Water-soluble copolymers. 49. Effect of the distribution of the hydrophobic cationic monomer dimethyldodecyl(2-acrylamidoethyl)ammonium bromide on the solution behavior of associating acrylamide copolymers

Abstract

A novel water-soluble monomer, dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (DAMAB), was synthesized. This monomer possesses a critical micelle concentration of 4.9 x 10(-3) M. A series of copolymers of DAMAB with acrylamide (AM) have been prepared by radical copolymerization by micellar and solution techniques. The rheological properties of the copolymers were strongly affected by their microstructures. A random copolymer with 5 mol % of DAMAB obtained by solution polymerization in tert-butyl alcohol showed a tendency for intramolecular hydrophobic association, while microheterogeneous copolymerization of AM with 5 and 10 mol % of DAMAB in water yielded microblocky structures which promoted intermolecular association of hydrophobes. The intermolecular association was enhanced by increasing the length of the hydrophobic block and/or the number of blocks in the polymer chain. Evidence of hydrophobic microdomains was obtained utilizing pyrene probe fluorescence.