The configurations and the collapsed polymer state of a semi-stiff chain under various temperatures

especially below the theta point

are presented in this paper. The Monte Carlo method is used to simulation the behavior of a semi-stiff polymer chain in simple cubic lattice. In our model the inter-segmental interactions included the hard core volume effect

longer ranged attractive part and the local stiffness potential. The stiffness of a chain is determined by the ratio of stiffness potential and attractive effect. Our results have been obtained show-ing a shrinkage of the coil dimension of a polymer chain with decrease temperature. But there has some differences between a flexible chain and a semi-stiff polymer chain. At first the soil demintion of a semi-stiff chain is expanded due stiffness potential

then it shrinkage with de-crease temperature. From the behaviou of the specific heat we concluded that the collapsed transitions of a polymer chain is a second-order phase transitions.