Advancements in Additive Manufacturing: Rheological Design, Sustainable Polyurethanes, and Novel Applications in Vat Photopolymerization

Additive manufacturing (AM) stands at the forefront of a paradigm shift in the fabrication of complex structures, unachievable by traditional polymer processing techniques. Within this transformative field, vat photopolymerization (VP) produces components with high geometric precision, excellent surface quality, and uniform mechanical properties, though the mass transport limitation of photocurable precursors restricts their maximum viscosity to less than 10 Pa·s. Previous studies primarily focused on employing colloidal styrene-butadiene rubber (SBR) in vat photopolymerization (VP), necessitating computer-vision-based adjustment of printing parameters and largely neglecting the potential of engineering segmented and block copolymers. In contrast, the research presented here overcomes these limitations by developing photocurable polymeric systems that enable the use of high molecular weight engineering polymers in VP, thereby expanding the technological capabilities of this process.This dissertation introduces a significant advancement employing engineering step-growth derived waterborne polyurethanes (WPUs) as vat photopolymerization (VP) feedstocks for crafting complex geometries. Investigation of the requisite ionic content enabled the determination of hard segment concentration, ensuring electrostatic stability of the WPUs. The end-capping of polyurethanes with n-butanol and methacrylate enabled radical copolymerization between the scaffold precursors and discontinuous phase methacrylate end groups. Comparative analysis revealed that low molecular weight polyurethanes facilitated simpler printing processes due to higher crosslink density, while high molecular weight WPUs necessitated novel printing parameters to achieve tensile elongations nearly 300%. Expanding to ABA triblock copolymers, poly(styrene-b-isoprene-b-styrene) (SIS), this research extended the latex printing platform to process morphologically complex polymers. ABA triblock copolymers in VP provided new structure-property relationships through nanoscale phase separation. Unlike traditional VP materials, which require a plateau storage modulus (GN0) greater than 105 Pa for structural integrity, this study successfully printed intricate geometries with a GN0 of 103 Pa by optimizing printer submergence and withdrawal speeds to minimize hydrogel stress. Moreover, replacing top-down VP with a bottom-up approach, this research eliminated the need for computer-vision algorithms, facilitating the creation of complex geometries using commercially available 3D printers. SAXS/WAXS analysis of the photocured ABA triblock copolymer unprecedented nanoscale phase separation in printed block copolymers, forming an interpenetrating network (IPN) with tensile elongations to 840%.