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•PUFAs are essentials for human health but are not synthesized and must be supplied by food.•Sources of PUFAs are vegetables or fishes but alternatives sources are possible.•Microorganisms (yeasts, fungi, microalgae and Thraustochytrids) can produce PUFAs.•Microbial lipids production needs to be improved essentially by the mode of culture.•Recent development in metabolic engineering improves microbial lipids production.

AbstractSemiotics of the body consists essentially, in a current use, in gestural and mimo-gestural semiotics. At best, in an integrated semiotic approach, communicative gesture involved the construction of a syncretic expression plane, combined with verbal discourse. The body as conceived by psychoanalysts is, on the contrary, the source and the seat of energy itself (impulses), from which psychic instances feed their representations. The psychoanalytical body is thus both the source and the significant substance from which the semiotic actant may take form. In the phenomological conception developed by Merleau-Ponty, the proper body is that entity, the “vehicle of our being in the world”, which belongs both to “I” and to “the world for me”, which takes shape in perception, where the first (I) experienced the second (world for me). The phenomenological body seems at first sight an adjuvant, which turns out to be, for a second sight, the very principle of actantiality and intentionality. In a quick overview of the different “implicit semiotics” of the body in human sciences (psychoanalysis, theory of “I-skin”, contemporary cognitive science, psychology, etc.) it acquires a status of an actantial basis, because, as an actant, it is directly involved in the process of incorporation of agentivity and intentionality, and with two different and recurrent representations: one according to movement, and the other according to envelope. Forces and form, in short. We decide to name them (arbitrarily for now, but we’ll return to this point) the first “Me” and the second “Myself”. • “Me” is the referent instance, consisting both of sensitive matter and energy, the substrate and the dynamic bodymark for all figures and all enunciations. In short, it will be the “Me-flesh.” • “Myself ” is the body-in-construction, the living vehicle of intentionality and the interactions support, and therefore, particularly the support of confrontation with otherness; and, through these interactions, it provides the actant a patterned form through which it may be identified. In short, this is “Myself-envelope”. Then the paper may display a new typology of semiotic body figures. At each of these figures of the body, is a figure of movement. At each of them, is a figure of enunciative instances, that is to say for each of them a modality of the imprint and of its interpretation.

AbstractThrough the signs that express or describe space in the Anatolian hieroglyphic writing, this study examines the process of creating signs. To do this, it is imperative to consider the materiality of the sign and to envisage signs not only in their context of appearance, their relations with other signs (integration into the system), their relationship with language (the linguistic Signified), but also with a non-linguistic Signified, and finally in their relationship with the society that gave birth to them. The limited scope of this study will not allow us to take into account all parameters, and thus only ideograms / logograms were selected. We have identified three groups of signs that seem to correspond to different types of procedures: (i) the pair ORIENS-OCCIDENS, (ii) signs which designate space or a portion of space (road, river, etc.) and (iii) the space words (that express spatial relationships).

Studies on the anionic polymerization of methyl methacrylate in tetrahydrofuran and in the presence of sparteine have revealed a beneficial effect due to this additive, resulting in a decrease in the extent of termination. Better control of the definition of the polymers formed can thus be achieved in the presence of this additive. On the other hand, macromolecular engineering requires a range of active species concentrations lower than 10−3 mol L−1 and particularly the synthesis of polymers of high molar masses. For a better understanding of the mechanism of chain growth under such concentration conditions, the kinetics of polymerization have been investigated with a technique based on adiabatic calorimetry. Sparteine has been found to lack sufficient cation‐binding power to prevent the propagating enolate ion pairs from aggregating. The rate constant of propagation of nonaggregated species has been estimated, as well as the aggregation constant of equilibrium. For very low initiator concentrations, termination reactions have been shown to profoundly alter the control of the polymerization and to prevent a quantitative monomer conversion. Theoretical maximal conversions have been calculated from kinetic data and compare well with the experimental values. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4964–4975, 2004

The kinetics of the “living” and “controlled” ring‐opening metathesis homo‐ and copolymerization of several cycloalkenes initiated by Mo‐based Schrock complexes were investigated in the context of a general study devoted to the relation between the monomer structure on its reactivity. First, the polymerizability of these monomers was measured as a function of both their ring strain and their bulkiness. In a second part, the intrinsic reactivity of both the monomers and the corresponding active centers was evaluated from the determination of the rate constants of homopropagation and the various reactivity ratios. The steric hindrance created by the monomer substituents has only a small effect on the intrinsic reactivity of the cycloalkene. The latter mainly depends on the ring strain exactly as does the polymerizability. Steric crowding around the acyclic double bonds of the polymer chain is another factor affecting the reactivity of the active propagating centers; the latter is indeed found to depend on the capability of these acyclic double bonds to compete with the double bond of the cyclic monomer for the complexation to the transition metal.

The influence of monophenoxymagnesium (2,6-di-tert-butyl-4-methylphenoxybutylmagnesium, BuMgOBT) and diphenoxymagnesium (bis(2,6-di-tert-butyl-4-methylphenoxy)magnesium, Mg(OBT)2) derivatives used as additives, on the structure and reactivity of polystyryllithium (PSLi) species in hydrocarbons was studied. The impact of these compounds on the thermal stability of active species and on the reactivity in the styrene anionic polymerization at high temperature was investigated and was compared with that of n,s-dibutylmagnesium (n,s-Bu2Mg). Kinetic measurements were carried out in cyclohexane at 100°C and the thermal stability of polystyryl end-groups was studied at 150°C in decahydronaphthalene. The presence of BuMgOBT or Mg(OBT)2 significantly increases the thermal stability of active species compared to dialkylmagnesium or alkylalkoxymagnesium derivatives. Unlike n,s-Bu2Mg, BuMgOBT and Mg(OBT)2 do not contribute to the formation of new PS chains in addition to those produced by PSLi seeds.

The possibility to initiate styrene retarded anionic polymerization in hydrocarbon solvents from bimetallic systems based on lithium alkoxide and metal−alkyl derivatives like trialkylaluminum or dialkylmagnesium was investigated. The combination of the two organometallic compounds, individually inactive, affords an active initiating system which can be an alternative to alkyllithium initiators. Activation involves a ligand exchange inside the bimetallic complex, thus in situ forming an alkyllithium compound complexed with a new alkoxymetal−alkyl derivative. The kinetics and extent of the ligand exchange process are highly dependent on the nature of both the ligand and the metal, magnesium alkyls being much more efficient than aluminum ones. The influence of the nature of both the lithium alkoxide and the metal−alkyl derivatives on the initiation efficiency and retardation of styrene polymerization was studied.

Zinc and boron derivatives were used as additives for the retardation of styrene polymerization initiated by sec-butyllithium. The formation of mixed complexes between polystyryllithium (PSLi) and alkyl zinc or boron derivatives as well as a transmetallation reaction between PSLi and alkoxyborane was studied by UV-vis spectroscopy. Kinetic studies performed in the presence of these additives show that the rate of polymerization is divided only by two with diethylzinc at [Zn]/[Li] = 8 suggesting the contribution of remaining non-complexed PSLi. On the contrary, the rate was found to decrease noticeably with triethylborane upon increasing the [B]/[PSLi] ratio, in agreement with the formation, at 20°C, of “ate” complexes more stable than with diethylzinc. However, the dissociation constant of the complexation equilibrium between R3B and PSLi is highly dependent on the temperature, and the retardation is not so effective at T > 100°C. The same retardation effect was observed with borane alkoxides. Transmetallation reaction involving PSLi and B—OR bonds is first observed yielding B(PS)x derivatives. Retardation is governed by the concentration of the remaining PSLi species.

The kinetics of the anionic polymerization of methyl methacrylate using THF as solvent, 1,1-diphenylhexyllithium as initiator and sparteine as ligand has been investigated in a flow-tube reactor for initiator concentrations higher than 1×10 mol l and a temperature range between −10 and 20 °C. Addition of sparteine induced a decrease in both the reactivity of the growing enolates and the extent of termination reactions. While a fractional kinetic order relative to the active centres was obtained in the presence of sparteine, this additive shifted the equilibrium between aggregated and unimeric species toward the formation of unimeric-ligated enolates as indicated by entropic and enthalpic parameters of the aggregation equilibrium. The rate constants of propagation and termination of these growing species were also determined.

This paper discusses the influence of dialkylphenoxyaluminum additives on the retardation of styrene polymerization initiated by alkyllithium. Data are compared with results obtained with trialkylaluminum. Similar decreases of the propagation rate can be achieved with both types of compounds. Although with R 3 Al additives ( i -Bu 3 Al, Et 3 Al, Me 3 Al), reactivity extinction appears with the formation of inactive 1:1 (Al/Li) mixed complexes, at a ratio of [Al]/[Li]=1, in the presence of diisobutyl-2,6-di- tert -butyl-4-methyl-phenoxyaluminum, extinction occurs at a ratio of [Al]/[Li]=0.5. This was correlated to an irreversible ligand exchange between the polystyryllithium and the phenoxyaluminum derivative, as proved by the formation of the corresponding lithium phenoxide, prior to formation of a 1:1 complex.

The kinetics of ring-opening metathesis polymerization of norbornene were investigated in cyclohexane using several Schrock complexes as initiators. Three different Schrock complexes were used: Mo(CHC(CH3)2Ph)(NAr)(O-t-Bu)2 (NAr = Ph^(iPr)2) (I), Mo(CHC(CH3)2Ph)(NAr)(OC(CF3)2CH3)2 (NAr = Ph^(iPr)2) (II) and W(CH-t-Bu)(NAr)(O-t-Bu)2 (NAr = Ph^(iPr)2) (III). The presence of alkoxy-fluorinated ligands on II and on the corresponding propagating species enhances the polymerizability of norbornene and modifies the kinetic scheme compared to that of polymerizations initiated by the tert-butoxy complex. The greater electropositive character of II compared to that of I results in a majority of metalla-alkylidenic growing species being complexed to monomer; therefore, the coordination of the monomer is not the rate-determining step for the process. In contrast, the major part of growing species, which are derived from the tert-butoxy complex are in a non-coordinated state and, thus, the ability of the initiator to complex the monomer is decisive. In addition, this study allows to quantify the stronger reactivity of W-based complexes compared to that of Mo-based ones. These results were all corroborated by prior theoretical studies using ab initio calculations.

The possibilities offered by the ring-opening metathesis polymerization (ROMP) of macromonomers were exploited to arrange polystyrene (PS) and polybutadiene (PB) subchains in various topologies. PSn-b-PBm and PSn-co-PBm miktoarm stars were obtained by sequential and statistical polymerization of norbornene-terminated PS and PB macromonomers, whereas (PS-b-PB)n star block copolymers were derived by homopolymerization of the corresponding macromonomers via ROMP. Umbrella-type and dumbbell-shaped copolymers are two other architectures that were prepared through the sequential ROMP of ω-norbornenyl PS macromonomer and cyclooctadiene.

The addition of triisobutylaluminum to a lithiated‐based anionic polymerization of styrene leads to the formation of aluminate complexes and provokes a drastic reduction of the styrene polymerizability in relation with the Al/Li ratio used. The reaction is first order in monomer and active species and is stopped for iBu3Al/PSLi > 1. From U.V. spectrometry, kinetic studies and viscometric measurements, it was possible to suggest the presence of various mixed complexes of different stoichiometries. The strong increase in the thermal stability of the new propagating species together with their much lower reactivity permits the controlled bulk polymerization of styrene at high temperature.

Oxidation of α-(N-alkylamino) phosphonic acid esters, carrying one or two alkyl groups as substituents on their α-carbon, by m-chloroperbenzoic acid afforded the corresponding stable β-phosphonylated nitroxides. The nitroxides derived from α-mono-tert-butyl α-alkylaminophosphonic acid esters are stable compounds despite the presence of a hydrogen atom on the α-carbon bound to the nitroxyl group. The ESR study of these nitroxides in solution showed that this β-hydrogen atom lies in the nodal plane to the nitroxyl function. These β-phosphonylated nitroxides were found to efficiently control the free radical polymerization reaction of styrene, with a much faster rate of propagation than that observed in TEMPO-mediated systems.

The influence of n,s-dibutylmagnesium on the kinetics of styrene polymerization initiated by s-butyllithium was investigated in cyclohexane at 50°C. The presence of n,s-dibutylmagnesium, in molar ratios ranging from 0 to 20 with respect to polystyryllithium, leads to a drastic and continuous reduction of the reactivity of the propagating species. The living character of the polymerization, especially the control of the molar mass is preserved over the entire range studied. The experimental molar masses are in agreement with the formation of one polystyrene chain per lithium and 0.5 to 0.8 chains per magnesium atom, indicating that both alkyllithium and dialkylmagnesium species are involved in the polymerization process through the formation of “ate” complexes. The UV-visible study of the PSLi/n,s-dibutylmagnesium systems shows that several types of “ate” complexes with different stoichiometry are formed depending on the proportion of the two metal derivatives.

This work focuses on the synthesis and the ring-opening metathesis polymerization of α-norbornenylpoly(ethylene oxide) macromonomers. Although obtained in 100% yield and with a narrow distribution of molar masses, the polymacromonomers exhibit degrees of polymerization that are systematically higher than expected. The reasons for this feature are thoroughly discussed.

A new method to synthesize comb-like polymeric liquid crystals with flexible main chains through the chemical modification of a low molecular weight polybutadiene is described. Polarized light optical microscopy and differential scanning calorimetry allow the mesophases to be identified as SA and their existence temperature range to be determined.

Polymerisable organic silane molecules [3-(trimethoxysilyl)propyl methacrylate, γ-MPS] have been grafted onto the surface of ceramic oxide powders (Al2O3 , ZrO2 , TiO2), via hydroxy groups of the latter oxides, in order to obtain organic–inorganic hybrid ‘macromonomers’. Densities of surface hydroxy groups have been determined using thermogravimetry (TG) and chemical titration. Quantification of γ-MPS grafting has been determined by FTIR spectroscopy, elemental analysis and TG. Typical grafting yields up to 6 mol m-2 were obtained. The influence of the relative amount of silane used has been studied. Silane multilayers and/or aggregates are formed as observed in 29Si CP MAS NMR spectroscopy.

Le comportement réactionnel, en polymérisation Ziegler-Natta de l'éthylène, de systèmes solubles à base de polydiényllithium ou de polystyryllithium/TiCl4/solvants apolaires, a été étudié. L'activité et l'efficacité de ces systèmes sont étroitement liées à la nature de l'organolithien et à celle du solvant ainsi qu'à la valeur du rapport r = [Li]/[Ti]. L'activité et l'efficacité optimales sont obtenues avec le système polybutadiényllithium/TiCl4/toluène pour le rapport r = 2,0. Le copolymère séquencé polybutadiène-polyéthylène obtenu est légèrement réticulé. L'utilisation du système soluble polystyrèneDPn=100-butadièneDPn=2butadiényllithium/TiCl4/toluène, en limitant la longueur de la séquence polydiènique, permet d'éviter cette réticulation parasite. Un tel système permet en outre d'accéder à la valeur de l'efficacité réelle du complexe amorceur. Celle-ci est égale à 0,44 par rapport à la concentration en titane; cette valeur, très élevée par rapport à celle des systèmes conventionnels, est responsable de la grande activité des systèmes que nous avons étudiés.

Poly(methyl methacrylate) (PMMA) has been anionically synthesized at high temperature and in apolar media, using diphenylhexyllithium (DPHLi) as initiator and a novel σ‐μ chelating ligand to curb the side reactions. It has been indeed found that lithium 2‐(dimethylamino‐)ethoxide is a very efficient σ‐μ ligand that prevents the anionic polymerization of methyl methacrylate (MMA) from being disrupted by significant secondary termination reactions. Ligand/initiator molar ratio, solvent polarity, temperature, monomer and active center concentrations are proved to be key parameters in the control of the polymerization process.

This paper reviews the possibilities of engineering novel macromolecular topologies via “living” ring‐opening metathesis polymerization (ROMP) of miscellaneous macromonomers. It is shown that multibranched polystyrene poly(ethylene oxide) and polybutadiene polymacromonomers of varying compactness and branch number can be prepared by ROMP of corresponding macromonomers, provided the macromonomers carry an end‐standing norbornene unsaturation. Janus‐type architectures are also accessible by this technique: such entirely novel topologies can be obtained by sequential ROMP of two different macromonomers whereas their statistical copolymerization affords heteroarmed macromolecules. Advantage has also been taken of the versatility of this technique to prepare compact polymeric architectures that behave like unimicellar systems: structures whose inner part and outer layer are chemically different can be derived through homopolymerization of macromonomers that are themselves block copolymers. © 1998 John Wiley & Sons, Ltd.

This paper concerns the synthesis of two different structures of styrene‐butadiene block copolymers that were respectively obtained viasequential and statistical ring‐opening metathesis copolymerization of norbornene‐terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene‐butadiene copolymers originates from the observation that phase‐separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (χ), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two types of copolymers ‐prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively‐ exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.

Monodisperse core−shell latex particles functionalized with surface groups that were introduced by the macromonomer technique were obtained by means of a two-step emulsion polymerization process in a batch reactor at 70 °C. In the first step the cores were synthesized by means of a batch emulsion polymerization of styrene (St), and in the second step, the shells were formed by batch emulsion copolymerizations of St and different macromonomers using the seeds obtained previously. Macromonomers were synthesized by anionic “living” polymerization. They are constituted of a poly(ethylene oxide) hydrophilic block and a hydrophobic block or sequence end-fitted with an unsaturation. The latexes were characterized by gravimetry, transmission electron microscopy (TEM), and conductometric titrations to obtain the conversion, the particle size distribution (PSD), and the surface charge density (σ), respectively. The colloidal stability of the cores and final latexes were determined by measuring the critical coagulation concentration (CCC) at two pHs (7 and 2) using KBr as electrolyte. The surface charges of the latexes were moderately low, with corresponding moderately low CCCs. The presence of spacers, confirmed with a disk centrifuge photosedimentometer (DCP) and photon correlation spectrophotometer (PCS), did not increase the CCC. During the CCC measurements, at high electrolyte concentrations, the reduced solubility of the spacer PEO moiety in the solution resulted in its collapse on the particle surface.