Polyisobutylene (PIB) is commonly used in both the industrial and commercial setting for numerous purposes such as a copolymer in rubber and lubrication. In previous work within our group, we had noted that attempts to arylate alkene terminated PIB led to formation of tert butyl toluene at reflux. Later work showed that this process occurs at room temperature when triflic acid was used. In this work we have investigated the degree of this polymer degradation as a function of acid strength, solvent, and the terminal functional group on the PIB. Large amounts of degradation only occur with very strong acid at ambient temperature. While the solvent has to be an arene, the reaction is less successful with electron-rich arenes like anisole. We postulate that this mechanism proceeds via loss of an isobutylene unit after protonation of the terminal group on functionalized PIB. The excess isobutylene that forms can then be protonated at which point it is consumed by the arene solvent. This excess solvent allows for a Le Chatelier driven degradation of the polymer chain as the normally minimal isobutylene unit is removed. While this reaction is reversible in the same way as the direct attack on the PIB cation, the large excess of the arene solvent drives this formation of tert-butylated arene, insuring complete degradation of the polyisobutylene. This process avoids the high temperature normally needed for such processes and making a potentially useful byproduct.

Le Chatelier’s principle driven depolymerization of functionalized polyisobutylene at 25<sup>o</sup> C

254th National Meeting (2017)

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Le Chatelier’s principle driven depolymerization of functionalized polyisobutylene at 25o C

Le Chatelier’s principle driven depolymerization of functionalized polyisobutylene at 25^o C