Alexander Blumen

Transient photoconductivity of polysiloxane with pendant carbazole groups

Abstract We report measurements of transient photocurrents in polysiloxane polymers with pendant carbazole groups. The experiments agree well with the continuous-time random-walk theory with an algebraic waiting-time distribution ψ(t)∼t −1-α. Our experiments yield α=0·58 for polysiloxane.

Stochastic Aspects in Reaction Kinetics

Randomness occurs in many areas of modern physics. For example, in the past decade interest has turned increasingly towards the investigation of amorphous solids such as polymers and glasses. Furthermore randomness can occur in many forms. Thus, transport properties of spatially random systems (mixed crystals, alloys) are triggered by a distribution of microscopic (site-to-site) transfer rates (temporal disorder) and by different interactions with the surroundings (energetic disorder).

Theory of Polymers on Fractal Lattices

Nowadays, There is much interest in the statistics of polymers (both of linear chain type and also branched) in good solvents1. The most salient feature of real polymers is the “excluded-volume” effect: the physical fact that no two different monomers composing the polymer can occupy the same spatial position at the same time. In the case of a linear chain polymer without the excluded-volume constraint the chain is Markovian (Gaussian) and can be modelled as a random walk (RW); whereas with inclusion of this constraint the chain becomes non-Markovian and corresponds to a self-avoiding random walk (SAW). In the case of branched polymers we call the analogous case excluded-volume-branched-polymers (EVB) and distinguish them from simple randomly branched polymers (RB), where no such restrictions apply. The statistical properties of SAW and EVB on several kinds of fractal lattices have been extensively discussed in recent years2–7. The motivation for analysing the statistical features of polymers on fractals comes from the wish to understand the controversial (and much studied) problem of establishing the critical behaviour of saw on random media8–10.