title: Tunable Morphology of Spiropyran Assemblies: From Nanospheres to Nanorods.
abstract: Spiropyran (SP), which can respond to acid, ultraviolet irradiation, and mechanical force, has received great attention as a classic molecule for the construction of stimuli-responsive materials. However, the self-assembly behavior of SP with a tunable morphology has rarely been investigated. In the present work, a SP derivative bearing two carboxyl groups and one hydroxyl group was prepared and used as a model to investigate the optical properties, molecular self-assembly, and morphology of SP. This pH-responsive derivative could undergo a large morphology variation from a sphere- to a rodlike structure by adjusting the acidity. The indoline and pyridopyran fragments contributed to π-π stacking, whereas the carboxyl groups contributed to hydrogen bonding. Both π-π stacking and hydrogen bonding contributed to the pH-responsive self-assembly. The morphologies of spiropyran aggregates formed under different conditions were characterized by SEM, TEM, and FTIR spectroscopy. Control of the morphology of the spiropyran nanostructure was achieved.
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Baozhong
authors.initials: B
authors.lastname: Lü
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Le
authors.initials: L
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Wantai
authors.initials: W
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, 100029, China.
authors.forename: Meizhen
authors.initials: M
authors.lastname: Yin
keywords: acidity; morphology; nanostructures; self-assembly; spiropyran