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.

Controllable Self‐Assembly of Amphiphilic Zwitterionic PBI Towards Tunable Surface Wettability of the Nanostructures

“…Although SAP has a planar perylene skeleton, it only formed random aggregates in chloroform/hexane (5:95, v/v) or DMSO/acetone (5:95, v/v) binary solvents. Because of its poor solubility, SAP aggregated rapidly but did not transform from free molecules to an ordered architecture . Therefore, an appropriate balance between hydrophilicity and hydrophobicity is important for the formation of a regular structure.…”

“…Due to the presence of both hydrophobic and hydrophilic moieties, amphiphilic molecules are rich in non‐covalent forces, including π–π stacking, H‐bonding and electrostatic interactions, which are beneficial to construct and regulate diverse well‐defined architectures . For instance, spiropyran derivative bearing hydrophilic carboxyl and hydroxyl group can undergo a large morphology variation from sphere to rod‐like structure because of weakened H‐bonding and stronger π–π stacking . Additionally, solvent–solute interactions also play a vital role in the self‐assembly process of amphiphilic molecules .…”

Visible Light–Induced Supra‐Amphiphilic Switch Leads to Transition from Supramolecular Nanosphere to Nanovesicle Activated by Pillar[5]arene‐Based Host–Guest Interaction

“…The peak at 515 nm indicates the spontaneous isomerization of G S to G M because water stabilizes G M due to hydrogen‐bonding interaction. However, the isomerization is incomplete, evidenced by the coexistence of two isomers in this system. The molar content of G M was calculated to be 30%.…”

Neue Mitglieder der chinesischen Akademie der Wissenschaften

“…Er kehrte 1996 an die Beijing University of Chemical Technology zurück, wo er seit 2005 Dekan des College of Materials Science ist. Er ist Coautor eines Beitrags in Chemistry—An Asian Journal über einen faserbasierten Ammoniaksensor …”