A thermotropic liquid crystalline polymer(LCP) containing a terephthaloyl bis(4-oxybenzoyl) (Triad) rigid moiety and a butylene terephthalate flexible unit was solution-polymerized and was subsequently partly sulfonated. It was found that the introduction of sulfonic acid groups to the LCP did not change the position of the DSC peak for the nematic-to-isotropic transition of the LCP (T(n-i)). However, the sulfonation induced a peak related to the melting of crystalline phase of the Triad domains (T(m(T))). When the acid groups of the sulfonated LCP were neutralized with NaOH, the T(n-i) DSC peak shifted to lower temperatures with a strong decrease in its size, but the T(m(T)) DSC peak did not change its position strongly. Furthermore, a new peak for the melting of crystalline phase of the butylenes domains (T(m(BT))) appeared at much lower temperatures. The above results suggested that the sulfonation introduced ionic characters to the TLCP polymer successfully; as expected, it changed the liquid crystalline characters of the TLCP significantly.