Synthesis of Polyphosphorinanes. 1. Homopolymerization and Telomerization of Allyl Ether Phosphite

Cyclic allyl phosphonated monomers were synthesized by transesterification reaction between a glycol bearing a double bond and a hydrogenophosphonate and were fully characterized by NMR and IR spectroscopy. Radical homopolymerization of these monomers was carried out at 70 °C in the presence of α,α′-azoisobutyronitrile (AIBN) as initiator and acetonitrile as solvent. The thus-obtained polymers showed two SEC distributions, one composed of oligomers (with Mn ≈ 800 g/mol) and one composed of high-molecular-weight polymers (with Mn ≈ 100 000 g/mol). The latter were hyperbranched polymers suffering from solubility limitations for future industrial applications. Therefore, telomerization of one phosphonated monomer using dimethyl hydrogenophosphonate (HP(O)(OMe)2) as a chain transfer agent (CTA) limited the hyperbranching through two concomitant mechanisms of polymerization, which are discussed. For R0 = 2 (R0 represents initial [CTA]0/[monomer]0 molar ratio), the results showed a limited chain length, whereas monoadduct formation occurred for a R0 value of 10

Synthesis and Characterizations of Novel Proton-Conducting Fluoropolymer Electrolyte Membranes Based on Poly(vinylidene fluoride-<i>ter</i>-hexafluoropropylene-<i>ter</i>-α-trifluoromethacrylic acid) Terpolymers Grafted by Aryl Sulfonic Acids

The synthesis and the characterization of new polymer electrolyte membranes made of fluorinated copolymers based on vinylidene fluoride (VDF) and hexafluoropropylene (HFP) and grafted by aryl sulfonic acids are presented. They were obtained in a three-step process. First, the conventional batch radical terpolymerization of α-trifluoromethacrylic acid (TFMAA), VDF and HFP, initiated by 2,5-bis­(<i>tert</i>-butylperoxy)-2,5-dimethylhexane led to original fluorinated functional terpolymers bearing carboxylic acid side groups in fair to good yields (>55%). The microstructure and the thermal properties of these macromolecules were studied. Interestingly, poly­[(VDF-<i>alt</i>-TFMAA)-<i>co</i>-HFP)] random terpolymers that contained alternated microblock structures based on VDF and TFMAA units separated by one HFP unit were evidenced by ¹⁹F nuclear magnetic resonance (NMR) spectroscopy. That technique also enabled us to assess the termonomer contents. Average molecular weights, glass transition temperatures, and decomposition temperatures (under air), determined by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), ranged between 10 000 and 21 400 g mol^–1, from −27 to −18 °C and from 140 to 275 °C, respectively. Indeed, the higher the TFMAA content, the lower the thermostability of the terpolymer that arised from decarboxylation. This degradation could be overcome by the reduction of the carboxylic acid dangling functions into hydroxyl ones. The third step concerned an etherification (Mitsunobu) reaction of such resulting primary hydroxyl groups with 4-sulfonic acid phenol. Both these reactions did not affect the contents of fluorinated termonomeric units as evidenced by ¹H, ¹⁹F, and ¹³C NMR characterization. The microstructures, physicochemical, and thermal properties of the grafted materials were evaluated by NMR and infrared spectroscopies, SEC and DSC, and TGA. Membranes incorporating these functional fluoropolymers were processed by casting, and their preliminary electrochemical properties (ionic exchange capacity, proton conductivity, and swelling rates that reached 1.2 mequiv mol^–1, 9 mS cm^–1, and 58%, respectively) were studied, discussed, and compared to those of Nafion and to other fluorinated aromatic membranes of different architectures

Living Radical ab Initio Emulsion Polymerization of <i>n</i>-Butyl Acrylate by Reverse Iodine Transfer Polymerization (RITP): Use of Persulfate as Both Initiator and Oxidant

Reverse iodine transfer polymerization (RITP) represents a new straightforward way to prepare controlled macromolecular architectures and relies on the use of molecular iodine (I2) as control agent. In this work, a one-step ab initio emulsion polymerization of n-butyl acrylate in the presence of molecular iodine has been successfully performed with potassium persulfate playing the dual role of radical initiator and oxidant. The polymerization was initiated by potassium persulfate at T = 85 °C with sodium 1-hexadecanesulfonate as surfactant, yielding a stable and uncolored latex. The hydrolytically disproportionated iodine was regenerated by potassium persulfate as oxidant (also serving as radical initiator), leading to the expected targeted molecular weight (e.g., butyl acrylate conversion = 99%, Mn,theoretical = 10 100 g mol-1, Mn,SEC = 9800 g mol-1, Mw/Mn = 1.8, particle diameter dp = 83 nm with a monomodal particle size distribution). The use of potassium persulfate as both radical initiator and oxidant offers a convenient way to overcome the upward deviation of the molecular weights due to hydrolytic disproportionation of iodine, which was a limitation for the implementation of the RITP process in dispersed aqueous media. The persulfate is able to regenerate iodine, and hence the molecular weight of the polymer chains can be accurately controlled by the concentration of iodine. Furthermore, a poly(butyl acrylate)-b-poly(butyl acrylate-co-styrene) block copolymer was synthesized in seeded emulsion polymerization, proving the living character of the polymerization

Reverse Iodine Transfer Polymerization of Methyl Acrylate and <i>n</i>-Butyl Acrylate

Solution polymerization of methyl acrylate initiated by 2,2‘-azobis(isobutyronitrile) (AIBN) at 65 °C in the presence of molecular iodine I2 has been studied. The process, called reverse iodine transfer polymerization (RITP), efficiently controls the molecular weight (determined by size exclusion chromatography, SEC) and the structure of the polymer. For instance, poly(methyl acrylate) samples of Mn,SEC = 5700 g mol-1 and Mw/Mn = 1.79 (Mn,theoretical = 5500 g mol-1), Mn,SEC = 10 900 g mol-1 and Mw/Mn = 1.91 (Mn,theoretical = 10 500 g mol-1), and Mn,SEC = 21 800 g mol-1 and Mw/Mn = 1.98 (Mn,theoretical = 20 700 g mol-1) were successfully prepared. The polymerization was followed by on-line 1H NMR spectroscopy to investigate the evolution of several compounds in the reaction medium, especially the adduct between primary radicals and iodine (A−I, where A stands for the radical fragment from the initiator), the monoadduct A−M1−I (where M stands for the monomer unit), and the monomer conversion. The iodine-end-capped structure of the polymers (A−Mn−I, where n is the mean number degree of polymerization) was further demonstrated by mass-assisted laser desorption ionization time-of-flight (MALDI-TOF). The inhibition period in RITP of n-butyl acrylate was shortened at higher temperature (about 30 min at 95 °C) without detrimental effect on the control of the molecular weight of the final polymer: Mn,SEC = 8600 g mol-1 and Mw/Mn = 1.88 (Mn,theoretical = 9200 g mol-1). Furthermore, RITP of acrylates was successfully performed in a large variety of media (in bulk, toluene, α,α,α-trifluorotoluene, anisole, methyl ethyl ketone, butyl acetate, propylene carbonate, propionitrile, and dimethylformamide). Last, the living nature of the polymer was confirmed by the preparation of a poly(methyl acrylate)-b-polystyrene block copolymer

Poly(vinylidene fluoride)-<i>b</i>-poly(styrene) Block Copolymers by Iodine Transfer Polymerization (ITP): Synthesis, Characterization, and Kinetics of ITP

The syntheses of poly(vinylidene fluoride)-b-poly(styrene) (PVDF-b-PS) block copolymers, from the iodine transfer polymerization (ITP) of styrene, in the presence of PVDF−I, are presented. In a first step, considering that the radical polymerization of vinylidene fluoride can lead to two different isomeric oligomers, bearing either −CH2I or −CF2I end groups, the kinetics of ITP of styrene in the presence of two chain transfer agents, C6F13−CH2CF2−I and HCF2−CF2CH2−I, were achieved as model reactions. The characterization of sampled aliquots by 19F NMR spectroscopy could monitor the average degree of polymerization in number (DPn) vs styrene conversion (αStyrene). ITPs of styrene with both these chain transfer agents showed two opposite behaviors, also confirmed by MALDI−TOF spectroscopy and SEC chromatography. (i) on the one hand, in the presence of C6F13−CH2CF2−I, the controlled character of ITP of styrene was evidenced (a linear dependence of DPn vs αStyrene was observed), theoretical DPn values were close to those of the targeted ones, with low polydispersity indexes (PDI = 1.5) and the transfer constant value was assessed (CTr ≅ 1); (ii) on the other hand, using HCF2−CF2CH2−I as the chain transfer agent, ITP of styrene did not occur since only a direct initiation for the polymerization of styrene was noted, with DPn value higher than the targeted one and a broad polydispersity distribution (PDI > 2). In a second part, PVDF-b-PS block copolymers were synthesized via a two step-procedure, ITP of VDF in the presence of C6F13I as the chain transfer agent leading to C6F13(VDF)n−I oligomers and, subsequently, ITP of styrene using those latter oligomers as macromolecular chain transfer agents. These block copolymers were characterized by 19F and 1H NMR and MALDI−TOF spectroscopies, and by SEC chromatography. Their morphological and thermal properties were also studied by atomic force microscopy (AFM) and by differential scanning calorimetry (DSC), respectively

First MALDI-TOF Mass Spectrometry of Vinylidene Fluoride Telomers Endowed with Low Defect Chaining

The radical telomerization of vinylidene fluoride (or 1,1-difluoroethylene, VDF) with iodotrifluoromethane initiated by tert-butyl peroxypivalate is presented. The VDF telomers obtained were characterized by 1H and 19F NMR spectroscopy and by matrix-assisted laser desorption−ionization time-of-flight mass spectrometry (MALDI TOF MS) that revealed low polydispersity indexes showing a pseudo-living character of this reaction regarded as an iodine transfer polymerization process. CF3 and CF2I end groups appear as suitable labels in the 19F NMR spectra to assess the number-average molar masses of these VDF telomers (M̄n). Both these techniques showed a good agreement in terms of degree of telomerization, and the first examples of MALDI−TOF mass spectra of fluorotelomers are presented. Interestingly, all telomers obtained exhibit the structure CF3CH2CF2(VDF)nI, showing that (i) the trifluoromethyl radical preferentially attacked the methylene site of VDF with a high regioselectivity; (ii) the only transfer reaction arose from that to the CF3I and not from the monomer, the initiator, the solvent, or the polymer; and (iii) a very low defect of VDF chaining (0.73% regarded as the lowest one noted in the literature) was observed

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethan

Original Fluorinated Copolymers Achieved by Both Azide/Alkyne “Click” Reaction and Hay Coupling from Tetrafluoroethylene Telomers

The synthesis and characterization of an original class of linear poly(alkyl aryl) ethers containing 1,2,3-triazolyl and fluorinated moieties based on oligo(tetrafluoroethylene) telomer are presented. These polymers were prepared, from α,ω-dipropargyl ether bisphenol AF and 1,10-diazido-1H,1H,2H,2H,9H,9H,10H,10H-perfluorodecane, in 62% overall yields via the azide/alkyne “click” reaction and/or oxidative coupling of acetylenes (Hay reaction). The latter reactant was produced from the ethylene end-capping of oligo(tetrafluoroethylene) followed by a nucleophilic substitution with sodium azide. A simple tuning of the reaction conditions allowed us to direct the originally favored “click” reaction toward a competitive homocoupling of the terminal alkynes, thus leading to copolymers with drastically different structures, as evidenced by size exclusion chromatography, DSC, Raman, and UV−vis spectroscopy. Hence, original poly(alkyl aryl) ether copolymers with a high thermal stability (higher than 300 °C) that exhibit alternating statistic or block microstructures were obtained

“Grafting From” Polymerization of Vinylidene Fluoride (VDF) from Silica to Achieve Original Silica–PVDF Core–Shells

A new method of surface modification based on the “grafting from” polymerization process enabled to prepare original silica nanoparticles covered with PDVF “hair”. This strategy involved two steps: (i) the radical addition of 1,4-diiodoperfluorobutane initiated by <i>tert</i>-butylperoxypivalate onto the double bonds of silica nanoparticles (specific area of 150 m² g^–1) led to silica that bore C₄F₈I end-groups on its surface, and (ii) its use as original macrochain transfer agent in the “grafting from” polymerization of vinylidene fluoride (VDF) initiated by bis(4-<i>tert</i>-butylcyclohexyl) peroxydicarbonate. The characterizations of both modified silica were achieved by elemental analysis, ¹H and ¹⁹F magic angle spinning solid state rotational-echo double resonance NMR spectroscopy, thermogravimetry, and water contact angle (WCA) assessments. The grafting efficiency was confirmed by three features: (i) the increase of weight percentage of fluorine atom (that ranged from 0 for the starting unsaturated silica to 2.50% for silica-bearing −C₄F₈I end-group and to 3.32% for original silica–PVDF core–shells), (ii) a high thermostability (that reached more than 400 °C under air), and (iii) a good hydrophobicity: the WCA values were ranging from 84° to 109° and to 126° for vinyl silica, for silica coated with −C₄F₈I, and for PVDF-covered silica nanoparticles, respectively

Radical Grafting of Tetrafluoroethylene and Vinylidene Fluoride Telomers onto Silica Bearing Vinyl Groups

Radical addition of ω-iodofluorinated telomers was used to modify silica (S50) nanoparticles bearing vinyl groups. These iodo terminated derivatives were either commercially available tetrafluoroethylene telomers, CnF2n+1I with n = 4 or 6, or vinylidene fluoride telomers, CnF2n+1[VDF]mI with m = 6 and 23. These latters were synthesized by radical telomerization of VDF with CnF2n+1I initiated by bis(4-tert-butylcyclohexyl) peroxydicarbonate in high yields (>85%). The resulting nanohybrids were characterized by solid state NMR spectroscopy, elemental analyses and thermogravimetry. A covalent grafting between double bonds and fluorinated iodotelomers was noted. The covering density of fluorinated chains was assessed and reported with respect to fluorinated chain lengths. These nanohybrids exhibited a high thermostability (higher than 400 °C under air), losing less than 10% by weight at 700 °C, and a low surface tension, γs, from around 15 mN·m–1 to about 44 mN·m–1 for silica