A Reconsideration of the Measurement of Polymer Interdiffusion by Fluorescence Nonradiative Energy Transfer. Dhinojwala, Ali; Torkelson, John M. Departments of Chemical Engineering and of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. Macromolecules (1994), 27(17), 4817-24. CODEN: MAMOBX ISSN: 0024-9297. Journal written in English. CAN 121:84498 AN 1994:484498 CAPLUS

A general formalism has been developed for quant. detn. of polymer self-diffusion coeffs., Dp, using fluorescence nonradiative energy transfer (NRET). The exptl. geometry consists of a "sandwich" of two thin polymer films, one labeled with NRET donor chromophores and the other with NRET acceptor chromophores. Dp can be characterized self-consistently by steady-state fluorescence intensity measurements of donors or acceptors or by transient donor fluorescence intensity decay measurements as a function of interdiffusion time, t. For t < x2/(16Dp), where x is the thickness of the donor-labeled polymer layer, increases in the normalized acceptor intensity and normalized energy transfer efficiency with interdiffusion are the same and equal to kn(Dpt)1/2/x, where kn is a function of the initial acceptor concn. Similarly, the decrease in the normalized donor intensity with interdiffusion is proportional to (Dpt)1/2/x. The general formalism presented here has been compared to earlier approaches, revealing that a previous method of analyzing the steady-state acceptor intensity in terms of polymer diffusion is merely a limiting case of the present formalism while a previous method of analyzing the donor intensity decays results in underestimates of Dp.