Co-solvent polarity tuned thermochromic nanotubes of cyclic dipeptide-polydiacetylene supramolecular system.

Mohammed Iqbal Khazi,Chenikkayala Balachandra,Thimmaiah Govindaraju,Gang-Hee Jang,Jong-Man Kim,Geon Shin

doi:10.1039/d0ra05656a

Abstract

The cooperative non-covalent interactions arising from structurally integrated multiple molecules have emerged as a powerful tool for the creation of functional supramolecular structures. Herein, we constructed cyclic dipeptide (CDP)–polydiacetylene (PDA) conjugate (CDP–DA) by introducing cyclo(l-Phe-l-Lys) to the linear 10,12-pentacosadiynoic acid. Owing to extensive hydrogen bonding characteristics, together with structural chirality of cyclo(l-Phe-l-Lys) and strong π–π stacking diacetylenic template, CDP–DA generated supramolecular nanotubes. The structural visualization using scanning and transmission electron microscopy revealed chloroform/methanol co-solvent polarity tuned morphological transformation of intrinsic lamellar assemblies into nanotubes comprising single-wall and multi-wall structure. The mechanistic understanding by X-ray diffraction patterns confirms bilayer organization in lamellar structure, which forms nanotubes via a gradual lamellar curling-to-scrolling process. The supramolecular CDP–DA nanotubes are transformed into the rigid covalently cross-linked blue-phase polydiacetylene (CDP–PDA) by UV irradiation. Very interestingly, the blue-phase nanotubes display reversible thermochromic changing temperature up to 150 °C with excellent repeatability over a dozen thermal cycles. This work provides an efficient strategy for precise morphological control and aiding the perspective for development in nanostructures for functional devices.

Highlights

The propensity of self-assembly extended to create hierarchical supramolecular polymer architectures has attracted increasing interest recently.[1,2,3,4,5,6] Self-assembled polymer architecture re ects the integrated structural and functional features of monomer components
This study demonstrates the concept of facile transformation of intrinsic supramolecular nanotubes of self-assembled linear cyclic dipeptide (CDP)–DA molecules into rigid covalently cross-linked chromogenic nanotubes by UV induce topochemical polymerization
A linear structure, CDP–DA, comprising polar CDP head group linked to the diacetylene chain was synthesized and studied for supramolecular structures in different solvent systems

Summary

Introduction

The propensity of self-assembly extended to create hierarchical supramolecular polymer architectures has attracted increasing interest recently.[1,2,3,4,5,6] Self-assembled polymer architecture re ects the integrated structural and functional features of monomer components. The results of this study show co-solvent polarity tuned morphology transformation from lamellar structure to nanotubes via scrolling mechanism. A clear illustration from Fig. 2 indicates that the initial step of the CDP–DA self-assembly is the formation of a sequential H-bonded network via a cooperative mechanism of non-covalent hydrogen bonding interactions and p–p stacking.

Results

Conclusion