Tailored Terminus Facilitates 3D Assembly of Peptoids

The rational construction of 3D crystals from synthetic short-chain polymers remains a significant challenge due to the lack of inherent driving forces for the growth in all three dimensions. Here, we report the design of 3D peptoid crystals from linear oligomeric peptoids derived from amphiphilic diblock copolypeptoids that typically form crystalline 2D nanosheets. By removing the amorphous domains and tuning the chain termini, crystalline lamellae up to 500 nm thick were achieved, far exceeding the thickness of typical nanosheets (on the order of a few nanometers). These 3D crystals form via stacking of unit cells with similar lattice parameters to those in 2D nanosheets. The terminal groups, particularly at the C-terminus, play a crucial role in enhancing crystallinity and vertical growth. This research advances our understanding of 3D crystal formation and highlights the importance of engineering chemical structure in designing 3D crystals from short-chain polymers.