Photophysical studies of intramolecular micelles in a hydrophobic polyacid

Investigation of intramolecular micelles in copolymers of maleic anhydride and alkyl vinyl ethers is accomplished by using luminescence probes and luminescence quenching. The pyrene probe is used to index the polarity of the microenvironment of intramolecular micelles. It is found that the polarity of the microenvironment sensed by a pyrene molecule in a polyacid micelle is about the same as in n-octanol. The luminescence intensity and lifetime of Ru(bpy){dollar}sbsp{lcub}3{rcub}{lcub}2{rcub}sp+{dollar} are also dependent on the rigidity of the microenvironment Ru(bpy){dollar}sbsp{lcub}3{rcub}{lcub}2{rcub}sp+{dollar} is in. This property is used to study the distribution of Ru(bpy){dollar}sbsp{lcub}3{rcub}{lcub}2{rcub}sp+{dollar} between the micellar phase (rigid) and the aqueous phase (less rigid). The equilibrium constant for the distribution of Ru(bpy){dollar}sbsp{lcub}3{rcub}{lcub}2{rcub}sp+{dollar} between micellized and non-micellized polyacid is estimated to be 28. The solubility of 9-methylanthracene (9-MeA) in polyacid is assumed to be proportional to the degree of micellization of polyacid molecules. The degrees of micellization of polyacid molecules are determined from solubilization experiment data and used to calculate the micelle size from luminescence quenching. The quenching of the luminescence of Ru(bpy){dollar}sbsp{lcub}3{rcub}{lcub}2{rcub}sp+{dollar} by 9-MeA in solutions of a hydrolyzed copolymer of maleic anhydride and n-hexyl vinyl ether, DP = 1700, was investigated in order to study the micellar behavior of this polyacid. The results indicate that the micelles inside the domain of a macromolecule encompass approximately 24 repeat units. This micelle size is unaffected by changes in the concentrations either of the polyacid or of the probe and is independent of the degree of micellization of the polyacid molecule. The dynamics of the quenching process are compared with those reported for solutions of surfactant micelles containing the same probe and quencher.