ABC TRIBLOCK POLYMETHACRYLATES - GROUP-TRANSFER POLYMERIZATION SYNTHESIS OF THE ABC, ACB, AND BAC TOPOLOGICAL ISOMERS AND SOLUTION CHARACTERIZATION

ABC triblock copolymers of methyl methacrylate (MMA), (dimethylamino)e thyl methacrylate (DMAEMA), and tetrahydropyranyl methacrylate (THPMA) consisting of 12 units of each type of monomer were synthesized by gr oup transfer polymerization (GTP). These were the three topological is omers with different block sequences: DMAEMA(12)-THPMA(12)-MMA(12), DM AEMA(12)-MMA(12)-THPMA(12), and THPMA(12)-DMAEMA(12)-MMA(12). The mole cular weights and molecular weight distributions of the copolymers wer e determined by gel permeation chromatography (GPC) in tetrahydrofuran , and their number-average degrees of polymerization and copolymer com positions were calculated by proton nuclear magnetic resonance spectro scopy (H-1-NMR). These molecular weights and degrees of polymerization corresponded closely to the values expected from the monomer/initiato r ratios. The polydispersities were low as expected for GTP, and range d from 1.09 to 1.25. The three triblocks were chemically modified by c onverting the THPMA units to methacrylic acid (MAA) units either by th ermolysis or acid hydrolysis. The resulting ABC triblock polyampholyte s were characterized by H-1-NMR spectroscopy and hydrogen ion titratio n. Aqueous GPC studies in 1.0 M NaCl at pH 8.5 showed that the tribloc k copolymers form micelles whose size depends on their block sequence. (C) 1998 John Wiley & Sons, Inc.