AMPHIPHILIC APPROACH FOR PREPARING HOMOPOLYROTAXANES OF POLY(ETHYLENEOXIDE)

A new concept was introduced for preparing homopolyrotaxanes that lack an enthalpic driving force for threading, and which are therefore tru ly a physical entrapment of non-interacting cyclic molecules and linea r polymer chains. It is based on the ability of amphiphiles to form la mellae and columnar micelles in solvents that selectively solvate one of its components. An amphiphilic macrocrown ether (MC-12) with an ave rage ring size of 42 atoms attached to a hydrophobic 12-carbon tail wa s prepared by formation of the macrocycle in the presence of multiple potassium template ions under pseudo-high dilution conditions. MC-12 i s almost insoluble in aliphatic hydrocarbon solvents, but forms micell es in benzene and toluene in the presence of water. The micellar solut ions of MC-12 macroscopically phase separate if water-soluble threads are added, but remain intact and solubilize less-water-soluble poly(et hylene glycol) (PEG) derivatives. PEG3350-bis(amine) threads do not re act, or react incompletely, with tert-butyltrityl end-capping agents f unctionalized with benzaldehyde and acid chloride groups, respectively . The optimum end-capping reaction for PEG-bis(amine) threads in the w ater-induced micellar solutions of MC-12 is the addition reaction with -p-[tris(p-tert-butylphenyl)methyl]phenoxy-methyl- 4,4-dimethylazlact one.