Dendrimer like star polymer based on β-cyclodextrin with ABC type miktoarms

Abstract

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.