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.     

Pentafluoroethylation of Arenediazonium Tetrafluoroborates Using On‐Site Generated Tetrafluoroethylene

Copper‐mediated pentafluoroethylation of arenediazonium tetrafluoroborates with tetrafluoroethylene (TFE) on‐site generated from TMSCF₃ has been developed as a new method to prepare pentafluoroethyl arenes. The active pentafluoroethylation reagent “CuC₂F₅” is pre‐generated from CuSCN, TFE and CsF, and its generation and further reaction are strongly solvent‐dependent. This pentafluoroethylation reaction represents the first example of Sandmeyer‐type pentafluoroethylation, which exhibits good functional group tolerance and potential applications for the synthesis of complicated bioactive compounds.     

Kinetics and mechanism of radiation telomerization of tetrafluoroethylene in hexafluoropropan-2-ol and trifluoroethanol

The kinetics of radiation telomerization of tetrafluoroethylene (TFE) in trifluoroethanol and hexafluoropropan-2-ol (HFIP) has been investigated by method of kinetic calorimetry. The nature of active centers initiating the process of telomerization of tetrafluoroethylene in hexafluoroisopropanol in the temperature range of 77—300 K was investigated by ESR spectroscopy. The molecular structure and properties of the obtained telomeres were studied by IR spectroscopy and TGA.     

Radiation synthesis of telomers at a constant tetrafluoroethylene concentration in acetone

Radiation-initiated polymerization of tetrafluoroethylene (TFE) in acetone has been carried out in a specially designed reactor, which makes it possible to maintain a constant concentration of the monomer in a solution during synthesis. The features of the telomerization process at different initial concentrations (pressures) of TFE have been studied. Concentrated solutions of telomers have been obtained. The carrying out of the process at different pressures in the reactor makes it possible to obtain telomers differing in molecular mass and thermal resistance.     

Post-irradiation grafting of tetrafluoroethylene at low temperatures

Low-temperature postirradiation grafting of tetrafluoroethylene (TFE) to polyolefines and silicone elastomers was the subject of study. After preliminary dissolution of TFE in the polymer at 273°K the system was slowly cooled to 77°K. In this process a certain part of TFE in polyolefines (ethylene-propylene copolymer and polypropylene) is retained by the vitreous polymer matrix. When slowly heated after radiolysis at 77°K this system shows graft polymerization of dissolved TFE after T_g. The graft copolymer is soluble and its IR spectra contain absorption bands characteristic of polytetrafluoroethylene. In polydimethylsiloxane rubber (SKT) the dissolved TFE when frozen to 77°K remains sorbed between the SKT crystallites rather than in a separate phase. When these radiolyzed samples are heated the graft-polymerization occurs primarily over the temperature range between the TFE and SKT melting points. The technique provedes for 100–150% grafting of TFE. This method also permits grafting to silicone rubbers and to several other polymers and elastomers.     

TMSCF3 as a Convenient Source of CF2=CF2 for Pentafluoroethylation, (Aryloxy)tetrafluoroethylation,and Tetrafluoroethylation

A new method for the on‐site preparation of tetrafluoroethylene (TFE) and a procedure for its efficient use in pentafluoroethylation by fluoride addition were developed by using a simple two‐chamber system. The on‐site preparation of TFE was accomplished by dimerization of difluorocarbene derived from (trifluoromethyl)trimethylsilane (TMSCF₃) under mild conditions. Other fluoroalkylation reactions, such as (aryloxy)tetrafluoroethylation and tetrafluoroethylation processes, were also achieved using a similar approach. This work not only demonstrates a convenient and safe approach for the generation and use of TFE in academic laboratories, but also provides a new strategy for pentafluoroethylation.     

TMSCF3 as a Convenient Source of CF2=CF2 for Pentafluoroethylation, (Aryloxy)tetrafluoroethylation,and Tetrafluoroethylation

A new method for the on‐site preparation of tetrafluoroethylene (TFE) and a procedure for its efficient use in pentafluoroethylation by fluoride addition were developed by using a simple two‐chamber system. The on‐site preparation of TFE was accomplished by dimerization of difluorocarbene derived from (trifluoromethyl)trimethylsilane (TMSCF₃) under mild conditions. Other fluoroalkylation reactions, such as (aryloxy)tetrafluoroethylation and tetrafluoroethylation processes, were also achieved using a similar approach. This work not only demonstrates a convenient and safe approach for the generation and use of TFE in academic laboratories, but also provides a new strategy for pentafluoroethylation.     

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.     

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.     

Radical polymerization of tetrafluoroethylene in solutions of trimethoxysilanes: Formation of colloidal solution and gel of oligomers

Radical polymerization of tetrafluoroethylene (TFE) in solutions of trimethoxysilanes leads to the formation of fluoroalkoxysilane oligomers and the products of their subsequent hydrolysis and dimerization that occur when methoxyl groups are replaced by hydroxyl groups and Si–O–Si links to bind the oligomers are subsequently formed. The chain length of the oligomers increases with the initial TFE concentration, thereby leading to the formation of colloidal solutions. Colloid particles contain oligomers and solvent molecules, the number of which per TFE unit decreases as the chain length grows to 4–6. Partial replacement of the starting solvents, which are also capable of creating a silicone skeleton during polycondensation, makes it possible to control the number of fluoroalkyl chains attached to this skeleton.     

Some kinetic aspects regarding the preparation of telomeric ω-hydroperfluoroalkanols

Telomerization of tetrafluoroethylene (TFE) with methanol in the presence of a free-radical initiator such as α, α′-azoisobutyronitrile (AIBN) has been carried out. The product composition was related to kinetic equations involving the chaintransfer coefficients and the concentration of telomeric fluoroalkanols obtained.     

Dielectric properties of polymers based on hexafluoropropylene

Dielectric measurements have been made at frequencies from 10 Hz to 100 kHz and temperatures from 4 K to at least 300 K on a number of polymers containing units of hexafluoropropylene (HFP). These included copolymers of tetrafluoroethylene (TFE) and HFP, the homopolymer of HFP, elastomeric copolymers of HFP and vinylidene fluoride, and alternating copolymers of methyl vinyl ether with TFE and HFP. The effect of an ether linkage between the CF₃ group and the chain was also considered. Most of these polymers exhibited a main chain local mode relaxation near 228 K and a side group relaxation near 93 K.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayWe appreciate the helpful discussions with W. W. Schmiegel.     

Radiation telomerization of tetrafluoroethylene in chlorinated telogens at a constant reactor pressure

The kinetics of the radiation-initiated telomerization of tetrafluoroethylene (TFE) in the solutions of telogens (butyl chloride, chloroform, methylene chloride, and carbon tetrachloride) at a constant monomer pressure in the reactor was studied. In the course of the Γ-irradiation of the reaction mixture, TFE telomers containing repeatedly soluble and insoluble fractions were formed. In chloroform, methylene chloride, and carbon tetrachloride, the rapidly occurring process of the synthesis of insoluble telomer made the main contribution to the total yield of products. For the solutions of TFE in butyl chloride, the rates of formation of soluble and insoluble telomers were almost the same. The average chain length and the thermal stability of the resulting telomers were evaluated.     

高温热处理对偏氟乙烯-四氟乙烯共聚物高次结构的影响

The effect of high temperature annealing on the higher order structure of a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE 2.8 mol %) has been studied by various method, primarily dynamic mechanical, by also dielectric and microspic. The controversy on the origin of a relaxations is discussed from the point of view of higher order structure studies.     

高温热处理对偏氟乙烯-四氟乙烯共聚物高次结构的影响

聚偏氟乙烯(PVDF)及其一些共聚物,例如偏氟乙烯-四氟乙烯共聚物(PVDF/TFE)经过处理后呈现较强的压电性。许多研究表明它们是铁电聚合物,而且压电活性与样品的高次结构有关。松弛谱是研究结晶高聚物的高次结构的有力工具,近来,Koizumi等人报道了PVDF/TFE的热处理与松弛现象的关系。本文作者也报道了     

Mechanism of the initiation of low-temperature radiation telomerization of tetrafluoroethylene in hexafluoroisopropanol

ESR and IR spectroscopy and scanning calorimetry are used to investigate the mechanism of low-temperature radiation telomerization of tetrafluoroethylene (TFE) in hexafluoroisopropanol (HFIP). It is found that the low-temperature telomerization of TFE in HFIP proceeds via an ion-radical mechanism. This process is initiated by the radical anions (CF₃)₂C^·-O^? formed during the deprotonation of OH groups of primary hydroxyl radicals (CF₃)₂C^·-OH exhibiting strong acidic properties. An interpretation of ESR spectra of irradiated HFIP recorded at 230–240 K is proposed with regard to the anisotropy on β-fluorine atoms and estimates of the angles between the corresponding C-F bonds and the axis of the unpaired electron orbital.     

Synthesis and Reactivity of Fluoroalkyl Copper Complexes by the Oxycupration of Tetrafluoroethylene

The copper(I)‐mediated generation of ‐OCF₂CF₂‐ moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2‐aryloxy‐1,1,2,2‐tetrafluoroethyl and 2‐alkoxy‐1,1,2,2‐tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE, and their structures in solution and in the solid state were unambiguously determined by multinuclear NMR spectroscopy and X‐ray diffraction analysis. These copper complexes subsequently reacted with aryl iodides (ArI) to afford ROCF₂CF₂Ar (R=aryl or alkyl) in high yields.     

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 of 3,6-dioxa-Δ-4-trifluoromethyl perfluorooctyl trifluoromethyl sulfonimide: bis[(perfluoroalkyl)sulfonyl] superacid monomer and polymer

A new type of ion exchange polymer, bis[(perfluoroalkyl)sulfonyl]imide ionomers (PFSI), were developed by the copolymerization of sodium 3,6-dioxa-Δ⁷-4-trifluoromethyl perfluorooctyl trifluoromethyl sulfonimide with tetrafluoroethylene (TFE) using an aqueous redox initiation system in an emulsion type polymerization. These polymers have been prepared in various equivalent weights and processed into functional membranes. The new ionomers exhibit excellent chemical and thermal stability. The materials have high potential for electrochemical applications especially as solid polymer electrolytes (SPE) in proton exchange membrane (PEM) fuel cells.     

Confined crystallization of PVDF and a PVDF‐TFE copolymer in nanolayered films

Layer‐multiplying coextrusion was used in conjunction with isothermal recrystallization to study the confined crystallization of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride‐tetrafluoroethylene (PVDF‐TFE) using polycarbonate (PC) and polysulfone (PSF) as confining materials. Three layered systems were produced (PC/PVDF, PSF/PVDF, and PC/PVDF‐TFE) with layer thicknesses ranging from 525 to 28 nm. The crystal morphology was affected by both layer thickness and recrystallization temperature. Specifically, increased recrystallization temperature and decreased layer thickness facilitated the formation of high aspect ratio in‐plane crystals in both PVDF based polymers. On the other side of the spectrum, thicker layers and lower recrystallization temperatures produced on‐edge PVDF crystals and isotropic PVDF‐TFE crystals. The morphology was correlated with oxygen permeability, which decreased by almost two orders of magnitude compared with the bulk. A variety of crystal structures were obtained and explained with nucleation and diffusion theory. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011