Danièle Reyx

Chemical modifications of polydiene elastomers: A survey and some recent results

By chemical modification of natural rubber, it is possible to modify its basic properties (for instance, improvement of gas permeability, resistance to oils or fire resistance) or to prepare new polymeric materials for specific applications (for instance, photocrosslinkable rubbers and rubbers support of active molecules). The purpose of the present paper is to give an overview of recent works carried out in the field of new rubber derivatives for specific applications, especially dealing with natural rubber degradation and products derived from liquid rubbers of type 1,4-polyisoprene (liquid natural rubbers, synthetic polyisoprenes) and/or their epoxidized forms. A reflexion on the perspectives of researches on natural rubber or its derivatives is given in conclusion.

Cold plasma surface modification of conventionally and nonconventionally plasticized poly(vinyl chloride)-based flexible films : Global and specific migration of additives into isooctane

The effect of plasma-induced surface crosslinking of poly(vinyl chloride) (PVC)-based flexible films was investigated to limit its migration from packaging into fatty foodstuffs. The global migration was monitored by immersion into isooctane and the specific migrations of di-2-ethylhexyladipate (DEHA) and epoxidized soybean oil (ESO) were monitored by supercritical fluid chromatography analysis of the resulting isooctane solution. The plasma induced modifications were monitored with respect to the surface energy, weight loss, and surface crosslinking. The global migration from conventionally plasticized film, whose composition corresponds to an ordinarily used formulation for the manufacture of PVC wrap films, was controlled by different plasma treatments and the best results were obtained with Ar plasma. Further decreases in global migration were obtained by treating permanently plasticized films containing an elastomeric ethylene-based terpolymer (EE) in complete or partial replacement of DEHA. Before treatment, the replacement of DEHA with EE increased the DEHA and ESO specific migrations. Argon plasma treatment of permanently plasticized films led to samples that did not exhibit any migration.

Ring-opening metathesis polymerization (ROMP) of isomerically pure functional monomers and acyclic diene metathesis depolymerization (retro-ADMET) of functionalized polyalkenamers

ROMP and retro-acyclic diene metathesis (ADMET) were used for the synthesis of new functional polymers and functional oligomers, respectively. Purely exo and enantiomerically pure norbornene and 7-oxanorbornene derivatives were prepared using stereospecific synthesis, effective fractionation and high yield condensation reactions. Successful ROMPs of those monomers were performed using either the new carbenic Schrock’s or Grubb’s catalysts or in some cases a classical bicomponent catalyst. New functional polymers such as optically active poly(norbornene-2-carboxylic acid), reactive poly(norbornene-2-azlactone), and side-chain liquid crystal polyoxanorbornenes were fully characterized. On the other hand, successful depolymerizations of 1,4-polyisoprene and of epoxidized 1,4-polybutadiene via cross-metathesis with 4-octene were performed using a stabilized bicomponent catalyst and the Grubb’s catalyst, respectively. Conditions for the controlled synthesis of epoxidized oligobutadienes and of epoxydienic monomers via retro-ADMET were clearly defined.

Synthesis and characterization of 4-cyanobiphenyl-4′-yloxy-functionalized poly(7-oxanorbornene-5,6-exo-dicarboximide)s via ring opening metathesis polymerization (ROMP)

N-[n-(4-cyanobiphenyl-4′-yloxy)alkyl]-7-oxanorbornene-5,6-exo-dicarboximide (CBON2–CBON8) with increasing number of methylene groups in the alkyl part (n = 2–8) were synthesized by Mitsunobu condensation between the appropriate alcohols (CBA2–CBA8) and 7-oxanorbornene-5,6-exo-dicarboximide (ON). The conditions for the ring opening metathesis polymerization of CBONn giving acceptable molecular weights and molecular distributions were established. Characterization of the resulting polymers (P2–P8) by 1H- and 13C-NMR has shown a high trans content. Differential scanning calorimetry and optical microscopy analysis have shown that the alcohols CBAn are thermotropic with some variations between the first and second heating-cooling cycles, the monomers CBONn melt with no evidence of any mesomorphic state, the polymers Pn show only the glass transition, and the glass transition temperature (Tg) decreases with increases in the spacer length.

Application of metathesis reactions to the synthesis of α, ω functional prepolymers

Abstract α,ω4 dimethylcarboxylate 1,4 polybutadiene like polyenes are synthesised by cometathesis between 1,5-cyclooctadiene and dihydromuconic methyl ester by use of the WCl6/SnMe4 catalytic system. Observed distribution of the lower metathesis products is not the statistical one. Metathesis involves preferentially, the double bonds in the neighbourhood of the ester groups. The same method with WCl6/EtAlCl2 catalytic system, applied to symmetrical α,ω dichloroalkenes and 1,5-cyclooctadiene, does not lead to α,ω dichloropolybutadiene-like polymers with good specificity. Studies on dichloroalkenes or on 1-chloro 4-pentene in coreaction with 4-octene or 1,5-cyclooctadiene have been carried out; near-cationic oligomerization and arylation as secondary reactions, and homoallylic isomerization occurs.

Ring‐opening metathesis polymerization of 2‐(S)‐(–)‐endo‐D‐pantolacton‐O‐yl norbornene‐2‐carboxylate using a classical ROMP catalyst. Synthesis and characterization of optically active poly(norbornene‐2‐carboxylic acid)

ROMP of the optical pure monomer of the title compound (1) was performed successfully using the classical WC1 6 /SnMe 4 catalyst. Beside the stereoregularity (σ c = 0.70), the 13 C NMR spectrum of the resulting polymer (P 1 ) evidenced a noticeable directional regularity (B = (HT + TH)/(HH + TT) = 1.6) which can be due to sterically induced regiospecificity in the norbornenyl ring opening during propagation. Significant optical activities were observed for P 1 and for poly(norbornene-2-carboxylic acid) (P 2 ) resulting from LiOH hydrolysis of P 1 is probably due to the homochiral pantolactonyl side chain and the (S) C 2 backbone carbon.

Dégradation controlée des polyisoprènes‐1,4 par le couple phénylhydrazine/oxygène, 2. Molécules modèles de structures phénylhydrazone non‐conjuguées d'extrémités de chaîne

With regard to the postulated intervention of phenylhydrazone structures during the degradation of 1,4-polyisoprenes by the phenylhydrazine (1)/oxygen system, UV, 1H NMR, 13C NMR and mass spectroscopy as well as steric exclusion chromatography were applied for the characterization of model phenylhydrazones deriving from non conjugated carbonyl derivatives. Comparison of the results with some possible coexistent structural parameters gave some indications on the validity of these analytical tools for the identification of phenylhydrazone structures in oxidized polyisoprene.

Synthèses de polysiloxanes organofonctionnels, 4. Les poly[(hydroxyméthyl)méthylsiloxane]s homogénes et hétérogènes†

Transformations of oxy(halomethyl)methylsilanediyle units or oxy(acetoxymethyl)methyl-silanediyle units into oxy(hydroxymethyl)methylsilanediyle units in homogeneous and heterogeneous polysiloxanes were investigated. Si-C-cleavage and SiOSi-rearrangement were studied on disiloxanes and oligosiloxanes used as models of the corresponding polymers. Methanolysis of poly[(acetoxymethyl)methylsiloxane]s and their copolymers catalysed by p-toluenesulfonic acid was applied to obtain poly[(hydroxymethyl)methylsiloxane]s and their copolymers.