Formation, structure and thermal properties of the ternary aggregate of polyethylene glycol, β-cyclodextrin and ferrocene

Abstract

In this study, we firstly describe the formation of a ternary aggregate of ferrocene (Fc), polyethylene glycol (PEG) and β-cyclodextrin (β-CD). Our results provide strong evidence for the fact that the intermolecular aggregation behaviour leads to a striking change in structure and thermal property of the components aggregated. First of all, several independent experiments give us sufficient information about the structure of the aggregate: (1) the ternary aggregate tends to form a uniform fine-grained sponge structure, generating small particles with higher surface areas; (2) there is a threading mechanism of the PEG chain into the cavities of β-CD, and Fc plays the role of a stabiliser for such an aggregation; (3) there is a continual decrease in electron density of the Fe 2p3/2 region from free Fc to the binary aggregates of Fc and to the ternary aggregate. Next, the ternary aggregate exhibits a one-step degradation mechanism and has much lower thermal stability than free components and especially the physical mixture of the components. We believe that these findings are important and valuable for designing and fabricating polypseudorotaxanes, soft matters and organic/inorganic composite materials.