A comprehensive study of the spontaneous formation of nanoassemblies in water by a “lock-and-key” interaction between two associative polymers

Schematic representation of spherically-shaped nanoassemblies resulting from the association of two water soluble polymers: i) alkylated dextran (in molecular or in micellar form) and ii) cyclodextrin polymer. [Display omitted] ► Nanoassemblies (NAs) with well-defined diameters were spontaneously formed in water according to an entropy-driven process after mixing a two associative water soluble polymers (cyclodextrin polymer and dextran grafted with alkyl side chains) ► The hydrophobic interaction between C 12 and the hydrophobic cavities of CDs was the main driving force for NAs’ formation, with a minor contribution arising from van der Waals’ interactions. ► The strong lock and key interactions between the two polymers are restricted neither by the dextran substitution yield, nor by its micellization in water. Nanoassemblies (NAs) with sizes ranging from 60 to 160 nm were spontaneously formed in water after mixing a host polymer (polymerized cyclodextrin (pβ-CD)) and a guest polymer (dextran grafted with lauroyl side chains (MD)). The combination of microscopy, dynamic light scattering (DLS), nuclear magnetic resonance ( 1H NMR), isothermal titration calorimetry (ITC) and molecular modelling was used to investigate the parameters which govern the association between MD and pβ-CD. Remarkably, when pβ-CD was progressively added to a solution of MD, NAs with a well-defined diameter were spontaneously formed and their diameter was constant whatever the composition of the system. According to NMR data, almost all the alkyl chains of MD were included into CDs’ cavities of the polymer when the molar ratio lauroyl chain (C 12)/CD was ⩾1. The hydrophobic interaction between C 12 and the hydrophobic cavities of CDs appears as the main driving force for NAs’ formation, with a minor contribution arising from van der Waals’ interactions. The inclusion of C 12 into β-CD cavities is almost a completely enthalpy-driven process, whereas the MD-C 12/pβ-CD interaction was found to be an entropy-driven process. Major conclusions which can be drawn from these studies are that the interactions between the two polymers are restricted neither by the MD substitution yield, nor by the micellization of MD. The simultaneous effects of several CD linked together in pβ-CD and of many alkyl chains grafted on dextran were necessary to generate these stable NAs.