Topological Biopassive Brushes. From Linear to Cyclic, from Atomistic to Coarse-Grained Poly(2-ethyl-2-oxazoline)

AA Galata and M Kröger, MACROMOLECULES, 57, 5313-5329 (2024).

DOI: 10.1021/acs.macromol.4c00174

In medicine, the quest for novel materials persists to ensure substances entering the human body are biopassive, less toxic, and possess improved properties compared to their predecessors. Poly(2-ethyl-2-oxazoline) (PEOXA), whether in linear or ring form, emerges as a promising alternative, outperforming its precursor, polyethylenglycol (PEG), in common PEG applications. This study aims to uncover the mechanical properties of PEOXA through a multiscale approach. To this end, atomistic simulations investigate single PEOXA chains (linear and ring) in water, revealing a helix-like structure due to hydrogen bond bridges along the polymer chain. Using these results, a computationally efficient coarse-grained (CG) model for a single PEOXA chain in water is developed. The CG model is then employed to create PEOXA polymer brushes with varying grafting densities (sigma), allowing the study of nanotribological properties, such as the coefficient of friction. Ring brushes exhibit a lower coefficient of friction, showing relative indifference to grafting density increases within certain limits when sheared against a explicit CG wall. In contrast, linear brush coefficients appear to rise at lower grafting densities, although an opposite trend is observed when shearing against a symmetric linear brush.

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