Programming Crystal Thickness by Precision Chain Folding in Architecturally Designed Polymers

The chain folding and packing of semicrystalline polymers are influenced by a complex interplay of thermodynamic and kinetic factors and present a significant challenge for achieving precise dimensional control of polymeric nanomaterials. This study addresses this challenge by demonstrating controlled chain folding, fine-tuning dimensions along the nongrowth direction, and subsequently fabricating uniform assemblies. While bulky groups are known to disrupt the ordered packing of polyethylene (PE) chains, their potential for precisely regulating crystallization to achieve custom-sized crystals has not been fully explored. In this work, we introduce cyclic units such as cyclohexane, phenyl, and naphthalene as defects within the PE backbone to manipulate chain packing. Our results show that ortho-disubstituted defects, when incorporated periodically, can dominate the chain folding process, resulting in consistently formed crystalline segments. By adjusting the spacing between these bulky substituents along the polymer chain, we were able to generate lamellae and single crystals with precisely tunable thickness. Notably, the crystal thickness exhibits a strictly linear dependence on defect spacing. This approach paves the way for the preparation of uniform nanomaterials with three-dimensional precision.