SynopsisConditions of epoxidation of unsaturated polymers were studied. Perphthalic monoacid appeared to be one of the most efficient epoxidation agents, particularly when the double bond is enriched with electrons. Some properties of the new polymers thus obtained were revealed and functional crosslinkings were achieved.Si certaines reactions d'oxydation des elastomeres! et en particulier du caoutchouc naturel,? ont fait l'objet de nombreux travaux, il ne semble pas que la creation de groupes epoxydes par reaction d'un peracide organique sur une double liaison ait ete clairement etudiee, En effet, les auteurs":" qui ont utilise les peracides dans les reactions de modification des polymeres n'ont pas mis en evidence les derives epoxydes, Ils obtiennent generalement des composes hydroxyles plus ou moins esterifies par les acides residuels. Quant a la chaine propre a I'elastomere, elle est fortement degrades.On a done utilise un reactif plus specifique des doubles liaisons polyiso-
The addition of different ethylene monomers to polyisoprene was studied in order to throw a light on reaction mechanisms and structures of reagents. It was attempted, during the planned transformations, to maintain as best as possible the shapes and sizes of initial macromolecules, upon which rests the property of high elasticity. For this purpose, it was decided to avoid grafting reactions, as well as any reactions affecting the nature of the polyisoprenic chain, e.g., scission, cross-linking, and cyclization. After the completion of the work carried out by one of the authors on the addition of maleic anhydride, the existence of two mechanisms was brought to light: the one is of a radical type, produced by adding an unsaturated reagent on a methylene close to a double bond of chain; the other is of a thermal nature, triggered by the action not of a catalyst, but of a rather high temperature. It is clear that the latter process does involve isomerization of a part of chain double bonds. The model to which maleic anhydride is connected has been deduced by examining the reaction aptitudes of a series of monomers. The major part of highly polymerizable materials, with the exception of acrylonitrile, were eliminated a priori, in order to avoid both homopolymerization reactions and graftings. The monomers in which double bonds are depleted in π electrons are more apt to give the desired reactions. The more favorable effect is obtained with α carbonyl (maleic anhydride and γ crotonolactone). Other factors were also taken into account. The work reviewed here enabled us to assess the way in which reactions evolve according to the considered mechanisms and produce new macromolecular materials. The resulting compounds have a high rubberlike elasticity and show a high chemical reactivity, due to anhydride or lactone side groups.
It has been verified that, in a number of cases, thermogravimetric analysis permits quantitative determination and identification of carbon blacks in the free state or in vulcanized compounds. The proper operating conditions can give sufficiently good repeatability and adequate precision for most routine analyses. As is the case in other methods for determining the loading, numerous difficulties were encountered with elastomers which graphitize on heating. However, quantitative analysis of black in nitrile rubbers remains possible, but the identification of different types of black is very difficult. The authors propose to continue this study, particularly into the new families of blacks, primarily into the function of the diameter of their elementary particles and their degree of structure.
On a étudié la fixation de carbonyles fortement électrophiles sur les polyènes macromoléculaires dont les doubles liaisons présentent une densité électronique élevée. Parmi les aldéhydes utilisés, il faut citer en premier lieu le chloral et le glyoxal. Le chloral se combine aux cis 1,4‐polyisoprènes en présence de AlCl3 ou de BF3 pour former des groupes latéraux —CHOH—CCl3 caractérisés par la spectrographie I.R. et l'analyse chimique. La cyclisation de la chaîne consécutive à l'action du catalyseur paraît être évitée dans le cas où l'on opère avec AlCl3, elle se manifesterait en présence de BF3. Le glyoxal se combine aux cis 1,4‐polyisoprènes en présence ou non d'acides de LEWIS pour donner des structures —CHOH—CHO. Le groupe aldéhyde libre de ces chaînes latérales est responsable de l'instabilité des polymères obtenus. D'autres structures aldéhydes ont été envisagées. Les résultats les plus favorables sont obtenus avec des carbonyles très électrophiles, parmi lesquels on peut citer le cas de l'aldéhyde glycidique.
In an earlier note the fixation of chloral onto cis-1,4-polyisoprene (natural or synthetic) in the presence of a catalyst such as AlCl3 or BF3 was discussed. A similar combination with glyoxal has already been mentioned. The fixation of chloral produces macromolecular products with a level of fixation of not higher than n=30 (n, number of reagent molecules attached to a chain of 100 C5H8 units). These compounds contain hydroxyl groups, the infrared bands of which appear at 3,300–3,500 cm−1, while the chlorines are identified at 570, 620, 680, 730, and 1,080 cm−1; these bands can be attributed to side chains —CHOH—CCl3. Also, the band which is characteristic for the cis configuration remains in the spectrum, but has decreased in comparison with the blank; the broadening of the peak at 1,640 cm−1 and the presence of a band at 860 cm−1 indicate the appearance of vinylidene double bonds not located in the chain. This observation is in agreement with our earlier work. The presence of side chains —CHOH—CCl3 is confirmed by the reactivity inherent to these functional groups. The expected reactions take place but are limited by the formation of a three dimensional network resulting in insoluble compounds. Thus, a modified polyisoprene (n=15) loses only 60% of its chlorine by heating to 130° C in xylene solution in presence of finely dispersed sodium. It is difficult to eliminate the remaining chlorine because the radicals formed by the —CCl3 groups produce crosslinking. Phenyllithium produces similar effects to those of sodium, in addition a certain number of phenyl groups are added and result in bands found at 1,495–1,580 cm−1. The presence of hydroxyl groups is also verified by reaction with acetyl chloride. Bifunctional reagents such as adipoyl dichloride or hexamethylene diisocyanate produce crosslinking reactions which become evident by rapidly increasing insolubility.
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