The thermal motion of polymer chains in a crowded environment is anisotropic and highly confined. Whereas theoretical and experimental progress has been made, typically only indirect evidence of polymer dynamics is obtained either from scattering or mechanical response. Toward a complete understanding of the complicated polymer dynamics in crowded media such as biological cells, it is of great importance to unravel the role of heterogeneity and molecular individualism. In the present work, we investigate the dynamics of synthetic polymers and the tube-like motion of individual chains using time-resolved fluorescence microscopy. A single fluorescently labeled polymer molecule is observed in a sea of unlabeled polymers, giving access to not only the dynamics of the probe chain itself but also to that of the surrounding network. We demonstrate that it is possible to extract the characteristic time constants and length scales in one experiment, providing a detailed understanding of polymer dynamics at the single chain level. The quantitative agreement with bulk rheology measurements is promising for using local probes to study heterogeneity in complex, crowded systems.Keywords: reptation; single molecule studies; time-resolved fluorescence microscopy;

Helical structures play a vital role in nature, offering mechanical rigidity, chirality and structural definition to biological systems. Little is known about the influence of the helical architecture on the intrinsic properties of polymers. Here, we offer an insight into the nano architecture of helical polymers by measuring helical polyisocyanopeptides with single molecule force spectroscopy. An unprecedented large heterogeneity in the stiffness of the polymers was found. The heterogeneity persisted when the stiffness of these polymers was steered by: (1) enhancing the formation of the hydrogen bonding network along the polymer, (2) via π–π stacking interactions of aromatic perylenes, and (3) by changing the stereochemistry of the side chain. However, the heterogeneity was lost after completely disrupting the secondary structure by the addition of trifluoroacetic acid. Molecular dynamics simulations revealed three possible structural conformations which can account for the observed heterogeneity and their corresponding energy landscape is proposed.

Helical structures play a vital role in nature, offering mechanical rigidity, chirality and structural definition to biological systems. Little is known about the influence of the helical architecture on the intrinsic properties of polymers. Here, we offer an insight into the nano architecture of helical polymers by measuring helical polyisocyanopeptides with single molecule force spectroscopy. An unprecedented large heterogeneity in the stiffness of the polymers was found. The heterogeneity persisted when the stiffness of these polymers was steered by: (1) enhancing the formation of the hydrogen bonding network along the polymer, (2) via π–π stacking interactions of aromatic perylenes, and (3) by changing the stereochemistry of the side chain. However, the heterogeneity was lost after completely disrupting the secondary structure by the addition of trifluoroacetic acid. Molecular dynamics simulations revealed three possible structural conformations which can account for the observed heterogeneity and their corresponding energy landscape is proposed.