The electronic structure of diblock copolymers consisting of poly (p-phenylene) and polyacetylene were studied in the framework of an inter-component coupling model. It was found that the band gaps could be tuned by the proportion of the homopolymers. The interfacial coupling between the components also affected the band gaps obviously. Localized states and hybridized states appeared in copolymers due to the interactions between the homopolymers. The doped charges accumulated in its one segment of a copolymer. The accumulation condition is discussed.

Spin-polarized current through a ferromagnetic/organic interface was studied theoretically. This study was stimulated by recent experiments on La1−xSrxMnO3 /Alq3/Co and La1−xSrxMnO3/sexithienyl/La1−xSrxMnO3 structures. According to the spin-diffusion equation, the current spin polarization was obtained by assuming that spin polarons as well as spinless bipolarons to be the carriers in the organic semiconductor. It was found that polarons are the effective spin carriers of a spin-polarized current, even though they constitute only a fraction of all carriers. Effects of interfacial electrochemical-potential difference and conductivity matching on spin polarization of the current are discussed.

Localized modes of lattice vibration in polythiophene are investigated numerically by considering a chain of finite length. th the periodic boundary condition, we find three even-parity and four odd-parity modes. One of the even modes due to the sulfur heteroatom in the heterocycle is believed to be re-sponsible for what is observed around 700 cm. in the Raman spectrum of polythiophene. With the free-end boundary condition, several modes from the highest optical branch become localized near the surface. These modes may be identified as the high-frequency modes observed in infrared-active vibra-tion and resonant. Raman. scattering absorption experiments.

The ground and excited state energies of the two-dimensional D−centre have been calculated, respectively, as a function of magnetic field. The critical magnetic field values at which the excited states change from unbound to bound have been found. The optical transition between two bound states is discussed. Numerical results with the hyperspherical approach are in good agreement with those obtained through other intensive numerical methods and those obtained through experiments.

The effect of atomic disorder or chain length on the stability of photoinduced polarization inversion has been studied. The atomic disorder was simulated by square-random or Gaussian-random model. It was found that for the square-random distribution case, photoinduced polarization inversion remains steadily when atomic disorder is less than 1 8a-a is the lattice constant of polyacetylene, the reversion polarization disappears and gets into normal polarized state when the disorder is stronger than over 1 8a. The reason of a normal polarization resulted from the strong lattice disorder was discussed. The relationship between the reverse polarization of biexciton state and the confinement constant te as well as the variation of chain length was also studied.