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 copolymerization of tetrafluoroethylene with vinyl ethers

Radiation-induced copolymerization of tetrafluoroethylene with various vinyl ethers has been studied. It was found that tetrafluoroethylene can be copolymerized with vinyl ethers to give alternating copolymers over a wide range of the initial monomer concentration in the monomer mixture. The monomer reactivity ratios were determined for the copolymerization of tetrafluoroethylene with n-butyl vinyl ether as 0.005 (r_TFE) and 0.0015 (r_NBVE). The rate of copolymerization is extremely high and has a maximum at an equimolar concentration of two monomers. The alternating structure of the copolymers was confirmed by the analysis of NMR spectra. Some thermal properties of the copolymers were measured by DSC and DTA.     

The radiation-induced copolymerization of tetrafluoroethylene and 3,3,3-trifluoropropene under pressure

A study was made of the gamma-ray-induced copolymerization of tetrafluoroethylene and 3,3,3-trifluoropropene. Copolymerizations were carried out at 100°C. and 5000 atm. pressure and at 21°C. and various pressures up to 8000 atm. The reactivity ratios calculated from the composition data indicate that the propagation rate constants favor addition of trifluoropropylene by a factor of 3–7; individual values depended little on the polymerization pressure and temperature. Polymerization rates changed little with monomer composition between 0 and 75% tetrafluoroethylene; between 75 and 95% tetrafluoroethylene they increased by a factor of 10. As many as 850,000 molecules were polymerized per 100 e.v. absorbed. The copolymers are soluble in hexafluorobenzene at 29.6°C. if they contain less than 70% tetrafluoroethylene. Intrinsic viscosities range from 0.1 to about 10 dl./g. From various considerations it appears likely that the degree of polymerization is about equal to the kinetic chain length in high-pressure polymerizations at 21°C.; at autogenous pressure or at 5000 atm and 100°C., monomer transfer reduces the value considerably.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. VI. Effects of pressure and temperature

In a radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene, the effects of pressure and temperature were investigated in the range of 0–40 kg/cm² and 7–53°C at emulsifier concentration of 0.5 and 2.0%. Both the polymerization rate and the molecular weight of copolymer increase with increasing pressure and decreasing temperature. These facts are mainly due to an increase of the monomer concentration in the polymer particles. The rate of polymer chain formation was found to be independent of pressure and temperature. The initiation reaction is due mainly to the entry of radicals generated in the aqueous phase into the polymer particles. The apparent activation energy is ?2.0 to ?3.8 kcal/mole for the polymerization in the presence of 0.5% emulsifier, but is nearly zero at an emulsifier concentration of 2.0%. This difference in apparent activation energies at emulsifier concentrations of 0.5 and 2.0% is explained in terms of the termination mechanisms.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. III. Polymerization mechanism

In the radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene, the dose rate dependence, the effect of emulsifier concentration, and the effect of monomer composition were studied. The rate of polymerization was proportional to the 0.90 power of the dose rate and the 0.26 power of the emulsifier concentration. The degree of polymerization was independent of the dose rate and the emulsifier concentration. Both the rate of polymerization and the degree of polymerization increased with tetrafluoroethylene content in the monomer mixture. The resulting copolymer was an alternating polymer over a wide range of monomer composition. It was concluded from the dose rate dependence of the rate of polymerization that the emulsion copolymerization is mainly terminated by degradative chain transfer of the propagating radical to propylene.     

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.     

The radiation-induced copolymerization of tetrafluoroethylene and styrene at high pressure

The radiation-induced copolymerization of tetrafluoroethylene (A) and styrene (B) was studied in bulk and in perfluorotoluene at 22°C at autogenous pressure and 260 and 510 MPa. The reactivity ratio for addition to A-ended radicals, r_A, is effectively zero at the two lower pressures and is in the range 0.002–0.008 at 510 MPa. The other reactivity ratio, r_B, is 6 at autogenous pressure and also at 260 and 510 MPa if the A content of the charge is less than 50%. If the A content is greater than 95%, r_B appears to be 100 at pressures of 260 and 510 MPa. The apparent variation in r_B cannot be explained by invoking a penultimate unit effect for B-ended radicals. Polymerization rates scatter somewhat, but all rates are quite small when the A content of the charge is in the range 95–99.8%. Polymers containing as much as 66% A appear to be inherently benzene soluble but frequently contain some gel because of radiation-induced crosslinking after their formation. No very high polymers were formed that contained more than a few percent A, even at high pressure. Features that complicated the study were immiscibility of the liquid monomers, extreme variation of the monomer—copolymer compatibility with charge composition, and freezing of B at high pressure.     

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 emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 10⁴ to 2 × 10⁵ R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number-average degree of polymerization are discussed in comparison with the Smith-Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith-Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.     

Radiation-induced copolymerization of hexafluoroacetone with 2-methyl-1-pentene

Copolymerization of hexafluoroacetone (HFA) with 2-methyl-1-pentene (2MP) in trichlorotrifluoroethane (R-113) was carried out by γ-ray irradiation in a low-temperature region of ?100 to 0°C. Though HFA does not homopolymerize and 2MP scarcely does, the copolymerization took place at various monomer compositions. The copolymerization rate and the molecular weight in the low-temperature region were much higher than those at 0°C. Above room temperature the copolymerization did not take place and only the adduct of monomers was formed. The copolymerization was inhibited to some extent by cation scavengers, but not by radical or electron scavengers. Elemental analysis and nuclear magnetic resonance (NMR) spectra show that the copolymer consists of almost equimolar monomer units and has two types of structure, head to tail and head to head or tail to tail. It has been concluded that copolymerization probably proceeds via a cationic mechanism to form an alternating copolymer.     

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 copolymerization of formaldehyde and styrene

The radiation-induced copolymerization of styrene with liquid formaldehyde in bulk and in solution has been studied at low temperatures. In bulk and in methylene chloride solution copolymerization took place, whereas in diethyl ether solution only homopolymerization of the formaldehyde was found. At ?78°C., in bulk and in methylene chloride solution, no evidence of polystyrene blocks could be found, whereas at ?30°C. in bulk about 30% of the styrene content of the copolymer was in the form of high molecular weight blocks. The rate of copolymerization in methylene chloride solution was found to be first-order with respect to dose rate and third-order with respect to formaldehyde concentration similar to results reported for formaldehyde in toluene solution. The thermal stabilities of the copolymers were found to be intermediate between those of pure polyoxymethylene and commercially stabilized polymers. Since the latter were of higher molecular weight and contain added stabilizers, the increased thermal stabilities of the copolymers were considered to be particularly significant.     

Radiation-induced terpolymerization of tetrafluoroethylene with propylene and isobutylene in bulk

Terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and isobutylene (iB) by γ radiation at temperatures of ?78 to 40°C, a dose rate of 5 × 10⁴?5 × 10⁵ rad/hr, and an iB/P molar ratio of 40/10?5/45 in the monomer mixture was carried out. Alternating copolymers of TFE and α-olefins, that is, P and iB, were formed at various monomer compositions. No crystalline structure was observed in the terpolymer obtained below an iB/P molar ratio of 15/35 in the monomer mixture but a partly crystalline order increased with the amounts of iB in terpolymer. The crystal lattice of the TFE–iB copolymer was affected by the introduction of P. The dose rate dependencies of the polymerization rate and inherent viscosity were 0.8 and ?0.2, respectively. The activation energy of polymerization was 2.4 kcal/mole, and the relative reactivity ratio of iB and P for a TFE radical chain end was estimated as 4.50 by the treatment of the free propagating mechanism.     

Radiation-induced solid-state polymerization of trioxane under high pressure

The in-source polymerization of trioxane in the solid state was investigated over a wide range of temperature and pressure, i.e., from 30 to 140°C and up to 7000 kg/cm², respectively. In the polymerization that was carried out slightly below the melting point under pressure, the higher the pressure, the higher the rate of polymerization. It was confirmed that the maximum rate of solid-state polymerization of trioxane occurs near the melting points, even under elevated pressure. The rate of polymerization decreased with increasing pressure at constant temperature. The shape of the time–conversion curves may be classified into two types, i.e., one which is typical of high pressure and low temperature, and the other which is typical of low pressure and high temperature. Changes in the shape of the conversion—intrinsic viscosity curves occurred coincidentally. Thus, three regions for the different “polymerization characteristic” were determined as functions of polymerization temperature and pressure. Explanations are given for the above-mentioned polymerization characteristic.     

Radiation-induced solid-state copolymerization of maleic anhydride and acenaphthylene

Radiation-induced solid-state copolymerization of the maleic anhydride–acenaphthylene system was carried out for the purpose of studying the solid-state polymerization of vinyl compounds in a binary system. Melting point measurement confirmed that this binary monomer system forms a eutectic mixture in the solid state. The solid-state polymerization of these monomers proceeds at maximum rate at the eutectic composition, and the polymerization products consist of a mixture of polyacenaphthylene and 1:1 maleic anhydride–acenaphthylene alternating copolymer. Since the 1:1 copolymer was obtained in solution polymerization also and maleic anhydride did not homopolymerize in solid state, it is considered that the solid-state copolymerization of maleic anhydride and acenaphthylene occurs in a liquidlike state at the boundary of the two monomer crystals.     

Radiation-induced copolymerization of methyl trifluoroacrylate with propylene

Copolymerization of methyl trifluoroacrylate (MTFA) with propylene in bulk was induced by γ irradiation. A wide range of the initial monomer composition gives an equimolar alternating co-polymer. The reactivity ratios of r₁ (MTFA) and r₂ (propylene) were determined to be 0.01 and 0.005, respectively. The polymerization rate at an equimolar monomer composition is proportional to the 1.0 power of the dose rate. The dose rate dependency of higher than 0.5 may be ascribed to unimolecular termination due to a degradative chain transfer of propagating radicals to propylene. The G values of the initiating radical formation and the polymerization reaction were calculated to be 1.78 and 1336, respectively. The dependence of the copolymerization rate on the temperature was small, and the activation energy of copolymerization was 1.1 kcal/mole from ?6 to 50°C.     

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.     

Radiation-induced copolymerization of phenylvinyl alkyl ethers and maleic anhydride

Alternating copolymers of phenylvinyl ethyl ether ( I ) and phenylvinyl sec-butyl ether ( II ) with maleic anhydride (MAn) were prepared in bulk or in benzene solution by high-energy irradiation at dose rates of 42, 160, and 540 Gy/h, respectively. The overall energies of activation in copolymerization of I and II with MAn were 15.5 and 18.8 kJ/mol, respectively. The reaction proceeds by the free-radical mechanism and was found to be largely dependent on the bulkiness of the alkyl group. In the copolymerization of I and MAn, the molecular weight increases with conversion. By applying the model described by Shirota and co-workers, it was established that participation of charge-transfer-complex monomers increases with the increase of the total monomer concentration and with the bulkiness of the alkyl group in electron donor monomer.