Quantum amplified isomerization in polymers based on triplet chain reactions.

Photoinitiated triplet quantum amplified isomerizations (QAI) of substituted Dewar benzene derivatives in polymeric media are reported. The quantum efficiencies and the ultimate extents of reactant-to-product conversions increase significantly with the incorporation of appropriate co-sensitizers; compounds whose triplet energies are similar to or lower than that of the sensitizer and close to that of the reactant. These co-sensitizers serve to promote chain-propagating energy transfer processes and thereby increase the action sphere of photosensitization.

Highly efficient triplet chain isomerization of Dewar benzenes: adiabatic rate constants from cage kinetics.

Quantum yields as high as 120 were achieved for triplet-sensitized photoisomerizations of several Dewar benzene reactants, R, to the corresponding benzene products, P. Considerable chain amplification is maintained even at high conversion. All relevant rate constants of this triplet chain reaction were extracted from laser flash photolysis plus steady-state photolysis experiments.

Spontaneous formation of an exfoliated polystyrene-clay nanocomposite using a star-shaped polymer.

Mixtures of five-arm star polystyrene with an organoclay spontaneously formed exfoliated nanocomposites when annealed, validating a recent theoretical prediction by Singh and Balazs (Polym. Int. 2000, 49, 469.