Distinct Nanostructures and Organogel Driven by Reversible Molecular Switching of a Tetraphenylethene-Involved Calix[4]arene-Based Amphiphilic [2]Rotaxane

Reguram Arumugaperumal, Putikam Raghunath, Ming-Chang Lin, Wen-Sheng Chung*

*Corresponding author for this work

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Aggregation induced emission (AIE) active and acid/base controllable amphiphilic [2]rotaxanes R1 and R2 were successfully constructed with tetraphenylethene (TPE) as a stopper and t-butylcalix[4]arene or calix[4]arene macrocycle as a wheel over the axle component. The AIE effect of [2]rotaxanes R1 and R2 was greatly affected by the molecular shuttling of t-butylcalix[4]arene or calix[4]arene macrocycle, which was triggered by the acid/base strategy. In the case of [2]rotaxane R1, aggregation was achieved in the presence of less amount of water compared with those of [2]rotaxane R2, and the deprotonated [2]rotaxanes R1-b and R2-b, owing to the stronger interaction between the TPE and t-butylcalix[4]arene macrocycle and restricted intramolecular rotation (RIR), thus making it responses in less quantity of water along with highly fluorescent emission. [2]Rotaxane R1-b started to aggregate at 70% water fraction (fw), while [2]rotaxane R2-b started to aggregate at 75% fw which allowed them to morph into hollow nanospheres, whereas they formed only nanospheres at 99% fw in CH3CN/water cosolvent system due to the higher degree of aggregation in aqueous media. To our delight, controllable morphology of self-assembled structures was indeed formed from these [2]rotaxanes. Interestingly, by the interplay of a wide range of multi-self-assembly driving forces, the slack stacking of rotaxane unit forms a hollow on the surface of nanospheres to become hollow nanospheres. Among the four [2]rotaxanes studied here, R1 possessed a narrower HOMO-LUMO band gap compared to those others, as confirmed by computational study. Furthermore, only [2]rotaxane R1 formed organogel in methanol solvent and its reversible gel-sol transition could be achieved by the addition of acid and base. This implies that the formation of dumbbell shape cross-linked 3D network structures were mainly governed by π- π stacking, van der Waals force, and intermolecular H-bonding interactions during the gelation processes.

Original languageEnglish
Pages (from-to)7221-7233
Number of pages13
JournalChemistry of Materials
Volume30
Issue number20
DOIs
StatePublished - 23 Oct 2018

Fingerprint Dive into the research topics of 'Distinct Nanostructures and Organogel Driven by Reversible Molecular Switching of a Tetraphenylethene-Involved Calix[4]arene-Based Amphiphilic [2]Rotaxane'. Together they form a unique fingerprint.

  • Cite this