ASSOCIATION AND PHASE-BEHAVIOR OF HYDROPHOBICALLY-MODIFIED PHOTORESPONSIVE POLY(ACRYLAMIDE)S IN THE PRESENCE OF IONIC SURFACTANT

The extent of association between the cationic surfactant TTAB and a s eries of hydrophobically modified polyacrylamides (HPAMs) containing a n N-n-alkyl and substituted azobenzene hydrophobic sidegroup has been studied utilizing a cationic surfactant-selective membrane electrode. Binding of TTAB to the polymer hydrophobes is found to increase with I ncreasing hydrophobicity of the hydrophobe. In the presence of electro lyte, aqueous solutions of HPAMs and ionic surfactant exhibit an assoc iative phase separation. The temperature or clearing point (CP) at whi ch the system goes from a one phase to two-phase system are reported. The area of the two-phase region is found to increase with increasing electrolyte concentration, hydrophobicity of the hydrophobe for the hi gh molecular weight HPAMs, and decreasing hydrophobicity for low molec ular weight HPAMs. Exposure of HPAMs containing an azobenzene hydropho be to UV light results in a decrease in interaction between the hydrop hobe and surfactant and a corresponding decrease in the CP due to conv ersion of azobenzene from the more hydrophobic trans form to the less hydrophobic cis isomer.