title: Properties and ionic self-assembled structures from mixture of a bola-type strong alkali dication and a branched phosphoric acid.
abstract: Ionic self-assembled structures have been prepared successfully between di-(2-ethylhexyl) phosphoric acid (DEHPA) and hexamethonium hydroxide (HMO(OH)2). The DEHPA/HMO(OH)2 complexes show good surface activity at a wide mixing molar ratio of DEHPA to HMO(OH)2 (ρ), within which the critical micellar concentration (cmc) is far below that of any single component. In bulk aqueous solutions, rich phase behavior was observed by varying cDEHPA and cHMO(OH)2. When the concentration of HMO(OH)2 is in the range of 10-100 mmol L(-1), isotropic L1 phases, birefringent Lα phases and a phase-separated region were successively observed with increasing cDEHPA. At high cHMO(OH)2 range (>78 mmol L(-1)), a narrow L1/Lα two-phase region with the Lα phase at the bottom was noticed between the single L1 and single Lα phase regions. The rheological properties of the samples in the single Lα phase region at 2.6 ⩽ ρ ⩽ 2.8 are quite similar. Cryo-TEM and freeze-fracture TEM (FF-TEM) observations revealed the presence of multilamellar vesicles with flexible and even branched bilayers. At 2.2 ⩽ ρ ⩽ 2.6, however, the rheological properties are highly sensitive to ρ due to the sophisticated self-assembly behavior as proved by imaging studies and (2)H NMR measurements. Closely-stacked flat structures which look like foams or cellular networks have been newly discovered. Interestingly, NaCl could arouse an L1 to Lα phase transition due to the suppression of the effective area of the hydrophilic headgroups of the ionic complexes, leading to an increase of the critical packing parameter p. The viscoelasticity properties of the salt-containing Lα phases decreased with increasing salinity. We hope our research can provide new ideas for the construction of supramolecular materials by surfactant ionic self-assembly (SISA) strategy.
authors.affiliation: College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University, Jinan, Shandong Province 250014, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Solid Lubrication & Laboratory of Clean Energy Chemistry and Materials, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000, China. Electronic address: hgli@licp.cas.cn.
authors.forename: Hongguang
authors.initials: H
authors.lastname: Li
authors.affiliation: College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University, Jinan, Shandong Province 250014, China. Electronic address: jlchai@sdnu.edu.cn.
authors.forename: Jinling
authors.initials: J
authors.lastname: Chai
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, Shandong Province 250100, China.
authors.forename: Mengjun
authors.initials: M
authors.lastname: Chen
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, Shandong Province 250100, China.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, Shandong Province 250100, China.
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Hao
keywords: Cryo-TEM; FF-TEM; Ionic self-assembly; L(α) phases; Rheological properties; Surfactant