Four different substituted 1,3,5-benzenetrisamides were synthesized and two of them were reported for the first time. Their effects on the crystal structure and morphologies of the iPP homopolymer (PPH) and propylene-ethylene random copolymers (PPR) were investigated. The results showed that they had versatile nucleating ability among the different crystal forms of PPH. The N,N',N ''-tris-tert-butyl-1,3,5-benzene-tricarboxamide, N,N',N ''-tris-cyclohexyl-1,3,5-benzene-tricarboxamide, and N,N',N ''-tris-isopropyl-1,3,5-benzene-tricarboxamide suppressed the formation of detectable spherulites with the common alpha-form of the PPH, as well as the N,N',N ''-n-butyl-1,3,5-benzene-tricarboxamide induced the spherulites of the beta-form. The combination of the ethylene segment and the nucleating agent facilitated the formation of the T-form. These trisamides had limited effects on the packing of the PPH segments but induced more compacted packing of the PPRs. The nucleation mechanism of such compounds was discussed for the first time, it was found that the nucleation ability of these compounds rooted in matching of their dimension of the b-axis with dimension of the c-axis of iPP, and their butterfly-shape further enhanced it. The (001) face of the trisamides was in contact with the (010) face of iPP This epitaxial crystallization led to preferential growth along the b-axis, and the ethylene segment indeed enhanced this effect. (c) 2008 Wiley Periodicals, Inc.