3D Printing via Polymerization-Induced Microphase Separation using Acrylate Macromonomers instead of MacroRAFT Agents

Abstract

Polymerization-induced microphase separation (PIMS) is a versatile technique for manufacturing nanostructured materials. Combining PIMS with 3D printing enables the fabrication of complex objects with nanoscale features, opening possibilities in diverse applications, including nanostructured ceramics, solid polymer electrolytes, and ion-exchange materials. Traditionally, PIMS utilizes polymers synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization (macromolecular Chain Transfer Agents, macroCTAs). However, RAFT-based PIMS can introduce undesirable color and odor into the final materials. To address these limitations, this study explores the use of macromonomers, polymers terminated with acrylate or methacrylate groups, as alternatives to macroCTAs. We synthesized a series of polycaprolactone (PCL) variants with identical molecular weights but differing terminal functionalities: acrylate, methacrylate, trithiocarbonate, and dithiobenzoate. This library enabled a direct comparison of macromonomer and macroCTA approaches for nanostructured material fabrication via PIMS. Small-angle X-ray scattering (SAXS) was employed to determine nanodomain sizes. Notably, both acrylate and trithiocarbonate-terminated PCLs yielded comparable nanodomain sizes. Exploiting PCL degradation, we fabricated nanoporous, 3D-printed objects by selectively etching the PCL from materials formed with both trithiocarbonate and acrylate-terminated PCL. Critically, the acrylate-terminated macromonomer-based PIMS system produced transparent, colorless materials with well-defined microstructures. This work demonstrates the potential of macromonomers to overcome the inherent limitations of RAFT-PIMS, providing a cleaner and more versatile pathway to advanced nanostructured materials.