Synthesis of cyclic methacrylic acid oligomers by atom transfer radical polymerization

Poly(methacrylic acid) (PMAA) oligomers were synthesized by combining template polymerization and copper-mediated atom transfer polymerization with multivinyl monomer of beta-cyclodextrin (CD) having 20.4 methacryloyl groups on both primary and secondary hydroxyl group sides of CD scaffold, with 1,3-dibromobutane as an initiator. The initiation and propagation sites of polymerized sequence of beta-CD were connected by postpolymerization of polymerized products with CuBr and tris[(2-dimethylamino)ethyl]amine (Me6TREN) in a methanol/water mixture of 10 wt % of water. Polymerized and cyclized sequences, PMAA oligomers formed on the primary and the secondary hydroxyl group sides, were detached from beta-CD scaffold by hydrolysis. Molecular weights of PMAA oligomers were measured by GPC and matrix assisted laser desorption ionization time-of-flight mass measurement. By H-1 NMR measurements, it was found that three types of cyclic PMAA were obtained by postpolymerization. The cyclization preferentially occurred on the secondary hydroxyl group side than on the primary hydroxyl group side. From the structures of cyclic PMAA, two reaction positions were proposed. (c) 2005 Wiley Periodicals, Inc.