Electronic excitation transport

Barzykin A V, Barzykina N S and Fox M A 1992 Electronic excitation transport and trapping in micellar systems— Monte-Carlo simulations and density expansion approximation Chem. Rhys. 163 1-12... 

The application of this technique as a morphological tool requites that there be a close coupling between polymer photophysics and polymer physics. In the photophysical studies described in this paper emphasis will be placed on the development of analytical models for electronic excitation transport (EET). The areas of polymer physics that we will consider involve the configurational statistics of Isolated chains and phase separation in multicomponent polymer systems. The polymer system of primary interest is the blend of polystyrene (PS) with poly(vinyl methyl ether) (PVME). 

There has been increasing interest in recent years in using incoherent electronic excitation transport as a probe of molecular interactions in solid state polymer systems. The macroscopic properties of such systems arise from the microscopic interaction of the individual polymer chains. The bulk properties of polymer blends are critically dependent on the mixing of blend components on a molecular level. Through the careful adjustment of the composition of blends technological advances in the engineering of polymer materials have been made. In order to understand these systems more fully, it is desirable to investigate the interactions... 

Due to the sensitivity of electronic excitation transport to the separation and orientation of chromophores, techniques which monitor the rate of excitation transport among chromophores on polymer chains are direct probes of the ensemble average conformation (S). It is straightforward to understand qualitatively the relationship between excitation transport dynamics and the size of an isolated polymer coil which is randomly tagged in low concentration with chromophores. An ensemble of tagged coils in a polymer blend will have some ensemble averaged root-mean-squared radius of gyration,... 

Description of the excimer photophysics for a two-phase system presented by Wandelt and co-workers [66] are based on both the two-phase model assumptions and the experimental results. The two-phase model describes the results of the experimental studies of photoenergy migration in heterogeneous solid-state polymer blends by Frank and collaborators [68, 69]. Tao and Frank [69] used three-dimensional electronic excitation transport to interpret the ratio of excimer to monomer fluorescence for poly-2-vinylnaphthalene with polycyclohexyl methacrylate. The assumptions of the two-phase model are ... 

Ediger MD, Fayer MD (1984) Electronic excitation transport in disordered finite volume systems. J Phys Chem 88(25) 6108-6116. doi 10.1021/jl50669a012... 

Ediger MD, Payer MD (1983) New approach to probing polymer and polymer blend structure using electronic excitation transport. Macromolecules 16(12) 1839-1844. doi 10.1021/ ma00246a008... 

Hussey DM, Payer MD (1999) Phase separation in binary and ternary polymer composites studied with electronic excitation transport. Macromolecules 32(20) 6638-6645. doi 10. 1021/ma9904114... 

In 1978, Salcedo, et al at Stanford University reported the measurement of singlet electronic excitation transport in a molecular crystal. The time scale of their measurement was 1 ns. Also in 1978, the first reports were published of the measurement of mass transport by transient grating techniques. Hervet, et al of the College de France reported the translational diffusion coefficient of the photochromic dye methyl red in an aligned liquid crystal, as a function of direction. The time scale was 0.1 s. Smith and McConnell at Stanford University used Fluorescence Redistribution After Pattern Photobleaching to measure the diffusion coefficient of dye-labeled phospholipid in oriented multibilayer films. The time scale was 100 s. 

ELECTRONIC EXCITATION TRANSPORT AS A TOOL FOR THE STUDY OF POLYMER CHAIN STATISTICS... 

A quantitative explanation of this behavior has been somewhat difficult to obtain, however. There have been several proposals to identify the experimentally resolved exponentials with physical entities, such as multiple monomer states [17-20] or multiple excimer states [15,21]. It is quite probable that the kinetics of the aryl vinyl pol)nners are indeed more complex than the simple Birks scheme would allow. However, recent theoretical studies on electronic excitation transport in random systems of donors and traps have shown that the fluorescence decays are in general, nonexponential [4,5, 22-26]. A key feature of these analyses is that the trapping dynamics in one dimensional and quasi one dimensional polymeric systems require that a trapping rate function k(t) rather than a trapping rate constant be used. In Section 2.1 we give the relationship of k(t) to the observables in a trapping experiment and provide the connection with G (t), which is obtained from theory. 

Although the number of EFS traps will be an important factor governing the observed fluorescence, a second factor of equal or sometimes greater importance is the phenomenon of electronic excitation transport (EET) [51, 58-61]. This involves the radiationless transfer of excitation energy, in the singlet state for compounds in this work, from one aromatic chromophore to another. This process may be viewed as a random walk with the rate of transfer between randomly oriented absorption and emission dipoles being given at each step by... 

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