Stretchable slide-ring supramolecular hydrogel for flexible electronic devices

Shuaipeng Wang,Yong Chen,Yuexiu Qin,Yonghui Sun,Hui Zhang,Yu Liu,Xiaoyong Yu

doi:10.1038/s43246-022-00225-7

Abstract

Slide-ring materials with movable cross-links have received attention due to their excellent mechanical properties. However, due to the poor solubility of polyrotaxane and low synthesis efficiency, their applications are hindered. Here, we use hydroxypropyl-modified α-cyclodextrin (Hy-α-CD) and Acrylamide-PEG20000-Acrylamide (ACA-PEG20000-ACA) to construct a polypseudorotaxane with good water solubility. Through photo-initiated polymerization of polypseudorotaxane with acrylamide in-situ, the capped polyrotaxane was easily obtained and further cross-linked by 1,4-butanediol diglycidyl ether in sodium hydroxide solution to form a slide-ring supramolecular hydrogel. The hydrogel can be stretched to 25.4 times its original length, which recovers rapidly on unloading, and the addition of Ca2+ ions during crosslinking enhances ionic conductivity. The Ca2+-doped hydrogels are used to prepare wearable strain sensors for monitoring human motion.

Highlights

Slide-ring materials with movable cross-links have received attention due to their excellent mechanical properties
We wish to report a type of new slide-ring supramolecular hydrogel constructed from (2-hydroxypropyl)-αCD (Hy-α-CD), which has good water solubility and biocompatibility[33,34,35,36], via a convenient photo-initiated polymerization with acrylamide-terminated polyethyleneglycol followed by the crosslink of hydroxypropyl-modified α-cyclodextrin (Hy-α-CD) sliding ring
Polyrotaxane was further cross-linked in a sodium hydroxide solution of 1,4-butanediol diglycidyl ether to give a ultrastretchable supramolecular hydrogel, which was stretched to 2540% of its original length and has a fracture energy of 17.4 MJ/m3 as well as an elastic modulus of 35.67 KPa

Summary

Introduction

Slide-ring materials with movable cross-links have received attention due to their excellent mechanical properties. Effect makes the internal stress evenly distributed to each chain segment and to the whole network This unique “pulley effect” gives the slide-ring hydrogel excellent mechanical properties[30,31,32], such as extremely soft characteristics, relatively low initial modulus and higher ductility. Slide-ring materials have excellent mechanical properties, its production and application are greatly limited due to the relatively low solubility of polypseudorotaxane in water as well as the complicated end-capping process of rotaxane. We wish to report a type of new slide-ring supramolecular hydrogel constructed from (2-hydroxypropyl)-αCD (Hy-α-CD), which has good water solubility and biocompatibility[33,34,35,36], via a convenient photo-initiated polymerization with acrylamide-terminated polyethyleneglycol followed by the crosslink of Hy-α-CD sliding ring. Further experiment indicated this hydrogel can be used to prepare a wearable strain sensor with high performance after doped with 0.2 M CaCl2 (to enhance the ions conductivity)

Methods

Results

Conclusion