Atom transfer radical dispersion polymerization in an ethanol/water mixture

The atom transfer radical dispersion polymerization of 4-vinylpyridine (4VP) in an ethanol/H2O mixture displayed two stages of polymerization; the first stage is the formation of a diblock copolymer with the polymerization rate of 1.21 mol center dot L-1 center dot h(-1) before 1 h of polymerization, and the second is the main polymerization in micelles formed from the aggregation of the resultant block copolymers with the polymerization rate of 0.009 mol center dot L-1 center dot h(-1). The 2-bromoisobutyryl-terminated poly(ethylene glycol) methyl ether used in the polymerization acts as both a stabilizer and an initiator. The stable micelles with functional core were synthesized by a one-pot strategy via atom transfer radical dispersion copolymerization (ATRDCP) of 4VP and N,N'-methylenebisacrylamide (MBA) in an ethanol/H2O solution for the first time. In the initial stage of polymerization, 4VP and MBA were copolymerized to form a block copolymer, PEG-b-(4VP-co-MBA), with pendent unreacted vinyl groups, and after phase separation at a critical chain length of P4VP-co-PMBA, the cross-linking reaction and polymerization occurred at the same time, resulting in cross-linked micelles. The volume ratio of ethanol/H2O had a big influence on the ATRDCP. An increase in the relative amount of ethanol in the solvent mixture will increase the solubility of P4VP in the polymerization system, the phase separation will be postponed, and the critical chain length of 4VP blocks at the phase separation becomes longer. As a result, the particles size and the 4VP content in the resultant micelles increase. The Au/polymer composite nanoparticles were successfully prepared by complexation of P4VP with HAuCl4 and following reduction with NaBH4.