The synthesis of amphiphilic star and cyclic diblock copolymers and their potential biomedical applications
Description
The preparation of well defined diblock copolymers has garnered great interest for their widespread applications. Because of the ever increasing need for innovative biomedical applications, we sought to prepare amphiphilic star and cyclic diblock copolymers with potential transdermal drug delivery and antimicrobial properties, respectively. Atom transfer radical polymerization (ATRP) was the chosen polymerization technique for the preparation of these polymers because its end group retention allows for preparation of block copolymers and for post-polymerization modification of the terminal halide to other functional end-groups. Amphiphilic star diblock copolymers of poly(oligo(ethylene glycol)methacrylate)- block-poly(lauryl methacrylate), bearing 6- and 12-arms demonstrated their ability to encapsulate proflavin dye and FITC-BSA protein. When compared with a self-assembled 1-arm diblock copolymer of the same composition, these star polymers also demonstrated an increase encapsulation of dye as a result of this unique architecture. They also demonstrated transdermal carrier capabilities, exhibiting the ability to traverse porcine skin, and simultaneously carry polar dyes through the stratum corneum. Combining ATRP and Cu(I)-catalyzed azide-alkyne 'click' coupling, cyclic diblock copolymers of poly(methyl acrylate)- block-poly(styrene) were successfully prepared in near quantitative yields. Preparation of amphiphilic cyclic poly(acrylic acid)-block -poly(styrene) was attempted by the acid-catalyzed methyl ester hydrolysis of previously prepared poly(methyl acrylate)-block-poly(styrene). While selective hydrolysis of the methyl esters was unsuccessful, use of the more labile tert-butyl acrylate ester side chains shows promise. Although block copolymers of poly(tert-butyl acrylate)- block-poly(styrene) were prepared, loss of the their bromide end group appears to be the remaining complication to accessing the desired amphiphilic cyclic polymers