Facile Williamson etherification of hyperbranched polyglycerol and subtle core-dependent supramolecular guest selection of the resulting molecular nanocapsule

Abstract

O-alkylation of highly polar polyglycerol with alkyl bromides, promoted just by sodium hydroxide in dimethyl sulfoxide (DMSO), is reported. Zimmermann–Dathe type Williamson etherification, which can be carried out by a mild base in DMSO, is very useful in preparing ethers. However, it is always limited to alkyl chlorides or methyl halides due to the elimination reaction. In this contribution, this reaction is promoted to alkyl bromides and iodides just by decreasing the reaction temperature and then it is further applied in preparing a series of O-alkylated hyperbranched polyglycerol (PG). It is found per-alkylation of PG is possible regardless of its dense hydroxyl groups. In addition, the modified method shows selectivity over the halogen species. The resulting core–shell amphiphilic macromolecules (CAMs) can be used for dye encapsulation and they show core-dependent selection over the dye species. For example, the ether-based CAM 1b (PG–O–(C16)0.61, 61% of OH groups are O-alkylated by cetyls) is with limited difference from the ester-based CAM 2a (PG–COO–(C16)0.60), but they show very different guest selection. Controlled release is also available by core design of the CAMs.