SYNTHESIS OF POLYISOPRENE AND POLYISOPRENE-CONTAINING AMPHIPHILIC BLOCK COPOLYMERS VIA RAFT FOR THE PREPARATION OF NANOPARTICLES WITH REGIOSELECTIVE FUNCTIONAL DOMAINS
David Sam Germack* †, Dean M. DeLongchamp*, and Karen L. Wooley†
*Polymers Division, Materials Science and Engineering Laboratory,
National Institute of Standards and Technology, Gaithersburg, MD, 20899.
†Center for Materials Innovation, Department of Chemistry and Department of Radiology, Washington University in Saint Louis, MO, 63130.
The application of nanomaterials synthesized by self-assembly of polymeric precursors in fields as diverse as marine anti-fouling coatings, lithographic templates and therapeutic drug delivery have provided increasing challenges for synthetic polymer chemists to prepare polymers that present chemical functionality to control the self-assembly process and provide for pre- and post-assembly crosslinking, modification, and degradation. Living free radical polymerization techniques have allowed for a number of advances in this field, however further work is still needed if these technologies are to realize their potential. This poster describes our recent efforts to prepare block copolymers that present latent, orthogonal, reactive groups by illustrating homo-, di-, and triblock copolymers prepared via reversible addition-fragmentation chain-transfer (RAFT) controlled radical polymerization and their use as building blocks, programmed for self assembly and regioselective crosslinking chemistries. Conditions were developed for these polymers to include polyisoprene segments as unique reactive components. Studies of linear ABC and ACB triblock copolymers prepared from tert-butyl acrylate, isoprene and styrene, were also conducted. Poly(tert-butyl acrylate) was prepared and used as a macromolecular RAFT agent for both topological isomers, poly(tert-butyl acrylate)-b-polyisoprene-b-polystyrene (ABC) and poly(tert-butyl acrylate)-b-polystyrene-b-polyisoprene (ACB). The atom-efficient preparation of poly(acrylic acid)-b-polyisoprene via RAFT by sequential polymerization of acrylic acid and isoprene as the ultimate expression of the goal of preparing a functional block copolymer for self-assembly will also be presented. The preparation of discrete nanoscale particles, based upon the self assembly of these block copolymers in selective solvents and their covalent stabilization via regioselective chemistries, is also described.