A Multiple Shape Memory Hydrogel Induced by Reversible Physical Interactions at Ambient Condition.

He Xiao,Wei Lu,Tuoping Hu,Tao Chen,Li Wang,Jiawei Zhang,Xiaoxia Le,Chunxin Ma,Patrick Theato

doi:10.3390/polym9040138

Abstract

A novel multiple shape memory hydrogel is fabricated based on two reversible physical interactions. The multiple shape memory property is endowed by a simple treatment of soaking in NaOH or NaCl solutions to form chitosan microcrystal or chain-entanglement crosslinks as temporary junctions.

Highlights

Shape memory polymers (SMPs) are a unique class of smart materials
In order to confirm the formation of microcrystal and chain entanglement, scanning electron microscopy (SEM), tensile and compression test, and rheological measurements were performed
The mechanical properties of the hydrogels are changed with the introduction of the two physical interactions (Figure S1), the tensile strain shows a downtrend (Figure 1d), the compressive strength presents an uptrend (Figure 1e), and the chain entanglement seems to have more obvious influence to the tensile strain and the compressive strength

Summary

Introduction

Shape memory polymers (SMPs) are a unique class of smart materials. They have the capability to recover to the initial shapes from temporary shapes triggered by external stimuli [1–10], so SMPs have attracted increasing attention in the fields of smart actuators, drug release, textiles, aerospace, etc. [11–14]. Shape memory polymers (SMPs) are a unique class of smart materials They have the capability to recover to the initial shapes from temporary shapes triggered by external stimuli [1–10], so SMPs have attracted increasing attention in the fields of smart actuators, drug release, textiles, aerospace, etc. As heat is not a convenient stimulus in practical biomedical and textiles applications, reversible interactions, such as metal-ligand coordination, host-guest interactions, and dynamic covalent bonds, have been applied to realize shape memory behavior in mild conditions [22–31]. Phenylboronic-diol ester bonds and the chelation of alginate with Ca2+ , Schiff base bonds, and the coordination between chitosan and metal ions are respectively combined as two non-interfering reversible switches in one system, and a triple shape memory effect is achieved [30,31]. To avoid a complex molecular design and synthesis of new polymers, new strategies have to be developed to achieve a multiple shape memory effect at ambient condition

Methods

Findings

Discussion

Conclusion