Graphene nanoribbons (GNRs) have emerged as promising materials for next-generation electronic, optoelectronic, and quantum devices due to their tunable bandgaps and edge-dependent properties. A critical challenge in their integration lies in the ability to precisely control their length and ensure structural uniformity. This review highlights three major synthetic strategies developed to address this challenge: living polymerization, conventional iterative synthesis, and protecting group-aided iterative synthesis (PAIS). Living polymerization approaches enable scalable access to GNRs with narrow length distributions, although they rely on specialized monomers and catalyst design to maintain a living character. The conventional iterative synthesis strategy provides a pathway for the preparation of specific GNRs with precise length, but it is still not possible to synthesize general GNRs with a desired length or a well-defined heterogeneous monomer sequence. The PAIS strategy stands out, allowing atomic-level control over GNR length, width, edge structure, and heterojunction placement. Iterative methods offer unparalleled atomic precision and architectural flexibility but are labor-intensive and limited by solubility constraints. Each method presents complementary advantages and trade-offs. Future advancements are expected to stem from hybrid synthetic platforms, catalyst innovations, and programmable template design, ultimately enabling deterministic control over GNR structures and properties for device applications.
Pyle et al. (Tue,) studied this question.