Syntheses and micellar properties of well‐defined amphiphilic AB₂and A₂B Y‐shaped miktoarm star copolymers of ε‐caprolactone and 2‐(dimethylamino)ethyl methacrylate

Abstract

Abstract Well‐defined amphiphilic PCL‐ b ‐(PDMA) 2 and (PCL) 2 ‐ b ‐PDMA Y‐shaped miktoarm star copolymers and PCL‐ b ‐PDMA linear diblock copolymer were synthesized via a combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP), where PCL is poly (ε‐caprolactone) and PDMA is poly(2‐(dimethylamino)ethyl methacrylate). All of these three types of copolymers have comparable PCL contents and overall molecular weights. The PCL block is hydrophobic while the PDMA block is hydrophilic, and they behave like polymeric surfactants and self‐assemble into PCL‐core micelles in aqueous media. The chain architectural effects on the micellization properties, including the aggregation number, size, polydispersity, and micelle densities of (PCL 29 ) 2 ‐ b ‐PDMA 45 , PCL 61 ‐ b ‐(PDMA 24 ) 2 , and PCL 56 ‐ b ‐PDMA 49 in dilute aqueous solution, were then explored by dynamic and static laser light scattering (LLS). The intensity–average hydrodynamic radius, 〈 R h 〉, the aggregation number per micelle, N agg , and the core radius, R core , of the PCL‐core micelles all increased in the order PCL 61 ‐ b ‐(PDMA 24 ) 2 < (PCL 29 ) 2 ‐ b ‐PDMA 45 < PCL 56 ‐ b ‐PDMA 49 . The surface area occupied per soluble PDMA block at the core/corona interface increased in the order PCL 61 ‐ b ‐(PDMA 24 ) 2 < PCL 56 ‐ b ‐PDMA 49 < (PCL 29 ) 2 ‐ b ‐PDMA 45 . PCL 61 ‐ b ‐(PDMA 24 ) 2 micelles had the largest overall micelle density, possibly because of that the presence of two soluble PDMA arms at the junction point favors the bending of the core–corona interface and thus the formation of densely‐packed core‐shell nanostructures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1446–1462, 2007