Nano- to macro-scale control of 3D printed materials via polymerization induced microphase separation

Abstract

Although 3D printing allows the macroscopic structure of objects to be easily controlled, controlling the nanostructure of 3D printed materials has rarely been reported. Herein, we report an efficient and versatile process for fabricating 3D printed materials with controlled nanoscale structural features. This approach uses resins containing macromolecular chain transfer agents (macroCTAs) which microphase separate during the photoinduced 3D printing process to form nanostructured materials. By varying the chain length of the macroCTA, we demonstrate a high level of control over the microphase separation behavior, resulting in materials with controllable nanoscale sizes and morphologies. Importantly, the bulk mechanical properties of 3D printed objects are correlated with their morphologies; transitioning from discrete globular to interpenetrating domains results in a marked improvement in mechanical performance, which is ascribed to the increased interfacial interaction between soft and hard domains. Overall, the findings of this work enable the simplified production of materials with tightly controllable nanostructures for broad potential applications.

Multimorphic Materials: Spatially Tailoring Mechanical Properties via Selective Initiation of Interpenetrating Polymer Networks

“…Synthetic multi-material all-polymeric structures have been previously prepared by spatially tailoring composition, particularly cross-link density. [3][4][5][6] For example, Suo and coworkers produced hydrogels comprising a macroscale, densely crosslinked rigid skeleton network (≈3 mm minimum dimension) of high modulus in a soft, lightly cross-linked acrylamide matrix, ultimately enhancing toughness and fatigue resistance (Figure 1Ai). [7] Work by Bowman and coworkers demonstrated synergistic effects in microscale patterned thiolacrylate materials (≈5-100 µm minimum dimension), wherein cross-link density was altered spatially using a photochemical approach.…”

Photoinduced RAFT Step‐Growth Polymerization toward Degradable Living Polymer Networks

“…[ 11‐12 ] More recently, some photoRDRP‐based 3D printing techniques have been developed for fabricating PNs with dormant initiating sites. [ 13‐22 ]…”

Application of RAFT in 3D Printing: Where Are the Future Opportunities?

“…The field of RAFT-mediated 3D printing has been quickly evolving since first reported. − and its application has been explored in different contexts such as surface functionalization, ,, direct laser writing/surface paterning, self-healing polymers, , polymerization-induced microphase separation, , fabrication of scaffolds with tailored hierarchical porosities, and customized drug delivery systems . The following sections provide a succinct, pertinent introduction and a summary of the reported applications of RAFT-mediated 3D printing in the literature.…”

“…The Boyer group recently employed this technique in 3D printing, which allows for the modulation of the morphology of nanostructured 3D printed materials by adjusting the macro-CTA chain length, architecture, and loading, a feat that was previously impossible with conventional 3D printing methods. It has been shown that 3D printed materials undergo morphological modifications as the chain length of macro-CTAs is increased (while the loading is maintained), changing from materials with isolated globular domains to those with elongated domains and eventually bicontinuous morphologies (Figure a,b) . The loading of the macro-CTAs in the resin formulations had an impact on the elongation of the globular domains and the development of bicontinuous morphologies .…”

“…Since it was initially published, − the field of RAFT-mediated 3D printing has rapidly developed and expanded beyond the creation of reprocessable/living 3D materials. ,, This technology has been utilized in cutting-edge applications such as self-healing polymers, surface patterning, nanostructuration, , and customized drug delivery . To accomplish these applications, several chemical mechanisms such as photoiniferter (direct photolysis), , photoinduced electron/energy transfer (PET)-RAFT, , cationic RAFT, , and photoinitiator RAFT , have been utilized.…”