Understanding the folding process of synthetic polymers by small-molecule folding agents

Abstract

Two acceptor containing polyimides PDI and NDI carrying pyromellitic diimide units and 1,4,5,8-naphthalene tetracarboxy diimide units, respectively, along with hexa(oxyethylene) (EO6) segments as linkers, were prepared from the corresponding dianhydrides and diamines. These polyimides were made to fold by interaction with specifically designed folding agents containing a dialkoxynaphthalene (DAN) donor linked to a carboxylic acid group. The alkali-metal counter-ion of the donor carboxylic acid upon complexation with the EO6 segment brings the DAN unit in the right location to induce a charge-transfer complex formation with acceptor units in the polymer backbone. This two-point interaction between the folding agent and the polymer backbone leads to a folding of the polymer chain, which was readily monitored by NMR titrations. The effect of various parameters, such as structures of the folding agent and polymer, and the solvent composition, on the folding propensities of the polymer was studied.

New bisamide compounds from the bark of Aglaia eximia (Meliaceae)

“…The relative stereochemistry of 1, was established by coupling constant of proton H-1 000000 and H-2 000000 at d H 5.90, 1,2 J = 4.5 Hz and comparison of the typical 13 C NMR resonance of C-1 000000 at d C 90.7 and other related compounds (Jian et al, 2010), indicated that 1 000000 to be S configuration and conformation of axial-equatorial of H-1 000000 and H-2 000000 . The down field chemical shift of nitrogenated methylenes at d C 64.5 of 1 different to nitrogenated methylenes in aglaithioduline at d C 40.1 (Saifah et al, 1999) due to effect of oxygenated methine which bonded in straight chain with amino hidroxyocthylamino together with folding process on amino hidroxyocthylamino chain which cuased by anisotropy effect (Vise et al, 2005;Ramkumar & Ramakrishnan, 2008). The gross structure of straight chain with amino hidroxyocthylamino was deduced from the 1 H-1 H-COSY and HMBC spectra (Fig 2).…”

Single-Site Binding of Pyrene to Poly(ester-Imide)s Incorporating Long Spacer Units: Prediction of NMR Resonance-Patterns from a Fractal Model

“…15 For copoly(ether-imide)s 15 and copoly(ester-imide)s 16 studied previously, it was found that tight chain-folding 22-24 allowed the aromatic "reader-molecule" (generally pyrene) to bind strongly to the polymer chain by intercalation between adjacent NDI residues ( Figure 1). [25][26][27] In this context, the chain-fold may be viewed as a "half-closed bis-diimide macrocycle", related to the true NDI-based macrocycles reported by Sanders et al as components of donor-acceptor catenanes with dialkoxynapthalenes as the donor groups. [28][29][30] Somewhat related rotaxane complexes, comprising 4,4-bipyridinium macrocycles threaded onto a high-MW, chain-folding poly(dialkoxynaphthalene), have been reported by Hodge et al, 31 and discrete oligomer-analogues of these, showing complex dynamic behaviour in solution and unusual end-group disorder (leading to pseudo-polymeric crystal structures) in the solid state were more recently described by Stoddart and co-workers.…”

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

“…1). [25][26][27] In this context, the chain-fold may be viewed as a "half-closed bis-diimide macrocycle", related to the true NDI-based macrocycles reported by Sanders et al as components of donor-acceptor catenanes with dialkoxynapthalenes as the donor groups. [28][29][30] Somewhat related rotaxane complexes, comprising 4,4-bipyridinium macrocycles threaded onto a high-MW, chain-folding poly(dialkoxynaphthalene), have been reported by Hodge et al, 31 and discrete oligomer-analogues of these, showing complex dynamic behaviour in solution and unusual end-group disorder (leading to pseudo-polymeric crystal structures) in the solid state were more recently described by Stoddart and coworkers.…”