Molecular Bottle Brushes with Positioned Selenols: Extending the Toolbox of Oxidative Single Polymer Chain Folding with Conformation Analysis by Atomic Force Microscopy

Abstract

A synthesis route to controlled and dynamic single polymer chain folding is reported. Sequence‐controlled macromolecules containing precisely located selenol moieties within a polymer chain are synthesized. Oxidation of selenol functionalities lead to diselenide bridges and induces controlled intramolecular crosslinking to generate single chain collapse. The cyclization process is successfully characterized by SEC as well as by 1H NMR and 2D HSQC NMR spectroscopies. In order to gain insight on the molecular level to reveal the degree of structural control, the folded polymers are transformed into folded molecular brushes that are known to be visualizable as single molecule structures by AFM. The “grafting onto” approach is performed by using triazolinedione−diene reaction to graft the side chain polymers. A series of folded molecular brushes as well as the corresponding linear controls are synthesized. AFM visualization is proving the cyclization of the folded backbone by showing globular objects, where non‐folded brushes show typical worm‐like structures. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 154–162

Ultra-High-Molecular-Weight Macrocyclic Bottlebrushes via Post-Polymerization Modification of a Cyclic Polymer

“…AFM analysis of CB-PS-1a revealed ring-shaped structures when a highly dilute solution of the polymer in THF (1 μg/ mL) was spin-coated on a mica surface (Figure S14). The circular shapes are consistent with the cyclic topology of the macrocyclic bottlebrushes 51 expected for backbone synthesis via REP of acetylenic monomers. The outer diameters of the circular structures range from 25 to 50 nm, which are well below the theoretical outer diameter of ∼180 nm (Table S4), calculated based on the M n,GPC of the backbone and side chains and assuming a fully extended backbone.…”

Photochemical Transformations of Peptides Containing the N-(2-Selenoethyl)glycine Moiety

“…Yield 0.81 g (81%). 1 H NMR (500 MHz, DMSO-d 6 ): δ = 7.19−7.16 (m, 4H), 6.89−6.86 (m, 4H), 3.89 (s, 4H), 3.73 (s, 6H); 13 72 (The reaction was carried out under a nitrogen atmosphere.) Sodium borohydride (0.4 g, 10.6 mmol) was added portionwise to a solution of 1,2-bis(4-methoxybenzyl)diselane (1.0 g, 2.5 mmol) in EtOH/DMF (30 mL, 1:1, v/v), and the reaction mixture was stirred for 2 h at room temperature.…”