Frontal Polymerization and Three-Dimensional Printing of Thermoset Polymers with Tunable Thermomechanical Properties

On-demand curing of thermoset polymers with tunable mechanical properties is of great interest for a variety of applications. In this work, we demonstrate rapid, solvent-free synthesis of a cross-linked copolymer using thermal frontal polymerization of dicyclopentadiene (DCPD) and linseed oil at ambient temperature. A series of thermoset copolymers with various concentrations of comonomers are readily prepared to produce polymers with a wide range of ultimate elongation (11-360%), elastic modulus (1.1 GPa to 5.6 MPa), and glass transition temperature (120-31 degrees C). The addition of linseed oil comonomers to DCPD resin to increase the molecular weight between crosslinks reduces the available energy density for frontal polymerization and improves the elastomeric properties of the produced polymers. Increasing the concentration of linseed oil comonomers results in highly stretchable and flexible elastomers with self-recovery capability after large mechanical deformations. The DCPD resin and the resin containing 50 wt % of linseed oil comonomers are used to demonstrate three-dimensional (3D) printing of stiff and flexible cellular structures, respectively. This study is the first demonstration of low-cost, facile, and energy-efficient 3D printing of stretchable elastomers via frontal polymerization.