Engineering internal nanostructure in 3D-printed materials via polymer molecular weight distribution

The distribution of molecular weights in polymers, known as the molecular weight distribution (MWD), plays a significant role in dictating the behavior of polymer self-assembly and influencing the characteristics of the resulting materials. This study investigates how MWD of macromolecular chain-transfer agents (macroCTAs) impact internal nanostructures in materials prepared by polymerization-induced microphase separation (PIMS) 3D printing. In the aim of elucidating this relationship, the study initially harnessed the precision offered by narrow-MWD macroCTAs, which provide precise control over phase separation, as assessed by atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) measurements. Through systematic variation of macroCTA molecular weights, the dimensions of the distinct domains were precisely tuned from 10 to 90 nanometers and a decrease of materials stiffness was observed with increased domain size. In contrast, the utilization of a broader MWD, achieved by blending two distinct macroCTAs, resulted in increased domain size dispersity and reduced interface sharpness, without significantly affecting the mechanical properties of the 3D-printed materials. Overall, this approach expands the strategies for manipulating the nanoscale architecture of 3D-printed PIMS materials, opening new possibilities for printing advanced engineering materials with tailorable properties.