Novel amphiphilic multi-arm, star-like block copolymers as unimolecular micelles

Xinchang Pang, Lei Zhao, Mufit Akinc, Jin Kon Kim, Zhiqun Lin

Research output: Contribution to journalArticlepeer-review

182 Scopus citations


A series of novel amphiphilic multiarm, star-like block copolymers, poly(acrylic acid)-b-polystyrene (PAA-b-PS) based on ?-cyclodextrin (β-CD) with well-defined molecular architectures, molecular weight, and ratio of two dissimilar blocks were prepared by sequential atom transfer radical polymerization (ATRP). β-CD with 21 hydroxyl groups was esterified by the reaction of its hydroxyl end groups with 2-bromoisobutyryl bromide, producing star-like heptakis[2,3,6-tri-O-(2-bromo-2-methylpropionyl]- β-cyclodextrin) (denoted 21-Br-β-CD). Subsequently, 21-Br-β-CD was utilized to initiate sequential ATRP of tert-butyl acrylate (tBA) and styrene (St). A series of 21-arm, star-like diblock copolymers, poly(tert-butyl acrylate)-b- polystyrene (PtBA-b-PS) were thus obtained. Finally, the ester groups of tBA in star-like PtBA-b-PS were selectively hydrolyzed by trifluoroacetic acid (TFA), thereby yielding amphiphilic 21-arm, star-like diblock copolymer PAA-b-PS with narrow molecular weight distribution (polydispersity index, PDI < 1.2). The intermediate and final products were systematically characterized and confirmed by GPC, 1HNMRand FT-IR. The unimolecular micelles (i.e., composed of single copolymer molecule) formed from amphiphilic star-like PAA-b-PS were analyzed by dynamic light scattering, TEM, and AFM.

Original languageEnglish
Pages (from-to)3746-3752
Number of pages7
Issue number10
StatePublished - 24 May 2011


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