Rational design of biomass-derived and UV-curable dynamic polymer for the encapsulation of paper-based flexible strain sensor

The paper-based flexible electronic devices with the virtues of light weight, porousness, sustainability and low cost by paper-making technology, however its application may be restricted by the poor tolerance of water due to the abundance of hydroxyl group of cellulose fibers. The encapsulation of such device requires to keep its sustainability and match the high efficiency of paper-making industry. In this work, a series of biomass-derived and UV-curable dynamic polymers were synthesized using itaconic acid and binary alcohols as raw materials. The diglycidyl ethers were firstly synthesized through the substitution reaction between binary alcohols and epichlorohydrin. The oligomer was then prepared by ring-opening reactions between the diglycidyl ethers and glycidyl-methacrylate-modified itaconic acid precursor. The dynamic polymers were finally obtained from photo-initiated polymerization, of which the mechanical property was regulated by the length of the binary alcohols. It is found that the polymer from 1,10-decanol possessed the highest tensile strength of 5.8 MPa and biggest elongation at break of 4.1%. The polymer can be self-healed and recycled, and was proved to be used as a photoresist for printed circuit board (PCB). Furthermore, the polymer was successfully applied to encapsulation of paper-based flexible strain sensor, which exhibited hydrophobicity and significantly higher working stability under high humidity or human sweating condition. The strategy reported in this work may pave a way for the development of sustainable thermosetting polymers and sustainable flexible electronic devices with high performance.