Ameliorating property gradients in photocured polymer lattices via thermal curing

• Photo-cured polymer lattices are optimized for compressive strength.
• The photo-curing induces through-thickness property gradients.
• Higher thermal curing stiffens the parent material and homogenizes properties.
• Models suggest level of curing can trigger buckling or yielding of lattice struts.

An experimental study has been performed to assess the efficacy of thermal curing in ameliorating the property gradients that ensue from photo-curing of thiol-ene lattices. Through measurements of glass transition temperatures and complex moduli of the constituent thiol-ene as well as strain distributions during compression testing of the lattices, we show that the lattice can be homogenized with a 24 h curing treatment at 160 °C. In addition to homogenization, the treatment yields an elevated glass transition temperature (to 50 °C) relative to that of the pristine material or that after a lower temperature (130 °C) cure. The resulting elastic response of the lattice at ambient temperature is essentially rate-independent over a strain rate range spanning four orders of magnitude. Finally, comparisons of the measured strengths with model predictions indicate that, through modest changes in either the slenderness ratio or the material properties, the mode of failure (yielding- vs. buckling-dominated) and hence the strain rate sensitivity of the lattice strength could be readily tailored.