Fluorescence of Polymers in Solution

The rigidity of the chain has been characterised by the value of the steric factor, a, which is defined as  

It has been demonstrated that the excimer emission intensity from chromophores incorporated into the vinyl polymer chain have been correlated with a change in the effective volume of random polymer coil in solution, and the volume of random polymer coil was correlated with viscosity, which is dependent on temperature. But a temperature change of a polymer solution does not always lead to expansion or contraction of the chain coil it can cause conformation change to a more or less packed polymer chain and to a more or less excimer forming conformation. Both of these structural changes in a polymer chain can affect the fluorescence, but each polymer needs to be considered individually. 

When a system contains two fluorescing chromophores such that the emission spectrum of the donor overlaps the absorption spectrum of the acceptor, excitation energy from the donor can be transferred to the acceptor over a considerable separation distance, R. The efficiency, , of this energy transfer would be governed by the equation proposed by Forster [40]  

There is always uncertainty if we adopt this equation for polymeric systems the most important consideration seems to be the inhomogeneity of the polymer solution when the polymer segments are constrained into local high and low concentrations by the distribution of macromolecules. 

We can observe emission from both PS excimer and PPO. The Xj = 12 ns due to pure PS in solution decreases with PPO increase and the relative intensity of the short-lived PPO component increases in the presence of PS. The decrease in the lifetime of PS subjected to Stern-Volmer analysis gave the slope 5.2 x 10 1 mol h Semi-quantitative analysis, assuming the mutual diffusion coefficient of 2 x 10 m s gave the distance of interaction in the order of magnitude 10 nm. Quenching efficiencies of this magnitude would be possible only 

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