Synthese d'elastomeres photoreticulables par modification chimique du caoutchouc naturel liquide-I. Introduction de l'anhydride maleique sur les structures polyisopreniques

With the aim of preparing photocrosslinkable elastomers, partial chemical modification of liquid natural rubber (LNR) by reaction with maleic anhydride has been studied. LNR was obtained by controlled degradation of natural rubber in latex state with the phenylhydrazine/oxygen system. As a first approach, 4-methyl-4-octene was studied as a model for the 1,4-polyisoprene structure. This led to the choice of a thermal fixation process, called the "ene reaction", which is more selective than the radical reaction system using initiators. A reliable method for determining the modification level by maleic anhydride was provided by titration of the formed acid functions which result from the succinic ring opening reaction by the action of methanol. With the exception of the partial succinic ring opening which occurs during the maleic anhydride addition process, a good match was observed between the maleinization study on LNR and those on liquid synthetic 1,4-polyisoprene. For a theoretical partial modification fixed at 20%, a maximum yield of 70% was achieved under optimum reaction conditions.