Dendrimer like star polymer based on β-cyclodextrin with ABC type miktoarms†
The present article reports the synthesis and self aggregation study of a novel dendrimer like star polymer based on β-cyclodextrin (β-CD), in which the primary alcoholic arms of β-CD have been linked to ABC type miktoarm star polymers. Initially, 6-heptaazido-6-deoxy-β-cyclodextrin (7N3-β-CD) has been clicked with alkyne terminated poly(methyl methacrylate) (alkynyl-PMMA-Br), which has been synthesized through atom transfer radical polymerization technique. Subsequently, azidation has been done in order to prepare β-CD(PMMA-N3)7. Parallelly, an amphiphilic block copolymer (alkynyl-PDLL-b-PNIPAAm), having an alkyne end group, has been synthesized by employing a mikto functional initiator having alcohol, xanthate and alkyne functionalities, in ring opening polymerization (ROP) of D,L-lactide (DLL) from –OH end, and reversible addition-fragmentation chain-transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm) from xanthate end. Then, the desired star polymer has been synthesized by the click reaction between β-CD(PMMA-N3)7 and alkynyl-PDLL-b-PNIPAAm. The polymers have been characterized by 1H NMR, and gel permeation chromatography. Self aggregation of the star polymers has been investigated by 1H NMR and fluorescence spectroscopy. Size of the micelles formed has been analyzed by dynamic light scattering and transmission electron microscopic techniques.