Radiation-induced polymerization of sodium allylsulfonate at high pressure

Irradiation of sodium allylsulfonate in aqueous solution at high pressure (up to 9000 kg/cm²) gave a deliquescent white powder which is insoluble in organic solvent. The product was addition polymer of allylsulfonate from the high-resolution NMR and infrared spectra. The rate of polymerization was proportional to the third and second powers of monomer concentration in the initial and later stages, respectively. From the high dependence of the rate on monomer concentration, the reaction was deduced to proceed in an associated monomer or micelle. The rate of polymerization was increased by addition of sodium chloride. The G value for monomer consumption was about 10⁴ at high pressure, which suggests that the degradative chain transfer is not important in the polymerization. Overall activation volumes were ?7 and ?5 ml/mole in the initial and later stages, respectively.     

Radiation-induced polymerization of 3,3,4,4,5,5,5-heptafluoropentene-1 at high pressure

A study was made of the radiation-induced polymerization under pressure of 3,3,4,4,5,5,5-heptafluoropentene-1. Polymerization rates increase with pressure (activation volume equals ? 11 cc/mole) and temperature (activation enthalpy equals 6.5 kcal/mole) in liquid phase. At 13800 atm and 25°C, freezing occurs; the polymerization rate in the solid is very small. In liquid phase polymerization can continue for many hours after the irradiation is terminated. An active species is formed by radiation which initiates polymerization in the dark period.     

Radiation-induced polymerization of hexafluoropropylene at high temperature and pressure

The radiation-induced polymerization of hexafluoropropylene was studied in the pressure and temperature ranges of 4,500–15,000 atm. and 100–230°C., respectively. Retardation was a serious problem; data thought to apply to the unretarded polymerization are summarized below. At 1,500 rad/hr. the polymerization rate was 15%/hr. at 230°C. and 15,000 atm. The activation enthalpy and volume are 9.5 kcal./mole and ?10 cc./mole, respectively. The rate varies as the square root of the radiation intensity. The largest intrinsic viscosity of the polymer is 2.0 dl./g.; values increase with temperature and pressure. At 130°C. and 10,000 atm. the intrinsic viscosity was the same at two radiation intensities.     

Radiation-induced polymerization of tetrafluoroethylene and 1,2,3,4,5-pentafluorostyrene at high pressure

Tetrafluoroethylene (A) and 1,2,3,4,5-pentafluorostyrene (B) were irradiated at 15°C at autogenous pressure by use of 30–92 mole-% A and at 5000 atm by use of 42–99.9 mole-% A. The high-pressure results indicate that the reactivity ratio r_A for monomer addition to A-ended radicals is 0.005; the other reactivity ratio r_B appears to vary from 15 to 60 generally increasing with the A content of the charge. At autogenous pressure r_A is small, but a precise determination is not possible because of the very low polymerization rate when the A content of the charge is high. However, if r_A is less than 0.01, then values of r_B vary from 15 to 50, again generally increasing with the A content of the charge. Mixtures of A and B exhibit positive deviations from Raoult's Law. Activity coefficients were measured at autogeneous pressure and used in an attempt to correct r_B for the nonideality of solution. The range of r_B was reduced only slightly to 8–27, and charges with high A contents now generally gave low values of r_B; consequently, this approach was not regarded as a success. Another attempt was made to account for the apparent variation in r_B by ascribing influence to the penultimate units of the radicals. Improved agreement between theoretical and observed compositions resulted, but significant discrepancies remained unexplained. Rate data agreed well with those calculated from a theoretical copolymer rate equation using values of r_A and r_B of 0.0045 and 40, respectively. The equation predicts an almost proportional decrease in rate with increasing proportions of A in the charge from 0 to 99 mole-% A.     

Radiation-induced polymerization of glass-forming systems. VII. Polymerization in supercooled state under high pressure

Radiation-induced polymerization of glass-forming monomers such as 2-hydroxyethyl methacrylate and glycidyl methacrylate under high pressure was studied. The glass transition temperature of these monomers was heightened by increased pressure. The temperature dependence of polymerizability showed a characteristic relation; similar to those in supercooled-phase polymerization under normal pressure, that had a maximum at T_v which shifted to higher levels of temperature as well as to T_g under high pressure. Polymerizability in the supercooled state also increased under increased pressure.     

Radiation-induced solid-state polymerization of methacrylic acid. II. In-source polymerization

The in-source polymerization of methacrylic acid in the solid state with γ-rays was studied. The conversion rates at various temperatures were obtained as well as the radical concentrations by the measurements of ESR spectrum. The rate of polymerization was found to be proportional to I^0.65 at 0°C. The results could be interpreted on the basis of the assumption that the rate of propagation is proportional to the concentration of the propagating radical, of the monomer, and of the polymer. The addition of water to the monomer seems to accelerate the polymerization reaction. The change of the line shape of the propagating radical during polymerization was interpreted in terms of the change of the matrix which surrounds the propagating radical.     

Low-temperature viscoelasticity of poly-oxymethylene by radiation-induced solid-state polymerization of trioxane single crystal

Summary The polymerizate is a porous, white cylinder of polyoxymethylene, whose direction of crystal axis is unique. The dynamic viscoelasticity was measured by the vibrating-reed-method at –180° +10 °C. The existence of the -dispersion is doubtful in this sample. Therefore we can conclude that (i) the amorphous part is negligibly small both on the surface and inside of this sample, and (ii) the vibration of molecular chains is prohibited even on the surface of a single crystal.

---

Zusammenfassung Das Polymerisat ist ein poröser, weißer Zylinder von Polyoxymethylen mit einheitlich ausgerichteter Kristallachse. Die dynamische Viscoelastizität wurde zwischen –180° und +10 °C nach der Methode des vibrierenden Stäbchens bestimmt. Die Existenz des-Dispersionsgebiets ist bei dieser Probe zweifelhaft. Wir können daher folgern, daß 1. der amorphe Anteil vernachlässigbar klein — sowohl an der Oberfläche wie im Innern — ist und daß 2. die Schwingung der Molekülketten sogar auch in der Grenzfläche eines Einkristalls behindert, unterbunden ist.

---

---

This work was presented at the 43rd Annual Meeting of Virginia Academy of Science, Richmond, Virginia, May 7, 1965.     

Radiation-induced copolymerisation of trioxane with penta-acetyl-glucose

Copolymerisation of trioxane (TOX) with penta-acetyl-glucose (PAG) in the solid state was investigated by gamma radiation. Effects of radiation doses, PAG concentration, and related parameters were studied and compared with that of the homopolymerisation of TOX. The yield of copolymer was lower than homopolymer and only a fraction of the PAG taken entered into the polymer. Chemical properties of the copolymer were determined; after amine treatment the copolymer showed good thermal stability. The kinetics of homopolymerisation were similar to those of TOX-homopolymerisation.     

Radiation-induced solid-state polymerization of methacrylic acid. III. Post-polymerization

The post-polymerization of methacrylic acid in the solid state was studied. The decay of the trapped radicals was also observed by ESR measurements. The decay of trapped radicals is a first-order reaction below 0°C but a second-order reaction at + 10°C. The results of the post-polymerization were compared with the results of radical decay measurements. A kinetic scheme was proposed for the post-polymerization of methacrylic acid. The effect of conditions of monomer crystallization on the polymer yield was also investigated. Fine crystals gave a greater limiting conversion than large crystals. The addition of water to the monomer increased the polymer yield. The change in the ESR spectrum during post-polymerization was interpreted in terms of the change in the matrix which surrounds the propagating radicals.     

Emulsion polymerization of styrene under high pressure

Summary The emulsion polymerization of styrene was studied at 40 °C over a pressure range of 1 to 1000 bar. By measuring the ratio of the overall reaction rate under high pressure and at atmospheric pressure, the activation volume for the prouagation was obtained as –23.5 cm³/mol which was rather smaller than the literature values. The underestimation by the method of emulsion polymerization would be due to the character of polymerization processes and the emulsion polymerization method is not appropriate to determine the accurate value of the activation volume of propagation reactions.

---

Zusammenfassung Es wird die Emulsionspolymerisation von Styrol bei 40 °C über den Druckbereich von 1 bis 1000 bar untersucht. Durch Messung des Verhältnisses der Reaktionsgeschwindigkeit unter hohem Druck und bei Atmosphärendruck wurde das Aktivierungsvolumen für die Ausbreitungsgeschwindigkeit zu –23,5 cm³/mol gefunden, ein Werr, der ziemlich kleiner als die Literaturwerte ist, Die Unterschätzung bei der Methode der Emulsionspolymerisation dürfte dem Charakter des Polymerisationsprozesses zuzuschreiben sein, und die Emulsionspolymerisation ist nicht geeignet, den exakten Wer für das Aktivierungsvolumen zu erhalten.

     

Radiation-induced polymerization at high pressure of 2,3,3,3-tetrafluoropropene in bulk and with tetrafluoroethylene

The radiation-induced polymerization of 2,3,3,3-tetrafluoropropene was studied as a function of temperature (22–100°C) and pressure (autogenous to 10⁴ atm). Rates have varied 100-fold for the same reaction conditions probably because of trace impurities. The most rapidly polymerizing material has a rate of 4.5%/hr at 6000 atm, 22°C, and 1500 rad/hr. The activation enthalpy and volume are 4 kcal/mole and ?13 cc/mole, respectively. Rates are proportional to the square root of the radiation intensity. Degrees of polymerization varied between 2 × 10³ and 2 × 10⁶. In copolymerization with tetrafluoroethylene the reactivity ratios at 22°C and 5000 atm are 0.37 (the ratio for addition to the tetrafluoroethylene-ended radical) and 5.4 (the ratio for addition to the tetrafluoropropene-ended radical). Comparison of ratios for the copolymerization of other fluorinej-containing monomers with tetrafluoroethylene shows that they generally disfavor incorporation of the latter.     

Radiation-induced solid-state polymerization in binary systems. IV. Solid-state polymerization in the glassy phase

The radiation-induced polymerization of glass-forming systems containing monomers has been investigated. It was found that irradiation below the second-order transition temperature T_g of the systems causes no in-source polymerization but causes a rapid postpolymerization on warming above the T_g after initial irradiation below the T_g. The post-polymerization was followed by differential thermal analysis and ESR spectra. It is caused above the T_g by the release of peroxy radicals trapped below the T_g, and its rate is proportional to the irradiation dose to some extent, often is explosively high, and brings about a remarkably large temperature rise by accumulation of polymerization heat. Irradiation above the T_g causes rapid in-source polymerization which is accelerated by the high viscosity of the monomeric system between T_g and T_s (WLF temperature) compared to crystal or ordinary solution polymerization. The temperature dependence of the in-source polymerization of glassy systems shows a peak between the T_g and T_s which may be the result of competing effects of the rate increase by the decreased termination near T_s and the rate decrease by the decreased propagation caused by the diffusion prevented near the T_g. The degree of polymerization was also investigated. The temperature dependence of the degree of polymerization of the polymers obtained by in-source polymerization shows a peak similar to that of the temperature dependence of conversion. Unusually large values of the Huggins constant k' are noted between T_g and T_s. The degree of polymerization of the polymer obtained by post-polymerized increases with the increase of irradiation dose and the polymerization rate; this may be the result of decreased chain transfer to nonpolymerizable components.     

Radiation-induced solid-state polymerization of derivatives of methacrylic acid. II. Postirradiation polymerization of octadecyl methacrylate

Octadecyl methacrylate (mpc ≈ 12°C.) polymerized readily in the solid state in the temperature range ?30 to +12°C. after gamma irradiation at ?196°C. The initial rate of polymerization and the “limiting” conversion increased with radiation dose and temperature. The temperature dependence of the rate corresponded to an “apparent” activation energy of 20 kcal./mole. Difficulties were experienced with polymerization during separation of the polymer from residual monomer, but these were minimized by using low radiation doses and a hot, selective solvent. The maximum conversion achieved was 70%. The polymer was crosslinked, even at low conversions.     

Radiation-induced bulk polymerization of vinyl chloride under centrifugation

Radiation-induced bulk polymerization of vinyl chloride has been carried out under centrifugation at 21°C. The polymerization rate and the molecular weight of the polymer produced were found to remain constant in the low-conversion region and to be equal to the corresponding values that were obtained by extrapolation at zero conversion in normal polymerization. This was at variance with the case of normal polymerization in which both quantities exhibit a continuous increase from the start of the polymerization. Such an increase is to be associated with the presence of large agglomerates, formed through flocculation of initially originated particles, in the liquid monomer phase during the polymerization under quiescent conditions. For the constancy of the kinetic parameters in the polymerization under centrifugation it should be assumed that in the system there remain dispersed only particles not yet flocculated.     

Radiation-induced,solid-state polymerization of derivatives of methacrylic acid. I. Postirradiation polymerization of zinc methacrylate

The postirradiation polymerization of the crystalline, anhydrous, monohydrate, and dihydrate forms of zinc methacrylate was studied. The anhydrous salt polymerized readily in the temperature range 50–150°C., the monohydrate did not polymerize at all, and the dihydrate polymerized at about 100°C. Aging of the anhydrous salts greatly affected the rate of polymerization; this was shown to be due mainly to the formation of peroxides by reaction with air. Polymerization could be initiated thermally, without irradiation, in monomer which had been aged in contact with air, apparently by decomposition of the peroxides. The rate of the postirradiation polymerization was increased when air was present during irradiation and decreased when air was present during polymerization. The rate of polymerization increased with temperature, corresponding to an apparent activation energy of 10 kcal./mole. The dihydrate lost one molecule of water rapidly under vacuum at 20°C. and slowly on heating at 50°C. in a sealed vessel, forming a crystalline monohydrate. Slow thermal polymerization and rapid postirradiation polymerization occurred at 100°C. without the formation of any monohydrate, indicating that the polymerization was concurrent with the phase change.     

Radiation-induced polymerization at high pressure of cis- and trans-1,3,3,3-tetrafluoropropene in bulk and with tetrafluoroethylene

The radiation-induced polymerization of cis- and trans-1,3,3,3-tetrafluoropropene in bulk and with tetrafluoroethylene was studied at pressures between 5000 and 15000 atm and temperatures between 21 and 100°C. At 10³ rad/hr the homopolymerization rates range from about 10^?4 to 1%/hr. The activation enthalpy and volume are about 8 kcal/mole (33 kJ/mole) and ?10 cm³/mole, respectively, for both isomers. The cis isomer polymerizes about twice as rapidly as the trans isomer. The latter freezes in the experimental range of temperature and pressure; the polymerization rate is very low in solid phase. Polymer intrinsic viscosities increase with polymerization pressure and decrease with polymerization temperature; the largest value obtained was 0.23 dl/g. In the copolymerizations all reactivity ratios favor incorporation of tetrafluoroethylene by factors of 6–16. The preference is stronger when the trans isomer is used.     

Radiation-induced postpolymerization of trioxane in the solid state. IV. Copolymerization of trioxane with dioxolane

The radiation-induced postpolymerization of trioxane with 1,3-dioxolane has been investigated. Trioxane and 1,3-dioxolane were carefully purified in a rigorously dry, high-vacuum system. In the present study it was found that trioxane can be easily copolymerized with 1,3-dioxolane to give a copolymer having high molecular weight and excellent thermal stability. Typically, the isothermal weight loss after heating for 60 minutes under nitrogen at 222°C was 3.5% for a copolymer of trioxane and 1.0 wt-%1,3-dioxolane preirradiated with a dose of 1.0 × 10⁵ Rad. The thermal stability of the copolymer was scarcely affected by the polymerization temperature and time, although it decreased slightly with increasing preirradiation dose. The dependences of the yield and inherent viscosity of the polymer on the preirradiation dosage, polymerization temperature and time were quite similar to those found for the homopolymerization of trioxane. The results were analyzed by using the kinetic scheme previously reported, and it was found that no chain transfer reaction occurs in this system. These results are discussed in comparison with those of homopolymerization reported previously.     

Deviations from topotaxy in trioxane polymerization

It is shown by photomicrographic techniques that the polymer does not always form in a unique crystallographic direction in the solid-state polymerization of trioxane. The polymerization in these instances cannot therefore be considered topotactic in the usually accepted sense. The crystallization of the polymer is attributed to factors which are, in a sense, secondary to the actual reaction mechanism.     

Radiation-induced solid-state polymerization of methacrylic acid. I. Crystalline transition of the monomer

The anomalous crystalline transition of methacrylic acid found by broad-line NMR measurements was studied in connection with the build-up and decay of trapped radicals. The build-up of radicals is smaller and the decay rate of the trapped radicals is faster in the low-temperature range (phase II), which gave the narrower maximum slope distance ΔH_msl of the NMR spectrum, than those in the higher temperature range (phase I), which gave the broader ΔH_msl. From these experiments it was concluded that in phase I the crystals have a more closely packed structure, resulting in a more rigid matrix for the trapped radicals than those in phase II. This interpretation is consistent with the temperature dependence of the ESR spectrum of the trapped propagating radicals previously reported. The existence of the crystalline transition was also confirmed by DSC measurements, and the effects of the crystallization conditions on the transition were investigated and were discussed with reference to the results of broad line NMR measurements.     

Electroinitiated polymerization of trioxane in chlorinated hydrocarbons

The electroinitiated polymerization of trioxane in chlorinated hydrocarbons, with tetrabutyl-ammonium perchlorate as background electrolyte, has been investigated. The initiation always involves perchlorate oxidation but the polymerization exhibits different features in the various solvents. It has been found that in 1–2 dichloroethane the polymerization, once started by a short pulse of current, proceeds without any induction period to moderate conversion of monomer to polymer. The initial rate of polymerization depends linearly on the monomer cone, and on the initiating charge, so allowing determination of some kinetic parameters. On the other hand, the electroinitiated polymerization of trioxane in dichloromethane requires continuous current to give reasonable conversions; it exhibits induction periods and acceleration which cannot be simply related to the current.