# Amorphous–Crystalline Solid Transformation-Induced Self-Actuation of Bending-to-Straightening Behavior via Helical Deformation

## TL;DR

This paper shows how sugar azides can self-actuate from bending to straightening through a unique crystallization process.

## Contribution

The study introduces a novel mechanism of self-actuation via amorphous–crystalline transformation and helical deformation.

## Key findings

- Sugar azides undergo spontaneous bending-to-straightening behavior during anisotropic self-assembly.
- The transformation involves helical deformation and screw dislocation into crystalline hollow tubes.
- Stereostructure and dipole arrangement regulate the aggregation and directional growth.

## Abstract

Bending-to-straightening behavior is vital for both natural
processes
and advanced materials design. Nonclassical crystallization pathways,
particularly amorphous–crystalline transformations, offer opportunities
to achieve such dynamic actuation. This study reveals that sugar azides
are capable of undergoing spontaneous bending-to-straightening behavior,
accompanied by helical deformation, driven by an amorphous–crystalline
transformation during anisotropic self-assembly. The process is initiated
with bending amorphous nanowires, which evolve into locally crystallized
twisted nanoribbons and ultimately straighten into crystalline rectangular
hollow tubes through screw dislocation. This transformation is governed
by the interplay between the stereostructure of the sugar backbone
and the collinear dipole arrangement of the azide group, which together
regulates initial helical aggregation and subsequent directional growth.
These findings not only clarify the molecular origins of bending-to-straightening
crystallization but also provide a strategy for designing responsive
materials capable of adapting to unstructured environments.