International audiencePolyurethanes (PUs) constitute a popular class of plastic materials with a wide range of applications in construction, coatings, and the automotive industry. PUs are usually synthesized by step-growth polymerization and, therefore, exhibit non-uniform molecular structures. Here, we show that uniform PUs can be prepared by a facile chemoselective multistep-growth approach. This strategy permits precise control of the chain lengths of the PUs formed and their primary structure, thus making the preparation of coded monomer sequences possible. Furthermore, it was found that these polymers are remarkably easy to analyze by tandem mass spectrometry sequencing. Thus, these precision polymers can potentially be used as molecular barcodes in various applications. As a proof of concept, their use as anti-counterfeiting tags for identification of materials is reported here

High-capacity digital poly(phosphodiester)s were synthesized by stepwise automated phosphoramidite chemistry. Coding libraries containing either 4 or 8 phosphoramidite monomers of different mass were used to encode the polymers, thus enabling storage densities of 2 or 3 bits/monomer, respectively. In addition, a monomer containing a cleavable alkoxyamine and nucleotide mass tags enabling fragment identification were included in the chains to allow their decryption by electrospray pseudo-MS 3 sequencing. As a proof of concept, black and white images with sizes ranging from 80 to 144 pixels were encoded in single polymer chains and decoded by mass spectrometry. Six different polymers were prepared in this work; three with the 4-monomers alphabet and three with the 8-monomers alphabet. In all cases, uniform macromolecules were obtained and deciphered. Yet, the bulkiest monomers of the 8-symbols alphabet required optimized protocols for uniform polymer synthesis. A macromolecular storage capacity of 144 bits per chain was obtained in this work, which is the highest capacity ever attained for a synthetic informational polymer.

Tandem mass spectrometry was evaluated as a reliable sequencing methodology to read codes encrypted in monodisperse sequence-coded oligo(triazole amide)s. The studied oligomers were composed of monomers containing a triazole ring, a short ethylene oxide segment, and an amide group as well as a short alkyl chain (propyl or isobutyl) which defined the 0/1 molecular binary code. Using electrospray ionization, oligo(triazole amide)s were best ionized as protonated molecules and were observed to adopt a single charge state, suggesting that adducted protons were located on every other monomer unit. Upon collisional activation, cleavages of the amide bond and of one ether bond were observed to proceed in each monomer, yielding two sets of complementary product ions. Distribution of protons over the precursor structure was found to remain unchanged upon activation, allowing charge state to be anticipated for product ions in the four series and hence facilitating their assignment for a straightforward characterization of any encoded oligo(triazole amide)s.

Digital polymers are uniform macromolecules that store monomer-based binary sequences. Molecularly stored information is usually extracted from the polymer by a tandem mass spectrometry (MS/MS) measurement, in which the coded chains are fragmented to reveal each bit (i.e. basic coded monomer unit) of the sequence. Here, we show that data-extraction can be greatly simplified by favoring the formation of MS/MS fragments containing two bits instead of one. In order to do so, digital poly(alkoxyamine phosphodiester)s, containing binary dyads in each repeat unit, were prepared by an orthogonal solid-phase approach involving successive phosphoramidite and radical-radical coupling steps. Three different sets of monomers were considered to build these polymers. In all cases, four coded building blocks-two hydroxy-nitroxides and two phosphoramidite monomers-were required to build the dyads. Among the three studied monomer sets, one combination allowed synthesis of uniform sequence-coded polymers. The resulting polymers led to clear dyad-containing fragments in MS/MS and could therefore be efficiently decoded. Additionally, an algorithm was created to detect specific dyad fragments, thus enabling automated sequencing.

Digital polymers are monodisperse chains with a controlled sequence of co-monomers, defined as letters of an alphabet, and are used to store information at the molecular level. Reading such messages is hence a sequencing task that can be efficiently achieved by tandem mass spectrometry. To improve their readability, structure of sequence-controlled synthetic polymers can be optimized, based on considerations regarding their fragmentation behavior. This strategy is described here for poly(phosphodiester)s, which were synthesized as monodisperse chains with more than 100 units but exhibited extremely complex dissociation spectra. In these polymers, two repeating units that differ by a simple H/CH variation were defined as the 0 and 1 bit of the ASCII code and spaced by a phosphate moiety. They were readily ionized in negative ion mode electrospray but dissociated via cleavage at all phosphate bonds upon collisional activation. Although allowing a complete sequence coverage of digital poly(phosphodiester)s, this fragmentation behavior was not efficient for macromolecules with more than 50 co-monomers, and data interpretation was very tedious. The structure of these polymers was then modified by introducing alkoxyamine linkages at appropriate location throughout the chain. A first design consisted of placing these low dissociation energy bonds between each monomeric bit: while cleavage of this sole bond greatly simplified MS/MS spectra, efficient sequencing was limited to chains with up to about 50 units. In contrast, introduction of alkoxyamine bonds between each byte (i.e. a set of eight co-monomers) was a more successful strategy. Long messages (so far, up to 8 bytes) could be read in MS experiments, where single-byte containing fragments released during the first activation stage were further dissociated for sequencing. The whole sequence of such byte-truncated poly(phosphodiester)s could be easily re-constructed based on a mass tagging system which permits to determine the original location of each byte in the chain. Copyright © 2017 John Wiley & Sons, Ltd.

A major step towards reliable reading of information coded in the sequence of long poly(phosphodiester)s was previously achieved by introducing an alkoxyamine spacer between information sub‐segments. However, MS/MS decoding had to be performed manually to safely identify useful fragments of low abundance compared to side‐products from the amide‐based alkoxyamine used. Here, alternative alkoxyamines were designed to prevent side‐reactions and enable automated MS/MS sequencing. Different styryl‐TEMPO spacers were prepared to increase radical delocalization and stiffness of the structure. Their dissociation behavior was investigated by EPR and best results were obtained with spacers containing in‐chain benzyl ring, with no side‐reaction during synthesis or sequencing. Automated decoding of these polymers was performed using the MS‐DECODER software, which interprets fragmentation data recorded for each sub‐segment and re‐align them in their original order based on location tags.

Digital polymers are uniform macromolecules that store monomer-based binary sequences.M olecularly stored information is usually extracted from the polymer by atandem mass spectrometry (MS/MS) measurement, in whichthe coded chains are fragmented to reveal each bit (i.e.b asic coded monomer unit) of the sequence.H ere,w es how that dataextraction can be greatly simplified by favoring the formation of MS/MS fragments containing two bits instead of one.I n order to do so,d igital poly(alkoxyamine phosphodiester)s, containing binary dyads in each repeat unit, were prepared by an orthogonal solid-phase approachi nvolving successive phosphoramidite and radical-radical coupling steps.T hree different sets of monomers were considered to build these polymers.I na ll cases,f our coded building blocks-two hydroxy-nitroxides and two phosphoramidite monomerswere required to build the dyads.A mong the three studied monomer sets,o ne combination allowed synthesis of uniform sequence-coded polymers.T he resulting polymers led to clear dyad-containing fragments in MS/MS and could therefore be efficiently decoded. Additionally,a na lgorithm was created to detect specific dyad fragments,t hus enabling automated sequencing.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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