A facile one-pot construction of supramolecular polymer micelles from alpha-cyclodextrin and poly(epsilon-caprolactone).

Weak interactions such as hydrogen bonds, ionic bonds, hydrophobic interactions, and p–p interactions govern the structural conformation of all biological macromolecules, for example the double helix of DNA and cell membranes formed by lipids. In the past few decades, chemists have made significant progress in rationalizing the fundamental rules of these interactions and have developed various self-assembling polymer systems including polymer micelles from amphiphilic block copolymers. Recently, block-copolymerfree strategies were developed to construct supramolecular polymer micelles (SMPMs) through the noncovalent interaction between a hydrophilic polymer host and a hydrophobic polymer guest. However, the fabrication of SMPMs still poses a tremendous challenge as it involves the multistep synthesis of carefully designed polymer hosts and guests; thus a more convenient method to construct SMPMs needs to be developed. Cyclodextrins (CDs) are an ideal species for the development of new self-assembling systems. The cone-shaped cavities of CDs can act as hosts for a great variety of macromolecular guests containing multiple binding sites to form polyrotaxanes, with the inclusion driven by the geometric compatibility and hydrophobic interactions between the CDs and the polymers. Various cyclodextrin/poly(ecaprolactone) (CD/PCL) based polyrotaxanes have been reported. These pioneering studies have provided a wealth of new insights into these CD-containing systems, but, from the standpoint of potential applications, a great challenge still exists as a result of the insolubility of polyrotaxanes in most solvents, especially water, because of the strong intermolecular hydrogen bonds that are formed between CDs. These bonds may be weakened by either physical or chemical methods, such as those already applied to cellulose. We report here an entirely new approach for the construction of SMPMs in which a-CD and PCL are used as building blocks. These species initially self-assemble in THF/ H2O to form an amphiphilic complex of PCL, only part of which is threaded through the a-CDs. Removal of the THF results in a second assembly process in which the supramolecular polymer amphiphiles form SMPMs (Figure 1). The second step occurs as the section of PCL threaded through the