Digital polymer multilayers for information-storage – Digital-LbL

The main objective of the project digital-LbL will be to investigate a simple approach for spatially organizing synthetic coded matter; a relevant scientific topic that has been barely addressed to date. To achieve this goal, 3D multilayered films containing successive layers of digital polymers will be prepared and characterized. In particular, negatively-charged digital poly(phosphodiesters)s will be synthesized and used as polyanions in a layer-by-layer (LbL) polyelectrolyte strategy.

Jean-François Lutz will be the coordinator of the project and responsible for the design and synthesis of the digital polymers. The sequence-coded poly(phosphodiester)s will be synthesized by automated solid-phase iterative phosphoramidite chemistry. In this project, different phosphoramidite monomer alphabets will be conceived and tested for the synthesis of digital polymers. An emphasis will be put on enhanced monomer sets (for example using four coded monomers) that permit to write consequent amounts of binary information in short monomer sequences. For instance, each poly(phosphodiester) will be designed to contain about a decabyte of data. Thus, using libraries of sequence-coded polyanions, it will be possible to construct model 3D thin films containing between 100 and 1000 bytes of digital data.

In order to form the polyelectrolyte films, the digital polyanion layers will be alternated with a polycation homopolymer playing the role of intermediate “mortar”. The LbL film construction will be investigated by the group of Gero Decher, who is the main pioneer of this technology. Different commercial polycations such as poly(allylamine hydrochloride) and poly(diallyldimethyl ammonium chloride) will be tested in this project. In order to avoid any chain creep from one coded layer to another, it will be required to find the right counter-polyelectrolytes that prevent exponential film growth when deposited with sequence-coded phosphodiesters. In addition, the interdistance between two coded layers will be tuned by creating several intermediate layers of non-coded polyelectrolytes, for example using poly(sodium 4-styrenesulfonate) as an intermediate polyanion. Preliminary data that have been recently obtained and published by the applicants indicate that these objectives are realistic.

The formed LbL digital films will be characterized using various techniques such as ellipsometry, quartz-crystal microbalance and atomic force microscopy. In particular, the morphology of the films will be screened, in order to detect possible defects and make sure that the coded layers are well-segregated from another. Furthermore, desorption electrospray ionization (DESI) will be tested for desorbing successively the coded layers and reading them by mass spectrometry sequencing. This part is particularly challenging but will be supervised by Laurence Charles, who is an expert for the mass spectrometry analysis of coded polymers. Through the stepwise analysis of model films (i.e. containing at first only one or two coded layers), optimal conditions (i.e. coded layers interdistance, type and mass of the intermediate non-coded polyelectrolytes) will be tested for depth profiling.