Sequences of Sequences: Spatial Organization of Coded Matter through Layer-by-Layer Assembly of Digital Polymers

A library of 16 digitally encoded polyanions was used in a layer-by-layer (LbL) polyelectrolyte assembly to nanofabricate thin films containing digitally coded strata. The polyanions were digital polyphosphodiesters (d-PPDE) prepared via an automated phosphoramidite process. Each component of the library contained 10 bytes of ASCII-encoded text (i.e. 80 coded monomers); thus the entire library allows the writing of a full sentence, which can be stored in a multilayer film as a sequence of sequences. To prepare fully segregated digital domains, non-coded layers composed of poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) were included between the d-PPDE coded layers as an intermediate barrier. Detailed analysis of the film homogeneity indicated formation of 70 nm-thick films in which digital layers are kept apart from another by non-coded interlayers. As a result, the sequence-coded polymer library could be piled-up in a defined sequence of layers.