Synthesis of linear and 4-arm star block copolymers of poly(methyl acrylate-b-solketal acrylate) by SET-LRP at 25 °C

The new SET-LRP (using Cu(0) powder for organic synthesis) was successfully used to produce well-defined linear and star homo- and diblock-copolymers of PMA, PSA, and P(MA-b-GA)(n) (where n = 1 or 4). The kinetic data showed that all SET-LRP were first order and reached high conversions in a short period of time. The other advantage of using such a system is that the copper can easily be removed through filtration, allowing the production of highly pure polymer. The molecular weight distributions were well controlled with polydispersity indexes below 1.1 and the number-average molecular weight close to theory, especially upon the addition of Cu(II)Br-2/Me-6-TREN complex. The linear and star block copolymers were then hydrolyzed to produce the biocompatible amphiphilic P(MA-b-GA)(n), where the glycerol side-groups make the outer block bydropbilic. These blocks were micellized into water and found to have a R-g/R-H equal to 0.8 and 1.59 for the liner and star blocks, respectively. This together with the TEM's supported that the linear blocks formed the classical core-shell micelles, where as, the star blocks formed vesicles. We found direct support for the vesicle structure from a TEM where one vesicle squashed a second vesicle consistent with a hollow structure. Such vesicle structures have potential applications as delivery nanoscaled devices for drugs and other important biomolecules. (C) 2008 Wiley Periodicals, Inc.