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Single-site binding of pyrene to poly(ester-imide)s incorporating long spacer-units: prediction of NMR resonance-patterns from a fractal model.

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Knappert, Marcus 
Jin, Tianqi 
Midgley, Scott D 


Co-polycondensation of the diimide-based diols N,N'-bis(2-hydroxyethyl)hexafluoroisopropylidene-diphthalimide, (HFDI), and N,N'-bis(2-hydroxy-ethyl)naphthalene-1,4,5,8-tetracarboxylic-diimide, (NDI), with aliphatic diacyl chlorides ClOC(CH2) x COCl (x = 5 to 8) affords linear copoly(ester-imide)s. Such copolymers interact with pyrene via supramolecular binding of the polycyclic aromatic at NDI residues. This interaction results in upfield complexation shifts and sequence-related splittings of the NDI 1H NMR resonances, but gives a very different final resonance-pattern from the copolymer where x = 2. Computational modelling of the polymer with x = 5 suggests that each pyrene molecule binds to just a single NDI residue rather than by intercalation between a pair of NDI's at a tight chain-fold, as was found for x = 2. The new single-site binding model enables the pattern of 1H NMR resonances for copolymers with longer spacers (x = 5 to 8) to be reproduced and assigned by simulation from sequence-specific shielding factors based on a type of fractal known as the last-fraction Cantor set. As this type of fractal also enables an understanding of pairwise binding systems, it evidently provides a general numerical framework for supramolecular sequence-analysis in binary copolymers.



3403 Macromolecular and Materials Chemistry, 3405 Organic Chemistry, 34 Chemical Sciences

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Chem Sci

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Royal Society of Chemistry (RSC)
Engineering and Physical Sciences Research Council (EP/L027151/1)
Leverhulme Trust (RP2013-SL-008)
European Research Council (726470)
This work was sponsored by the H2020 program of the European Union under the ITN project Euro-Sequences, H2020-MSCA-ITN-2014, grant No. 642083 (Marie Skłodowska-Curie PhD studentship to MK). Further support was provided by the Leverhulme Trust, (Emeritus Fellowship to HMC, grant No. EM-2018-0161/4) EPSRC (programme grant No. EP/L027151/1, to OAS).