Responsive morphology transition from micelles to vesicles based on dynamic covalent surfactants. Issue 12 (28th February 2019)

• Record Type: Journal Article
• Authors: Wang, Pengxiang; Zhu, Tongyu; Hou, Xiaoyu; Zhao, Yilu; Zhang, Xiangfeng; Yang, Hongbin; Kang, Wanli
• Is Part Of: Soft matter. Volume 15:Issue 12(2019)
• Page Start: 2703
• Page End: 2710
• Publication Date: 2019-02-28
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c9sm00009g
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : A pH-responsive morphology transition system based on the ionization and formation of a dynamic covalent surfactant has been developed. Abstract : A dynamic covalent bond is widely used to fabricate stimuli responsive systems due to its reversible molecular recognition properties. In this study, we developed a pH-responsive morphology transition system based on a mixture of a cationic surfactant CTAB and two nonamphiphilic precursors, 4-hydroxybenzaldehyde (HB) and octylamine (OA), at a molar ratio of 100 : 60 : 60 (CTAB/HB/OA). The morphology transition of CTAB/HB/OA was characterized by 1 H NMR spectroscopy, Fourier transform infrared spectroscopy, macroscopic appearance observation, dynamic light scattering, and rheological and cryo-TEM measurements. The phase behavior of CTAB/HB/OA solutions underwent transition from a water-like fluid to a transparent gel-like solution and then converted into a turbid low-viscosity solution upon increasing the pH. Upon increasing the pH from 4.93 to 7.99, the morphology was transformed from spherical micelles to wormlike micelles. Upon further increasing the pH to 12.02, the wormlike micelles gradually disappeared with the formation of vesicles. Thus, a morphology transition from micelles to vesicles can be triggered by varying the pH of CTAB/HB/OA solutions. This drastic variation in morphology behavior was attributed to the pH dependent ionization and formation of the anionic surfactant HB–OA − . Besides, over 3 cycles of morphological alternation among spherical micelles, wormlike micelles and vesicles of the CTAB/HB/OA solutions can be obtained by adjusting the pH.