Thermal-Mechanical ICN-SMG Gels for Smart Devices

Abstract

Transparent shape memory gels (SMGs) were developed in our group recently. They are smart materials having the ability to return from a deformed state (temporary shape) to their original (permanent) shapes upon application of a temperature change, which is named the shape memory. One of medical applications of SMGs is tried to use as a smart bandage material. The shape memory property of SMGs is good for fixing, removing and repeating, while their poor ductility is not good for wrapping. In order to improve the ductility of SMGs, a new network structure named as the inter-crosslinking network (ICN), which is composed of both flexible and easily broken chains and rod-like and durable chains, is introduced into the SMGs. Seven SMGs having ICN structure (ICN-SMGs) were synthesized by changing the ratio of monomers and the amount of crosslinker. The dependence of the mechanical properties on synthesis conditions and temperature changing of samples were investigated. The thermal-mechanical ICN-SMG showing the highest mechanical properties with the maximum stress of 4.6 MPa and the maximum strain of 7.4 (elongation 740%) was prepared. The Young’s modula of ICN-SMGs change quickly and reversibly between high temperature and low temperature from 0°C to 80°C. The water content was also discussed. The prepared ICN-SMGs in this paper have the water content in the range of 45∼72wt%. A trial medical bandage for treatment of broken finger was also made by the ICN-SMGs. It works well just by changing the temperature to wrap it around the finger and remove it after healing. The thermal-mechanical ICN-SMGs are supposed to be a very promising medical material for the future.