Recyclable and Degradable Covalent Adaptable PolymerNetworks (CANs) Based on Dynamic Thiol–Yne Reactions

Covalent adaptable networks (CANs) have been introduced as an alternative to classical thermosets. The presence of dynamic covalent bonds can be utilized to enable (re-)processability and, consequently, the recyclability of these polymer networks. Within this context, we have utilized reversible covalent bonds based on activated alkynes and multifunctional thiols as reversible cross-linkers. Three differently substituted alkynes were crosslinked using a trithiol and a tetrathiol, respectively, resulting in different CANs. The materials were characterized by thermogravimetric analysis, differential scanning calorimetry (DSC), Raman spectroscopy and dynamic mechanical thermal analysis (DMTA). Two different recycling strategies have been utilized for these polymer networks: (i) mechanical recycling and (ii) chemical recycling. The mechanical and thermal properties of the recycled polymers were characterized in detail. In case of mechanical recycling, all samples were successfully recycled over three times, whereas for the chemical recycling only three samples based on aromatic alkynones could successfully be recycled.