Mechanical Property Modification of Living Networks via PET-RAFT Photopolymerization

Living polymer networks have the ability to grow in size and mass after initial polymerization through the insertion of new monomers. In this work, a one-pot method is used to prepare living polymer networks and modify their mechanical properties via the photo-electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) photopolymerization method. The living networks are made from company-bought constituents (N,N-dimethylacrylamide [DMAm] monomer and poly(ethylene glycol) diacrylate [PEGDA] 700 crosslinker) so that no synthesis is involved. The study uses two different RAFT agents: asymmetric 2-(n-butyltrithiocarbonate) propionic acid (BTPA) and symmetric S,S-dibenzyl trithiocarbonate (DBTTC). The study then modifies these parent networks with three monomers (acrylamide [AAm], DMAm, and methyl acrylate [MA]) by recommencing the PET-RAFT process. Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) are conducted on the living networks to investigate the effects of monomer insertion after photo-growth. The networks are also subjected to compression testing, where the daughter networks display modified mechanical properties dependent on both the choice of monomer and RAFT agent symmetry.

Automated summary

Living polymer networks are modified using the PET-RAFT photopolymerization method, where new monomers are inserted to change their mechanical properties. Two different RAFT agents are used to modify the parent networks, and characterization is carried out using FTIR spectroscopy and TGA. The results demonstrate that the choice of inserted monomers and RAFT agents affect the mechanical properties of the daughter networks.