1-Hexyl-3-methylimidazolium perfluorobutanesulfonate ([C₆mim][PFBS]), a fluorinated ionic liquid (fIL), exhibited complicated phase behaviors under high pressure (HP). The asymmetric [PFBS]⁻ anion possesses conformational degrees of freedom. Using X-ray diffraction, HP crystal structures were determined upon compression and decompression. 00ℓ Bragg reflections at the small scattering angle representing the layered structures appeared reentrantly. The reentrant phase behavior is described by layering of [PFBS]⁻ (layering I) below 3.7 GPa (P₁) and the hybrid layered structure of [PFBS]⁻ (layering II) above 7.6 GPa. The layering II caused irreversible crystal polymorph in the pressure cycle. Below P₁, HP-phase transition changed to reversible crystal polymorph. The complicated HP-crystal polymorphs and multiple pathways were derived from the conformation-driven molecular packing states.

1-Hexyl-3-methylimidazolium perfluorobutanesulfonate ([C ₆ mim][PFBS]) 是一种氟化离子液体 (fIL)，在高压 (HP) 下表现出复杂的相行为。不对称[PFBS] ^-阴离子具有构象自由度。使用 X 射线衍射，在压缩和减压时确定 HP 晶体结构。代表层状结构的小散射角处的 00ℓ 布拉格反射重入出现。重入相行为通过低于 3.7 GPa ( P _{1 ) 的 [PFBS]} ^- (层I) 的分层和高于 7.6 GPa ( P 1 ) 的 [PFBS] ^- (层II)的混合分层结构来描述。层次感II 在压力循环中引起不可逆的晶体多晶型。在P ₁之下，HP 相变转变为可逆晶体多晶型物。复杂的 HP 晶体多晶型和多种途径源自构象驱动的分子堆积状态。