Guy Levesque

Calorimetric study of fluorinated methacrylic and vinyl polymer blends: part 2: correlation between miscibility, chemical structure and χ12 interaction parameter in binary systems

Abstract The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester–MMA) copolymers (MMA–MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA–MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA–MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory–Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ 12 increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ 12 values as compared to VDF–TFE or particularly to VDF–TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values.

Calorimetric study of fluorinated methacrylic and vinyl polymer blends: 1. Binary systems: determination of miscibility domains and correlation of glass transition temperatures with blends composition— application to plastic optical fibre cladding

This paper reports a calorimetric study of binary polymer blends prepared by solution mixing of fluoroalkyl methacrylic ester-methyl methacrylate (MMA) copolymers with poly(vinylidene difluoride) (PVDF) or VDF-hexafluoropropene (HFP) (or VDF-trifluoroethylene) copolymers and examines their use as materials in plastic optical fibres (POF) technology. Some interesting blends were also obtained through mechanical mixing in the molten state. As compared to the well known PVDF-poly(methyl methacrylate) (PMMA) system, miscibility domains in copolymer blends become wider when less crystalline VDF copolymers are used in place of PVDF, whereas the opposite is found for the introduction of fluorinated alkyl ester side chains in PMMA. Correlation of the observed glass transition temperatures of homogeneous phases to their compositions failed with the Fox and Gordon-Taylor relations, whereas good fits could be observed using both Kwei and Jenckel-Heutsch relations. The q and b (specific interactions) parameters in these relations are well correlated to the chemical composition, indicating the influence of strong intermolecular interactions. In fluoroalkyl methacrylic ester-containing polymers, internal interactions are competing efficiently with intermolecular ones, thus limiting the miscibility of these polymers with VDF-homo- and copolymers. Some blends of the MMA-trifluoromethyl methacrylate with VDF-HFP copolymers give good performances as POF cladding material. A more simple solution lies in the use of VDF-HFP copolymers themselves.

Nanoparticles from vesicle polymerization: Characterization and kinetic study

The polymerization of isodecyl acrylate (ISODAC) in vesicles made from an anionic surfactant—sodium di-2-ethylhexyl phosphate (SEHP)—and from water is studied by 1H-NMR, transmission electron microscopy, and quasielastic light scattering. High polymerization rates and high conversion rates are achieved with both water-soluble initiator, K2S2O8 (potassium persulfate), and oil-soluble initiator, AIBN (azoisobisbutyronitrile). ISODAC is probably located inside the vesicle bilayer(s) because of its high hydrophobicity. Particles stable at room temperature with a mean diameter of about 50 nm are obtained. Kinetic orders of ISODAC polymerization are determined and the characterization of the resulting particles during and after polymerization are studied.

Functional polythiiranes: 3. Synthesis and characterization of polythiiranes containing biphenyl units in the side chain

Abstract The synthetic route to polythiiranes bearing side chain biphenyl groups is described. [(4-Biphenyl)methylthio]methylthiirane afforded relatively low molecular weight polymers in 50% yield, while (4-biphenyl)methyl 2-[(2,3 epithiopropyl)-thio]ethanoate afforded high molecular weight polymers in high yields.

Functional polythiiranes: 1. Comparative study of the anionic polymerization of mercaptomethylthiirane and hydroxymethylthiirane initiated by quaternary ammonium dithiobenzoate

Abstract The occurrence of chain transfers has been studied during the anionic polymerization of protic thiiranes in dimethylformamide initiated by tetramethylammonium dithiobenzoate. Results on polymer molecular weights and 13 C nuclear magnetic resonance spectra as well as polymerization rates have been used in a comparative study of hydroxymethylthiirane and mercaptomethylthiirane polymerizations. We have demonstrated that chain transfers occur significantly with mercaptomethylthiirane while they may be considered as non-existent with hydroxymethylthiirane. This is due to the equilibrium between ‘thiolate’ and ‘olate’ ions being more favourable to thiolate because of the relative acidity of thiols and alcohols.

Preparation and characterization of poly(thiirane) block copolymers with pendent hydroxy groups

Abstract 13 C n.m.r. spectroscopy was used to differentiate between block and statistical copolymers of hydroxy-methylthiirane and methylthiirane. Block copolymers could be exclusively obtained if hydroxymethylthiirane constituted the first sequence; however, if the first sequence consisted of methylthiirane, the synthesis of block copolymers failed because of a termination reaction. We demonstrate that the termination reaction is partially avoided in a protic medium.

Reaction d'addition des dithioacides aliphatiques aux alcynes

Resume Alkynes and aliphatic dithioacids react together to give vinyl dithioesters and/or heterocycles according to Michael, concerted on free radical chain additions.

Synthesis of thioamide‐containing polystyrenes by Friedel–Crafts reaction and by thioamidation of (co)polydithioesters

Thioamide groups were introduced into polystyrenes by the Friedel–Crafts reaction, with phenyl isothiocyanate in nitromethane solution, in the presence of anhydrous aluminium chloride. Free radical copolymerization of 4-vinyl dithiobenzoate with styrene followed by low-temperature solution condensation reactions, with excess of amines in N,N-dimethylformamide, offered another synthetic route to (co)polymers containing thioamine groups in the side chains without crosslinking.

Polyoxyethylenic macromers from polyoxyethylene monomethyl ethers and isocyanatoethyl methacrylate. Synthesis and characterization of copolymers with styrene and methyl methacrylate, obtained through bulk, solution and soap-free emulsion polymerizations

Abstract Polyoxyethylenic (POE) macromers were prepared from polyoxyethylene methyl ethers and isocyanatoethyl methacrylate and characterized by 13 C and 1 H nuclear magnetic resonance spectroscopy. Copolymers with styrene and methyl methacrylate (MMA) were obtained from these macromers upon free-radical initiation under various conditions (solution, bulk, soap-free emulsion) and some physical properties were studied (e.g. glass transition temperatures, stability of latex). Phase separation was observed in some copolymers with MMA as determined through dilatometry. Polystyrene latices, prepared without any emulsifying agent other than POE macromers themselves, were stable in the presence of high electrolyte concentrations.

Synthesis and characterization of naphthalene-containing polythioamides

New semi-aromatic polythioamides have been synthesized, based on aliphatic diamines and a new bis(dithioester) derived from 2,6-naphthalenedicarboxylic acid. Polythioamides were prepared by solution polycondensation at low temperature, in high yields and moderate to high inherent viscosities. The presence of naphthalene rings instead of benzene rings or aliphatic groups affected the thermal transitions in these polythioamides. By comparison with aliphatic or benzene polythioamides, polythioamides containing naphthalene revealed lower glass transition temperatures and a tendency to form liquid crystal mesophases. Noticeable solubility improvements were also observed.