Core-Shell Particles with Glycopolymer Shell and Polynucleoside Core via RAFT: From Micelles to Rods

Amphiphilic block copolymers were synthesized via the reversible addition fragmentation chain transfer (RAFT) copolymerisation of 2-methacrylamido glucopyranose (MAG) and 5'-O-methacryloyl uridine (MAU). Homopolymerisations of both monomers using (4-cyanopentanoic acid)-4-dithiobenzoate (CPADB) proceeded with pseudo first order kinetics in a living fashion, displaying linear evolution of molecular weight with conversion and low PDIs. A bimodal molecular weight distribution was observed for PMAU at low conversions courtesy of hybrid behavior between living and conventional free radical polymerization. This effect was more pronounced when a PMAG macroRAFT agent was chain extended with MAU, however, in both cases, good control was attained once the main RAFT equilibrium was established. A stability study on PMAU found that its hydrolysis is diffusion controlled, and is accelerated at physiological pH compared with neutral conditions. Self-assembly of four block copolymers with increasing hydrophobic (PMAU) block lengths produced micelles, which demonstrated an increased tendency to form rods as the PMAU block length increased. Interestingly, none of the block copolymers were surface-active. An initial assessment of PMAU's ability to bind the nucleoside adenosine through base pairing was highly promising, with DSC measurements indicating that adenosine is fully miscible in the PMAU matrix. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1706-1723, 2009