SYNTHESIS AND SOLUTION PROPERTIES OF WATER-SOLUBLE HYDROPHILIC-HYDROPHOBIC BLOCK-COPOLYMERS

A series of water-soluble diblock copolymers containing 2-(dimethylami no)ethyl methacrylate and various alkyl methacrylates has been synthes ized using group transfer polymerization. These hydrophilic-hydrophobi c copolymers have been characterized with respect to chemical composit ion and molecular weight by NMR spectroscopy, elemental microanalyses, and gel permeation chromatography. Block copolymers containing methyl methacrylate as the hydrophobic component were water-soluble provided that the hydrophilic monomer content was greater than 60 mol % of the overall block copolymer. Quaternization of the DMAEMA block with meth yl iodide was near-quantitative and considerably enhanced the water-so lubility of the copolymers. NMR studies, surface tension measurements, and photon correlation spectroscopy all indicated that the PDMAEMA-b- MMA block copolymers form micelles in deionized water. However, in aci dic solution (pH 2), copolymer micellization occurred only in the pres ence of added electrolyte. The block copolymer micelles initially incr eased in size on addition of added electrolyte at pH 9.5. Further elec trolyte addition led to macroscopic precipitation.