Nine polyisobutylene (PIB) derivatives with different end groups (chlorine, vinyl, isobutenyl, 2,2-diphenylvinyl, and carboxyl) and molecular weights (1000 to 4500 g/mol), initiated by monofunctional and aromatic bifunctional initiators were studied by atmospheric pressure photoionization mass spectrometry (APPI-MS) in both negative and positive ion modes. Consistent with previous findings, negative ion APPI-MS revealed end-group identities through the formation of PIB adducts with chloride ions formed in situ from a chlorinated solvent (e.g., CCl₄) in the presence of a dopant (toluene). In positive ion mode, considerable fragmentation of these PIB derivatives was observed, rendering end-group determinations very difficult. The M _n values obtained by APPI(−)-MS were considerably lower than those determined by SEC for PIB derivatives with M _n higher than 2000 g/mol. PIBs containing carboxyl termini can undergo collision-induced dissociation, yielding structurally important product ions. The resulting APPI-MS/MS intensities were found to reflect the “arm-length” distribution for PIBs with bifunctional aromatic moieties. In positive ion mode, [M+COCl]⁺ adducts were observed for PIBs with an aromatic initiator moiety. The origin of the COCl⁺ species is also discussed.

在大气压下研究了九种具有不同端基（氯、乙烯基、异丁烯基、2,2-二苯基乙烯基和羧基）和分子量（1000 至 4500 g/mol）的聚异丁烯 (PIB) 衍生物，这些衍生物由单官能和芳香族双官能引发剂引发负离子和正离子模式下的光电离质谱 (APPI-MS)。与先前的发现一致，负离子APPI-MS 通过与从氯化溶剂（例如CCl ₄）在掺杂剂（甲苯）存在下原位形成的氯离子形成PIB 加合物来揭示端基同一性。在正离子模式下，观察到这些 PIB 衍生物有相当大的碎裂，使得端基测定变得非常困难。在M _ñ 对于 M _n高于 2000 g/mol 的PIB 衍生物，APPI(-)-MS 获得的值远低于 SEC 确定的值。含有羧基末端的 PIB 可以发生碰撞诱导解离，产生结构上重要的产物离子。发现所得的 APPI-MS/MS 强度反映了具有双功能芳族部分的 PIB 的“臂长”分布。在正离子模式下，对于带有芳香族引发剂部分的 PIB，观察到[M+COCl] ⁺加合物。还讨论了 COCl ⁺物种的起源。