Real‐Time Scanning Force Microscopy of Macromolecular Conformational Transitions

Abstract

Summary: Comb‐like macromolecules were adsorbed on mica and imaged by scanning force microscopy in real time as they underwent a transition from an extended worm‐like conformation to globuli and vice versa. The conformational transition was effected by coadsorption of ethanol and water molecules. Coadsorption of the small molecules allowed manipulation of the adherence and spreading of the macromolecules, thus effecting the reptation like stretching and collapse of the single molecules.SFM images of three individual PMA‐g‐PnBuA brush molecules on mica 27 min (left, first collapse cycle) and 18 min (right, second collapse cycle) after injection of ethanol into the sample space.imageSFM images of three individual PMA‐g‐PnBuA brush molecules on mica 27 min (left, first collapse cycle) and 18 min (right, second collapse cycle) after injection of ethanol into the sample space.

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…Besides, it was possible to perform many successive cycles of conformational manipulation with the same macromolecules when after first cycle of compaction/extension one might induce second, third and so on, by means of cyclic changing of the vapour environment. [212,215] Even after a dozen of successive cycles performed during several days in total, at every single step the general course of the transformations was observed to be absolutely the same. [215] This observation somehow disagrees with the report of Glynos et al [273] They found out that a macromolecular island of an amphiphilic polymer was spontaneously compacting on mica at ambient conditions during two days of SFM observation.…”

“…Indeed, they used to be observed also for definitely isolated single macromolecules, as can be noticed in Figure 5 and 6, see also ref. [212] for further details. Besides, it was possible to perform many successive cycles of conformational manipulation with the same macromolecules when after first cycle of compaction/extension one might induce second, third and so on, by means of cyclic changing of the vapour environment.…”

“…Then one would observe swift collapse at high ethanol content in the in the vapour, and straightforward continuous extension at high water content, see ref. [210,212] Therefore, very interesting question is what equilibrium conformations may be observed after very long exposure of the macromolecules to vapours of some intermediate composition.…”

Block Copolymer Based Molecular Motor

“…Another possibility to induce collapsereadsorption comprises an exposure of the molecule to different vapors. [9,10] Relying on periodical variation of the number of adsorbed monomer units of one of the blocks and, therefore, of the friction force, one can expect fulfillment of the second condition. Finally, the third condition is provided by the structure of the surface which is patterned by the stripes, Figure 1.…”

Synthesis, Characterization and Thermally-Activated Curing of Azobenzene-Containing Benzoxazines

“…Various types of stimuli, e.g., temperature, pH, ionic strength, solvent vapors, light, or an electrical field, can affect properties and conformation of polymers [22][23][24][25][26][27][28][29][30].…”