Density Function Theory Study on Thiophene Polymers(C4H4S)n(n=1～8)

Thiophene polymers（C4H4S）n（ n = 1 ～ 8）have been studied on B3LYP / 6-31G theory level. Vibrational frequencies，total energy（ET），zero point energy（ZPE），capacity（C0P），entropy（S0 ）and energy gap（ΔE）was calculated based on the optimized equilibrium structures. By means of frequency analysis，the equilibrium structures were confirmed. The relationships between ET，ZPE，C0P，S0，ΔE and n were studied. The formation enthalpy of thiophene polymers was calculated with the total energies. The polymerized process and relative stability of the title compounds was determined according to the data of the formation enthalpy. The calculated results indicated that the thiophene molecular which has a planar structure exists in the stable chain polymers and the chain structures（C4H4S）n（ n > 1）present different stabilities when n is an even or odd number. ZPE，C0P，and S0 show a linear increasing trend with n. The energy gaps ΔE show a direct proportion to n too，which indicated that the conduct property increases with n. The results also illustrated that the stepsize polymerized process is the primary way in the polymerized reactions.