Polyisobutenylsuccinic anhydride (PIBSA) has been analyzed using negative ion electrospray ionization mass spectrometry (ESI-MS). This mild technique gives the molecular ion distribution for the PIBSA mono-succinic acid polymer as the major product. Unexpectedly, small amounts of the PIBSA bis-succinic acid polymer were also observed. This can form a basis for a method to determine the succinic ratio of samples of PIBSA. Commercially available samples of PIBSA made from BF 3-catalyzed poly-(isobutylene) and AlCl3-catalyzed poly(isobutylene) were compared. While the PIBSA made from BF3catalyzed poly(isobutylene) consisted of polymers separated by 56 Da, the PIBSA made from AlCl3catalyzed poly(isobutylene) consisted of polymers separated by 14 Da. We attribute this to different molecular weight distributions of the starting poly(isobutylene). Poly(isobutylene) from AlCl3 catalysis is postulated to form via a mechanism that consists of carbenium ion rearrangements and β scission reactions at the active site.

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Communications to the Editor 7409 References and Notes(1) This work was performed under the auspices of the Division of Basic Energy Sciences of the U.S. Department of Energy. We also wish to acknowledge the partial support of this collaborative research by the National Science