Preparation And Characterization Of Ferrocenyl Derivative Polyrotaxanes Based On β-Cyclodextrins

1,1’-Ferrocenedicarboxylic acid was allowed first to undergo the esterifications with tetraethylene glycol(TEG)to give rise to the ditetraethylene glycol 1,1’-ferrocenedicarboxylic ester in a way of carefully-controlled feeding ratio and slow feeding raw materials.Then a distal 2-bromoisobutyryl end-capped ditetraethylene glycol 1,1’-ferrocenedicarboxylic ester(Br-TEG-Fc-TEG-Br)was prepared as an initiator from the further reaction with 2-bromoisobutyryl bromide.The resulting initiator was self-assembled with β-cyclodextrins(β-CDs)in water to create a polypseudorotaxane(PPR)as a supramolecular initiator.The initiator and PPR were used to initiate in situ atom transfer radical polymerization(ATRP)of varying amounts of N-isopropyl acrylamide(NIPAAm)to prepare the corresponding multiblock copolymers and polyrotaxane containing multiblock copolymers.From the results of detailed structural characterization,β-CDs were found to self-assemble with the initiator moiety to present a characteristic tunnel-type crystal structure in both the PPR and polyprotaxane containing multiblock copolymers,but the poly(N-isopropyl acrylamide)(PNIPAAm)segments are not bulky enough to prohibit β-CDs dropping out the polymeric backbone.During the dialysis process,β-CDs were noted to move over the PNIPAAm segments and slip off the chain gradually.Futhermore,when the multiblock copolymers were self-assembled with β-CDs in aqueous solution,added β-CDs included mainly with the PNIPAAm segments and nearly cannot pass through to include with the initiator moiety,suggested that the self-assembly between β-CDs and PNIPAAm is a relatively slow and danymic process.Besides,a novel monoclinic crystal structure obtained from the inclusion complexation of β-CDs and PNIPAAm segements was also elucidated in this study.