Reversible addition-fragmentation chain transfer polymerization was employed to synthesize a set of copolymers of styrene (PS) and 2,3,4,5,6-pentafluorostyrene (PPFS), as well as block copolymers with tert-butyl acrylate (PtBA)-b-PS-co-PPFS, with control over molecular weight and polydispersity. It was found that the copolymerization of styrene and PFS allowed for the preparation of gradient copolymers with opposite levels of monomer consumption, depending on the feed ratio. Conversion to amphiphilic block copolymers, PAA-b-(PS-co-PPFS), by removing the protecting groups was followed by fitting with monomethoxy poly(ethylene glycol) chains. Solution-state assembly and intramicellar crosslinking afforded shell crosslinked knedel-like (SCK) block copolymer nanoparticles. These fluorinated nanoparticles (ca. 20 nm diameters) were studied as potential magnetic resonance imaging (MRI) contrast agents based on the 19F-nuclei; however, it was found that packaging of the hydrophobic fluorinated polymers into the core domain restricted the mobility of the chains and prohibited 19F NMR spectroscopy when the particles were dispersed in water without an organic cosolvent. Packing of perflouro-15-crown-5-ether (PFCE) into the polymer micelle was demonstrated with good uptake efficiency; however, it was necessary to swell the core with a good solvent (DMSO) to increase the mobility and observe the 19F NMR signal of the PFCE.
|Number of pages||15|
|Journal||Journal of Polymer Science, Part A: Polymer Chemistry|
|State||Published - Feb 15 2009|
- Amphiphilic polymers
- Block copolymers
- Reversible addition-fragmentation chain transfer (RAFT) polymerization