Recyclable methylcellulose-based reversibly cross-linked hydroplastics with excellent environmental stability for use in flexible printed circuit boards capable of safe disposal

Recyclable and degradable flexible bio-based plastics integrating high stability and efficient disintegration on demand are suitable for the fabrication of flexible printed circuit boards (FPCBs) capable of safe disposal. However, it is challenging to develop a facile and environmentally friendly method to fabricate such bio-based plastic substrates. Herein, recyclable and degradable reversibly cross-linked hydroplastics with high thermal stability and water stability used as the substrates of FPCBs are fabricated through the complexation of methylcellulose (MC) and tannic acid (TA) in pure water, followed by hot-pressing. Because of dynamic nanoconfinement phases, the bio-based hydroplastic (denoted as TA-MC) with a breaking strength of 109.6 MPa possesses a high storage modulus of 2.85 GPa at 180 °C. Even being immersed in water for 15 days, the hydroplastic still retains a high breaking strength of 40.4 MPa. Owing to the reversibility of hydrogen bonds, the hydroplastic can be recycled for several times. Moreover, FPCBs composed of flexible TA-MC substrates and 3D printed sensing components can be employed for reliable underwater detection. Electronic components can be easily separated from the FPCBs by dissolving TA-MC substrates in medical alcohol and residue polymer matrices, which degrade into non-toxic substances in soil, can be safely discarded without polluting the environment.