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

Abstract

Interaction between naphthalene-labeled poly(hydrochloride quaternized 2-norbornene-5-methyleneamine), poly(HCQNBMA)/NA (luminophore), and quencher, emulsifier 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 of 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 higher in the aqueous phase than in microemulsion. Furthermore, the aqueous solution of ionic emulsifier increased the monomer emission. The increase in the monomer emission can be ascribed to the shielding of the naphthalene (NA) groups by SDS micelles. This separates NA groups from each other, which depresses 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 freedom of NA groups, which increases interaction between the probe and the quencher. The formation of nonfluorescence clusters is not ruled out. The quenching of NA emission by nitromethan (NM) is much stronger in microemulsion than in the aqueous phase, and the quenching is more pronounced for the low molecular weight 2-norbornene-5-methoxylnaphthalene (NBMNA) than for its polymer. The extent of penetration of reactants into the interfacial layer governs quenching of hydrophobic NA probe by hydrophilic quencher. Furthermore, the quenching events are connected with the thickness and density of the interfacial layer, as well as its charge. The addition of coemulsifier (1-pentanol) increases the total surface area of the microdroplets, the entry rate of reactants into the microdroplets, and the interaction of hydrophobic and hydrophilic reactants. The quenching events are more pronounced in the close packed o/w interfacial layer than in the loosely packed one. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 101–114, 2001