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.

The electron.. electron interactions and the creation energy of a soliton in highly conducting polymers were calculated by using a correlated--basis-function method with a general screening Coulomb potential within the Kronig. Penny. model framework. Our results showed that even when the electron-electron interactions are considered，solitons are still the main charge carriers. The strong long-range electron-electron interaction is seen to reduce the creation energy of a soliton. A comparison with results based on the Hubbard model has been made. The 1imitations of the Hubbard model in this application were discussed.

The electrical transport of DNA is closely related to the density of itinerant π electrons because of the strong electron-lattice interaction. The resistivities of two typical DNA molecules [poly(dG)-poly(dC) and λ-DNA] with varied densities of itinerant π electrons are calculated. It is found that the dependence of the resistivity on the density of itinerantπelectrons is symmetrical about the half-filling state of itinerant π electrons in poly(dG)-poly(dC). At the half-filling state, the Peierls phase transition takes place and poly(dG)-poly(dC) has a large resistivity. When the density of itinerant π electrons departs far from the half-filling state, the resistivity of poly(dG)-poly(9dC) becomes small. Forλ-DNA, there is no Peierls phase transition due to the aperiodicity of its base pair arrangement. The resistivity of poly(dG)-poly(dC) decreases with increasing length of the molecular chain, but the resistivity of λ-DNA increases with increasing length. The conducting mechanisms for poly(dG)-poly(dC) and a few λ-DNA molecules with varied densities of itinerantπelectrons are analyzed.

with a local site-impurity potential in the framework of the su, schrieffer, and Heeger (SSH) model, both the dopant dependence and the chain-length dependence of the vibrational modes related to charged solitons in a finite trans-polyacetylene chain have been studied. The numerical calcultions showed that the well-known Goldstone mode will be pinned by the dopant potentials as well as by the chhain ends. Two localized modes were found in the acoustic-frequency branch. The results are in agree-ment with the infrared- active vbibrational modes also observed in lightly doped polyacetylene cases. A comparison with the phtoexcitation measurements has been given.

In the framework of the tight-binding model, the effects of longitudinal as well as transverse coupling between polyacetylene chains with different lengths and the electron–electron interactions on excitations have been studied. A new spinless charged polaronic excitation (q=±e; s=0) was obtained due to the transverse interchain coupling, which is different from the general magnetic polaron (q=±e; s=1/2) obtained in the perfect one-dimensional model. Due to its end positioning, a polaron is more easily stimulated energetically in a longer chain than in a shorter one, and it can hop to the longer chains nearby via either transverse or longitudinal interchain coupling. In addition, the transverse coupling decreases the energy of creation of a polaron. Considering the strong electron–electron interactions and the end positioning of chains in actual materials, we concluded that the one-dimensional model of conducting polymers is fairly appropriate in certain circumstances.