PHOTOPHYSICAL AND RHEOLOGICAL PROPERTIES OF NAPHTHALENE-LABELED CATIONIC POLY(DIMETHYL SULFATE QUATERNIZED ACRYLAMIDE N,N-DIMETHYLAMINOPROPYLMALEIMIDE COPOLYMER)/

The synthesis, rheological, and fluorescence properties of a cationic water-soluble copolymer, naphthalene-labeled cationic poly(dimethyl su lfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolyme r), poly(DSQADMAPM)/NA, are reported. When fluorescent hydrophobes (na phthyl group) are incorporated into the cationic copolymer, the photop hysical response may effectively probe solution behavior on the micros copic level. The salt and pH responsiveness inherent to the cationic c opolymer systems is a function of ionic group type. Experimental resul ts indicate that I-E/I-M increases steadily with increases in polymer concentration and I-E/I-M values for a given polymer concentration are higher in salt. At low pH values, I-E/I-M is high and excimer emissio n increases as the quaternary amino groups (R4N+) are screened out. Dy namic light scattering (QELS) measurements indicate that diffusion coe fficients of the cationic copolymer increase and the hydrodynamic diam eters decrease with increasing salt concentration. Viscosity studies r eveal that the polymer coil shrinks as salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of thallium (Tl+) with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer mice llization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty in reacting with bound naphthalenes lo cated in the shrunk polymer coil. The cationic copolymer is depicted a s an expanded polymer coil in deionized water because of intra- and in terchain repulsions. Consequently, salt addition breaks down the repul sions and enhances intrapolymer micellization. (C) 1998 John Wiley & S ons, Inc.