DYNAMICS OF SLIGHTLY FLEXIBLE RODS IN THE LIQUID-CRYSTALLINE STATE

A molecular theory for the reptational dynamics of rods with a small p ersistent flexibility in the liquid crystalline state is developed. A closed diffusion equation for the orientational distribution function is obtained by expanding in the small parameter L/l, where L is the co ntour length of the rodlike polymer chain and l is the persistence len gth. The Leslie viscosities alpha3 and alpha2 are calculated, and it i s found that the ratio alpha3/alpha2 is nonmonotonic with L/l. It is c oncluded that slightly flexible rodlike polymers are more prone to tum bling nematics than fully rigid rods.