A critical evaluation of direct energy transfer as a tool for analysis of nanoscale morphologies in polymers. Application to block copolymer interfaces

Simulations of energy-transfer kinetics were carried out for a lamellar block copolymer system in which donor and acceptor dyes were attached to the block junction. Ln such a system, the distribution of donors and accepters follows P(J)(z), which describes the distribution of the junctions across the interface. We use these simulations to examine the type of information about the block copolymer morphology available from analysis of fluorescence decay profiles generated by these systems. Within the context of a Helfand-Tagami distribution for P(J)(z), one can obtain reliable estimates of the ratio of the period spacing to interface thickness (H/delta) but not the individual parameters H and delta. Since H can be determined independently in a scattering experiment, this approach is useful for obtaining values of delta with better than 5% accuracy. Attempts to distinguish a Helfand-Tagami profile from a Gaussian profile were not successful, The energy-transfer experiment may be employed to reject the wrong morphology only if prior values of H and delta are determined by other methods.