Polymer-inorganic hybrid colloids for ultraviolet-assisted direct ink write of polymer nanocomposites

Inorganic-polymer hybrid colloids present a modular and tunable route to fabricate polymer nanocomposites from low viscosity precursors; however, their use in additive manufacturing remains limited. This manuscript describes photocurable “hybrid colloids” to enable layered fabrication of elastomeric nanocomposites, i.e., combination of continuous-phase photocrosslinking chemistry with hybrid colloids of water-dispersible silica nanoparticles and styrene-butadiene rubber (SBR) latex particles. Varying the relative concentrations of polymeric and inorganic particles afforded precise tuning of filler loading in the final nanocomposite and introduced a bimodal particle size distribution with desirable rheological behavior for extrusion-based additive manufacturing. Specifically, ultraviolet-assisted direct ink write (UV-DIW) processing of the photocurable hybrid colloid pastes generated free-standing green bodies, which contained a combination of SBR and silica nanoparticles. Subsequent drying of the green bodies allowed SBR particle coalescence and penetration through the scaffold and surrounding the silica nanoparticles, which yielded a semi-interpenetrating network (sIPN) nanocomposite. Facile tuning of silica concentrations in the hybrid colloid enabled tuning of both the colloidal ink rheology and mechanical properties of the final sIPN nanocomposites to achieve additive manufacturing of silica-SBR nanocomposites with ultimate tensile strains exceeding 300 % and ultimate tensile strengths above 10 MPa.