Digital Polymers Based on Cyclic Monomers

The preparation of digital polymers with high information storage density, efficient information encoding, and easy information decoding characteristics is challenging. Using small cyclic compounds, such as δ-valerolactones, β-amino acid N-thiocarboxyanhydrides, and anhydrides, as monomers, we developed iterative growth methods to prepare novel types of digital polymers. The use of small cyclic monomers provides significant advantages for iterative growth methods and the resulting digital polymers. First, small cyclic monomers with a large variety of side group structures can be easily obtained, which significantly expands the monomer alphabet and increases the information storage density of the digital polymers produced (reaching 0.023 bit/Da). Second, small cyclic monomers contain self-protected reactive groups, eliminating the need for protective groups or orthogonal reactive–group pairs. These cyclic monomers also exhibit high nucleophilic ring-opening reactivity under mild reaction conditions, facilitating the use of new efficient iterative growth methods to encode information. Third, the simple ring structure of cyclic monomers results in digital polymers with simple backbone structures that contain only two types of functional groups: esters and amides. As a result, the encoded information can be easily and reliably decoded by using tandem mass spectrometry sequencing, selectively cleaving ester bonds with lower dissociation energies. This study demonstrates that small cyclic monomer codes are promising for the development of efficient iterative growth methods to prepare high-storage-density digital polymers with easy and reliable readability.