title: Insight into a Fast-Phototuning Azobenzene Switch for Sustainably Tailoring the Foam Stability.
abstract: A photoresponsive surfactant of 4-octoxy-4'-[(trimethylamino)ethoxy]azobenzene (OTAEAzo) has been synthesized for developing a fast-phototuning foam switch based on its high sensitivity, reversibility, and fatigue resistance of the photoisomerization capability. Ultraviolet (UV)-light irradiation for 1 s enabled conversion from the trans isomer to the cis configuration, while exposure to visible (Vis)-light for 3 min induced a cis-to-trans transformation, which maintains an excellent cycling stability for 20 cycles of photoisomerization. The photoisomerization speed depended on the concentration of OTAEAzo, and a lower concentration facilitated a faster photoisomerization process. Because of the low critical micelle concentration (CMC), OTAEAzo with a small dosage of 0.2 g·L-1showed foamability, which accelerated the photoisomerization speed, enabling it to become a highly efficient switch. The surface activities of trans-OTAEAzo presented distinct differences from those of cis-OTAEAzo, resulting in the foam stabilization effects of trans-OTAEAzo (t1/2= 2.58 min) and the destabilization effects of cis-OTAEAzo (t1/2= 0.38 min). Moreover, the foam properties varied slightly in the phototuning cycles. OTAEAzo with low CMC presents high sensitivity and reversible photoisomerization capability, providing an environmental and sustainable approach for tailoring the foam stability.
authors.affiliation: Key Laboratory of Eco-Textile, Ministry of Education, College of Textile & Clothing, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Shaoyu
authors.initials: S
authors.lastname: Chen
authors.affiliation: Key Laboratory of Eco-Textile, Ministry of Education, College of Textile & Clothing, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eco-Textile, Ministry of Education, College of Textile & Clothing, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Kunlin
authors.initials: K
authors.lastname: Chen
authors.affiliation: Key Laboratory of Eco-Textile, Ministry of Education, College of Textile & Clothing, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Key Laboratory of Eco-Textile, Ministry of Education, College of Textile & Clothing, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Chaoxia
authors.identifier: http://orcid.org/0000-0001-6322-7606
authors.initials: C
authors.lastname: Wang
keywords: azobenzene; fast foam switch; low CMC; photoisomerization; surface activity