Self-Complementary Multiple Hydrogen-Bonding Additives Enhance Thermomechanical Properties of 3D-Printed PMMA Structures

Nonbonded interactions provide a way to guide the assembly and alter the physical properties of soft polymeric materials. Here, self-complementary hydrogen-bonding interactions conveyed through polymeric additives dramatically enhance thermomechanical properties of poly(methyl methacrylate) (PMMA) specimens printed by fused filament fabrication (FFF). Random copolymer additives composed of methyl methacrylate (MMA) and a methacrylate monomer containing 2-ureido-4-pyrimidone (UPy) pendant group (UPyMA), which self-dimerize through quadruple hydrogen-bonding interactions, were incorporated at 1 wt % in a high molecular weight PMMA matrix. Results from dynamic mechanical analysis measurements made in the glassy regime show that as the UPyMA comonomer content in the p(MMA-r-UPyMA) copolymer additive increases up to 5 mol %, there is a 50% increase in Young's modulus and a 62% increase in the storage modulus. Concomitantly, there is an 85% increase in ultimate tensile strength and a 100% increase in tensile modulus. Additionally, rheology measurements indicate that at temperatures well above the glass transition temperature, the storage modulus and complex viscosity of the multicomponent blends are unaffected by the incorporation of p(MMA-r-UPyMA) additives, regardless of the UPyMA content. In aggregate, these results suggest that using reversible, nonbonded intermolecular interactions, such as multidentate hydrogen bonding, provides a novel route to overcome the mechanical property limitations of FFF-printed materials without affecting melt processability.