted. The rates of polymerization were found to be much lower than anticipated from the reported k_p values for butadiene and for the comonomer mixtures. Styrene, on the other hand, polymerizes at normal rates. A number of possible explanations for this behavior is discussed.     

Radiation-Induced Solid-State Polymerization of Allylthiourea and Crystal Structure Effects

Allylthiourea crystals grown from water and from ethanol have been found to belong to the space groupP2_1/c and P2_1/m or related, respectively. The corresponding unit cell parameters are a = 13.45 Å, b = 17.33 Å,c = 14.38 Å, β = 96.6°, and d = 1.18g/cm³ for water-grown crystals, and a = 14.65 Å, b = 17.18 Å, c = 13.15 Å, β = 95.5°, and 1.17 g/cm³ for ethanol-grown crystals.     

Kinetic Studies on the Radiation-Induced Solution Polymerization of Tetrafiuoroethyiene

Abstract

Kinetic studies on the radiation-induced polymerization and postpolymerization of tetrafiuoroethyiene were carried out using chlorofluorohydrocarbons as the solvents. The mechanism of the radiochemical formation of radicals and the kinetics of the radical decay during in-source and postpolymerization are discussed. The remarkable post-polymerization is explained by the unusually slow rate of the bimolecular chain termination. The mechanism of chain transfer reactions is also discussed.     

Radiation-Induced Graft Polymerization of Glycidyl Methacrylate onto Nonwoven Polypropylene

The influence of the major grafting parameters (irradiation dose, reaction time, and inhibitor concentration) on graft polymerization of glycidyl methacrylate from its 10% solution in methanol onto nonwoven polypropylene upon irradiation with an electron accelerator in air was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 827–830.Original Russian Text Copyright © 2005 by Bondar’, Hong Je Kim, Yong Jin Lim.     

Absolute Rate Constants of Radiation-Induced Polymerization of Isobutyl Vinyl Ether

A basic limitation in the processing of thermoplastics lies in the high viscosity of their melts. Since high viscosity is largely a consequence of high average molecular weight, this problem would be solved if a polymer could be provided in the form of polymer blocks which are essentially independent at elevated temperatures and which bond together reversibly at ambient temperatures. The theoretical possibility of achieving such a system is considered from the point of view of thermodynamic arguments as applied to an idealized system of monodisperse polymer blocks linearly connected by weak chemical bonds. Average molecular weights are expressed in terms of a molar Gibbs function contribution associated with a weak bond in the polymer. Assuming a requirement for substantial decomposition at 500°K, arguments are presented for an entropy contribution of ca. 200 J °K^?1 mole^?1 for such bonds, and on this basis an optimum weak bond energy of 60 ± 20 kJ mole^?1 is indicated. Possible block terminations giving energies of this magnitude are considered.     

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.     

Radiation-Induced Polymerization and Pressure-Volume Behavior of Acrylonitrile at High Pressure

Radiation-induced polymerization and pressure-volume (P-V) measurements of acrylonitrile (AN) were studied up to 8000 kg/cm² in the temperature range of 6–72°C. P-V isotherms of AN have several small breaks, A phase diagram of AN was obtained from the breaking pressures and temperatures. Liquid phases were named L_I, L_II, and L_III, from low to high pressure. The polymerization behavior and volume contraction on polymerization changed in L_I, L_II, and L_III. The difference in entropy between original and activated states decreased with increasing pressure at the same phase, but increased with phase change in L_I to L_II and L_II to L_III. It was concluded from these results and from IR data on PAN that molecular packing of AN in liquid changed in L_I, L_II, and L_III. In L_II and L_III, AN molecules aligned in a less suitable geometry for polymerization than in L_I.     

Mechanism of Immobilization of Enzymes by Radiation-Induced Polymerization of Glass-Forming Monomers

Immobilization of enzymes by radiation-induced polymerization has been studied at low temperatures by use of various hydrophilic and hydrophobic glass-forming monomers such as hydroxy-alkyl methacrylate and poly(ethylene glycol diacrylate). Activity yield of the immobilized enzyme depends on the monomer concentration in polymerization. In the immobilized enzymes with strongly hydrophobic matrices, the activity shows a maximum at an optimum monomer concentrations in a certain stage of repeated usage for the enzyme reaction. The decrease of activity with repeated use is very little in strongly hydrophobic systems, particularly in diethylene glycol diacrylate polymer matrices. The hydrophobic polymer-enzyme composite has the microsphere form. In the present method, a model scheme for immobilization mechanism is proposed, which is compared with that formed in the polymerization of a nonglass-forming monomer system and also by the solution polymerization at higher temperatures.     

Gamma Radiation-Induced Template Polymerization of Acrylic Acid in the Presence of Polyactrylamide

Abstract

Poly(acrylamide-acrylic acid) resin p(AM-AA) was prepared by gamma radiation-induced polymerization of acrylic acid in the presence of polyacrylamide as a template polymer. The polymerization was studied by a free radical mechanism at different experimental conditions such as: absorbed dose, monomer concentration, polymer/monomer molar ratio and the weight-average molecular weight or the swelling degree of added polymer. The resin was obtained at dose > 10 KGy and there is no significant change in the swelling degree of the resin. The results showed that the capacity of the resin increases by increasing the monomer concentration, the weight-average molecular weight of the added polymer and decreases by increasing polymer/monomer molar ratio and the swelling degree of the added polymer. It was also found that the capacity of the resin depends on the radiation dose.     

Radiation-Induced Polymerization of Vinylidene Chloride in Bulk and Included in Thiourea Crystals

Vinylidene chloride (VDC) or 1,1-dichloroethylene was polymerized with γ radiation in bulk or as inclusion complex in thiourea crystals (inclusion polymerization). The resulting poly(vinylidenechloride) (PVDC) samples obtained from the two different polymerization techniques were characterized by FT-IR and electronic absorption spectroscopies, by ozonolysis and by thermal analysis (TGA, DTG and DTA). It was found that two selective secondary reactions occur in the two PVDC samples, respectively obtained from bulk polymerization or from inclusion polymerization. In the former case, the main reaction is only a crosslinking reaction, while in the latter case, with the PVDC included into the thiourea channels, the crosslinking reaction is fully inhibited and instead a dehydrohalogenation reaction takes place producing the polyene structures. The presence of polyene structures in the PVDC synthesized by the inclusion polymerization was demonstrated by electronic absorption spectroscopy and by ozonolysis experiments. The presence of polyene segments in the PVDC causes a reduction in the thermal stability of the polymer, lowers its melting point and reduces its crystallinity.