Irène Campistron

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.

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.

Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender nature and their equivalent ratios on the mechanical and thermal properties of PUs

Abstract New segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain extender nature were found between the weight loss (%) and the percentages of hard segments. A classification of thermal stability in terms of weight loss was established. With the aim of a thermo-mechanical comparative study, polyurethane elastomers based on HTPI and isocyanates without chain extender, were also synthesized.

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.

Antifouling action of polyisoprene-based coatings by inhibition of photosynthesis in microalgae

Previous studies have demonstrated that ionic and non-ionic natural rubber-based coatings inhibit adhesion and growth of marine bacteria, fungi, microalgae, and spores of macroalgae. Nevertheless, the mechanism of action of these coatings on the different micro-organisms is not known. In the current study, antifouling activity of a series of these rubber-based coatings (one ionic and two non-ionic) was studied with respect to impacts on marine microalgal photosynthesis using pulse-amplitude-modulation (PAM) fluorescence. When grown in contact with the three different coatings, an inhibition of photosynthetic rate (relative electron transport rate, rETR) was observed in all of the four species of pennate diatoms involved in microfouling, Cocconeis scutellum, Amphora coffeaeformis, Cylindrotheca closterium, and Navicula jeffreyi. The percentage of inhibition ranged from 44% to 100% of the controls, depending on the species and the coating. The ionic coating was the most efficient antifouling (AF) treatment, and C. scutellum and A. coffeaeformis are the most sensitive and tolerant diatoms tested, respectively. Photosynthetic inhibition was reversible, as almost complete recovery of rETR was observed 48 h post exposure, after detachment of cells from the coatings. Thus, the antifouling activity seemed mostly due to an effect of contact with materials. It is hypothesized that photosynthetic activity was suppressed by coatings due to interference in calcium availability to the microalgal cells; Ca(2+) has been shown to be an essential micro/macro nutrient for photosynthesis, as well as being involved in cell adhesion and motility in pennate diatoms.

Preparation of New Polyols Based on Cis-1,4-Polyisoprene by Using 1,3-Dipolar Cycloaddition

This research focuses on synthesis and modification of polyol precursors derived from cis-1,4-polyisoprene (PI). These new polyol precursors can be converted to high value-added polyurethane (PU). The epoxidized hydroxytelechelic PI (EHTPI) prepared by chemical modification from PI was used as starting material for polyol synthesis. 1,3-Dipolar cycloaddition between a terminal alkyne and an azide has rapidly become the most popular click reaction. We applied this reaction to couple azide-functionalized PI and alkyne-functionalized sugar for preparing polyols. For azide functionalization, 1-methyl epoxidized cyclohexane was used as a model molecule, and various conditions for epoxide ring opening of 1-methyl epoxidized cyclohexane and EHTPI were investigated. The cycloaddition of alkyne and azide was carried out in the presence of sodium ascorbate and copper sulfate. The polyol precursors obtained might be used to prepare biodegradable polyol PU.

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.