Reverse Thermo-Responsive Nanoshells: The Interplay Between the Composition of Their Building Blocks and Their Temperature-Responsive Morphing

This research lies at the intersection of two fields, combining their respective unique features: nanosized structures and reverse thermo-responsive (RTR) morphing. Hollow RTR polymeric nanoshells exhibiting a temperature-triggered sharp and notable reversible volumetric change in an aqueous medium, are engineered. These supramolecular structures that shrink above the relevant thermal transition and expand below it, are generated by crosslinking intramicellarly various polyethylene oxide–polypropylene oxide–polyethylaene oxide (PEO–PPO–PEO) amphiphiles, end-capped with C-C double bonds to render them crosslinkable. Systematic variation of the polymeric building blocks enables to engineer various hollow RTR nanoshells with tunable hydrodynamic diameters spanning ≈300 to 2500 nm, with broad translational potential in biomedical applications. Collectively, the nanoshells demonstrate extreme volumetric expandability, with volume increases of up to 630×. The objective of this study is to investigate the interplay between the coiling–uncoiling capability of the individual unimeric PEO–PPO–PEO amphiphiles and their collective effect on the resulting temperature-dependent dimensional behavior of the nanoshells. After studying the basic PEO–PPO–PEO dimethacrylate nanoshells, fundamental features of the amphiphiles forming the nanoshells, such as their composition, degree of methacrylation, and molecular weight, are fine-tuned, and their cooperative impact on the morphing of the nanoshells is studied.