Interaction of naphthalene-labeled poly(hydrochloride quaternized 2-norbornene-5-methyleneamine) with O/W microemulsion droplets

Interaction between naphthalene-labeled poly(hydrochloride quaternized 2-no rbornene-5-methyleneamine), poly(HCQNBMA)/NA (luminophore), and quencher, e mulsifier or coemulsifier in the aqueous or microemulsion media was studied by using steady-state fluorescence measurements. Fluorescence experiments were carried out with poly(HCQNBMA)/NA dissolved in the aqueous solutions o f ionic and nonionic emulsifiers, emulsifier/n-hexane/water microemulsion ( A) and emulsifier/n-hexane/1-pentanol/water microemulsion (B), respectively . The intensity of fluorescence emission of poly(HCQNBMA)/NA was much highe r in the aqueous phase than in microemulsion. Furthermore, the aqueous solu tion of ionic emulsifier increased the monomer emission. The increase in th e monomer emission can be ascribed to the shielding of the naphthalene (NA) groups by SDS micelles. This separates NA groups from each other, which de presses the deactivation of excited states. The strong decrease in monomer emission within the microemulsion media probably results from the elongated conformation structure of the polymer molecule, and higher conformation fr eedom of NA groups, which increases interaction between the probe and the q uencher. The formation of nonfluorescence clusters is not ruled out. The qu enching of NA emission by nitromethan (NM) is much stronger in microemulsio n than in the aqueous phase, and the quenching is more pronounced for the l ow molecular weight 2-norbornene-5-methoxylnaphthalene (NBMNA) than for its polymer. The extent of penetration of react ants into the interfacial laye r governs quenching of hydrophobic NA probe by hydrophilic quencher. Furthe rmore, the quenching events are connected with the thickness and density of the interfacial layer, as well as its charge. The addition of coemulsifier (l-pentanol) increases the total surface area of the microdroplets, the en try rate of reactants into the microdroplets, and the interaction of hydrop hobic and hydrophilic reactants. The quenching events are more pronounced i n the close packed o/w interfacial layer than in the loosely packed one. (C ) 2000 John Wiley & Sons, Inc.