Thermodynamics and morphology of latex blend films

We propose a model to describe direct nonradiative energy transfer (DET) between donors and acceptors chemically attached to the two different components of a latex blend. The model describes the case of one polymer dispersed as spheres of identical diameter in a continuous matrix of the second polymer. The segment distribution of the two polymers in the interface region is calculated taking into account the binodal compositions of the polymers in the different blend domains, the amount of each component, and the theory of the interfacial region between two polymers. The model was used to characterize the interface between poly(butyl methacrylate) (PBMA) and poly(2-ethylhexyl methacrylate) (PEHMA) domains in a binary blend, that we have examined previously (Macromolecules 2000, 33, 5863). We found a drastic dependence of the donor fluorescence survival probability curves on the Flory-Huggins X parameter and on the PBMA:PEHMA weight ratio. Since the latter ratio is known from the experimental conditions, we were able to calculate chi = 0.021 from the measurements with very low uncertainty, and infer the interface thickness between the domains in the blend as approximately 5.5 nm.