Influence of a Covalent Network Structure on the Vat Photopolymerization of Poly(styrene- <i>b</i> -isoprene- <i>b</i> -styrene) (ABA) Latex Interpenetrating Networks

Aqueous polymeric latexes combined with water-soluble, network-forming scaffold precursors enable additive manufacturing (AM) of triblock thermoplastic elastomers with excellent resolution and high elasticity. Ultraviolet (UV) crosslinking of the surrounding scaffold imparts structural rigidity to enable three-dimensional (3D) printing, while thermal post-processing promotes coalescence through the scaffold network to yield an interpenetrating network (IPN). Previously, photorheological analysis identified 15 wt % aqueous scaffold precursors (N-vinylpyrrolidone (NVP)/PEGDA 575) provide sufficient plateau storage moduli for vat photopolymerization (VPP) of poly(styrene-b-isoprene-b-styrene) (SIS). This work elucidates the impact of scaffold composition on VPP of the ABA triblock thermoplastic elastomer SIS and reveals structure–property relationships for 3D printed structures. Photorheological experiments further demonstrated that incorporation of 2-hydroxyethyl acrylate (HEA) into the crosslinked scaffold induced a 10-fold increase in plateau storage modulus compared to vinyl-containing NVP. Thermal analysis of HEA-containing IPNs suggested a more homogeneous network structure and a more well-defined phase structure in contrast to broad thermal transitions for NVP-containing IPNs. Tensile testing confirmed elongation and strain hardening behavior for HEA-containing IPNs, achieving tensile elongation exceeding 350%, emphasizing the significant impact of scaffold composition on photorheology, morphology, and corresponding thermomechanical performance of the resulting IPN. Overall, our learnings advance aqueous 3D printing of commercially available high-molecular-weight thermoplastic elastomers and describe the influence of covalent network design for printed thermoplastic elastomers for diverse applications, suggesting tunability of latex-based VPP processes.