Rheological behavior and mechanism of pH-responsive wormlike micelle variations induced by isomers of phthalic acid. Issue 22 (25th April 2018)

• Record Type: Journal Article
• Authors: Kang, Wanli; Zhao, Yilu; Wang, Pengxiang; Li, Zhe; Hou, Xiaoyu; Huang, Zitong; Yang, Hongbin
• Is Part Of: Soft matter. Volume 14:Issue 22(2018)
• Page Start: 4445
• Page End: 4452
• Publication Date: 2018-04-25
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c8sm00467f
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Responsive wormlike micelles (WLMs) constructed by different carboxylic acids are fascinating. Abstract : Responsive wormlike micelles (WLMs) constructed by different carboxylic acids are fascinating. However, it is unknown how the position of the carboxylic groups alters the stimuli-response of wormlike micellar systems. Herein, three pH-responsive WLMs based on Gemini-like surfactants (named o -EAPA, m -EAPA, and p -EAPA) were formed and studied through the complexation of N -erucamidopropyl- N, N -dimethylamine (UC22 AMPM) and o -phthalic acid ( o -PA), m -phthalic acid ( m -PA), or p -phthalic acid ( p -PA) at the molar ratio of 2 : 1. The viscoelasticity, phase behavior and aggregate microstructure were separately explored by rheological, appearance observation and cryo-TEM methods. The results show that all phthalic acids can protonate UC22 AMPM, thereby forming WLMs. However, with the shorter spacer distance between two carboxyl groups in phthalic acid, o -EAPA exhibits the longer length scale of aggregates and a more efficient thickening ability compared to the other two systems. Similar results in the N, N -dimethyl oleoaminde-propylamine (DOAPA) and o -PA, m -PA, and p -PA systems further verify the applicability of this mechanism. Furthermore, the phthalic acid based WLMs are found to exhibit intriguing reversible pH-responsive behaviors, which include promptly switching between a high elastic system and a low viscosity fluid by pH control. The o -EAPA system possesses a larger viscosity maximum, which produces more precipitous viscosity changes as the pH varies. This study is beneficial for the formation of pH-responsive WLMs and to determine their advantages for applications.