SYNTHESIS AND CHARACTERIZATION OF ZWITTERIONIC BLOCK-COPOLYMERS

Zwitterionic poly(2-(dimethylamino)ethyl methacrylate-bloch-methacryli c acid) (PDMAEMA-block-PMAA) copolymers are synthesized by group trans fer polymerization using 2-tetrahydropyranyl methacrylate (THPMA) as a protected monomer for the acid block. Subsequent thermolysis led to q uantitative removal of the tetrahydropyranyl groups, but control exper iments indicated significant broadening of the molecular weight distri bution (MWD) of a PDMAEMA. homopolymer under the same conditions. Henc e this deprotection route was considered unsatisfactory. Acid hydrolys is of the block copolymers under mild conditions also led to quantitat ive removal of the THP groups, as judged by H-1 NMR spectroscopy. This deprotection chemistry was adopted as our preferred route, since it d id not lead to MWD broadening of the same PDMAEMA homopolymer. A serie s of zwitterionic blocks were synthesized with good control over both molecular weight and copolymer composition. The aqueous solubility vs. pH behavior of these copolymers was determined by acid titration. Fin ally, the reversible micellization of these copolymers in aqueous medi a was examined using dynamic light scattering and variable temperature H-1 NMR spectroscopy.