Tuning the Mechanical Properties of 3D-Printed Objects by Mixing Chain Transfer Agents in Norrish Type I Photoinitiated RAFT Polymerization

Photoinduced 3D printing via photocontrolled reversible-deactivation radical polymerization (photoRDRP) techniques has emerged as a robust technique for creating polymeric materials. However, methods for precisely adjusting the mechanical properties of these materials remain limited. In this study, we present a facile approach for adjusting the mechanical properties of 3D-printed objects by adjusting the polymer dispersity within a Norrish type I photoinitiated reversible addition-fragmentation chain transfer (NTI-RAFT) polymerization-based 3D printing process. We investigated the effects of varying the concentrations and molar ratios of trithiocarbonate (BTPA) and xanthate (EXEP) on the mechanical properties of the printed materials. Our findings demonstrate that increased concentrations of RAFT agents or higher proportions of the more active BTPA lead to a decrease in Young's modulus and glass transition temperatures, along with an increase in elongation at break, which can be attributed to the enhanced homogeneity of the polymer network. Using a commercial LCD printer, the NTI-RAFT-based 3D printing system effectively produced materials with tailored mechanical properties, highlighting its potential for practical applications. This study introduces a novel method to fine-tune the mechanical properties of 3D-printed polymeric materials using mixed chain transfer agents in a Norrish type I photoinitiated RAFT polymerization process. image