FLUORESCENCE STUDIES OF POLYMER COLLOIDS .24. ENERGY-TRANSFER IN RESTRICTED DIMENSIONS - A NEW APPROACH TO LATEX MORPHOLOGY

Poly(vinyl acetate) [PVAc] particles were prepared by dispersion polymerization in isooctane using a copolymer of 2-ethylhexyl methacrylate [EHMA] and 2-isocyanatoethyl methacrylate as a steric stabilizer. These reactive particles were treated with 2-(1-naphthyl)ethanol and with 2-(9-anthryl)ethanol to produce particles singly or doubly labeled specifically in the stabilizer phase. Energy transfer experiments were carried out first on the N-labeled particles doped with a hydrocarbon-soluble anthracene derivative which dissolved exclusively in the rubbery PEHMA phase and also on the doubly labeled particles. Donor fluorescence decay profiles were measured, and the data were fitted to the Klafter-Blumen model for energy transfer on fractal surfaces. The finding that the effective dimensionally d = 2 for this energy transfer process is interpreted in terms of a crossover in a restricted geometry: the PEHMA domains in this material are characterized by at least one linear dimension that is small and on the order of the R0 value (26 Å) for the energy transfer. In support of this idea, we find that swelling agents for PEHMA cause the d found in the experiments to increase systematically from 2 to 3. © 1990, American Chemical Society. All rights reserved.